JP5065352B2 - Optical waveguide and optical axis adjustment method - Google Patents

Description

  The present invention relates to an optical waveguide and an optical axis adjusting method.

There are a wide variety of optical components that make up the current optical network. Among them, the optical waveguide occupies an important position for performing advanced light processing.
As a method of introducing light into the optical waveguide from the outside or extracting light from the inside of the optical waveguide, there are mainly a method of directly matching parts together to obtain optical coupling, and a method of obtaining optical coupling via a lens. .

  The method of directly matching parts together to obtain optical coupling corresponds to a case where two members, that is, an optical waveguide and an optical fiber, are directly abutted without passing through other parts. For example, in many cases, the coupling between a quartz-based planar lightwave circuit and an optical fiber is performed by a butting method. In addition, a quartz-based planar lightwave circuit and a quartz-based planar lightwave circuit are also matched. Furthermore, there are hybrid parts in which a semiconductor laser is mounted on a quartz-based planar lightwave circuit, and these also correspond to matching.

  However, when optical coupling is obtained by butting two optical components, the coupling loss increases if the mode field is not close at the butting location between the two. Therefore, in such a case, optical coupling is obtained through a lens. In particular, in the case of an optical waveguide made of a semiconductor, the refractive index of the semiconductor material is high, and the size of the core of the waveguide that propagates the single mode is small. Therefore, when optical coupling is performed by direct matching, the position tolerance is extremely narrow. In such a case, optical coupling is often obtained through a lens.

FIG. 6 is a diagram showing an optical axis adjusting method in the case of a conventional optical fiber and waveguide butt.
Here, FIG. 6A is a diagram showing a state before the optical axis adjustment, and FIG. 6B is a diagram showing a state after the optical axis adjustment. Further, the x, y, and z axis directions are defined as shown in FIG.

  In FIG. 6, the case where a tip-end fiber having a configuration in which a lens and an optical fiber are combined is used as the optical fiber 10 as an example, but this is a case where an optical fiber having a flat cleave end face is used. However, since the optical axis adjustment method does not change, the conventional optical axis adjustment method will be described by taking a case where a tip-spherical fiber is used as an example.

  The optical axis adjustment method for the optical fiber 10 and the optical waveguide 11 includes a case where the optical axis is adjusted by moving the optical fiber 10 side and a case where the optical axis is adjusted by moving the optical waveguide 11 side. Since it is the same, the case where the optical fiber 10 side is moved will be described here.

  First, regarding the optical axis adjustment method in the x-axis direction, the end face of the waveguide is observed from above using a microscope to obtain an image as shown in FIG. In this state, the position of the core 10a of the optical fiber 10 and the position of the core 11a of the waveguide 11 can be visually confirmed, so that the core 10a of the optical fiber 10 and the core 11a of the waveguide 11 are approximately in a straight line. The optical fiber 10 is moved in the x-axis direction. At this time, it is not necessary to know whether light is guided to the waveguide.

  Next, as the optical axis adjustment method in the z-axis direction, as in the optical axis adjustment method in the x-axis direction, the optical fiber is adjusted so that the distance between the end of the optical fiber 10 and the end surface of the optical waveguide 11 is an appropriate distance. 10 is moved in the z-axis direction. Here, the distance between the end of the optical fiber 10 and the end face of the optical waveguide 11 is the focus distance of the tip spherical fiber when the tip spherical fiber is used, and approximately 3 to 3 when the optical fiber of the cleave end face is used. It is about 5 μm.

  Finally, a method for adjusting the optical axis in the y-axis direction is to monitor the light intensity of light propagating in the core 11a of the optical waveguide 11, and in the y-axis direction so as to maximize the light intensity. The optical axis is adjusted by moving the optical fiber 10. When monitoring the intensity of light propagating in the core 11 a of the optical waveguide 11, a method of guiding the light emitted from the opposite end face of the core 11 a of the same optical waveguide 11 to an optical power meter, or monitoring the optical waveguide 11 When the device itself is made of a semiconductor, there is a method of monitoring current generated by the photoelectric effect.

  As another method, a structure for converting the optical path of light upward is provided in the optical waveguide 11, the propagating light is bounced upward, and a point that becomes brighter visually from above is searched for. The intensity of light propagating in the core 11a can be seen. Here, there are various structures for converting the optical path of light upward in the waveguide optical waveguide 11, but light can be extracted upward by scattering only by providing a recess in the optical waveguide 11.

