JP7126689B2 - Optical vortex generation method and optical vortex generator - Google Patents

Description

The present invention relates to an optical vortex generation method and an optical vortex generator.

The optical vortex generator described in Patent Document 1 has a light source section and a spiral phase plate. The light source section generates laser light. The helical phase plate transforms the laser light into an optical vortex.

JP 2015-163912 A

However, in order to generate a plurality of optical vortices, the optical vortex generator described in Patent Literature 1 requires preparation of the same number of helical phase plates as the number of optical vortices. As a result, the cost of the optical vortex generator increases as the number of helical phase plates increases.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical vortex generation method and an optical vortex generator capable of generating a plurality of optical vortices while suppressing costs.

According to one aspect of the present invention, an optical vortex generation method includes the steps of: generating a plurality of beams; giving a phase difference to two or more beams among the plurality of beams; irradiating a target with said plurality of beams, including said two or more beams. In the irradiating step, the plurality of beams impinge on the target from different directions and the plurality of beams interfere. The interference pattern of the multiple beams includes multiple spots. In the imparting step, the phase difference is imparted to the two or more beams such that the plurality of spots rotate about a plurality of centers of rotation, respectively. The spot indicates a portion where the light intensity is higher than the portion where the center of rotation is located.

In the optical vortex generation method of the present invention, it is preferable that the angles between adjacent beams in the plurality of beams are substantially equal. Preferably, the angles of incidence of said plurality of beams on said target are substantially equal.

In the optical vortex generation method of the present invention, each of the phase differences imparted to the two or more beams indicates a phase difference with reference to a beam different from the two or more beams among the plurality of beams, It is preferably M times the predetermined value (M is an integer equal to or greater than 1). It is preferable that the value of M is set for each of the phase differences imparted to the two or more beams.

In the optical vortex generation method of the present invention, the plurality of beams is preferably six beams. The predetermined value is preferably π/3 radians or -π/3 radians.

In the optical vortex generating method of the present invention, it is preferable that, in the step of irradiating, a plurality of optical vortices arranged in a triangular lattice pattern are formed by interference of the plurality of beams.

Preferably, the optical vortex generation method of the present invention further includes a step of adjusting the plurality of beams, performed between the applying step and the irradiating step. In the adjusting step, the plurality of beams are adjusted to determine the size of a region in which the plurality of optical vortices are generated based on the plurality of beams, the interval between the plurality of optical vortices, and the generation of the plurality of optical vortices. It is preferred to adjust at least one of the position.

According to another aspect of the present invention, an optical vortex generator includes a multi-beam generator, a phase difference generator, and an irradiator. A multi-beam generator generates a plurality of beams. The phase difference imparting unit imparts a phase difference to two or more beams among the plurality of beams. The irradiation unit irradiates a target with the plurality of beams including the two or more beams to which the phase difference is given. The multiple beams impinge on the target from different directions, and the multiple beams interfere. The interference pattern of the multiple beams includes multiple spots. The phase difference imparting unit imparts the phase difference to the two or more beams such that the plurality of spots rotate around a plurality of rotation centers. The spot indicates a portion where the light intensity is higher than the portion where the center of rotation is located.

According to the present invention, it is possible to generate a plurality of optical vortices while suppressing costs.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the optical eddy generator based on Embodiment 1 of this invention. (a) is a diagram showing an interference pattern including a plurality of optical vortices generated by the optical vortex generator according to Embodiment 1. FIG. (b) is a diagram showing the intensity of each of a plurality of optical vortices generated by the optical vortex generator according to the first embodiment; 4(a) to 4(e) are diagrams showing temporal changes in interference patterns of a plurality of beams generated by the optical vortex generator according to Embodiment 1. FIG. 4A is a perspective view showing a plurality of beams generated by the optical vortex generator according to Embodiment 1; FIG. 4B is a plan view showing a plurality of beams generated by the optical vortex generator according to Embodiment 1; FIG. (a) is a diagram showing an example of phase differences of six beams generated by the optical vortex generator according to the first embodiment. 8B is a diagram showing another example of the phase difference between the six beams generated by the optical vortex generator according to the first embodiment; FIG. 4 is a flowchart showing an optical vortex generation method executed by the optical vortex generator according to Embodiment 1; (a) is a diagram showing an example of phase differences of six beams generated by the optical vortex generator according to Embodiment 2 of the present invention. (b) is a perspective view showing an optical vortex based on six beams having phase differences shown in (a). (c) is a diagram showing a phase difference when the phase difference shown in (a) is inverted. (d) is a perspective view showing an optical vortex based on the six beams having the phase differences shown in (c). (a) is a diagram showing another example of the phase difference between a plurality of beams generated by the optical vortex generator according to the second embodiment. (b) is a diagram showing an example of a phase difference when the phase difference shown in (a) is inverted. (c) is a diagram showing another example of the phase difference when the phase difference shown in (a) is inverted. It is a figure which shows the optical eddy generator based on Embodiment 3 of this invention. 10 is a flow chart showing an optical vortex generation method executed by the optical vortex generator according to Embodiment 3. FIG. (a) is a diagram showing a plurality of optical vortices according to Example 1 of the present invention. 8B is a diagram showing phase differences of six beams according to Example 1. FIG. It is a figure which shows the general optical eddy based on a comparative example. 4(a) to 4(l) are diagrams showing the movement of a spot forming an optical vortex according to Example 1. FIG. (a) is a diagram showing a plurality of optical vortices according to Example 2 of the present invention. (b) is a diagram showing phase differences of six beams according to Example 2. FIG. (a) to (l) are diagrams showing the movement of a spot forming an optical vortex according to Example 2. FIG. (a) is a figure which shows the optical vortex based on Example 3 of this invention. (b) is a diagram showing phase differences of four beams according to Example 3. FIG. (a) to (l) are diagrams showing movement of a spot forming an optical vortex according to Example 3. FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
An optical vortex generating device 100 and an optical vortex generating method according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 to 6. FIG. First, the optical vortex generator 100 will be described with reference to FIG. FIG. 1 is a diagram showing an optical vortex generator 100 according to Embodiment 1. FIG.

As shown in FIG. 1 , the optical vortex generator 100 includes a laser oscillator 1 , a multi-beam generator 3 , a collimating lens 5 , a phase difference imparting section 7 and a condenser lens 9 . The condenser lens 9 corresponds to an example of the "irradiation section".

A laser oscillator 1 generates laser light LT. The laser light LT may be a continuous wave, or may include a plurality of pulsed lights. The laser light LT may be visible light or invisible light, and the wavelength of the laser light LT is not particularly limited.

The multi-beam generator 3 generates a plurality of beams Bn (n is an integer equal to or greater than 1) based on the laser light LT. Specifically, the multi-beam generator 3 divides the laser beam LT to generate a plurality of beams Bn. A plurality of beams Bn enter the collimator lens 5 .

Specifically, the multi-beam generator 3 includes a diffraction grating 31 . The diffraction grating 31 is, for example, a transmissive diffraction grating. The diffraction grating 31 transmits a part of the laser light LT without diffracting it, and emits it as a beam B0. Beam B 0 is blocked in the optical path between diffraction grating 31 and condenser lens 9 . Therefore, the beam B0 does not irradiate the target TA. Also, the diffraction grating 31 diffracts the laser light LT to split a portion of the laser light LT into a plurality of beams Bn.

Note that the multi-beam generator 3 may include a beam splitting optical system instead of the diffraction grating 31 . A beam splitting optical system splits the laser light LT to generate a plurality of beams Bn. The beam splitting optical system includes, for example, multiple half mirrors. The beam splitting optical system may include, for example, one or more cubic beam splitters in addition to multiple half mirrors.

A collimating lens 5 collimates the beams Bn. A plurality of collimated beams Bn enter the phase difference applying section 7 . The collimator lens 5 is, for example, a convex lens.

The phase difference imparting unit 7 imparts a phase difference to two or more beams Bn among the plurality of beams Bn. A plurality of beams Bn including two or more beams Bn having phase differences are incident on the condenser lens 9 .

