JP5120953B2 - Four-wave mixing stimulated scattering system - Google Patents

Description

  The present invention relates to a stimulated scattering device, an amplifier, and a generator that efficiently convert high-power four-wave mixed stimulated scattered light.

  Conventional stimulated scattering amplifiers convert excitation light energy into Stokes light energy via stimulated scattering waves to increase the intensity of amplified light. FIG. 10 shows an example of a conventional general stimulated scattering amplifier. The excitation light 1 and the amplified light 41 are incident on the stimulated scattering container 12 with the wavelength selection mirror 10 superimposed thereon, and the amplified light 41 is amplified and separated by the wavelength selection mirror 11 on the output side. The principle of amplification will be described with reference to FIG. 11 showing the energy levels of the stimulated Raman scattering process in such a conventional stimulated scattering amplifier. In the conventional stimulated scattering amplifier, the stimulated scattering medium molecules that were at the base energy level A are excited to the energy level C by the excitation light 1. When the molecule transitions from the excitation energy level C to B, it is divided into the energy of the amplified light and the wave energy 9 of the stimulated scattering medium molecule, and the energy of the amplified light 41 is increased.

  A stimulated Raman pulse amplifier (see Patent Document 1) developed by the inventors of the present application is known as a stimulated scattering amplifier in which reflecting mirrors are arranged so as to form a hollow quadrangular prism. This stimulated Raman pulse amplifier is a stimulated scattering amplifier having high conversion efficiency and high output power density by suppressing generation of self-emission from pump light and spontaneous high-order light from amplified light.

  In addition, as a laser beam integrator that converts a large number of laser beams into a single high-power Stokes light by using stimulated scattering amplification, a pair of upper and lower reflecting mirrors constituting a light guide developed by the present inventors, etc. There is a laser beam integrator (see Patent Document 2) using a pair of right and left reflecting mirrors.

  As a technique using four-wave mixed stimulated scattering, an anti-Stokes Raman spectroscopy called CARS (coherent anti-Stokes light Raman scattered light generation) is known, and is used for analysis of components of a medium. FIG. 12A shows the configuration of CARS. As shown in FIG. 12A, the generation light 42 is generated at a position P that is an intersection of the excitation light 1 and the Stokes light 2.

In the conventional four-wave mixed stimulated scattering of CARS (coherent anti-Stokes light Raman scattering light generation), it is necessary to satisfy the following wave number vector matching condition (formula 1) as shown in FIG. K1, K2, and K42 are wave number vectors of the excitation light 1, the Stokes light 2, and the generated light 42, respectively. The direction of the wave vector is the propagation direction of each light, and the magnitude of the wave vector is the reciprocal of the wavelength.
K1 + K1 = K2 + K42 (Formula 1)

FIG. 13 is a diagram showing the energy levels of the Raman scattering process in the four-wave mixed stimulated scattering. Stimulated scattering medium molecules at the ground energy level A (components at the point P to be analyzed in the case of CARS) are excited to the excitation energy level B by the excitation light 1 and the Stokes light 2. The stimulated scattering medium molecule having the excitation energy level B is excited again from the energy level B to D by the excitation light 1. When the excited molecule transitions from energy level D to A, generated light 42 was generated. As shown in FIG. 12A, the generated light 42 propagates in a specific direction determined by the excitation light 1 and the Stokes light 2, so that measurement was easy.
JP-A-6-37407 JP-A-10-111525

  In the conventional stimulated scattering amplifier, as shown in FIG. 11, the excitation light 1 energy is divided into the amplified light 41 energy and the wave energy 9 of the stimulated scattering medium molecule, so that the excitation light is amplified to the amplified light energy. However, there was a problem that the conversion efficiency of the inevitably became smaller by the amount of wave energy. There is a reduction in efficiency of 36% when using glass laser light and a hydrogen gas medium having an infrared wavelength range, and 9% when using an ultraviolet excimer laser and a hydrogen gas medium.

  In the stimulated scattering amplifier (see Patent Document 1) in which the reflecting mirrors are arranged so as to form a hollow quadrangular prism, the conversion efficiency from the excitation light to the amplified light energy is inevitably wave energy as in the conventional stimulated scattering amplifier of FIG. There was a problem of getting smaller by the minute. Further, the conventional laser beam integrator (see Patent Document 2) also has a problem that the conversion efficiency from the excitation light to the amplified light energy is inevitably reduced by the amount of wave energy, like the conventional stimulated scattering amplifier of FIG. It was.

  On the other hand, in the conventional four-wave mixed stimulated scattering used in the measurement field such as CARS, it is necessary to satisfy the wave vector matching condition (Equation 1) as shown in FIG. FIG. 12C shows the propagation directions of the excitation light 1 and the Stokes light 2 and the propagation direction of the generated light 42 at the measurement point P where the excitation light 1 and the Stokes light 2 overlap. If the intersection angle between the excitation light 1 and the Stokes light 2 is T1, the intersection angle between the generation light 42 and the excitation light 1 is T2.

  As described above, in the four-wave mixed stimulated scattering generation, the propagation directions of the excitation light 1, the Stokes light 2, and the generated light 42 are specified. FIG. 14 shows losses due to differences in the propagation directions of the excitation light 1, the Stokes light 2, and the generated light 42 in the four-wave mixed stimulated scattering generation. The excitation light 1 and the Stokes light 2 are incident from the incident window 13 (left side in FIG. 14) of the stimulated scattering container 12. Excitation light 1 and Stokes light 2 are superimposed on the incident window 13. The generated light 42 is generated by the excitation light 1 and the Stokes light 2 in the stimulated scattering container in a direction that satisfies the wave vector matching condition. Beam cross sections of the excitation light 1, the Stokes light 2 and the generated light 42 on the entrance window 13 of the stimulated scattering container are shown in the range of 51 and 52. In the four-wave mixed stimulated scattering, the excitation light 1, the Stokes light 2, and the generated light 42 are limited in the propagation direction, which is the matching condition of the wave vector, so that the beam cross section of the excitation light 1 is 55 and 58 on the exit window 14. The beam cross section of the Stokes light 2 is in the range of 53 and 57, and the beam cross section of the generated light 42 is in the range of 56 and 59. Except for a portion where the excitation light 1, the Stokes light 2 and the generation light 42 are completely overlapped (a quadrilateral portion where the vertices 51, 54, 56, and 57 are apexes), there are portions where the generation light 42 cannot grow. For this reason, there is a problem that the conversion efficiency is lowered and the spatial intensity distribution of the beam is disturbed.