  Further, there are a method of extracting a light upward by forming a mirror in the waveguide by etching or the like, and a method of extracting a light upward by forming a grating in the optical waveguide 11. However, the conventional visual optical axis adjustment method functions only when light is guided into the core 11a of the optical waveguide 11, and light propagates through the core 11a of the optical waveguide 11 at the initial stage of optical axis adjustment. Does not work when not.

  Further, in this state, since the optical axis is only roughly adjusted, the optical axis is precisely adjusted in the x, y, and z axis directions while monitoring the light intensity of the light propagating in the core 11a of the optical waveguide 11. Then, the optical axis adjustment is finished at the point where the maximum light intensity is obtained. For precise axis adjustment, the optical fiber 10 is installed on a stage operable in the x, y, and z axis directions, the light intensity of light propagating in the core 11a of the optical waveguide 11 is monitored, and the light intensity is monitored. It is also possible to perform automatic and precise optical axis adjustment using a computer so that it stops at the position where the maximum value is reached. Therefore, it is most difficult to guide the light into the core 11a of the optical waveguide 11, and light can be introduced into the core 11a of the optical waveguide 11 once. The light intensity of the light propagating into the core 11a of the optical waveguide 11 As long as it becomes possible to monitor, precise optical axis adjustment is not so difficult.

  However, in the conventional optical axis adjustment method described above, the x and z axis directions out of the x, y, and z axis directions are visually observed without monitoring the light intensity propagating in the core 11a of the optical waveguide 11. The optical fiber 10 can be moved to an approximate position, and the light intensity of light propagating in the core 11a of the optical waveguide 11 is monitored at least in the y-axis direction, and light is introduced into the core 11a of the optical waveguide 11. This is a simple method.

FIG. 7 is a diagram showing an optical axis adjustment method for obtaining optical coupling in a waveguide through a conventional lens.
Here, FIG. 7A is a diagram showing a state before the optical axis adjustment, and FIG. 7B is a diagram showing a state after the optical axis adjustment. Note that the x-axis direction which is the horizontal direction of the substrate, the y-axis direction which is the vertical direction of the substrate, and the z-axis direction which is the propagation direction of light propagating in the waveguide are defined as shown in FIG. In FIG. 7, the broken line indicates the path of light, but it cannot be visually observed.

  When optical coupling is obtained in the waveguide through the lens, depending on the focus distance of the lens used, in many cases, even if the end surface of the optical waveguide 11 is observed from above using a microscope, the lens and the optical waveguide 11 The end face cannot be captured within the same field of view. Further, the focus point f (the position of the beam waist in FIG. 7) is basically unknown.

  Therefore, the lens is appropriately moved while monitoring the light intensity of the light propagating in the optical waveguide 11 from the state shown in FIG. 7A to the state shown in FIG. There is no choice but to search for the point where light is introduced into 11. Once the light can be guided into the core 11a of the optical waveguide 11, automatic optical axis adjustment or the like can be used. However, the work up to the introduction of the light into the core 11a of the optical waveguide 11 requires considerably skill. It is a necessary work.

  That is, in the case of the optical axis adjustment in the case of the above-described conventional optical fiber 10 and optical waveguide 11 butting, two of the three axes were able to perform rough optical axis adjustment visually. In the case of an optical axis adjustment method for obtaining optical coupling to the optical waveguide 11 through a lens, the optical axis adjustment cannot be performed at all by visual observation. Therefore, the optical axis adjustment through the lens requires more time for the optical axis adjustment than the alignment of the optical fiber 10 or the like that can be visually adjusted. As a result, the problem is that throughput is reduced.

S. M.M. Csutak, 2 others, “CMOS-Compatible Planar Silicon Waveforme-Grating-Coupler Photodetectors Fabricated on Silicon-on-Insulator (SOI) SUBIC. 38, NO. 5, May 2002, p. 477-480

  As described above, when optical coupling is obtained in the optical waveguide 11 via the lens, light is introduced into the core 11a of the optical waveguide 11 and the light intensity of the light propagating through the core 11a of the optical waveguide 11 is monitored. There was a problem that it took time until it was completed, and this caused a decrease in throughput.