The phase difference applying unit 7 includes, for example, an optical retarder including a plurality of glass plates. The optical retarder adjusts the tilt angle of the glass plate to delay the beams Bn and impart a phase difference to two or more beams Bn. Alternatively, the phase difference imparting unit 7 delays a plurality of beams Bn in one glass plate, for example, and imparts a phase difference to two or more beams Bn. Alternatively, the phase difference imparting unit 7 has, for example, one helical phase plate, and allows a plurality of beams Bn to be incident on a plurality of different locations on the one helical phase plate, so that two or more beams Bn Gives a phase difference. A plurality of different locations in one helical phase plate have different thicknesses. Alternatively, the phase difference imparting unit 7 has, for example, a plurality of glass plates with different thicknesses, and causes a plurality of beams Bn to enter each of the plurality of glass plates to impart a phase difference to two or more beams Bn.

Alternatively, the phase difference applying unit 7 includes, for example, a spatial phase modulator. A spatial phase modulator includes a plurality of pixels arranged in a matrix. The spatial phase modulator can modulate the phase of light incident on each pixel. The spatial phase modulator modulates the phase of the wavefront of the beam Bn to impart a phase difference to two or more beams Bn. Alternatively, the phase difference applying section 7 may include, for example, a plurality of piezo drive mirrors. A piezo-driven mirror is a mirror driven by a piezo element. The phase difference imparting unit 7 adjusts the optical paths of the beams Bn using piezo drive mirrors to impart phase differences to two or more beams Bn.

The condenser lens 9 irradiates the target TA with a plurality of beams Bn. Therefore, the condenser lens 9 functions as an objective lens. The condenser lens 9 is, for example, a convex lens. The target TA is, for example, solid, liquid, or gas. The multiple beams Bn that have passed through the condenser lens 9 are incident on the target TA from different directions, and the multiple beams Bn interfere with each other. Specifically, multiple beams Bn interfere on or in the target TA. As a result, a plurality of optical vortices (more specifically, a large number of optical vortices) are generated on or in the target TA. Specifically, a plurality of optical eddies (specifically, a large number of optical eddies) are generated simultaneously on or in the target TA. An optical vortex is light that has a singular point and whose equiphase plane forms a spiral plane.

The condenser lens 9 has a focal length d1 on the target TA side and a focal length d2 on the collimator lens 5 side. The focal length d1 and the focal length d2 are substantially the same. On the other hand, the collimator lens 5 has a focal length d3 on the condenser lens 9 side and a focal length d4 on the multi-beam generator 3 side. The focal length d3 and the focal length d4 are substantially the same. It is preferable that the focal plane of the condenser lens 9 located at the focal length d2 substantially coincides with the focal plane of the collimator lens 5 located at the focal length d3. In this preferred example, the multiple beams Bn can be superimposed on or in the target TA with high precision, and the multiple beams Bn can be effectively interfered on or in the target TA. As a result, a plurality of optical vortices (more specifically, a large number of optical vortices) can be effectively generated on or in the target TA.

The multiple optical vortices are observed as interference patterns of multiple beams Bn on or in the target TA. The interference pattern represents the spatial distribution of light intensity based on the interference of multiple beams Bn. Specifically, when multiple beams Bn interfere, the electric field at a coordinate is the sum of the electric fields of all beams Bn at that coordinate. On the other hand, the light intensity is proportional to the square of the electric field intensity. Therefore, when multiple beams Bn interfere, the light intensity at a coordinate is proportional to the square of the sum of the electric field intensities of all beams Bn at that coordinate. The interference pattern represents the light intensity based on the interference of the multiple beams Bn at each coordinate of the orthogonal coordinate system.

Next, the optical vortex VT will be described with reference to FIGS. 2(a) and 2(b). FIG. 2(a) is a diagram showing an interference pattern PT including a plurality of optical vortices VT generated by the optical vortex generator 100. FIG. In FIG. 2(a), the interference pattern PT on or inside the target TA (FIG. 1) is shown. FIG. 2(b) is a diagram showing the intensity of each of the plurality of optical vortices VT. In FIG. 2(b), light intensity is represented by shading from black to white. The closer to white, the stronger the light intensity. Although the light intensity is weak between the optical vortices VT, the regions between the optical vortices VT are made transparent in FIG. 2B so that the shape of the optical vortices VT can be seen. 2(a) and 2(b) show a part of the optical vortices VT among the large number of optical vortices VT.

As shown in FIG. 2(a), the interference pattern PT includes a plurality of optical vortices VT (more specifically, a large number of optical vortices VT). Each of the multiple optical vortices VT has a singular point SG. The light intensity at the singular point SG is approximately zero. A plurality of optical vortices VT are arranged periodically. In the example of FIG. 2A, a plurality of optical vortices VT are arranged in a triangular lattice. As shown in FIG. 2B, the light intensity in the Z-axis direction of each of the plurality of light vortices VT is substantially constant. The light intensities of the plurality of light vortices VT are substantially the same.

The interference pattern PT shown in FIG. 2(a) is calculated by integrating the square of the sum of the electric field intensities of all the beams Bn for one period T of the beams Bn. One period T is a value obtained by dividing the wavelength λc of the beam Bn by the speed of light vc (T=λc/vc).

Specifically, the interference pattern PT is expressed as an integration of a plurality of interference patterns for one period T (hereinafter referred to as "interference pattern PTD") arranged on the time axis. For example, each of the plurality of interference patterns PTD is calculated by integrating the square of the sum of the electric field intensities of all beams Bn over time t. The time t is, for example, a value obtained by dividing one cycle T by K (K is an integer equal to or greater than 2). That is, t=T/K. The length of time t is not particularly limited, and "K" can be set to any integer of 2 or more. For example, the value of "K" is set such that the time t is sufficiently shorter than one cycle T.

Next, the interference pattern PTD will be described with reference to FIGS. 3(a) to 3(e). FIGS. 3(a) to 3(e) are diagrams showing temporal changes in the interference pattern PTD. In FIGS. 3(a) to 3(e), auxiliary lines AL orthogonal to each other are added for easy understanding. Also, the interference pattern PTD is calculated by integrating the square of the sum of the electric field intensities of all the beams Bn over time t (=T/5). That is, the plurality of interference patterns PTD shown in FIG. values and integrated values from 4t to 5t.

As shown in FIG. 3A, the interference pattern PTD of the multiple beams Bn includes multiple spots P (specifically, multiple spots P). A spot P1 and a spot P2 adjacent to each other among the plurality of spots P form a spot pair SP. Therefore, the interference pattern PTD includes a plurality of spot pairs SP (specifically a large number of spot pairs SP). A spot P indicates a light intensity peak in the interference pattern PTD.

Here, focus on one spot pair SP. As shown in FIGS. 3(a) to 3(e), the spot pair SP rotates once per period T around the center of rotation RC. As a result, an optical vortex VT for one period T is formed. That is, one optical vortex VT for one period T is formed by one rotation of one spot pair SP. One rotation of the spot pair SP indicates that the spot pair SP rotates 360 degrees. Specifically, each of the spot P1 and the spot P2 rotates once in one period T around the rotation center RC.

At the center of rotation RC, the light intensity is substantially zero. Therefore, each of the spots P1 and P2 indicates a portion where the light intensity is higher than the portion where the rotation center RC is located. Rotation center RC corresponds to singular point SG. The center of rotation RC is located between the spots P1 and P2. In FIGS. 3(a) to 3(e), each of the spots P1 and P2 rotates counterclockwise around the rotation center RC.

As described above with reference to FIGS. 3A to 3E, one optical vortex VT is generated by one spot pair SP rotating around the rotation center RC. That is, in a state in which the spot pair SP rotates around the rotation center RC at which the light intensity is approximately zero, the equiphase plane rotates around the singular point at which the light intensity is approximately zero in a general optical vortex. This corresponds to a state in which orbital angular momentum is generated by Therefore, by rotating the spot pair SP around the rotation center RC, an optical vortex VT similar to a general optical vortex can be generated.