  Similar problems can be considered when considering a stimulated scattering device that uses four-wave mixed stimulated scattering, including a generator that uses four-wave mixed stimulated scattering.

  The present invention is intended to solve these problems. The amplification efficiency from the excitation light to the amplified light energy is high, or the generation efficiency from the excitation light to the generation light is high. Further, the spatial intensity distribution of the beam An object of the present invention is to realize a four-wave mixed stimulated scattering device, an amplifier, and a generator with improved uniformity.

  And this invention has the following characteristics, in order to achieve the said objective.

  The four-wave mixed stimulated scattering device according to the present invention includes a light guide including a reflecting mirror that reflects light having wavelengths of excitation light, Stokes light, amplified light, and generated light in a stimulated scattering container. It is characterized by being. Here, it is desirable to use a dielectric multilayer mirror having a wavelength selectivity in the reflectance as the reflecting mirror.

  The four-wave mixed stimulated scattering apparatus according to the present invention is characterized in that at least the excitation light and the Stokes light are incident in a direction satisfying a wave number vector matching condition in the four-wave mixed stimulated scattering process.

  The four-wave mixed stimulated scattering apparatus according to the present invention adds another excitation light and Stokes light to each of the excitation light and the Stokes light at an axially symmetric angle rotated by 180 degrees with respect to the central axis of the light guide. It is characterized by doing.

  The four-wave mixed stimulated scattering device of the present invention makes excitation light, Stokes light, and amplified light enter in a direction that satisfies the matching condition of the wave vector of the four-wave mixed stimulated scattering process, and rotates 180 degrees around the central axis of the light guide. When another pump light, Stokes light, and light to be amplified are incident at such an axially symmetric angle, it operates as a four-wave mixed stimulated scattering amplifier.

  The four-wave mixed stimulated scattering device of the present invention is axially symmetric when the excitation light and Stokes light are incident in the direction satisfying the matching condition of the wave vector of the four-wave mixed stimulated scattering process and rotated by 180 degrees about the central axis of the light guide. When another excitation light and Stokes light are incident at an angle and no light to be amplified is incident, it operates as a four-wave mixed stimulated scattering generator.

  The four-wave mixed stimulated scattering amplifier of the present invention is a four-wave mixed stimulated scattering amplifier that receives excitation light, Stokes light, and amplified light, and uses four excitation light, two Stokes light, and two amplified light. A stimulated scattering container including a light guide composed of opposing reflecting mirrors that reflect excitation light, Stokes light, and amplified light is used. Here, as the reflecting mirror that reflects the excitation light, the Stokes light, and the amplified light, it is desirable to use a dielectric multilayer mirror having a wavelength selectivity in reflectance.

  In the four-wave mixing stimulated scattering amplifier of the present invention, two excitation light, one Stokes light, and one amplified light are surfaces including the normal line of the reflecting mirror facing the light guide and the central axis of the light guide. The incident angle is such that the angle satisfies the wave vector matching condition of the four-wave mixed stimulated scattering process and overlaps the light guide entrance surface.

  The four-wave mixed stimulated scattering amplifier of the present invention is axially symmetric rotated by 180 degrees with respect to the central axis of the light guide with respect to each of two excitation lights, one Stokes light, and one amplified light. Two other excitation lights, one Stokes light, and one amplified light are incident at an angle so as to overlap at the light guide entrance surface.

  The four-wave mixed stimulated scattering generator according to the present invention is a four-wave mixed stimulated scattering generator that receives excitation light and Stokes light, and uses four excitation light, two Stokes light, and two generated light. A stimulated scattering container having a light guide composed of opposing reflecting mirrors that reflect Stokes light and generated light is used. Here, as the reflecting mirror that reflects the excitation light, the Stokes light, and the generated light, it is desirable to use a dielectric multilayer mirror having a wavelength selectivity in reflectivity.

  In the four-wave mixed stimulated scattering generator according to the present invention, the two excitation lights and the one Stokes light include the normal line of the reflecting mirror of the light guide disposed in the stimulated scattering container and the central axis of the light guide. It is characterized in that it is incident on the surface so as to satisfy the wave vector matching condition of the four-wave mixed stimulated scattering process and to overlap with the light guide entrance surface.

  The four-wave mixed stimulated scattering generator according to the present invention has two other two excitation light beams and one Stokes light beam that are rotated by 180 degrees with respect to the central axis of the light guide at two angles. Excitation light and one Stokes light are incident so as to overlap at the light guide entrance surface.

  In order to solve the above-described problems, a four-wave mixed stimulated scattering device according to the present invention is a four-wave mixed stimulated scattering device that receives at least excitation light and Stokes light, and includes excitation light and Stokes light in a stimulated scattering container. A light guide composed of a reflecting mirror that reflects light having a wavelength of the amplified light and the generated light, and at least the excitation light and the Stokes light are incident on each of the excitation light and the Stokes light. Excitation light and Stokes light are incident at an axially symmetric angle rotated 180 degrees with respect to the central axis of the light guide.

  In order to solve the above-described problem, a four-wave mixed stimulated scattering amplifier according to the present invention is a four-wave mixed stimulated scattering amplifier that receives excitation light, Stokes light, and amplified light. A light guide composed of a reflecting mirror that reflects the Stokes light and the amplified light, the two excitation lights, the one Stokes light, and the one amplified light being transmitted from the reflecting mirror facing the light guide. The two excitation lights are incident on the surface including the normal line and the center axis of the light guide in a direction satisfying the wave vector matching condition of the four-wave mixed stimulated scattering process and overlapping the light guide entrance surface, For each of the one Stokes light and the one light to be amplified, two excitation lights, one Stokes light, and an axis-symmetric angle rotated by 180 degrees with respect to the central axis of the light guide. A single amplified light Wherein the incident so as to overlap with Togaido inlet face.

