JPS606518B2 - Manufacturing method of hologram wavefront conversion element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a holographic wavefront conversion element used to efficiently guide light emitted from a semiconductor light emitting element such as a semiconductor laser or a light emitting diode to an optical fiber.

Optical fiber communication systems that use semiconductor light-emitting devices such as semiconductor lasers and light-emitting diodes and optical fibers are currently attracting a lot of attention because they are excellent communication systems with a wide range of applications, and research and development is progressing in various places with the aim of putting them into practical use. It is being

One of the important themes of this research and development is how to increase the optical coupling efficiency between semiconductor light emitting devices and optical fibers. This is because the active layer of the semiconductor laser has a rectangular shape, so the radiation angle of the light emitted from the semiconductor laser is significantly different between the direction parallel to the p-n junction surface and the direction perpendicular to it, and the light emitted from the light emitting diode is This is because the light has very poor directivity due to the spread of the light emitting part, and cannot be concentrated at one point simply by converging with a lens, making it impossible to efficiently input the light into the optical fiber. Therefore, in order to improve the optical coupling efficiency between the semiconductor light emitting device and the optical fiber, there are methods using cylindrical lenses, methods using spherical lenses, methods using a combination of hemispherical lenses, and methods using holograms (
A number of methods are being studied, including methods using holographic wavefront conversion elements.

Among these methods, the method using a hologram wavefront conversion element has the following characteristics: complex wavefront conversion is possible, and the positional relationship between the semiconductor light emitting element and the optical fiber can be arbitrarily selected depending on the manufacturing conditions of the hologram wavefront conversion element. Therefore, it is possible to increase the conversion efficiency. The coupling between a semiconductor light emitting device and an optical fiber using a method using a holographic wavefront conversion device is performed as follows. Coherent diverging light (with the same wavefront as the light emitted from the semiconductor light emitting device) that passes through an aperture with the same size as the cross section of the light immediately emitted from the semiconductor light emitting device and is recirculated by the closing of the aperture, and a convergent spherical surface. A hologram wavefront conversion element is manufactured by recording interference fringes formed by wave interference on a recording material, and the positional relationship between the hologram wavefront conversion element and the semiconductor light emitting element is the same as when the hologram wavefront conversion element was manufactured. In order to maintain the same positional relationship between the aperture and the recording material, when combined with a semiconductor light emitting element, the light emitted from the semiconductor light emitting element is converted by the hologram wavefront conversion element into a convergent spherical wave with the same properties as the convergent spherical wave when manufacturing the hologram wavefront conversion element. The wavefront is converted into light. Therefore, if the end face of the optical fiber is placed where the light whose wavefront has been converted by the holographic wavefront conversion element converges,
The convergent light efficiently enters the optical fiber. If the diffraction efficiency of the hologram wavefront conversion element is 100%, the efficiency of optical coupling between the semiconductor light emitting element and the optical fiber by the method used for this hologram wavefront conversion element is almost 100%.
%.

However, the diffraction efficiency of most practical holograms is approximately 60
%, the coupling efficiency between the semiconductor light emitting device and the optical fiber will inevitably be less than 60%, and about 40% of the light will not be used at all. If the hologram wavefront conversion element is made into an in-line hologram, the light near the optical axis among the 0th-order diffracted light and -1st-order diffracted light (co-regenerated light) will also enter the optical fiber, and the optical energy will be transferred to the optical axis. Since they are concentrated in the vicinity, the coupling efficiency improves considerably, but in order to obtain high optical coupling efficiency, it is necessary to reduce the distance between the semiconductor light emitting element and the hologram wavefront conversion element to less than a few ribs. Sometimes it is very difficult to insert a semi-transparent mirror between Sekiguchi and the recording material to make the coherent diverging light and the converging spherical wave coaxial, and even if it could be inserted, the back reflection of the semi-transparent mirror would cause All conventional hologram wavefront conversion elements are of off-axis type, and it is not possible to make them in-line type, because they may cause harmful interference fringes or cause the wavefront of divergent light emitted by the closed aperture to be exposed. could not. As a result, the optical coupling efficiency of conventional hologram wavefront conversion elements is not necessarily sufficient.
For this reason, practical application was delayed. An object of the present invention is to provide a method for manufacturing an in-line type hologram wavefront conversion element in order to improve the insufficient optical coupling efficiency of the conventional off-axis type hologram wavefront conversion element. The principle of this invention is as follows.