In Embodiment 1, the phase difference imparting unit 7 applies a phase difference to two or more beams Bn out of the plurality of beams Bn so that the plurality of spot pairs SP rotate around the plurality of rotation centers RC, respectively. Granted. As a result, a plurality of optical vortices VT (FIG. 2(a)) can be generated. In this case, the phase difference imparting unit 7 imparts a phase difference to two or more beams Bn such that the spot pair SP rotates once in one cycle T of the beams Bn. Particularly, in the first embodiment, the optical vortex generator 100 does not need to prepare a plurality of helical phase plates, so the cost of the optical vortex generator 100 can be reduced while generating a plurality of optical vortices VT.

Specifically, one optical vortex VT has a spiral first equal phase surface corresponding to the rotation of the spot P1 and a spiral second equal phase surface corresponding to the rotation of the spot P2. Each of the first equal phase surface and the second equal phase surface has a period T. Therefore, the rotation of only the spot P1 around the center of rotation RC generates an optical vortex (first spiral equiphase surface), and the rotation of only the spot P2 around the center of rotation RC also generates an optical vortex (a spiral ) is generated.

In Embodiment 1, the phase difference applying unit 7 gives phase differences to two or more beams Bn of the plurality of beams Bn so that the plurality of spots P1 rotate around the plurality of rotation centers RC. is doing. As a result, a plurality of optical vortices (helical first equal phase fronts) can be generated. In this case, the phase difference imparting unit 7 imparts a phase difference to two or more beams Bn such that the spot P1 makes one rotation in one period T of the beam Bn. In particular, in Embodiment 1, since the optical vortex is generated by imparting a phase difference, there is no need to prepare a plurality of helical phase plates. can.

Similarly, the phase difference imparting unit 7 imparts a phase difference to two or more beams Bn out of the plurality of beams Bn so that the plurality of spots P2 each rotate around a plurality of rotation centers RC. there is As a result, a plurality of optical vortices (helical second equal phase fronts) can be generated. In this case, the phase difference imparting unit 7 imparts a phase difference to two or more beams Bn such that the spot P2 makes one rotation in one period T of the beam Bn.

Note that when all the beams Bn have the same phase, the spatial distribution of the light intensity remains constant without rotating, and only the light intensity repeats a change in intensity.

Next, a plurality of beams Bn will be described with reference to FIGS. 1, 4(a), and 4(b). FIG. 4(a) is a perspective view showing a plurality of beams Bn. FIG. 4(b) is a plan view showing a plurality of beams Bn. In FIG. 4(b), a plurality of beams Bn are viewed from the Z-axis direction shown in FIG. 4(a).

As shown in FIG. 4A, the origin O of the three-dimensional orthogonal coordinate system is set on the surface of the target TA. The Z-axis is orthogonal to the target TA. Each of the X-axis and Y-axis is parallel to the surface of the target TA. The X-axis, Y-axis and Z-axis are orthogonal to each other. The Z-axis is the central axis of the multiple beams Bn. Therefore, as shown in FIGS. 4(a) and 4(b), the multiple beams Bn are axially symmetrical with respect to the Z axis. In addition, two beams Bn facing each other across the Z-axis among the plurality of beams Bn are line-symmetrical with respect to the Z-axis. As shown in FIG. 1, when the multi-beam generator 3 includes the diffraction grating 31, the beam B0, which is non-diffracted light, substantially coincides with the Z axis. Also, the traveling direction of the beam B0 substantially coincides with the Z-axis direction.

Incident angles θn (n is an integer equal to or greater than 1) of the beams Bn to the target TA are substantially equal. For example, if the multiple incident angles θn are within ±Qx% of the average value θA with respect to the average value θA, the multiple incident angles θn are substantially equal. The average value θA indicates the average value of a plurality of incident angles θn. "Qx%" is, for example, 20%, preferably 10%, more preferably 5%, and even more preferably 1%.

Each of the multiple incident angles θn indicates the incident angle of the beam Bn with respect to the Z-axis. The incident angle θn is an acute angle. The incident angles θn of the plurality of beams Bn are set by the multi-beam generator 3, the collimator lens 5, and the condenser lens 9. FIG. The multi-beam generator 3, the collimator lens 5, and the condenser lens 9 adjust the multiple beams Bn so that the incident angles θn of the multiple beams Bn are substantially the same.

In the plurality of beams Bn, the angles Φn (n is an integer equal to or greater than 1) between the beams Bn adjacent to each other in the circumferential direction CD around the Z axis are substantially equal. That is, the angles Φn are substantially equal. The angle Φn indicates the azimuth of one of the two beams Bn adjacent to each other in the circumferential direction CD with respect to the other beam Bn. Therefore, the angle Φn is hereinafter referred to as "azimuth angle Φn". For example, if the azimuth angles Φn are within ±Qy% of the average value ΦA with respect to the average value ΦA, the azimuth angles Φn are substantially equal. The average value ΦA indicates the average value of multiple azimuth angles Φn. "Qy%" is, for example, 20%, preferably 10%, more preferably 5%, and even more preferably 1%.

A plurality of azimuth angles Φn are set by the multi-beam generator 3 . The multi-beam generator 3 generates a plurality of beams Bn such that the azimuth angles Φn of the plurality of beams Bn are substantially equal. For example, the multi-beam generation unit 3 divides the laser light LT to generate a plurality of beams Bn such that the azimuth angles Φn of the plurality of beams Bn are substantially equal. Alternatively, for example, the multi-beam generator 3 divides the laser light LT to generate a plurality of beams Bn, and then adjusts the plurality of beams Bn so that the azimuth angles Φn of the plurality of beams Bn are substantially equal. .

The light intensities of the multiple beams Bn are substantially equal. That is, the multi-beam generator 3 divides the laser light LT to generate a plurality of beams Bn such that the light intensities of the plurality of beams Bn are substantially the same. Note that the wavelengths of the multiple beams Bn are the same.

As described above with reference to FIGS. 1, 4(a), and 4(b), the incident angles θn of the plurality of beams Bn are substantially equal. Additionally, in the beams Bn, the azimuth angles Φn are substantially equal. Therefore, the multiple beams Bn interfere with each other under the same condition except for the phase difference. As a result, according to the first embodiment, it is possible to generate a plurality of periodically arranged optical vortices VT (FIG. 2(a)) according to the phase difference given to two or more beams Bn. This point is clear from Examples 1 to 3 to be described later.

The phase difference imparted to the beam Bn by the phase difference imparting unit 7 will now be described with reference to FIG. 4(b). Each of the phase differences imparted to the two or more beams Bn indicates a phase difference with reference to a beam Bn different from the two or more beams Bn to which the phase difference is imparted among the plurality of beams Bn. That is, each phase difference indicates a phase difference with respect to the reference beam Bn to which no phase difference is applied. For example, each phase difference indicates a phase difference with respect to beam B1. Hereinafter, unless otherwise specified, the phase difference indicates the phase difference with respect to the reference beam Bn.

For example, when the phase of the beam B2 leads the phase of the reference beam B1, the sign of the phase difference given to the beam B2 is "positive". On the other hand, for example, when the phase of the beam B2 lags behind the phase of the reference beam B1, the sign of the phase difference given to the beam B2 is "negative".

In Embodiment 1, each of the phase differences given to the two or more beams Bn is M times (M is an integer equal to or greater than 1) a predetermined value (hereinafter referred to as "predetermined value J"). A value of M is set for each of the phase differences given to the two or more beams Bn. As a result, a plurality of periodically arranged optical vortices VT (FIG. 2(a)) can be generated according to a phase difference that is M times the predetermined value J. FIG. This point is clear from Examples 1 to 3 to be described later. Note that the value of M may be different for each of the two or more beams Bn to which the phase difference is given, or may be the same for the two or more beams Bn to which the phase difference is given.