  In order to solve the above-described problems, a four-wave mixed stimulated scattering generator according to the present invention is a four-wave mixed stimulated scattering generator that receives excitation light and Stokes light, and includes excitation light and Stokes light in a stimulated scattering container. A light guide composed of a reflecting mirror that reflects light and generated light, including two excitation light and one Stokes light, including the normal of the reflecting mirror facing the light guide and the central axis of the light guide In the direction satisfying the wave vector matching condition of the four-wave mixed stimulated scattering process on the surface and overlapping with the entrance surface of the light guide, and for each of the two excitation lights and the one Stokes light Thus, two excitation lights and one Stokes light are incident on the light guide entrance surface so as to overlap each other at an axisymmetric angle rotated by 180 degrees with respect to the central axis of the light guide.

  According to the present invention, in the four-wave mixing stimulated scattering device, it is possible to improve the conversion efficiency from the excitation light to the anti-Stokes light and to improve the spatial uniformity of the beam intensity distribution. Further, in the four-wave mixed stimulated scattering amplifier, the amplification efficiency from the excitation light to the amplified light and the spatial uniformity of the beam intensity distribution can be improved. Further, in the four-wave mixed stimulated scattering generator, it is possible to improve the conversion efficiency from the excitation light to the generated light and improve the spatial uniformity of the spatial intensity distribution of the beam. Furthermore, by using a dielectric multilayer mirror having a wavelength selectivity in reflectivity as a reflecting mirror of the four-wave mixed stimulated scattering apparatus of the present invention, it is possible to obtain a wavelength other than the wavelengths of excitation light, Stokes light, amplified light, and generated light. Light reflection can be reduced.

  A four-wave mixed stimulated scattering apparatus will be described below with reference to FIG.

  As shown in FIG. 1, the four-wave mixed stimulated scattering device includes excitation light (1, 3, 5, 7), Stokes light (2, 6), amplified light (41, 81), and generated light (42, 82). The stimulated scattering container 12 is provided with a light guide 30 composed of opposing reflecting mirrors that reflect light having a wavelength of 1). In FIG. 1, X represents an X axis that is a vertical direction on a plane parallel to the entrance surface of the light guide, Y represents a Y axis that is a lateral direction on a plane parallel to the entrance surface of the light guide, Z indicates the Z axis which is the central axis direction of the light guide. Two excitation lights (1, 3) and one Stokes light (2) are produced in a four-wave mixed stimulated scattering process on a plane including the normal of the reflecting mirror facing the light guide and the central axis of the light guide. Incident light is incident in such a direction as to satisfy the wave vector matching condition and at the entrance surface of the stimulated scattering container.

  Here, excitation light 1 and 3, Stokes light 2, and amplified light 41 are wave vector matched in a four-wave mixed stimulated scattering process on a plane including the normal of the reflecting mirror facing the light guide and the central axis of the light guide. The light is incident in a direction that satisfies the conditions, and the other excitation lights 5 and 7, Stokes light 6, and amplified light 81 are guided to the excitation light 1 and 3, Stokes light 2, and amplified light 41, respectively. When incident at an axisymmetric angle rotated by 180 degrees around the central axis of the light guide in the scattering container, it operates as a four-wave mixed stimulated scattered light amplifier. Output amplified light is obtained as 41 and 81 described on the right side of the drawing in FIG.

  Also, the excitation light 1 and 3 and the Stokes light 2 are directed in a direction that satisfies the matching condition of the wave vector of the four-wave mixed stimulated scattering process on the plane including the normal line of the reflecting mirror facing the light guide and the central axis of the light guide. Along with the incident light, another excitation light 5 and 7 and Stokes light 6 are rotated by 180 degrees with respect to each of the excitation light 1 and 3 and Stokes light 2 about the central axis of the light guide in the stimulated scattering container. When it is incident at a symmetric angle and no light to be amplified is incident, it operates as a four-wave mixed stimulated scattering generator. The output generated light is obtained as 42 and 82 described on the right side of the drawing in FIG. In FIG. 1, the shape of the light guide has a quadrangular cross section, but it may be not only a quadrilateral but also other polygons. Further, when a dielectric multilayer mirror having a wavelength selectivity in reflectance is used as the reflecting mirror, reflection of light other than the wavelengths of the excitation light, Stokes light, amplified light, and generated light can be reduced.

  Next, a four-wave mixed stimulated scattering amplifier in which the four-wave mixed stimulated scattering apparatus of the present invention is applied to an amplifier will be described below with reference to FIGS.

  FIG. 2A shows the optical paths of the excitation light 1, Stokes light 2, excitation light 3 and amplified light 41 in the light guide 30. FIG. 2B shows optical paths of the excitation light 5, Stokes light 6, excitation light 7, and amplified light 81 in the same light guide 30. For ease of viewing, the optical paths are shown in separate drawings. In the amplifier of the present invention, the light guide 30 is supplied with the excitation light 1, Stokes light 2, excitation light 3, amplified light 41, excitation light 5, Stokes light 6, excitation light 7, and amplified light 81 in FIG. ) And the light path in FIG. 2 (a) and 2 (b), the optical paths of the excitation lights 1 and 5, the optical paths of the Stokes lights 2 and 6, the optical paths of the excitation lights 3 and 7, and the optical paths of the amplified light 41 and 81 are mutually The light guide 30 disposed in the stimulated scattering container 12 is in an axisymmetric position rotated by 180 degrees with respect to the central axis of the light guide 30. The stimulated scattering container 12 includes a light guide 30 composed of opposing reflecting mirrors (38, 39) and is filled with a stimulated scattering medium.