The light emitted from the semiconductor light-emitting device passes through a Sekiguchi whose cross section is approximately the same size as the cross-section of the light, and is diffracted by the Sekiguchi.
Due to interference between a coherent convergent light that travels in the same direction as the coherent diverging light on almost the same optical axis as the coherent diverging light and converges at an arbitrary point behind the recording surface, and a reference wave having the same properties as the reference wave. A hologram is produced by recording interference fringes on the same recording material, and when this hologram is illuminated with light that has the same properties as the reference wave during recording, ``the hologram produces a coherent beam that travels in the same direction on almost the same optical axis.'' Divergent light and coherent convergent light are reproduced and interfere with each other, so if this interference pattern is recorded, an in-line type hologram wavefront conversion element can be manufactured.Therefore, the method for manufacturing a hologram wavefront conversion element according to the present invention The feature is that the light passes through a Sekiguchi whose size is almost the same as the cross section of the light immediately after being emitted from the semiconductor light emitting device, and interference fringes are formed due to the interference between the coherent divergent light diffracted by the Sekiguchi and the reference light, and the coherent divergent light and the reference light. Coherent convergent light that travels in the same direction as the coherent diverging light on almost the same optical axis and converges at an arbitrary point behind the recording surface and interference fringes caused by interference with a reference wave having the same properties as the reference wave are recorded in the same way. A hologram is produced by overlapping recording on a material, and interference fringes formed by the interference of coherent divergent light and coherent convergent light that are simultaneously reproduced from this hologram are recorded on another recording material placed behind the aforementioned recording material. It is in the point of doing.

The present invention will be explained below with reference to the drawings. FIG. 1 is a diagram showing an example of the configuration of an optical device conventionally used to manufacture an off-axis type holographic wavefront conversion element, in which 101 is a coherent light generator such as a laser device, 102 is a coherent light generating device, and 102 is a coherent light generating device such as a laser device. A coherent light beam emitted from a generator 101, 103 a beam splitter for splitting the coherent light beam 102 into two directions;
104 and 105 are reflecting mirrors, 106 is an inverted telescope type optical system for expanding the diameter of the coherent light beam, and 107 is a coherent optical system for efficiently inputting the thick coherent light beam 108 expanded by the inverted telescope type optical system 106 into the optical fiber. A lens for converging light, 109 is a shielding plate having a Sekiguchi 110 that is approximately the same size as the cross section of the light just emitted from the semiconductor light emitting element. This is a rectangular Sekiguchi etc. Reference numeral 111 denotes a recording material, the side of which faces the opening 110.

When this optical device records interference fringes formed by the coherent divergent light 112 diffracted and diverged by the aperture 110 and the coherent convergent light 113 converged by the lenses 107 on the recording material 111, an off-axis hologram wavefront conversion element is generated. I can do it. FIG. 3 is a diagram showing an optical arrangement for optically coupling a semiconductor light emitting device and an optical fiber by an ophaxis-type hologram wavefront conversion device made using the optical device shown in FIG. 1, and 301 is a semiconductor light emitting device; 3
02 is the diverging light emitted from the semiconductor light emitting element, 303 is an off-axis type hologram wavefront conversion element made using the optical device shown in FIG. light, 3
05 is an optical fiber.