Note that the method of expressing the phase difference is not particularly limited. For example, the phase difference may indicate the difference between the phase of one beam Bn and the phase of the other beam Bn of two beams Bn adjacent to each other in the circumferential direction CD. For example, when the phase of one beam Bn leads the phase of the other beam Bn, the sign of the phase difference given to the one beam Bn is "positive". On the other hand, for example, when the phase of one beam Bn lags behind the phase of the other beam Bn, the sign of the phase difference given to the one beam Bn is "negative".

Next, the optical vortex generator 100 will be described with specific examples with reference to FIGS. 1 and 4(a) to 5(b). In a specific example, the plurality of beams Bn is six beams Bn.

That is, as shown in FIGS. 1, 4(a), and 4(b), the multi-beam generator 3 generates six beams B1 to B6 based on the laser light LT. Specifically, the multi-beam generator 3 divides the laser beam LT to generate six beams B1 to B6.

The phase difference imparting unit 7 imparts a phase difference to two or more beams Bn among the six beams B1 to B6. A collimating lens 5 collimates the six beams B1-B6. The condenser lens 9 irradiates the target TA with the six beams B1 to B6. The six beams B1 to B6 are incident on the target TA from different directions, and the six beams B1 to B6 interfere with each other.

The interference pattern PTD of the six beams B1-B6 includes a plurality of spots P (FIGS. 3(a)-3(e)). The phase difference imparting unit 7 imparts phase differences to the two or more beams Bn so that the plurality of spots P rotate around the plurality of rotation centers RC.

Incident angles θ1 to θ6 of the six beams B1 to B6 are substantially equal. Each of the incident angles θ1 to θ6 is, for example, 20 degrees. Among the six beams B1 to B6, the azimuth angles Φ1 to Φ6 between the beams Bn adjacent to each other in the circumferential direction CD are substantially equal. Each of the azimuth angles Φ1 to Φ6 is approximately 60 degrees.

In Embodiment 1, each of the phase differences given to two or more beams Bn among the six beams B1 to B6 is M times the predetermined value J. FIG. Specifically, the predetermined value J is π/3 radians or -π/3 radians. As a result, according to the first embodiment, a plurality of light vortices VT (Fig. 2 (a)) can be generated. This point is clear from Example 1 and Example 2 to be described later.

FIG. 5(a) is a diagram showing phase differences given to five beams B2 to B6 out of the six beams B1 to B6. In FIG. 5A, for easy understanding, the phase difference indicates the phase difference between two beams Bn adjacent to each other in the circumferential direction CD. As shown in FIG. 5(a), the phase difference imparting unit 7 applies a circumferential direction CD is given a phase difference of "+π/3" in the counterclockwise direction.

In other words, in FIG. 5A, the phase difference imparting unit 7 applies a phase difference of "+π/3" to the beam B2 in the counterclockwise direction in the circumferential direction CD with respect to the reference beam B1 to which no phase difference is imparted. ”, gives a phase difference of “+2π/3” to the beam B3, gives a phase difference of “+3π/3” to the beam B4, gives a phase difference of “+4π/3” to the beam B5, gives a phase difference of “+4π/3” to the beam B6 A phase difference of “+5π/3” is given. That is, the predetermined value J is "+π/3". The values of M for the phase differences of beams B2, B3, B4, B5 and B6 are 1, 2, 3, 4 and 5, respectively.

It should be noted that the phase difference imparting unit 7 adds a phase difference " -π/3” may be given. That is, of the six beams B1 to B6, the phase difference imparting unit 7 applies a phase difference " +π/3” may be added.

In other words, the phase difference imparting unit 7 imparts a phase difference of "+π/3" to the beam B5 clockwise in the circumferential direction CD with respect to the reference beam B6 to which no phase difference is imparted, and to the beam B4. A phase difference of "+2π/3" is imparted, a phase difference of "+3π/3" is imparted to beam B3, a phase difference of "+4π/3" is imparted to beam B2, and a phase difference of "+5π/3" is imparted to beam B1. may be given. That is, the predetermined value J is "+π/3". The values of M for the phase differences of beams B5, B4, B3, B2, and B1 are 1, 2, 3, 4, and 5, respectively.

As described above with reference to FIG. 5A, according to the first embodiment, among the six beams Bn, except for the reference beam Bn, each of the other beams Bn has a circumferential A phase difference of "+π/3" or a phase difference of "-π/3" is given clockwise or counterclockwise in the direction CD. As a result, it is possible to generate a plurality of optical vortices VT arranged in a triangular lattice. This point is clear from Example 1 described later.

FIG. 5(b) is a diagram showing phase differences given to three beams B3, B5 and B6 out of the six beams B1 to B6. In FIG. 5(b), each phase difference indicates a phase difference with respect to the reference beam B1 to which no phase difference is given. As shown in FIG. 5(b), the phase difference imparting unit 7 gives each of the beams B1 to B6, of the six beams B1 to B6, a beam B3 and a beam B6 that face each other across the Z-axis with a phase difference of +π/3. ' is given, and a phase difference of "+π/3" is given to one beam B5 out of the other four beams B1, B2, B4, and B5. That is, the phase difference of beam B2 with respect to beam B1 is zero, and the phase difference of beam B4 with respect to beam B1 is zero. Further, the phase difference of beam B3 with respect to beam B1 is "+π/3", the phase difference of beam B5 with respect to beam B1 is "+π/3", and the phase difference of beam B6 with respect to beam B1 is "+π/3". is. Note that the predetermined value J is "+π/3". The value of M for the phase difference of beams B3, B5, and B6 is "1".

It should be noted that the phase difference imparting unit 7 imparts a phase difference of “−π/3” to each of the beams B3 and B6, which are opposed to each other via the Z axis, among the six beams B1 to B6, and to the other beams B1 to B6. One beam B5 out of the four beams B1, B2, B4, and B5 may be given a phase difference of “−π/3”. That is, the phase difference of beam B2 with respect to beam B1 is zero, and the phase difference of beam B4 with respect to beam B1 is zero. Further, the phase difference of beam B3 with respect to beam B1 is "-π/3", the phase difference of beam B5 with respect to beam B1 is "-π/3", and the phase difference of beam B6 with respect to beam B1 is "-π /3".

As described above with reference to FIG. 5B, according to the first embodiment, each of the two beams Bn facing each other has a phase difference of "+π/3" or a phase difference of "−π/3". At the same time, one beam Bn out of the other four beams Bn is given a phase difference of "π/3" or a phase difference of "-π/3". As a result, it is possible to generate a plurality of optical vortices VT arranged in a triangular lattice. This point is clear from Example 2 described later.

Next, a method for generating an optical vortex will be described with reference to FIGS. 1 and 6. FIG. FIG. 6 is a flow chart showing the optical vortex generation method. The optical vortex generation method is performed by the optical vortex generator 100 . As shown in FIG. 6, the optical vortex generation method includes steps S1 to S5.

As shown in FIGS. 1 and 6, in step S1, the multi-beam generator 3 generates multiple beams Bn (for example, six beams Bn).

In step S3, the phase difference imparting unit 7 imparts a phase difference to two or more beams Bn among the plurality of beams Bn. Specifically, in step S3, the plurality of spots P included in the interference pattern PTD (FIGS. 3(a) to 3(e)) are rotated about a plurality of rotation centers RC. A phase difference is given to the above beam Bn.

In step S5, the condenser lens 9 irradiates the target TA with a plurality of beams Bn including two or more beams Bn having phase differences. In step S5, the multiple beams Bn are incident on the target TA from different directions, and the multiple beams Bn interfere with each other. The interference pattern PTD of multiple beams Bn includes multiple spots P (FIGS. 3(a) to 3(e)).

For example, in step S5, a plurality of optical vortices VT arranged in a triangular lattice are formed by interference of a plurality of beams Bn (FIG. 2(a)). For example, in steps S1 to S5, a plurality of light vortices VT arranged in a triangular lattice are formed by changing "a plurality of beams Bn" into "six beams B1 to B6". Then, in step S3, the phase difference imparting unit 7 imparts a phase difference to the two or more beams Bn so that the plurality of optical vortices VT are arranged in a triangular lattice.