  In view of the above, an object of the present invention is to provide an optical waveguide and an optical axis adjustment method capable of easily adjusting the optical axis visually.

The optical waveguide according to the first invention for solving the above-mentioned problems is
A waveguide that propagates light;
A slab waveguide that propagates light disposed on at least one side of the waveguide in the horizontal direction of the substrate;
Two or more rows are formed in the slab waveguide at different distances from the end face of the slab waveguide, and optical path conversion means for converting the optical path of light in the direction perpendicular to the substrate is provided.

An optical axis adjustment method according to a second invention for solving the above-described problem is as follows.
A waveguide that propagates light;
A slab waveguide that propagates light disposed on at least one side of the waveguide in the horizontal direction of the substrate;
In the optical waveguide comprising two or more rows formed at different distances from the end face of the slab waveguide in the slab waveguide, and optical path conversion means for converting the optical path of the light in the substrate vertical direction,
A lens is arranged on the side of the end face of the waveguide,
While observing the light whose optical path has been converted by the optical path conversion means from the vertical direction of the substrate, the focus point of the lens is moved in the vertical direction of the substrate by moving the lens in the vertical direction of the substrate, and the optical path by the optical path conversion means The movement of the lens is stopped at a position where the light intensity of the converted light becomes the strongest.

An optical axis adjustment method according to a third aspect of the present invention for solving the above problem is the optical axis adjustment method according to the second aspect of the invention,
Further, by moving the lens in the propagation direction of the light propagating in the waveguide, the optical path is changed by the optical path converting means while moving the focus point of the lens in the propagation direction of the light propagating in the waveguide. The converted light is observed from the vertical direction of the substrate, and the movement of the lens is stopped at a position where the number of light path changing means that becomes brightest is minimized.

An optical axis adjustment method according to a fourth aspect of the present invention for solving the above problem is the optical axis adjustment method according to the second aspect of the invention,
Further, by moving the lens in the propagation direction of the light propagating in the waveguide, the optical path is changed by the optical path converting means while moving the focus point of the lens in the propagation direction of the light propagating in the waveguide. The converted light is observed from the direction perpendicular to the substrate, and the number of the light path conversion means in the first row counted from the end face of the waveguide becomes bright, and the number of the light path conversion means in the second and subsequent rows counted from the end face of the waveguide. The movement of the lens is stopped at a position where the ratio to the number of brightening is maximized.

An optical axis adjustment method according to a fifth aspect of the present invention for solving the above problem is the optical axis adjustment method according to the third aspect or the fourth aspect of the invention,
Further, by moving the lens in the horizontal direction of the substrate and moving the focus point of the lens in the horizontal direction of the substrate, the light whose optical path has been converted by the optical path conversion unit is observed from the vertical direction of the substrate, and the optical path conversion unit The movement of the lens is stopped at a position where the number of brightening elements becomes the smallest.

  ADVANTAGE OF THE INVENTION According to this invention, the optical waveguide and optical axis adjustment method which can perform an optical axis adjustment easily visually can be provided.

It is the figure which showed the optical waveguide and optical axis adjustment method which concern on the 1st Example of this invention. It is the figure which showed the optical waveguide and optical axis adjustment method which concern on 2nd Example of this invention. It is the figure which showed the optical waveguide and optical axis adjustment method which concern on the 3rd Example of this invention. It is the figure which showed the various structures which change the optical path of the light to the upper direction of the optical waveguide in the optical waveguide and optical axis adjustment method which concern on 1st Example of this invention. It is the figure which showed the method of forming the circular micromirror structure in the optical waveguide and optical-axis adjustment method which concern on 1st Example of this invention. It is the figure which showed the optical axis adjustment method in the case of the matching of the conventional optical fiber and waveguide. It is the figure which showed the optical axis adjustment method which obtains optical coupling to a waveguide via the conventional lens.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out an optical waveguide and an optical axis adjusting method according to the present invention will be described with reference to the drawings.