  In this four-wave mixed stimulated scattering amplifier, two excitation lights (1, 3), one Stokes light (2), and one amplified light (41) are normal lines of the reflecting mirrors facing the light guide. On the plane including the central axis of the light guide and in a direction satisfying the wave vector matching condition of the four-wave mixed stimulated scattering process and so as to overlap with the light guide entrance surface. The other two excitation lights (5, 7), one Stokes light (6) and one amplified light (81) are composed of the other two excitation lights (1, 3) and one Stokes. The light (2) and one amplified light (41) are incident so as to overlap at the light guide entrance surface at an axisymmetric angle rotated by 180 degrees about the central axis of the light guide.

  As described above, the excitation light (1, 3, 5, 7), the Stokes light (2, 6), and the amplified light (41, 81) enter the incident window 13 of the stimulated scattering container 12 as shown in FIG. b) Incident light is incident in the illustrated incident direction, and excitation light (1, 3, 5, 7), Stokes light (2, 6), and amplified light (41, 81) are emitted from the output window 14 of the stimulated scattering container 12. Then, the energy of the excitation light is converted into the energy of the amplified light.

  As the excitation light (1, 3, 5, 7), output light from the laser device is used. Stokes light (2, 6) is light that is less than the excitation light energy by the wave energy of the stimulated scattering medium. The Stokes light (2, 6) is generated by converging the output light from the laser device on the stimulated scattered light generator, and wavelength dispersion such as prisms. Light separated using an element is used. The amplified light is light that is larger than the excitation light energy by the wave energy of the stimulated scattering medium, and the amplified light is also generated by converging the output light from the laser device on the stimulated scattered light generator, and wavelength dispersion such as prism A device that is separated using an element is used.

  In the case of a dye laser device or a titanium sapphire laser with a wide oscillation wavelength width, the oscillation wavelength is the excitation light wavelength, the Stokes light wavelength smaller than the excitation light energy by the wave energy of the stimulated scattering medium, and the stimulated scattering medium than the excitation light energy. The light from the three laser devices adjusted to the amplified light wavelength that is larger by the wave energy can be used as excitation light, Stokes light, and amplified light.

FIG. 3A shows the wave number vector matching condition in the four-wave mixed stimulated scattering process of the excitation light, Stokes light, and amplified light. The wave number vectors of the pumping lights 1, 3, 5, and 7 are respectively K1, K3, K5, and K7, the wave number vectors of the Stokes lights 2 and 6 are respectively K2 and K6, and the wave number vectors of the amplified light 41 and 81 are each K41. , K81, the wave vector satisfies the following matching conditions (Equation 2) and (Equation 3).
K1 + K3 = K2 + K41 (Formula 2)
K5 + K7 = K6 + K81 (Formula 3)

  FIGS. 3B and 3C show the incident directions of the excitation light, Stokes light, and amplified light at the center point 15 of the light guide entrance window in the stimulated scattering container of FIG.

  FIG. 4 shows the state of energy transition of the stimulated scattering medium molecule. Stimulated scattering medium molecules at the ground energy level A are excited to the excitation energy level B by the excitation lights 1 and 5 and Stokes lights 2 and 6. Stimulated scattering medium molecules having an excitation energy level B are excited from energy levels B to D by excitation light 3 and 7. When the excited molecule transitions from the energy level D to A, energy is given to the light to be amplified 41 and 81, and the light energy increases.

  5A and 5B show optical paths in the light guide of the Stokes lights 2 and 6. FIG. As shown in FIG. 5A, the Stokes light 2 is incident from the incident cross section (cross section perpendicular to the paper surface) of the light guide determined by the points 31 and 32 of the light guide, is reflected by the upper mirror 38, and is in the light guide. It propagates to the position of the cross section determined by the points 34 and 35. The light guide propagates from the cross section determined by the points 34 and 35 to the cross section determined by the points 36 and 37 (the exit cross section of the light guide) in the same manner as the cross section determined by the points 31 and 32. Exit. The Stokes light 2 does not propagate through the portion surrounded by the points 32, 33, and 35 in the light guide. Therefore, as shown in FIG. 5B, the Stokes light 6 is propagated in a direction symmetrical to the Stokes light 2, and the portions surrounded by the points of the stimulated scattering containers 32, 33, and 35, which are blank portions of the Stokes light 2. Then, the Stokes light 6 is propagated.

  The optical path of the Stokes light in the light guide is upwardly symmetrical with respect to the central axis 40 of the container with the Stokes light 2 and 6 in the portion surrounded by the points 31, 32 and 33 in the light guide. Downward Stokes light is propagating. In the portion surrounded by the points 31, 33 and 34 in the light guide, the light before and after being reflected by the upper mirror 38 of the Stokes light 2 is symmetric upward and downward on the paper surface with respect to the central axis of the container. Stokes light is propagating. The portion surrounded by the points 32, 33, and 35 in the light guide is the light before and after the Stokes light 6 is reflected by the lower mirror 39, and is upwardly symmetrical with respect to the central axis 40 of the container. Downward Stokes light is propagating. The portions surrounded by the points 33, 34, and 35 in the light guide are the Stokes lights 2 and 6 reflected by the light guide, and the upward and downward Stokes lights that are symmetrical with respect to the central axis 40 of the container are propagated. ing. In this way, the Stokes wave vector K2 and K6 shown in FIG. 3A can be present in all regions of the light guide. Similarly, the excitation light 1, 3, 5, 7 and the light to be amplified 41, 81 can be made to exist in all regions of the light guide by being incident in an axially symmetric direction with respect to the central axis of the light guide. With the four-wave mixing stimulated scattering light amplifier of the present invention, it becomes possible to amplify the light to be amplified spatially and uniformly.

  The efficiency of the four-wave mixed stimulated scattering amplifier of the present invention will be described in comparison with a conventional stimulated scattering amplifier. In the conventional stimulated scattering amplifier, as shown in FIG. 11, the energy of the excitation light 1 is divided into the amplified light 41 and the wave energy 9 of the stimulated scattering medium. On the other hand, in the four-wave mixing stimulated scattering amplifier of the present invention, as shown in FIG. 4, the energy of the excitation light (1, 5) is divided into Stokes light (2, 6) and wave energy 9 of the stimulated scattering medium. Is done. The stimulated scattering medium molecule at the energy level B is further excited to the energy level D by the excitation light (3, 7), the wave energy 9 of the medium is added to the energy of the excitation light (3, 7), and the amplified light (41 , 81). Therefore, the four-wave mixed inductive scattering amplifier can improve efficiency by eliminating the loss of the wave energy of the medium.