In step S5, a plurality of optical vortices arranged in a square lattice may be formed by interference of a plurality of beams Bn. For example, in steps S1 to S5, by replacing the "plurality of beams Bn" with "four beams B1 to B4", a plurality of optical vortices arranged in a square grid are formed. Then, in step S3, the phase difference imparting unit 7 imparts a phase difference to the two or more beams Bn so that a plurality of optical vortices are arranged in a rectangular grid pattern.

For example, each of the phase differences given to two or more beams Bn among the four beams B1 to B4 is M times the predetermined value J. FIG. Specifically, the predetermined value J is π/2 radians or -π/2 radians. As a result, a plurality of periodically arranged optical vortices can be generated according to a phase difference that is M times the predetermined value J (π/2 radians or −π/2 radians). This point is clear from Example 3 to be described later. In this example, the phase difference indicates the phase difference with respect to the reference beam Bn.

For example, among the four beams B1 to B4, excluding the beam Bn as a reference, each of the other beams Bn is given a phase difference of "+π/2" or a phase difference in the clockwise or counterclockwise direction of the circumferential direction CD. A phase difference of "-π/2" is given. As a result, a plurality of optical vortices arranged in a square lattice can be generated. This point is clear from Example 3 to be described later. In this example, the phase difference indicates the phase difference between two beams Bn adjacent to each other in the circumferential direction CD.

Note that the number of the plurality of beams Bn is not limited to 6 or 4 as long as the plurality of spots P included in the interference pattern PTD each rotates around the plurality of rotation centers RC.

As described above with reference to FIGS. 1 to 6, according to the first embodiment, the phase difference imparting unit 7 imparts a phase difference to two or more beams Bn, so that a large number of beams Bn extend over the entire surface of the interference pattern PT. of optical vortices VT can be arranged. Specifically, a large number of optical vortices VT are generated simultaneously and arranged regularly. More specifically, a large number of optical vortices VT are generated simultaneously and arranged periodically. Therefore, parallel work or parallel processing using multiple optical vortex VTs is possible. For example, in fields such as multiplexed optical communication, quantum information processing, nonlinear spectroscopy, materials synthesis, and materials processing, parallel processing or parallel work using multiple simultaneously generated optical vortex VTs becomes possible.

(Embodiment 2)
An optical vortex generating device 100 and an optical vortex generating method according to a second embodiment of the present invention will be described with reference to FIGS. 1 and 7(a) to 8(c). The second embodiment is mainly different from the first embodiment in that the optical vortex generator 100 according to the second embodiment inverts the phase difference. In addition, the configuration of the optical vortex generator 100 according to the second embodiment is the same as the configuration of the optical vortex generator 100 according to the first embodiment. In the following, differences of the second embodiment from the first embodiment will be mainly described.

First, an optical vortex generator 100 according to Embodiment 2 will be described with reference to FIG. The phase difference imparting unit 7 of the optical vortex generator 100 imparts phase differences to two or more beams Bn among the plurality of beams Bn such that the phase differences imparted to the two or more beams Bn are inverted. Therefore, the rotation direction of the spot pairs SP shown in FIGS. 3(a) to 3(e) is reversed. For example, the direction of rotation of the spot pair SP is reversed from counterclockwise to clockwise. As a result, according to the second embodiment, the direction of rotation of the optical vortex VT can be reversed.

Specifically, the phase difference applying unit 7 reverses the direction of change in phase difference in the plurality of beams Bn arranged in the circumferential direction CD. Alternatively, the phase difference imparting unit 7 inverts the sign of the phase difference imparted to the two or more beams Bn.

Next, the optical vortex generator 100 will be described with specific examples with reference to FIGS. 7(a) to 8(c). In a specific example, the plurality of beams Bn is six beams Bn.

FIG. 7(a) is a diagram showing phase differences given to five beams B2 to B6 out of the six beams B1 to B6. In FIG. 7A, for ease of understanding, the phase difference indicates the phase difference between two beams Bn adjacent to each other in the circumferential direction CD. FIG. 7(b) is a perspective view showing the optical vortex VT based on the six beams Bn having the phase difference shown in FIG. 7(a).

As shown in FIG. 7(a), the phase difference imparting unit 7 applies a circumferential direction CD is given a phase difference of "+π/3" in the counterclockwise direction. As a result, the spot pair SP included in the interference pattern PTD rotates, for example, counterclockwise (FIGS. 3(a) to 3(e)), and as shown in FIG. 7(b), the optical vortex VT Occur. The optical vortex VT rotates counterclockwise toward the traveling direction D of the optical vortex VT. This point is the same as the first embodiment described with reference to FIG.

Note that one optical vortex VT includes a spiral first equal phase surface 51 corresponding to the rotation of the spot P1 shown in FIGS. and a second equal phase surface 52 . Each of the first equal phase surface 51 and the second equal phase surface 52 has a period T. FIG. The orbital angular momentum of the optical vortex VT is "+2".

FIG. 7(c) is a diagram showing the phase difference when the phase difference shown in FIG. 7(a) is inverted. In FIG. 7C, for ease of understanding, the phase difference indicates the phase difference between two beams Bn adjacent to each other in the circumferential direction CD. FIG. 7(d) is a perspective view showing the optical vortex VTR based on the six beams Bn having the phase difference shown in FIG. 7(c).

As shown in FIG. 7(c), the phase difference imparting unit 7 applies a circumferential direction CD is given a phase difference of "+π/3" clockwise. As a result, the phase difference shown in FIG. 7(a) is inverted. That is, the phase difference applying unit 7 reverses the phase difference shown in FIG. 7A by inverting the direction of change in the phase difference in the six beams B1 to B6 arranged in the circumferential direction CD. As a result, the spot pair SP rotates, for example, clockwise (opposite to the direction of rotation shown in FIGS. 3(a) to 3(e)), and as shown in FIG. 7(d), the optical vortex VTR Occur. Since the rotating direction of the spot pair SP is reversed, the rotating direction of the light vortex VTR is reversed with respect to the rotating direction of the light vortex VT shown in FIG. 7(b). That is, the optical vortex VTR rotates clockwise toward the traveling direction D of the optical vortex VTR.

One optical vortex VTR has a spiral first equal phase surface 61 corresponding to the rotation of the spot P1 and a spiral second equal phase surface 62 corresponding to the rotation of the spot P2. Each of the first equal phase surface 61 and the second equal phase surface 62 has a period T. FIG. The orbital angular momentum of the optical vortex VTR is "-2".

FIG. 8(a) is a diagram showing phase differences given to three beams B3, B5, and B6 out of the six beams B1 to B6. FIG. 8(b) is a diagram showing an example of the phase difference when the phase difference shown in FIG. 8(a) is inverted. FIG. 8(c) is a diagram showing another example of the phase difference when the phase difference shown in FIG. 8(a) is inverted. In FIGS. 8(a) and 8(b), each phase difference indicates a phase difference with respect to the reference beam B1 to which no phase difference is applied. In FIG. 8(c), each phase difference indicates a phase difference with respect to the reference beam B2 to which no phase difference is applied.

As shown in FIG. 8(a), the phase difference imparting unit 7 imparts a phase difference of "+π/3" to each of the beams B3 and B6 facing each other among the six beams B1 to B6. , to one beam B5 out of the other four beams B1, B2, B4, and B5 with a phase difference of “+π/3”. As a result, the spot pairs SP included in the interference pattern PTD rotate, for example, counterclockwise (FIGS. 3(a) to 3(e)) to generate the optical vortex VT shown in FIG. 7(b). This point is the same as the first embodiment described with reference to FIG.