Hereinafter, a first embodiment of the optical waveguide and the optical axis adjusting method according to the present invention will be described.
In the optical waveguide and the optical axis adjustment method according to the present embodiment, a waveguide for guiding light, and a slab waveguide for guiding light disposed on at least one side of the waveguide in the horizontal direction of the substrate, In the optical waveguide comprising two or more rows formed in the slab waveguide at different distances from the end face of the slab waveguide and having optical path conversion means for converting the optical path of the light in the direction perpendicular to the substrate, on the side of the end face of the waveguide By locating the lens and moving the lens in the vertical direction of the substrate while observing the light whose optical path has been converted by the optical path conversion means from the vertical direction of the substrate, the focus point of this lens is moved in the vertical direction of the substrate, thereby changing the optical path The movement of the lens is stopped at a position where the light intensity of the light whose light path has been converted by the above becomes the strongest.

FIG. 1 is a diagram illustrating an optical waveguide and an optical axis adjusting method according to a first embodiment of the present invention.
Here, FIG. 1A is a diagram illustrating a state before the optical axis adjustment is performed, and FIG. 1B is a diagram illustrating a state after the optical axis adjustment is performed. Note that the x-axis direction that is the horizontal direction of the substrate, the y-axis direction that is the vertical direction of the substrate, and the z-axis direction that is the propagation direction of light propagating in the waveguide are defined as shown in FIG. Moreover, although the broken line in FIG. 1 shows the path of light, it cannot actually be visually observed.

  FIG. 1A shows a case where the focus point f before the optical axis adjustment is closer to the lens than the end face of the waveguide 1 in the z-axis direction and exists above the waveguide 1. However, the procedure for adjusting the optical axis is the same whether it is on the inner side of the waveguide 1 with respect to the end face of the waveguide 1 in the z-axis direction or on the lower side of the waveguide 1. is there.

  As shown in FIG. 1A, the optical waveguide according to this embodiment includes a core 2 of a waveguide 1 that guides light, and a cladding of the waveguide 1 that is disposed on the side of the core 2 of the waveguide 1. 3 and a slab waveguide 4 which is disposed on the side of the waveguide 1 in the x-axis direction and has the same height as the height of the waveguide 1 in the y-axis direction. In this embodiment, the slab waveguide 4 is disposed on both sides of the waveguide 1 in the x-axis direction. However, the slab waveguide 4 is at least one side of the waveguide 1 in the x-axis direction. It is good also as arrange | positioning.

  In the slab waveguide 4, a large number of pits that are square recesses each having a side of 2 μm are arranged in a row in the x-axis direction at a pitch of 2 μm at a location 1 μm away from the end surface in the z-axis direction of the slab waveguide 4. . In this embodiment, this pit is referred to as the front row pit 5. This front row pit 5 functions as a structure for changing the optical path of light above the slab waveguide 4, that is, above the optical waveguide.

  Also, the slab waveguide 4 has a side that is 2 μm in the same manner in a state shifted from the position in the x-axis direction in which the front row pits 5 are arranged at a position 50 μm away from the end surface in the z-axis direction of the slab waveguide 4 A large number of square pits, which are concave portions, are arranged in rows in the x-axis direction at a pitch of 2 μm in the x-axis direction. In this embodiment, this pit is referred to as a rear row pit 6. This rear row pit 6 functions as a structure for changing the optical path of the light above the optical waveguide.

  In this embodiment, square-shaped concave portions are arranged as the front row pits 5 and the rear row pits 6, but it is only necessary to observe light from above the optical waveguide. The shape may be arbitrarily set including the size. Further, in this embodiment, the pitches for arranging the front row pits 5 and the rear row pits 6 are set at equal intervals, but can also be arranged at random intervals.

  In this embodiment, when the optical waveguide is formed, the front row pits 5 and the rear row pits 6 are simultaneously formed by etching. For this reason, the front row pits 5 and the rear row pits 6 have good vertical shapes. Note that the optical waveguide according to the present embodiment may be a structure having a slope in the cross-sectional structure as long as the slope faces the end face side where light is incident and operates as a mirror.

  In this embodiment, an embedded waveguide in which a core 2 made of InGaAP is formed on an InP substrate is used as the optical waveguide. In this embodiment, the width of the core 2 is 2 μm, the thickness of the core 2 is 0.4 μm, and the depths of the front row pits 5 and the rear row pits 6 are sufficiently deeper than the thickness of the core 2. did.

  In this embodiment, a light source having a wavelength of 1.55 μm is used, and the front row pit 5 and the rear row pit 6 having a structure for changing the optical path of light from the upper side of the optical waveguide to the upper side of the optical waveguide are extended to the near infrared. The photo was taken with a sensitive camera, and the optical axis was adjusted while checking the taken image.