  The opposing reflectors 38 and 39 in the light guide of the four-wave mixed inductive scattering amplifier have a wavelength selectivity in reflectivity, and reflect only the wavelengths of the excitation light, Stokes light, and amplified light. Is used. As a result, when the amplified light becomes high in intensity, it is possible to suppress the generation of four-wave mixed stimulated scattered light of the amplified light and the excitation light so that the light becomes even shorter.

Next, a four-wave mixed stimulated scattering generator will be described with reference to FIGS.
FIG. 6A shows the optical paths of the excitation light 1, Stokes light 2, excitation light 3, and generated light 42 in the light guide 30. FIG. 6B shows the optical paths of the excitation light 5, Stokes light 6, excitation light 7, and generated light 82 in the same light guide 30. For ease of viewing the figures, they are shown in separate figures. In the generator of the present invention, the excitation light 1, the Stokes light 2, the excitation light 3, the excitation light 5, the Stokes light 6 and the excitation light 7 are incident on the light guide 30 through the optical paths in FIGS. . The excitation light 1, 3, 5, 7 and the Stokes light 2 and 6 are incident from outside the light guide, and the generated light 42 and 82 is a matching condition of the wave vector in the four-wave mixed stimulated scattering process by the excitation light and the Stokes light. It is generated in the light guide in the direction filled by. 6A and 6B, the optical paths of the excitation lights 1 and 5, the optical paths of the Stokes lights 2 and 6, the optical paths of the excitation lights 3 and 7, and the optical paths of the generated lights 42 and 82 are mutually guided by the stimulated scattering container 12. It is in an axially symmetric position rotated 180 degrees with respect to the central axis of the light guide 30 disposed therein. The stimulated scattering container 12 is a container filled with a stimulated scattering medium, which includes a light guide 30 composed of opposing reflecting mirrors (38, 39).

In this four-wave mixed stimulated scattering generator, two excitation lights (1, 3) and one Stokes light (2) are surfaces including the normal line of the reflecting mirror facing the light guide and the central axis of the light guide. The incident light is in the direction that satisfies the wave vector matching condition of the four-wave mixed stimulated scattering process and overlaps the light guide entrance surface. One generated light (42) grows in the angle direction satisfying the wave number vector matching condition using the light of the noise level intensity (intensity 10 ⁻¹¹ times the excitation light intensity) in the stimulated scattering container as a seed. The other two excitation lights (5, 7) and one Stokes light (6) are the other two excitation lights (1, 3), one Stokes light (2) and the center of the light guide. The light is incident so as to overlap with the light guide entrance surface at an axisymmetric angle rotated by 180 degrees on the axis. Another generated light (82) grows in an axially symmetric direction rotated 180 degrees around the central axis of the generated light (42) and the light guide.

  As the excitation lights 1, 3, 5, and 7, output light from the laser device is used. Stokes lights 2 and 6 are light less than the excitation light energy by the wave energy of the stimulated scattering medium. The output light generated by condensing the laser light into the stimulated scattered light generator can be dispersed and used as Stokes light. Moreover, the output light of two laser apparatuses which adjusted the oscillation wavelength to excitation light wavelength and Stokes light wavelength can also be used.

FIG. 7A shows the matching condition of the wave vector in the four-wave mixed stimulated scattering process of the excitation light, Stokes light, and generated light. The wave number vectors of the pumping light (1, 3, 5, 7) are respectively K1, K3, K5, and K7, the wave number vectors of the Stokes light (2, 6) are respectively K2 and K6, and the generated light (42, 82). When the wave number vectors are K42 and K82, respectively, the wave number vectors satisfy the matching conditions of the following (Expression 4) and (Expression 5).
K1 + K3 = K2 + K42 (Formula 4)
K5 + K7 = K6 + K82 (Formula 5)

  FIGS. 7B and 7C show the propagation directions of excitation light, Stokes light, and generated light at the center point 15 of the entrance window of the light guide in the stimulated scattering container of FIG.

  FIG. 8 shows a state of energy transition of the stimulated scattering medium molecule. Stimulated scattering medium molecules at the ground energy level A are excited to the excitation energy level B by the excitation light (1, 5) and Stokes light (2, 6). Stimulated scattering medium molecules having an excitation energy level B are excited from energy levels B to D by excitation light (3, 7). When the excited molecule transitions from the energy level D to A, energy is given to the generated light (42, 82), and the light energy increases.

  FIG. 9A shows an optical path of the generated light 42 generated in the angle direction satisfying the matching condition of the wave number vectors of the excitation light and the Stokes light in the stimulated scattering medium. The generated light 42 propagates in the right direction from the incident cross section (cross section perpendicular to the paper surface) of the light guide determined by points 61 and 62 in the light guide of FIG. 9A, is reflected by the lower mirror 39, and is reflected in the container. The light propagates to the position of the cross section (light guide cross section of light guide) determined by the points 64 and 65 and exits. The generated light 42 does not propagate through the portion surrounded by the points 61, 63, and 64 in the container. Therefore, as shown in FIG. 9B, the generated light 82 is propagated in a direction axially symmetric with the generated light 42, and is surrounded by points 61, 63, and 64 in the light guide that are blank portions of the generated light 42. The generated light 82 is propagated to the part.