Semiconductor light emitting device 301 and hologram wavefront conversion device 303
Since the positional relationship between the Sekiguchi 110 and the recording material 111 in FIG. 1 is the same as that between the Sekiguchi 110 and the recording material 111 in FIG. The light enters the fiber 305 efficiently. However, in this case, the divergent light 302 and the convergent light 3
Since the optical axis of 04 necessarily forms a certain angle (off-axis), the coupling efficiency cannot exceed the diffraction efficiency of the hologram wavefront conversion element 303, and the 0th-order diffracted light and the 11th-order diffracted light (coarticulated) All of the playback light) is wasted.
FIG. 4 is a diagram showing the configuration of an embodiment of an optical device for performing the first exposure in the method for manufacturing an in-line type hologram wavefront conversion element according to the present invention. A light generator, 402 is a coherent light beam emitted from the coherent light generator 401, 403 is a beam splitter for splitting the coherent light beam 402 into two directions, 404, 405
is a reflecting mirror, 406 is an inverted telescope type optical system for expanding the diameter of the coherent light beam, and 407 is an aperture □4 whose size is approximately the same as the cross section of the light immediately after it is emitted from the semiconductor light emitting device.
08, the opening 408 is a closed opening such as a rectangle as shown in FIG.

409 is a recording material whose side faces toward the open square 408.

By this optical device, coherent divergent light 410 diffracted and diverged by the aperture 408 and the inverted telescope type optical system 406
The recording material 409 is exposed to interference fringes formed by the coherent light beam (reference light) 411 expanded by the laser beam. At this stage, the recording material 409 is not yet subjected to processing such as development. FIG. 5 is a diagram showing the configuration of an embodiment of an optical device for performing the second exposure in the method of manufacturing an in-line type holographic wavefront conversion element according to the present invention, and shows the structure of an embodiment of the optical device for performing the second exposure in the method of manufacturing an in-line type hologram wavefront conversion element according to the present invention. A shielding plate 407 having 408 converts the inverted telescope type optical system 501 for expanding the coherent light beam and the thick coherent light beam 502 expanded by the inverted telescope type optical system 501 into coherent convergent light that efficiently enters the optical fiber. The only difference from the optical device shown in FIG. 4 is that it is replaced with a lens 503.

However, care is taken so that the optical axis 5041 of the coherent convergent light 504 converged by the lens 503 and the optical axis 4101 of the coherent diverging light 410 almost coincide. With this optical device, interference fringes formed by the coherent convergent light 504 and the coherent light beam (reference light) 411 are transferred onto the recording material 409 by the previously exposed coherent diverging light 411.
0 and the interference fringes formed by the coherent light beam 411 are recorded, and then the recording material 409 is subjected to processing such as development to complete a hologram. As shown in FIG. 6, the hologram produced in this way is a coherent light beam at the time of hologram recording, in which the diameter of a coherent light beam 602 emitted from a coherent light generator 601 is expanded by an inverted telescope type optical system 603. (Reference light) 41
Coherent light beam (reference light) 41 during hologram production by coherent light beam 604 having the same properties as 1.
When illuminated at the same incident angle as 1, each hologram 605 emits coherent divergent light 410 during hologram recording.
A coherent divergent beam 606 corresponding to the coherent convergent beam 504 and a coherent convergent beam 607 are reproduced, and these beams interfere to form interference fringes. 60
8, and by subjecting the recording material 608 to processing such as development, an in-line hologram wavefront conversion element is obtained.

FIG. 7 shows an optical device for optically coupling a semiconductor light emitting element and an optical fiber using an inline type holographic wavefront conversion element manufactured by the manufacturing method according to the present invention, where 701 is a semiconductor light emitting element, and 702 is a semiconductor light emitting element. The emitted diverging light 703 is an in-line hologram wavefront conversion element manufactured by the manufacturing method according to the present invention, 704 is a convergent light whose wavefront is converted from the diverging light 82 by the hologram wavefront conversion element 703, and 705 is an optical fiber.

Since the convergent light 704 converges in the same manner as the coherent convergent light 584 that efficiently enters the optical fiber during hologram recording, it efficiently enters the optical fiber 705. Furthermore, in this case, since the optical axes of the diverging light 702 and the converging light 704 are almost the same, not only the convergent light 784 but also some of the 0th-order diffracted light and -1st-order diffracted light (coarticulated regenerated light) are also connected to the optical fiber 70.
Even if the diffraction efficiency of the hologram wavefront conversion element 703 is not 100%, the efficiency of optical coupling between the semiconductor light emitting element 7QI and the optical fiber 705 becomes considerably high. In the above embodiment, even if the hologram 605 generates co-reproducing beams in addition to the necessary reproducing beams 606 and 687, it is not a big problem as long as it is not very strong, but if it is harmful, the so-called thick recording material 409 Record the hologram 605 using a recording material.