  As shown in FIG. 1A, when the optical axis adjustment in the y-axis direction is greatly deviated, light does not come out above the optical waveguide. Therefore, when the focus point f is moved in the y-axis direction and the focus point f approaches the position of the end face of the slab waveguide 4 in the y-axis direction, light gradually couples into the slab waveguide 4. In accordance with the spread angle of light incident from the end face of the slab waveguide 4 in the z-axis direction, the front row pits 5 and the rear row pits 6 within the light spread angle become bright as shown in FIG.

  When the position of the core 2 and the position of the focus point f in the y-axis direction coincide with each other, the light intensity of the light propagating in the slab waveguide 4 becomes the strongest and is observed from the front row pit 5 and the rear row pit 6. The light intensity is the strongest.

  By the way, since the front row pits 5 are arranged near the end face of the slab waveguide 4 in the z-axis direction in the slab waveguide 4, the position of the core 2 and the position of the focus point f in the y-axis direction do not coincide with each other. The position of the core 2 in the y-axis direction and the position of the focus point f may not be known.

  However, since the rear pit 6 is arranged far from the end face of the slab waveguide 4 in the z-axis direction in the slab waveguide 4, it is difficult to become bright when light is not propagated in the slab waveguide 4. . Therefore, in order to prevent stray light from brightening the front row pits 5 and making it difficult to determine whether the position of the core 2 and the position of the focus point f in the y-axis direction coincide with each other, the pits are arranged in two or more rows. I decided to.

  Further, in the present embodiment, the rear pit 6 is disposed at a position 50 μm from the end face of the slab waveguide 4 in the z-axis direction in the slab waveguide 4, but may be disposed at a position of 100 μm, for example, z When the distance from the end face of the slab waveguide 4 in the axial direction is far, the light does not reach the rear pit 6 unless the light propagates through the slab waveguide 4. Therefore, the position of the core 2 in the y-axis direction It can be easily determined whether or not the position of the focus point f coincides.

  In this embodiment, as the structure for converting the optical path of the light above the optical waveguide, a structure for observing the light scattered by hitting the pits from above the optical waveguide is used. It has been confirmed that the same action as that of the pits according to the present embodiment can be obtained even when a structure for converting the optical path of light to the upper side of the optical waveguide is formed by using a grating or a grating.

Here, various structures for converting the optical path of light upward of the optical waveguide other than the pits formed by the square recesses will be described.
FIG. 4 is a diagram showing various structures for converting the optical path of light upward of the optical waveguide in the optical waveguide and optical axis adjusting method according to the first embodiment of the present invention.
Here, FIG. 4A shows a pit formed by a square recess, FIG. 4B shows a circular micromirror structure, and FIG. 4C shows dry etching from an oblique direction. FIG. 4D is a diagram showing a micromirror structure formed by using the grating, and FIG. 4D is a diagram showing a grating structure using a grating.

First, a number of structures are already known as the micromirror structure, and any structure can be realized, but a smaller one is preferable for improving the accuracy of optical axis adjustment.
FIG. 5 is a view showing a method of forming a circular micromirror structure in the optical waveguide and optical axis adjusting method according to the first embodiment of the present invention.
Here, FIG. 5A shows a slab waveguide provided with a mask in which holes are formed, and FIG. 5B shows a slab waveguide provided with a mask in which holes subjected to wet etching are formed. FIG.

  As shown in FIG. 5 (a), a hole 7 formed in the mask 7 is formed by wet etching as shown in FIG. 5 (b) after a mask 7 having holes formed in the slab waveguide 4 is applied. Further, the curved surface 9 is etched in the slab waveguide 4. The curved surface 9 is used as a micromirror. In addition, as shown in FIG. 4C, a micromirror structure formed by using dry etching from an oblique direction is conceivable. FIG. 4C shows an example of a micromirror structure inclined by an angle θ ° from the vertical direction of the slab waveguide 4.

  Next, regarding the grating structure, it is possible to adjust the optical axis in the same manner by arranging a group of grating structures instead of pits formed by square recesses. The grating structure on the waveguide has long been known as a structure for taking light in and out from the upper surface of the optical waveguide.