  The light path of the generated light in the light guide is upwardly symmetrical with respect to the central axis 40 of the container with the generated light 42 and 82 in the portion surrounded by the points 61, 62, and 63 in the light guide. Downward generated light propagates. In the portion surrounded by the points 61, 63, and 64 in the light guide, the light before and after the generated light 82 is reflected by the upper mirror 38, and upward and downward that are symmetrical with respect to the central axis of the container. The generated light is propagating. The portions surrounded by the points 62, 63, and 65 in the light guide are the light before and after the generated light 42 is reflected by the lower mirror 39, and are upwardly symmetrical with respect to the central axis 40 of the container. Downward generated light propagates. The portions surrounded by the points 63, 64, and 65 in the light guide are the generated lights 42 and 82 reflected by the light guide, and the upward and downward generated lights that are symmetrical with respect to the central axis 40 of the container are propagated. ing. In this way, the wave vectors K42 and K82 of the generated light shown in FIG. 7A can be present in all regions of the light guide. Excitation light 1, 3, 5, 7 and Stokes light 2, 6 can likewise be present in all regions of the light guide. The four-wave mixed stimulated scattering generator of the present invention makes it possible to grow the generated light spatially and uniformly.

  The efficiency of the four-wave mixed stimulated scattering generator of the present invention will be described. In the four-wave mixed stimulated scattering generator of the present invention, as shown in FIG. 8, the energy of the excitation light (1, 5) is divided into Stokes light (2, 6) and wave energy 9 of the stimulated scattering medium. The stimulated scattering medium molecule of energy level B is further excited to the energy level D by the excitation light (3, 7), and then transitions from the energy level D to A to the energy of the excitation light (3, 7). Wave energy 9 is added and converted into energy of generated light (42, 82). Therefore, in the four-wave mixed stimulated scattering generator of the present invention, the loss of the wave energy of the medium is eliminated, so that the efficiency can be improved.

  The opposing reflectors in the light guide of the four-wave mixed stimulated scattering generator use a dielectric multilayer that reflects the wavelength of the excitation light, Stokes light, and generated light, with reflectivity being wavelength selective. ing. As a result, when the generated light becomes high intensity, generation of four-wave mixed induced scattered light of the generated light and the excitation light can be suppressed from becoming light with a shorter wavelength.

  As an example of an amplifier and a generator as a four-wave mixed stimulated scattering apparatus, the effects of the apparatus are described, and the loss of the wave energy of the medium is eliminated by the generation of the four-wave mixed stimulated scattered light. Can be improved. In addition, excitation light, Stokes light, amplified light, or generation is generated in all areas of the light guide by adding incident excitation light and Stokes light at an axially symmetric angle rotated by 180 degrees with respect to the central axis of the light guide. Light can be present and the spatial uniformity of the intensity distribution of the beam can be improved.

Example 1
The four-wave mixed stimulated scattering optical amplifier of the embodiment uses a stimulated scattering container filled with hydrogen gas that is a stimulated scattering medium. A light guide composed of a reflecting mirror that reflects excitation light, Stokes light, and amplified light is provided on opposing surfaces of the stimulated scattering container. The reflecting mirror is composed of a dielectric multilayer film mirror having wavelength selectivity in reflectance, and reflects the excitation light wavelength (248.6 nm), Stokes light wavelength (277.2 nm), and amplified light wavelength (225.3 nm). The rate is 95% or more, and the reflectance at other wavelengths is 1% or less. Each incident condition of excitation light, Stokes light, and amplified light is shown below. The beam shape is a 1 cm × 1 cm quadrangle that is the same as the cross-sectional shape of the light guide composed of the opposing reflecting mirrors. In the cross section of the light guide entrance window, the cross sections of the excitation light, the Stokes light, and the light to be amplified overlap. The excitation lights 1 and 3, the Stokes light 2 and the amplified light 41 are incident at an angle satisfying the matching condition of the wave number vector, and the excitation lights 5 and 7, the Stokes light 6 and the amplified light 81 are input to the light guide. The light is incident on the cross section of the incident window. Here, the excitation light 5 and 7, the Stokes light 6, and the amplified light 81 are rotated by 180 degrees around the central axis of the light guide with respect to each of the other excitation light 1 and 3, the Stokes light 2 and the amplified light 41. The incident light is incident at an axisymmetric angle.

Stimulated scattering medium Hydrogen gas (atmospheric pressure)
Properties of incident light (1) Excitation light 1, 5 Wavelength 248.6 nm
(2) Stokes light 2, 6 wavelength 277.2 nm
(3) Excitation light 3, 7 wavelength 248.6 nm
(4) Amplified light 41, 81 wavelength 225.3 nm
(5) Angle T1 formed by excitation light 1 and Stokes light 2
4.0 mrad (0.23 degrees)
(6) Angle T2 formed by excitation light 1 and excitation light 3
3.5mrad (0.2 degree)
(7) Angle T3 formed by excitation light 1 and amplified light 41
0.05 mrad (3 × 10 ⁻³ degrees)

Here, the angle between the excitation light 5 and the Stokes light 6 is the same as the angle T1 between the excitation light 1 and the Stokes light 2, and the angle between the excitation light 5 and the excitation light 7 is the same as the excitation light 1 and the excitation light 3. The angle formed between the pumping light 5 and the amplified light 81 is the same as the angle T3 formed between the pumping light 1 and the amplified light 41. The length of the light guide is 100 cm, and the cross section of the light guide is a square of 1 cm × 1 cm. There are quartz windows at both ends of the stimulated scattering vessel. The intensities of the excitation lights 1 and 3 are 5.7 × 10 ⁶ W / cm ² , the Stokes light 2 is 1.1 × 10 ⁷ W / cm ² , and the amplified light 41 is 1.1 × 10 ⁵ W. in / cm ^2, the incident superimposed them with light guide inlet, from the container the output end, converts excitation light to the light to be ^{amplified, 1.1 × 10 7 W / cm} 2 of the light to be amplified 41 intensity obtained It is done. The intensity of the excitation light 5 and 7 is 5.7 × 10 ⁶ W / cm ² , which is symmetric with respect to these and the central axis of the light guide, and is 5.7 × 10 ⁶ W / cm ^{2. The} Stokes light 6 is 1.1 × 10 ^7. W / cm ² , amplified light 81 is 1.1 × 10 ⁵ W / cm ² , and is incident upon being overlapped with the light guide entrance. From the container output end, the excitation light is converted into amplified light, and 1.1 × Amplified light 81 having an intensity of 10 ⁷ W / cm ² is obtained. Thus, the amplification efficiency of the light to be amplified is improved, and the excitation light, the Stokes light, and the light to be amplified are present in all regions of the light guide, so that the spatial uniformity of the intensity distribution of the beam is improved.