As shown in FIG. 8(b), the phase difference imparting unit 7 imparts a phase difference of “−π/3” to each of the beams B3 and B6 that face each other among the six beams B1 to B6. At the same time, a phase difference of "-π/3" is given to one beam B5 out of the other four beams B1, B2, B4, and B5. That is, the phase difference applying unit 7 inverts the phase difference shown in FIG. 8A by inverting the sign of the phase difference to be applied to the two or more beams Bn. As a result, the spot pair SP rotates, for example, clockwise (opposite to the rotating direction shown in FIGS. 3(a) to 3(e)) to generate the optical vortex VTR shown in FIG. 7(d). The direction of rotation of the optical vortex VTR is reversed with respect to the direction of rotation of the optical vortex VT shown in FIG. 7(b).

As shown in FIG. 8(c), the phase difference imparting unit 7 imparts a phase difference of "+π/3" to each of the beams B3 and B6 facing each other among the six beams B1 to B6. , and gives a phase difference of "+π/3" to one beam B1 out of the other four beams B1, B2, B4, and B5. That is, the phase difference applying unit 7 reverses the phase difference shown in FIG. 8A by inverting the direction of change in the phase difference in the plurality of beams Bn arranged in the circumferential direction CD. As a result, the spot pair SP rotates, for example, clockwise (opposite to the rotating direction shown in FIGS. 3(a) to 3(e)) to generate the optical vortex VTR shown in FIG. 7(d). The direction of rotation of the optical vortex VTR is reversed with respect to the direction of rotation of the optical vortex VT shown in FIG. 7(b).

As described above with reference to FIGS. 7(a) to 8(c), in the second embodiment, the phase difference applying unit 7 includes the spot pairs SP or the spots P (see FIG. 3 ( A phase difference is imparted to two or more beams Bn so that the directions of rotation in a) to FIG. 3(e) are reversed. As a result, the direction of rotation of the optical vortex can be reversed.

(Embodiment 3)
An optical vortex generating device 100A and an optical vortex generating method according to Embodiment 3 of the present invention will be described with reference to FIGS. 9 and 10. FIG. The third embodiment is mainly different from the first embodiment in that the optical vortex generator 100A according to the third embodiment includes an adjustment unit 20 that adjusts a plurality of beams Bn. In the following, differences of the third embodiment from the first embodiment will be mainly described.

FIG. 9 is a diagram showing an optical vortex generator 100A according to the third embodiment. As shown in FIG. 9, the optical vortex generator 100A further includes an adjustment section 20 in addition to the configuration of the optical vortex generator 100 described with reference to FIG. A plurality of beams Bn emitted from the condensing lens 9 enter the adjusting section 20 . The adjustment unit 20 adjusts the plurality of beams Bn to irradiate the target TA.

Specifically, the adjustment unit 20 adjusts the plurality of beams Bn to adjust the size of the area in which the plurality of optical vortices VT are generated based on the plurality of beams Bn on or in the target TA. That is, the adjuster 20 adjusts the diameter of each beam Bn on or in the target TA. For example, the larger the diameter of each beam Bn, the larger the size of the region where the plurality of optical vortices VT are generated on or in the target TA.

The adjustment unit 20 adjusts the multiple beams Bn to adjust the intervals of the multiple optical vortices VT on or in the target TA. For example, the larger the incident angle θn (FIG. 4A) of each beam Bn, the narrower the interval between the plurality of optical vortices VT.

The adjustment unit 20 adjusts the positions at which the plurality of optical vortices VT are generated by adjusting the plurality of beams Bn. That is, the adjustment unit 20 transfers the plurality of optical vortices VT generated in the optical path onto or into the target TA. In Embodiment 3, the adjustment unit 20 transfers a plurality of optical vortices VT generated at a specific position RP in the optical path onto or into the target TA. For example, the longer the optical path of each beam Bn in the adjustment unit 20, the farther the plurality of optical vortices VT can be transferred. A specific position RP indicates a position corresponding to the focal length d1 of the condenser lens 9 .

As described above with reference to FIG. 9, according to the third embodiment, the adjustment unit 20 controls the size of the region where the plurality of optical vortices VT are generated, the intervals between the plurality of optical vortices VT, and the plurality of light vortices VT. Adjust at least one of the position at which the vortex VT is generated. In other words, it is possible to freely adjust the forms of the plurality of optical vortices VT. As a result, the range of application of multiple optical vortex VTs to the industrial field can be further expanded.

Specifically, the adjusting section 20 includes a collimating lens 21 , a phase difference providing section 22 and a condensing lens 23 . The collimator lens 21 collimates the multiple beams Bn emitted from the condenser lens 9 . A plurality of collimated beams Bn enter the phase difference applying section 22 . The collimator lens 21 is, for example, a convex lens.

The phase difference imparting unit 22 imparts a phase difference to two or more beams Bn among the plurality of beams Bn. A plurality of beams Bn including two or more beams Bn having phase differences are incident on the condenser lens 23 . The configuration of the phase difference imparting section 22 is the same as the configuration of the phase difference imparting section 7 . By providing the phase difference applying unit 22 in addition to the phase difference applying unit 7, phase differences can be applied to the two or more beams Bn with higher accuracy. Note that the adjustment section 20 may not include the phase difference applying section 22 . Also, the optical vortex generator 100A does not have to include the phase difference imparting section 7 . In this case, only the phase difference applying unit 22 gives a phase difference to two or more beams Bn among the plurality of beams Bn.

The condenser lens 23 irradiates the target TA with a plurality of beams Bn. Therefore, the condenser lens 23 functions as an objective lens. The condensing lens 23 corresponds to an example of the "irradiation section". The condenser lens 23 is, for example, a convex lens. The multiple beams Bn that have passed through the condenser lens 23 are incident on the target TA from different directions, and the multiple beams Bn interfere with each other. As a result, a plurality of optical vortices (more specifically, a large number of optical vortices) are generated on or in the target TA.

The condenser lens 23 has a focal length d5 on the target TA side and a focal length d6 on the collimating lens 21 side. The focal length d5 and the focal length d6 are substantially the same. On the other hand, the collimator lens 21 has a focal length d7 on the condensing lens 23 side and a focal length d8 on the condensing lens 9 side. The focal length d7 and the focal length d8 are substantially the same. It is preferable that the focal plane of the condenser lens 23 located at the focal length d6 substantially coincides with the focal plane of the collimating lens 21 located at the focal length d7. In this preferred example, the multiple beams Bn can be superimposed on or in the target TA with high precision, and the multiple beams Bn can be effectively interfered on or in the target TA. As a result, a plurality of optical vortices (more specifically, a large number of optical vortices) can be effectively generated on or in the target TA.

For example, the shorter the focal length d5 (=focal length d6) of the condensing lens 23, the larger the incident angle θn of each beam Bn and the narrower the interval between the plurality of light vortices VT. For example, the longer the focal length d7 (=focal length d8) of the collimator lens 21, the larger the incident angle θn of each beam Bn, and the narrower the interval between the plurality of light vortices VT. For example, if the focal length d5 (=focal length d6) of the condenser lens 23 and the focal length d7 (=focal length d8) of the collimating lens 21 are substantially the same, the intervals between the plurality of optical vortices VT generated at the specific position RP are A plurality of optical vortices VT can be generated on or in the target TA while maintaining. That is, it is possible to transfer the plurality of optical vortices VT onto or into the target TA while maintaining the intervals between the plurality of optical vortices VT generated at the specific position RP.

For example, the shorter the focal length d5 (=focal length d6) of the condensing lens 23 and the focal length d1 (=d2) of the condensing lens 9, the larger the incident angle θn of each beam Bn. , the intervals between the plurality of optical vortices VT become narrower. For example, as the focal length d7 (=focal length d8) of the collimating lens 21 and the focal length d3 (=focal length d4) of the collimating lens 5 are each lengthened, the incident angle θn of each beam Bn increases. The interval between the optical vortices VT becomes narrower.

Also, the optical vortex generator 100A may include a plurality of adjustment units 20 . A plurality of adjustment units 20 are arranged in series, for example.