  For example, the one-dimensional grating disclosed in Non-Patent Document 1 is conceivable. Depending on the material of the optical waveguide, it is necessary to appropriately design the pitch, depth, etc. of the grating structure. Can be put on the top surface.

  In the above-mentioned Non-Patent Document 1, the case of a silicon-on-insulator (SOI) optical waveguide is disclosed, but many similar structures are known for other materials such as quartz, polymer, and compound semiconductor. Therefore, it can be used in place of a pit formed by a square recess.

  In this embodiment, the optical axis adjustment is performed by visual observation with the human eye, but the optical axis adjustment in the y-axis direction is automatically performed by using an image recognition technology using a camera and a computer. Is also possible.

  As described above, according to the present embodiment, the optical axis adjustment in the y-axis direction can be performed only by visual observation. Thereby, the optical axis adjustment can be performed at a higher speed than the conventional method of adjusting the optical axis by relying only on the light intensity of the light propagating through the core 2, and the throughput can be improved. Therefore, the mounting cost can be reduced.

  Further, in the conventional method of visually adjusting the optical axis from above the optical waveguide, a structure for converting the optical path of light upward in the optical waveguide is formed in the waveguide 1. Since it is possible to convert the optical path of the light to the upper side of the optical waveguide only after the light is guided to the optical waveguide, it does not function at all in a state where the light is not guided into the waveguide 1. However, according to the optical waveguide and the optical axis adjustment method according to the present embodiment, the information on the position of the focus point f can be visualized from the stage of the coarse optical axis adjustment, so that simple optical axis adjustment is provided. Can do.

Hereinafter, a second embodiment of the optical waveguide and the optical axis adjusting method according to the present invention will be described.
The optical waveguide and the optical axis adjustment method according to the present embodiment are the same as those in the optical waveguide and the optical axis adjustment method according to the first embodiment, in the z-axis direction, that is, the propagation direction of light propagating in the waveguide 1. The optical axis adjustment is performed.

FIG. 2 is a diagram showing an optical waveguide and an optical axis adjusting method according to the second embodiment of the present invention.
Here, FIG. 2A is a diagram showing a state in which the focus point f is moved slightly toward the waveguide 1 from the state of FIG. 1B, and FIG. 2B is a focus from the state of FIG. It is the figure which showed the state which moved the point f further to the waveguide 1 side. Note that the x-axis direction which is the horizontal direction of the substrate, the y-axis direction which is the vertical direction of the substrate, and the z-axis direction which is the propagation direction of light propagating in the waveguide are defined as shown in FIG. In FIG. 2, the broken line indicates the path of light, but it cannot be visually observed.

  In this embodiment, the optical axis adjustment in the y-axis direction is performed by changing the light intensity of light propagating in the core 2 which is the optical axis adjustment method according to the first embodiment or the conventional optical axis adjustment method. It is assumed that it has been completed by the method of monitoring and adjusting the optical axis.

  As shown in FIG. 2A, when the focus point f is moved in the z-axis direction in the state where the optical axis adjustment in the y-axis direction is completed, the number of front row pits 5 that are brightened decreases. As shown in FIG. 2B, when the beam waist at the focus point f is smaller than or equal to the front row pit 5 and the focus point f just matches the front row pit 5, Only one of the five is bright.

  Further, depending on the size and pitch of the front row pit 5, the focus point f may be between the front row pits 5, that is, light may not hit the front row pits 5 at all. In this case, the front row pit 5 that has become bright disappears, but if the rear row pit 6 remains in a bright state, it can be confirmed that the optical axes in the y-axis direction are aligned.

  If there is no rear row pit 6 and no light hits the front row pit 5, it is difficult to determine whether the optical axis in the y-axis direction is correct, so the optical axis in the y-axis direction is correct. However, the focus point f is moved appropriately.

  On the other hand, when the rear pit 6 is present, it can be confirmed that the optical axis in the y-axis direction is aligned with the rear pit 6, so that it is possible to prevent the y-axis direction from being moved by mistake. In such a case, the optical axis can be easily adjusted by moving the focus point f slightly in the x-axis direction so that light strikes the front row pits 5.

  Depending on the size of the beam waist or pit, a plurality of front row pits 5 may be brightened. Even in this case, the focus point f is moved in the z-axis direction so that the number of bright front row pits 5 is minimized. The optical axis may be adjusted.