(Example 2)
A four-wave mixed stimulated scattering light amplifier was prepared under the following conditions in the same manner as in Example 1 except that the excitation light 1 and the excitation light 3 were in the same direction.

Stimulated scattering medium Hydrogen gas (atmospheric pressure)
Properties of incident light (1) Excitation light 1, 5 Wavelength 248.6 nm
(2) Stokes light 2, 6 wavelength 277.2 nm
(3) Excitation light 3, 7 wavelength 248.6 nm
(4) Amplified light 41, 81 wavelength 225.3 nm
(5) Angle T1 formed by excitation light 1 and Stokes light 2
1.4 mrad (0.08 degrees)
(6) Angle T2 formed by excitation light 1 and excitation light 3
0 mrad (excitation lights 1 and 3 are in the same direction)
(7) Angle T3 formed by excitation light 1 and 5 and amplified light 41 and 81
1.1 mrad (0.06 degrees)

The length of the light guide is 100 cm, and the cross section of the light guide is a square of 1 cm × 1 cm. There are quartz windows at both ends of the stimulated scattering medium container. The total intensity of the excitation lights 1 and 3 is 1.1 × 10 ⁷ W / cm ² , the intensity of the Stokes light 2 is 1.1 × 10 ⁷ W / cm ² , and the intensity of the amplified light 41 is 1. When these are overlapped and incident at the light guide entrance at 1 × 10 ⁵ W / cm ² , the excitation light is converted into amplified light from the container output end, and the intensity is 1.1 × 10 ⁷ W / cm ^2. Amplified light 41 is obtained. The intensities of the axially symmetric excitation lights 5 and 7 rotated 180 degrees around the central axis of the light guide are 1.1 × 10 ⁷ W / cm ² in total, and the intensity of the Stokes light 6 is 1.1 × 10 ⁷ W / cm ^2. At cm ² , the intensity of the amplified light 81 is 1.1 × 10 ⁵ W / cm ² , and when it is incident on the light guide entrance, the excitation light is converted into the amplified light from the container output end. Amplified light 81 having an intensity of × 10 ⁷ W / cm ² is obtained. As described above, the amplification efficiency of the amplified light is improved, and the excitation light, the Stokes light, and the amplified light are present in all regions of the light guide, so that the spatial uniformity of the intensity distribution of the beam is improved. .

(Example 3)
The four-wave mixed stimulated scattering optical amplifier of Example 3 was prepared using the same stimulated scattering medium container as in Example 1 except that pure water was used as the stimulated scattering medium under the following conditions. The light guide includes a dielectric multilayer mirror having a wavelength selectivity in reflectivity at the following excitation light wavelength, Stokes light wavelength, and amplified light wavelength as a reflection mirror.

Stimulated scattering medium Pure water Properties of incident light (1) Excitation light 1, 5 Wavelength 248.6 nm
(2) Stokes light 2, 6 wavelength 271.7 nm
(3) Excitation light 3, 7 wavelength 248.6 nm
(4) Amplified light 41, 81 wavelength 229.1 nm
(5) Angle T1 formed by excitation lights 1 and 5 and Stokes lights 2 and 6
0.12 rad (6.9 degrees)
(6) Angle T2 formed by excitation lights 1 and 5 and excitation lights 3 and 7
0.1 rad (5.7 degrees)
(7) Angle T3 formed by excitation light 1 and 5 and amplified light 41 and 81
0.0063 rad (0.36 degrees)

The length of the light guide is 100 cm, and the cross section of the light guide is a square of 1 cm × 1 cm. There are quartz windows at both ends of the stimulated scattering vessel. The intensity of excitation light 1, 3, 5, and 7 is 4.3 × 10 ⁷ W / cm ² , and the intensity of Stokes light 2 and 6 is 8.5 × 10 ⁷ W / cm ^2. The intensities of 41 and 81 are 9.0 × 10 ⁵ W / cm ² , and when they are incident on the light guide entrance, the excitation light is converted into amplified light from the container output end, and 8.6 × 10 ⁷ W respectively. Amplified light 41, 81 grown to an intensity of / cm ² is obtained. Thus, the amplification efficiency of the light to be amplified is improved, and the excitation light, the Stokes light, and the light to be amplified are present in all regions of the light guide, so that the spatial uniformity of the intensity distribution of the beam is improved.

(Example 4)
The four-wave mixed stimulated scattering generator of the embodiment uses a stimulated scattering container filled with hydrogen gas as a stimulated scattering medium. A light guide composed of a reflecting mirror that reflects excitation light, Stokes light, and generated light is provided on opposing surfaces in the stimulated scattering container. The incident conditions of excitation light and Stokes light are shown below. The beam shape is a 1 cm × 1 cm square that is the same as the cross-sectional shape of the light guide. At the light guide entrance, the sections of the excitation light and Stokes light overlap.

Stimulated scattering medium Hydrogen gas (atmospheric pressure)
Properties of incident light (1) Excitation light 1, 5 Wavelength 248.6 nm
(2) Stokes light 2, 6 wavelength 277.2 nm
(3) Excitation light 3, 7 wavelength 248.6 nm
(4) Angle T1 formed by excitation light 1 and Stokes light 2
4.0 mrad (0.23 degrees)
(5) Angle T2 formed by excitation light 1 and excitation light 3
3.5mrad (0.2 degree)

The length of the light guide is 100 cm, and the cross section formed by the reflecting mirrors facing each other is a square of 1 cm × 1 cm. There are quartz windows at both ends of the stimulated scattering vessel. The intensity of the excitation light 1, 3, 5, 7 is 9.4 × 10 ⁶ W / cm ² , and the intensity of the Stokes light 2 and 6 is 1.9 × 10 ⁷ W / cm ^2. When incident on the scattering container, the excitation light is converted into generated light from the container output end, and the following generated lights 42 and 82 having an intensity of 1.9 × 10 ⁷ W / cm ² are obtained.