Next, an optical vortex generating method according to the third embodiment will be described with reference to FIGS. 9 and 10. FIG. FIG. 10 is a flow chart showing the optical vortex generation method. The optical vortex generation method is performed by the optical vortex generator 100A. As shown in FIG. 10, the optical vortex generation method includes steps S21 to S29. Step S21 and step S23 are the same as step S1 and step S3 described with reference to FIG. 6, respectively, and description thereof will be omitted as appropriate.

As shown in FIGS. 9 and 10, in step S21, the multi-beam generator 3 generates multiple beams Bn (for example, six beams Bn).

In step S23, the phase difference imparting unit 7 imparts a phase difference to two or more beams Bn among the plurality of beams Bn.

In step S25, the condensing lens 9 converges a plurality of beams Bn including two or more beams Bn having phase differences at a specific position RP to generate a plurality of optical vortices VT at the specific position RP.

In step S27, the adjustment unit 20 adjusts the multiple beams Bn. Specifically, in step S25, the adjusting unit 20 adjusts the plurality of beams Bn to determine the size of the region where the plurality of optical vortices VT are generated, the distance between the plurality of optical vortices VT, and the distance between the plurality of optical vortices VT. at least one of the position at which . Step S27 is performed between step S23 and step S29. Specifically, step S27 is performed between step S25 and step S29.

In step S29, the adjusting unit 20 irradiates the target TA with the adjusted plurality of beams Bn. As a result, multiple optical vortices VT are generated on or in the target TA.

Note that the number of the plurality of beams Bn is not limited to six as long as the plurality of spots P included in the interference pattern PTD each rotate around the plurality of rotation centers RC.

EXAMPLES Next, the present invention will be specifically described based on examples, but the present invention is not limited by the following examples. In FIGS. 11(a) to 17(l), light intensity is represented by shading from black to white. The closer to white, the stronger the light intensity.

In Examples 1 to 3 of the present invention, generation of an optical vortex was simulated assuming the optical vortex generator 100 described with reference to FIG. Moreover, as shown in FIG. 4A, a three-dimensional orthogonal coordinate system was set.

Equation (1) was calculated to calculate the light intensity I (x, y, z) when the multiple beams Bn interfere. x, y, and z indicate the X coordinate, Y coordinate, and Z coordinate, respectively. The spatial distribution of light intensity I(x,y,z) represented the interference pattern of multiple beams Bn.

…（１）

…(1)

In equation (1), "En" denotes the electric field strength of beam Bn. "N" indicates the number of beams Bn. "α" represents the incident angle θn of the beam Bn. The incident angles θn of the multiple beams Bn were equal. “Ψn” indicated the absolute azimuth angle. The absolute azimuth angle indicates the azimuth angle of the beam Bn with respect to the beam B1, as shown in FIGS. 4(a) and 4(b). Therefore, the absolute azimuth angle Ψ1 of beam B1 was zero. "βn" indicated the phase difference of beam Bn. The phase difference indicated the phase difference with respect to the reference beam B1. Therefore, the phase difference β1 of the reference beam B1 was set to zero. In addition, when there is no phase difference with respect to the reference beam B1, that is, the phase difference βn of the beam Bn having the same phase as the reference beam B1 was also set to zero. "t" indicated time.

"En" in formula (1) was represented by formula (2). In equation (2), "E0n" denoted the electric field amplitude proportional to the square root of the intensity of beam Bn. "k" indicated the wave number of the beam Bn. "ω" indicated the angular frequency of the beam Bn.

…（２）

…(2)

(Example 1)
Example 1 of the present invention and a comparative example will be described with reference to FIGS. 11(a) to 13(l). In Example 1, N=6, and a simulation was performed in which six beams B1 to B6 interfere according to equation (1). The incident angle α was 20 degrees. The wavelength of each of beams B1-B6 was 785 nm. The absolute azimuth angles were Ψ1 = 0 degrees, Ψ2 = 60 degrees, Ψ3 = 120 degrees, Ψ4 = 180 degrees, Ψ5 = 240 degrees, and Ψ6 = 300 degrees.

FIG. 11A is a diagram showing an interference pattern PT according to Example 1. FIG. FIG. 11(b) is a diagram showing phase differences given to the six beams B1 to B6 according to the first embodiment. FIG. 12 is a diagram showing a general optical vortex according to a comparative example.

In Example 1, as shown in FIG. 11(b), beams B2, B3, B4, B5, and B6 have phase differences of "+π/3" and "+2π/3", respectively, as phase differences with respect to the reference beam B1. ”, “+3π/3”, “+4π/3”, and “+5π/3”. The phase difference in Example 1 was the same as the phase difference shown in FIG. 5(a).

As shown in FIG. 11(a), the interference pattern PT included a large number of optical vortices VT arranged in a triangular lattice. Each of the optical vortices VT had a light intensity similar to that of the general optical vortex shown in FIG. 12 and had a singularity SG. The outer diameter of the optical vortex VT was approximately hexagonal. The interference pattern PT was calculated by integrating the square of the electric field strength En over one period T of the beam Bn using equation (1). Specifically, about 16 million optical vortices VT were confirmed in a rectangular area of 1 cm×1 cm. Note that FIG. 11(a) shows a part of the optical vortices VT among the large number of optical vortices VT.

Next, the time change within one period T of the interference pattern PT was simulated. Specifically, one period T is divided into 12 to calculate a plurality of interference patterns PTD. Each of the interference patterns PTD was calculated by integrating the square of the electric field intensity En over time γ (=T/12) using equation (1).

FIGS. 13(a) to 13(l) are diagrams showing temporal changes in the interference pattern PTD for each time γ. Time progressed from FIG. 13(a) to FIG. 13(l).

As shown in FIGS. 13(a) to 13(l), during one cycle T, each of the spots P1 and P2 rotates 360 degrees around the rotation center RC. The direction of rotation was counterclockwise.

Specifically, as shown in FIGS. 13A to 13G, each of spot P1 and spot P2 rotates 180 degrees counterclockwise about rotation center RC. Furthermore, as shown in FIGS. 13(g) to 13(l) and 13(a), each of the spots P1 and P2 further rotates 180 degrees counterclockwise around the center of rotation RC. Therefore, it was confirmed that each of the spot P1 and the spot P2 made one rotation in one period T of the beam Bn. As a result, it could be estimated that each of the optical vortices VT shown in FIG. 11(a) has a helical equiphase plane, like the general optical vortex (FIG. 12).

(Example 2)
Embodiment 2 of the present invention will be described with reference to FIGS. 14(a) to 15(l). In Example 2, N=6, and a simulation was performed in which six beams B1 to B6 interfere according to equation (1). Other conditions for the beams B1 to B6 according to Example 2 are the same as those for the beams B1 to B6 according to Example 1, except for the phase difference.

FIG. 14A is a diagram showing an interference pattern PT according to Example 2. FIG. FIG. 14B is a diagram showing phase differences given to the six beams B1 to B6 according to the second embodiment.

In the second embodiment, as shown in FIG. 14(b), the phase difference applying unit 7 gives a phase difference of "+π/3 ” was given, and a phase difference of “+π/3” was given to one beam B5 out of the other four beams B1, B2, B4 and B5. In addition, the phase difference of Example 2 was the same as the phase difference shown in FIG.5(b).

As shown in FIG. 14(a), the interference pattern PT contained a large number of optical vortices VT arranged in a triangular lattice. Each of the optical vortices VT had a light intensity similar to that of the general optical vortex shown in FIG. 12 and had a singularity SG. The outer diameter of the optical vortex VT was approximately triangular. The interference pattern PT was calculated by integrating the square of the electric field strength En over one period T of the beam Bn using equation (1). Specifically, about 16 million optical vortices VT were confirmed in a rectangular area of 1 cm×1 cm. Note that FIG. 14(a) shows a part of the optical vortices VT among the large number of optical vortices VT.

Next, the time change within one period T of the interference pattern PT was simulated. Specifically, one period T is divided into 12 to calculate a plurality of interference patterns PTD. Each of the interference patterns PTD was calculated by integrating the square of the electric field intensity En over time γ (=T/12) using equation (1).

FIGS. 15(a) to 15(l) are diagrams showing temporal changes in the interference pattern PTD for each time γ. Time progressed from FIG. 15(a) to FIG. 15(l).

As shown in FIGS. 15(a) to 15(l), during one period T, each of the spots P1 and P2 rotates 360 degrees around the rotation center RC. The direction of rotation was counterclockwise.

Specifically, as shown in FIGS. 15(a) to 15(g), each of the spots P1 and P2 rotates 180 degrees counterclockwise about the center of rotation RC. Furthermore, as shown in FIGS. 15(g) to 15(l) and 15(a), each of the spots P1 and P2 further rotates 180 degrees counterclockwise about the center of rotation RC. Therefore, it was confirmed that each of the spot P1 and the spot P2 made one rotation in one period T of the beam Bn. As a result, it could be estimated that each of the optical vortices VT shown in FIG. 14(a) has a helical equal phase surface, like the general optical vortex (FIG. 12).

(Example 3)
Embodiment 3 of the present invention will be described with reference to FIGS. 16(a) to 17(l). In Example 3, N=4, and a simulation was performed in which four beams B1 to B4 interfere according to equation (1). The incident angle α was 20 degrees. The wavelength of each of beams B1-B4 was 785 nm. The absolute azimuth angles were Ψ1 = 0 degrees, Ψ2 = 90 degrees, Ψ3 = 180 degrees, and Ψ4 = 270 degrees.

FIG. 16A is a diagram showing an interference pattern PT according to Example 3. FIG. FIG. 16(b) is a diagram showing phase differences given to the four beams B1 to B4 according to the third embodiment.

In Example 3, as shown in FIG. 16B, beams B2, B3, and B4 have phase differences "+π/2", "+2π/2", and "+3π /2” was given. Note that the predetermined value J was "+π/2". The values of M for the phase differences of beams B2, B3 and B4 were 1, 2 and 3, respectively.

As shown in FIG. 16(a), the interference pattern PT contained a large number of optical vortices VT arranged in a square lattice. Each of the optical vortices VT has a singular point SG, although the intensity distribution is slightly different from that of the general optical vortex shown in FIG. The interference pattern PT was calculated by integrating the square of the electric field strength En over one period T of the beam Bn using equation (1). Note that FIG. 16(a) shows a part of the optical vortices VT among the large number of optical vortices VT.

Next, the time change within one period T of the interference pattern PT was simulated. Specifically, one period T is divided into 12 to calculate a plurality of interference patterns PTD. Each of the interference patterns PTD was calculated by integrating the square of the electric field intensity En over time γ (=T/12) using equation (1).

FIGS. 17(a) to 17(l) are diagrams showing temporal changes in the interference pattern PTD for each time γ. Time progressed from FIG. 17(a) to FIG. 17(l).

As shown in FIGS. 17(a) to 17(l), during one cycle T, each of the spots P1 and P2 rotates 360 degrees around the rotation center RC. The direction of rotation was clockwise.

Specifically, as shown in FIGS. 17A to 17G, each of spot P1 and spot P2 rotates 180 degrees counterclockwise about rotation center RC. Furthermore, as shown in FIGS. 17(g) to 17(l) and 17(a), each of the spots P1 and P2 further rotates 180 degrees counterclockwise about the center of rotation RC. Therefore, it was confirmed that each of the spot P1 and the spot P2 made one rotation in one period T of the beam Bn. As a result, it could be estimated that each of the optical vortices VT shown in FIG. 16(a) has a helical equiphase surface, like the general optical vortex (FIG. 12).

The embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to the above embodiments and examples, and can be embodied in various aspects without departing from the spirit of the present invention. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be omitted from all components shown in the embodiments. In order to make the drawings easier to understand, the drawings mainly show each component schematically. may be different. In addition, the material, shape, dimensions, etc. of each component shown in the above embodiment are examples and are not particularly limited, and various changes are possible without substantially departing from the effects of the present invention. be.

INDUSTRIAL APPLICABILITY The present invention provides an optical vortex generation method and an optical vortex generator, and has industrial applicability.

1 laser oscillator 3 multi-beam generator 5 collimator lens 7, 22 phase difference applying unit 9, 23 condenser lens (irradiation unit)
100, 100A optical vortex generator

Claims (9)

generating a plurality of beams;
a step of imparting a phase difference to two or more beams among the plurality of beams;
irradiating a target with the plurality of beams including the two or more beams with the phase difference,
In the step of irradiating, the plurality of beams are incident on the target from different directions, and the plurality of beams interfere;
the interference pattern of the plurality of beams comprises a plurality of spots;
In the applying step, by applying the phase difference to the two or more beams so that the plurality of spots rotate around a plurality of rotation centers , a plurality of light vortices are generated in the step of irradiating. to generate
the plurality of rotation centers each represent a singular point of the plurality of light vortices,
The light vortex generating method, wherein the spot indicates a portion where the light intensity is higher than the portion where the center of rotation is located. In the plurality of beams, the azimuth angle, which is the angle between adjacent beams, is within ±20% of the first average value with respect to the first average value ,
The first average value indicates an average value of a plurality of the azimuth angles,
angles of incidence of the plurality of beams on the target are within ±20% of the second average value with respect to a second average value ;
2. The optical vortex generation method according to claim 1 , wherein said second average value indicates an average value of said plurality of incident angles . Each of the phase differences imparted to the two or more beams indicates a phase difference when a beam different from the two or more beams among the plurality of beams is used as a reference, and is M times a predetermined value (M is 1 an integer greater than or equal to
3. The optical vortex generation method according to claim 1, wherein the value of M is set for each of the phase differences imparted to the two or more beams. the plurality of beams is six beams;
4. The optical vortex generating method according to claim 3, wherein said predetermined value is π/3 radians or -π/3 radians. The optical vortex generating method according to any one of claims 1 to 4, wherein in the step of irradiating, the plurality of optical vortices arranged in a triangular lattice pattern are formed by interference of the plurality of beams. performing between the applying and irradiating steps of adjusting the plurality of beams;
In the adjusting step, the plurality of beams are adjusted to determine the size of the region where the plurality of optical vortices are generated based on the plurality of beams, the interval between the plurality of optical vortices, and the generation of the plurality of optical vortices. 6. The optical vortex generation method according to any one of claims 1 to 5, wherein adjusting at least one of the position where the Spots adjacent to each other among the plurality of spots constitute a spot pair,
In the applying step, the phase difference is applied to the two or more beams so that the plurality of spot pairs rotate about the plurality of rotation centers, respectively. to generate a light vortex of
Each of the plurality of optical vortices has a spiral first equal phase surface corresponding to the rotation of one of the spots forming the spot pair and a spiral corresponding to the rotation of the other spot forming the spot pair. 7. The optical vortex generation method according to claim 1, further comprising a second equal phase surface having a shape. 8. The phase difference according to any one of claims 1 to 7, wherein in the providing step, the plurality of beams are incident on a plurality of different locations on one helical phase plate to provide the phase difference to the two or more beams. 1. The optical vortex generation method according to 1. a multi-beam generator that generates a plurality of beams;
a phase difference imparting unit that imparts a phase difference to two or more beams among the plurality of beams;
an irradiation unit that irradiates a target with the plurality of beams including the two or more beams with the phase difference,
the plurality of beams are incident on the target from different directions, and the plurality of beams interfere;
the interference pattern of the plurality of beams comprises a plurality of spots;
The phase difference imparting unit imparts the phase difference to the two or more beams so that the plurality of spots rotate around a plurality of rotation centers, respectively, so that the plurality of spots by interference of the plurality of beams to generate a light vortex of
the plurality of rotation centers each represent a singular point of the plurality of light vortices,
The light vortex generator, wherein the spot indicates a portion where the light intensity is higher than the portion where the center of rotation is located.

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