  Further, when the focus point f moves in a direction away from the front row pit 5 than in the state shown in FIG. 2B, the number of bright front row pits 5 increases again. At this time, the focus point f is set slightly inward of the core 2 from the end surface in the x-axis direction of the core 2 where the focus point f is to be originally set. However, at this point, it is sufficient if a rough optical axis adjustment is possible, and this is not a problem since it is corrected by monitoring the light intensity of light propagating through the core 2 and performing a precise optical axis adjustment later.

  Note that it is desirable that pits are formed in the slab waveguide 4 in the optical axis adjustment in the y-axis direction. This is because, when pits are formed in the waveguide 1, it is possible to adjust the optical axis in the y-axis direction for the first time by confirming that the pits are brightened by the light propagating through the core 2. It is. However, in the optical axis adjustment in the z-axis direction, it is not always necessary to form pits in the slab waveguide 4. If the optical axes in the y-axis direction are aligned, the pits formed in a convex shape may be similarly arranged without forming the slab waveguide 4.

  The optical axis adjustment in the z-axis direction is performed by observing the light whose optical path has been converted by the front row pit 5 and the rear row pit 6 from above the optical waveguide while moving the focus point f in the direction perpendicular to the end face of the waveguide 1. The movement of the lens may be stopped at a position where the ratio between the number of brightening front row pits 5 and the number of brightening rear row pits 6 becomes maximum.

  When three or more pits are formed, the number of pits in the first row counted from the end face of the waveguide 1 and the number of pits in the second and subsequent rows counted from the end face of the waveguide 1 are increased. The movement of the lens may be stopped at a position where the ratio is maximum.

  In this embodiment, the optical axis adjustment is performed by visual observation with the human eye. However, the optical axis adjustment in the z-axis direction is automatically performed by using an image recognition technique using a camera and a computer. Is also possible.

  As described above, according to the present embodiment, rough optical axis adjustment in the z-axis direction can be performed only by visual observation. As a result, the optical axis can be adjusted at higher speed than the conventional method of adjusting the optical axis by relying only on the light intensity of the light propagating through the core 2, and the throughput can be improved. Therefore, the mounting cost can be reduced.

  In addition, when two or more pits are formed, it is possible to confirm that the optical axis in the y-axis direction is correct in the rear row pit 6 even if a bright pit is lost in the front row pit. Moving the focus point f in the y-axis direction can be prevented, and the time required for the entire optical axis adjustment can be shortened as compared to the case where the pits are arranged in a single row.

Hereinafter, a third embodiment of the optical waveguide and the optical axis adjusting method according to the present invention will be described.
The optical waveguide and the optical axis adjusting method according to the present embodiment are characterized in that the optical axis adjustment in the x-axis direction, that is, the substrate horizontal direction is further performed following the second embodiment.

FIG. 3 is a diagram showing an optical waveguide and an optical axis adjusting method according to the third embodiment of the present invention.
Here, FIG. 3A shows the state of FIG. 2B, and FIG. 3B shows the state where the focus point f is further moved to the waveguide 1 side from the state of FIG. 3A. It is a figure. Note that the x-axis direction, which is the horizontal direction of the substrate, the y-axis direction, which is the vertical direction of the substrate, and the z-axis direction, which is the propagation direction of light propagating in the waveguide, are defined as shown in FIG. Moreover, although the broken line in FIG. 3 shows the path of light, it cannot actually be visually observed.

  As shown in FIG. 3A, when the focus point f is moved in the x-axis direction when the number of bright front row pits 5 is minimum, the position of the bright front row pits 5 is sequentially shifted by the amount moved in the x-axis direction. go. When the focus point f reaches the waveguide 1, as shown in FIG. 3B, since a lot of light is guided into the waveguide 1, the number of bright front row pits 5 is reduced or the front row is bright. The brightness of pit 5 becomes dark.

  When the optical axis adjustment is finished at the point where both the front row pit 5 and the rear row pit 6 are darkest, the optical axis adjustment by visual observation in the x-axis direction is finished. At this time, since the light has already been guided into the waveguide 1, the optical axis can be precisely adjusted by a conventional method.

  Note that it is desirable that pits are formed in the slab waveguide 4 in the optical axis adjustment in the y-axis direction. This is because, when pits are formed in the waveguide 1, it is possible to adjust the optical axis in the y-axis direction for the first time by confirming that the pits are brightened by the light propagating through the core 2. It is. However, in adjusting the optical axis in the x-axis direction, it is not always necessary to form pits in the slab waveguide 4. If the optical axes in the y-axis direction are aligned, the pits formed in a convex shape may be similarly arranged without forming the slab waveguide 4.

  Further, the optical axis in the z-axis direction is not necessarily the state described in the second embodiment, and the focus point f is moved to the position of the core 2 by moving the focus point f in the x-axis direction. Coarse optical axis adjustment in the x-axis direction that can confirm that light has been guided into the core 2 at the darkest point can be performed.

  In this embodiment, the optical axis adjustment is performed by visual observation with the human eye, but the optical axis adjustment in the x-axis direction is automatically performed by using an image recognition technology using a camera and a computer. Is also possible.

  As described above, according to the present embodiment, coarse optical axis adjustment in the x-axis direction can be performed only by visual observation. As a result, the optical axis can be adjusted at higher speed than the conventional method of adjusting the optical axis by relying only on the light intensity of the light propagating through the core 2, and the throughput can be improved. Therefore, the mounting cost can be reduced.

  As described above, by performing through the first to third embodiments, the focus point f of the lens can be adjusted to the waveguide 1 only by visual observation. Also, in the method of adjusting the optical axis by monitoring the light intensity of the light propagating in the core 2, which is a conventional method, the optical axis adjustment method according to the present invention is used in combination, so that the speed is higher than that of the conventional method. Optical axis adjustment can be realized.

  The present invention can be used for, for example, an optical waveguide and an optical axis adjustment method.

1 Waveguide 2 Core 3 Clad 4 Slab Waveguide 5 Front Row Pit 6 Back Row Pit 7 Mask 8 Hole 9 Curved Surface

Claims (5)

A waveguide that propagates light;
A slab waveguide that propagates light disposed on at least one side of the waveguide in the horizontal direction of the substrate;
An optical waveguide comprising: two or more rows formed in the slab waveguide at different distances from the end face of the slab waveguide, and optical path conversion means for converting the optical path of light in the direction perpendicular to the substrate. A waveguide that propagates light;
A slab waveguide that propagates light disposed on at least one side of the waveguide in the horizontal direction of the substrate;
In the optical waveguide comprising two or more rows formed at different distances from the end face of the slab waveguide in the slab waveguide, and optical path conversion means for converting the optical path of the light in the substrate vertical direction,
A lens is arranged on the side of the end face of the waveguide,
While observing the light whose optical path has been converted by the optical path conversion means from the vertical direction of the substrate, the focus point of the lens is moved in the vertical direction of the substrate by moving the lens in the vertical direction of the substrate, and the optical path by the optical path conversion means The optical axis adjustment method is characterized in that the movement of the lens is stopped at a position where the light intensity of the converted light is the strongest. Further, by moving the lens in the propagation direction of the light propagating in the waveguide, the optical path is changed by the optical path converting means while moving the focus point of the lens in the propagation direction of the light propagating in the waveguide. 3. The optical axis adjustment method according to claim 2, wherein the converted light is observed from a direction perpendicular to the substrate, and the movement of the lens is stopped at a position where the number of the light path changing means becomes the smallest. Further, by moving the lens in the propagation direction of the light propagating in the waveguide, the optical path is changed by the optical path converting means while moving the focus point of the lens in the propagation direction of the light propagating in the waveguide. The converted light is observed from the direction perpendicular to the substrate, and the number of the light path conversion means in the first row counted from the end face of the waveguide becomes bright, and the number of the light path conversion means in the second and subsequent rows counted from the end face of the waveguide. The optical axis adjustment method according to claim 2, wherein the movement of the lens is stopped at a position where the ratio to the number of brightening is maximized. Further, by moving the lens in the horizontal direction of the substrate and moving the focus point of the lens in the horizontal direction of the substrate, the light whose optical path has been converted by the optical path conversion unit is observed from the vertical direction of the substrate, and the optical path conversion unit The optical axis adjustment method according to claim 3 or 4, wherein the movement of the lens is stopped at a position where the number of the lightening becomes the smallest.

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