Properties of generated light (1) Generated light 42, 82, wavelength 225.3 nm
(2) Angle T3 formed by excitation lights 1 and 5 and generated lights 42 and 82
0.05 mrad (3 × 10 ⁻³ degrees)
Thus, the generation efficiency of the generated light is improved, and the excitation light, the Stokes light, and the generated light are present in all regions of the light guide, so that the spatial uniformity of the intensity distribution of the beam is improved.

  According to the present invention, the amplification efficiency from the excitation light to the amplified light in the four-wave mixed stimulated scattering amplifier is improved, and the conversion efficiency from the excitation light to the generated light in the four-wave mixed stimulated scattering generator is improved. Spatial uniformity can be improved. As a result, the four-wave mixed stimulated scattering process, which has been used only in the field of measurement, can be used as a stimulated scattering device such as a generator or amplifier for stimulated scattered light.

The perspective view which shows the four-wave mixing stimulated scattering apparatus of this invention (A) and (b) are diagrams showing a four-wave mixed stimulated scattering amplifier and an optical path of the present invention. The figure which shows the mechanism of the four-wave mixing induction scattering amplification process of this invention. (A) shows the wave vector matching condition, and (b) and (c) show the incident direction at the center point of the incident window of the light guide in the stimulated scattering container. Diagram of energy levels of stimulated scattering medium molecules illustrating the mechanism of the four-wave mixed stimulated scattering amplification process of the present invention (A) (b) is a figure which shows the optical path in the light guide of the Stokes light of this invention (A) and (b) are diagrams showing a four-wave mixed stimulated scattering generator and an optical path of the present invention. The figure which shows the mechanism of the four-wave mixing induced scattering production | generation process of this invention. (A) shows the wave vector matching condition, and (b) and (c) show the propagation direction at the center point of the entrance window of the light guide in the stimulated scattering container. Diagram of energy levels of stimulated scattering medium molecules illustrating the mechanism of the four-wave mixed stimulated scattering generation process of the present invention (A) (b) is a figure which shows the optical path in the light guide of the production | generation light of this invention Conventional stimulated scattering amplifier Diagram of energy levels of stimulated Raman scattering processes in conventional stimulated scattering amplifiers Diagram showing the mechanism of a conventional four-wave mixed stimulated scattering process The figure which shows the energy level of the Raman scattering process in the conventional four wave mixed stimulated scattering The figure which shows the propagation direction of excitation light, Stokes light, and generated light in the conventional four-wave mixing induced scattered light generation

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 3, 5, 7 Excitation light 2, 6 Stokes light 9 Wave energy 10 of a stimulated scattering molecule | numerator Wavelength selection mirror 11 which superimposes excitation light and to-be-amplified light 11 Wavelength-selection mirror 12 which isolate | separates excitation light and to-be-amplified light 13 Inductive scattering container entrance window 14 Inductive scattering container exit window 15 Center position 30 of light guide entrance surface in guided scattering container Light guides 31 to 37 composed of opposing reflecting mirrors Light guide showing optical path of Stokes light Position 38, 39 Reflector 40 Center axis 41, 81 Light guide Amplified light 42, 82 Generated light 51-59 Light path 61-65 of excitation light, Stokes light, generated light in a conventional stimulated scattering container Position in the light guide indicating the optical path of

Claims (3)

A four-wave mixed stimulated scattering device that receives at least excitation light and Stokes light,
In the stimulated scattering container, a light guide composed of a reflecting mirror that reflects light having the wavelengths of excitation light, Stokes light, amplified light, and generated light is provided.
At least the excitation light and the Stokes light are in a direction satisfying the wave vector matching condition of the four-wave mixed stimulated scattering process on the plane including the normal of the reflecting mirror facing the light guide and the central axis of the light guide, and the light guide entrance The excitation light and the Stokes light are incident on the light guide entrance surface at an axially symmetric angle rotated 180 degrees with respect to the central axis of the light guide with respect to each of the excitation light and the Stokes light. Incident to overlap ,
A four-wave mixed stimulated scattering apparatus , wherein excitation light is converted into anti-Stokes light satisfying a wave vector matching condition in the light guide . A four-wave mixed stimulated scattering amplifier that receives excitation light, Stokes light, and amplified light,
A light guide composed of a reflecting mirror that reflects excitation light, Stokes light, and amplified light is provided in the light scattering container.
A wave number vector of a four-wave mixed stimulated scattering process on two planes of excitation light, one Stokes light, and one amplified light on a plane including the normal of the reflecting mirror facing the light guide and the central axis of the light guide. The light guide is incident on the light guide entrance surface in a direction satisfying the alignment condition, and the light guide is applied to each of the two excitation light, the one Stokes light, and the one light to be amplified. Two excitation light beams, one Stokes light beam, and one amplified light beam are incident on the light guide entrance surface so as to overlap each other at an axially symmetric angle rotated by 180 degrees with respect to the central axis of the light guide. A four-wave mixed stimulated scattering amplifier. A four-wave mixed stimulated scattering generator for injecting excitation light and Stokes light,
The stimulated scattering container has a light guide composed of a reflecting mirror that reflects excitation light, Stokes light, and generated light.
Two excitation lights and one Stokes light in a direction satisfying the wave vector matching condition of the four-wave mixed stimulated scattering process on the plane including the normal of the reflecting mirror facing the light guide and the central axis of the light guide, In addition, the light beams are incident on the entrance surface of the light guide so as to overlap with each other, and each of the two excitation lights and the one Stokes light has an axially symmetric angle rotated by 180 degrees with respect to the central axis of the light guide. the excitation light and one Stokes light of the incident so as to overlap with the light guide inlet face,
A four-wave mixed stimulated scattering generator, wherein generated light that satisfies a wave vector matching condition is generated in the light guide .

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