All you have to do is turn it into a gram and suppress the co-master regeneration light. Further, in the above embodiment, first, the recording material 4 is formed on the interference fringes caused by the coherent diverging light 410 and the coherent light beam 411.
89 is exposed to light, and then interference fringes caused by the coherent convergent light 504 and the coherent light beam 411 are formed on the recording material 489.
However, conversely, the recording material 4 is first recorded on the interference fringes caused by the coherent convergent light 504 and the coherent light beam 411.
09 is exposed to light, and then interference fringes caused by the coherent divergent light 410 and the coherent light beam 411 are formed on the recording material 409.
Of course, it does not matter if it is recorded.

As described in detail above, according to the present invention, an in-line hologram wavefront conversion element with high optical coupling efficiency between a semiconductor light emitting element and an optical fiber can be manufactured easily and inexpensively.

[Brief explanation of the drawing]

Figure 1 shows an example of the configuration of an optical device conventionally used to manufacture an off-axis type hologram wavefront conversion element. 1 of the shielding plates with the same size gates
An example is shown stereoscopically in Figure 3, which shows an optical arrangement for optically coupling a semiconductor light emitting element and an optical fiber using an ophaxis-type holographic wavefront conversion element made using the optical device shown in Figure 1. FIG. 4 is a diagram showing the configuration of an embodiment of an optical device for performing the first exposure in the method of manufacturing an in-line type hologram wavefront conversion element according to the present invention. FIG. 5 is a diagram illustrating the configuration of two adjacent embodiments of an optical device for performing the first exposure in the in-line hologram wavefront conversion method according to the invention, 1
FIG. 5 is a diagram showing the configuration of an embodiment of an optical device for performing the second fog light in the method for manufacturing an in-line type hologram wavefront conversion element according to the present invention, and FIG.
A diagram showing the configuration of an embodiment of an optical device for recording interference fringes formed by interference between coherent diverging light and coherent converging light reproduced from a hologram produced by the optical device shown in FIGS. FIG. 7 shows an optical arrangement for optically coupling a semiconductor light emitting device and an optical fiber using an in-line type holographic wavefront conversion element manufactured by the manufacturing method according to the present invention. In the figure, 101, 401, 601' are coherent light generators, 102, 402, 602 are coherent light beams, and 103, 483 are beams. Splitter, i04, 05, 404, 405 are reflectors, 106, 406, 501, 603 are inverted telescope type optical systems, 107, 503 are Shins. 108, 411, 502
, 604 is a thick coherent light beam, 109,407
is a shielding plate, 110,488 is open □, 111,409,6
08 is a recording material, 112, 410 is a coherent diverging beam, 113, 504 is a coherent converging beam, 301, 78
1 is a semiconductor light emitting device, 302, 02 is a diverging light, 303
, 703 are hologram wavefront conversion elements, 384 and 704 are convergent lights, 305 and 705 are optical fibers, 4101 is the optical axis of the coherent divergent light 410, 5041 is the optical axis of the coherent convergent light 504, and 605 is the hologram.
607 is the reproduced coherent divergent light, and 607 is the reproduced coherent convergent light. Fukuro' diagram, 2nd figure, hair figure, colored figure, 5th figure, purple figure, hair figure 7

Claims (1)

[Claims] 1 Interference fringes due to interference between the reference light and the coherent diverging light that passes through an aperture that is approximately the same size as the cross section of the light immediately after being emitted from the semiconductor light emitting element and is diffracted by the aperture, and the coherent divergent light and the reference light. Coherent convergent light that travels in the same direction as the coherent diverging light on almost the same optical axis and converges at an arbitrary point behind the recording surface and interference fringes caused by interference with a reference wave having the same properties as the reference wave are recorded in the same way. A hologram is produced by overlapping recording on a material, and interference fringes formed by interference of coherent diverging light and coherent converging light that are simultaneously reproduced from the hologram are recorded on another recording material placed behind the recording material. A method for manufacturing a holographic wavefront conversion element, characterized in that the hologram wavefront conversion element is manufactured by: