JPH0784155A - Method for optically coupling optical element or electro-optic element to each other - Google Patents

Abstract

PURPOSE:To lower optical coupling loss and to improve position adjusting accuracy by disposing a photoreceptor between optical elements or electro-optic elements for transmitting and receiving light signals and forming holograms or transmission holograms on the photoreceptor by irradiation with light from the optical elements. CONSTITUTION:The light emitting elements 2 and the light receiving elements 3 are installed with accuracy of about + or -5mum on a substrate 5 and the photoreceptor 4 is interposed between the light emitting elements 2 and the light receiving elements 3 in order to produce an optical module 1 by optically coupling the light emitting elements 2 and the light receiving elements 3. The photoreceptor 4 is irradiated with the light from the light emitting elements 2 to form optimum fluctuations in refractive index and to form the holograms 6 in such a manner that low-loss coupling is attained. The need for making delicate position adjustment between the light emitting elements 2 and the light receiving elements 3 after formation of the holograms 6 is eliminated if the holograms 6 are formed by this method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element or electro-optical element composed of an optical fiber, a laser diode (LD), a light emitting diode (LED), a photodiode (PD), an optical integrated circuit (OEIC) and the like. The present invention relates to an optical coupling method between optical elements or electro-optical elements that transmit and receive an optical signal via a hologram.

[0002]

2. Description of the Related Art Conventionally, in order to reduce the loss of coupling between a light emitting element and a light receiving element, a focusing lens or a hologram is interposed between the light emitting element and the light receiving element. A method has been performed in which the light emitted from the light source is condensed or the optical path is changed to efficiently guide the light to the light receiving element.

[0003]

However, in the conventional focusing lens or hologram, the coupling lens and the hologram are manufactured so that the coupling position of the light emitting element and the light receiving element is predicted to some extent and the optimum condition is obtained in advance. In order to install it, it is necessary to move the light emitting element and the light receiving element subtly to make the final position adjustment after installing the focusing lens and the member to be the hologram, but the position adjustment requires an order of 1 μm or less. There is a problem that it takes a lot of time and effort to do so. When optically coupling a plurality of light emitting elements and a light receiving element, a focusing lens and a member to be a hologram are installed, and then a combination 1 of each light emitting element and a light receiving element is provided.
It is necessary to perform delicate position adjustment for all of them one by one, or to perform collective adjustment so that the loss is averaged, and an element such as an optical fiber array in which a plurality of optical fibers are integrated is required. There is a problem that it is not possible to adjust the positions of all the elements at once and efficiently.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is a method of optically coupling an optical element for transmitting and receiving an optical signal or an electro-optical element with a hologram interposed therebetween. A hologram is provided on the photoconductor by arranging the photoconductor between the optical elements or the electro-optical elements, and irradiating light from the element or an external optical element.
Alternatively, it is an optical coupling method between optical elements or electro-optical elements for forming a transmission hologram or for arranging a spatial light modulator between the elements and forming a computer-generated hologram (CGH) in the spatial light modulator. .

The photosensitive member is a member that forms a hologram by changing the refractive index by the irradiation of light from the outside. Further, the transmissive hologram refers to a hologram which can form a hologram by irradiation with light from the outside and can transmit the light from the front surface to the back surface. In addition, computer generated holograms (CGH, Computer Genera)
The ted hologram) refers to a hologram that forms a hologram in a spatial modulator such as a liquid crystal whose refractive index can be modulated by inputting a condition from an external computer.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show four embodiments of the present invention, in which the same members are designated by the same reference numerals. Further, the optical module is a module in which a light emitting element and a light receiving element are fixed and integrated. FIG. 1 is a schematic view showing a first embodiment of an optical coupling method of optical elements or electro-optical elements of the present invention, and an optical module 1 comprises a semiconductor laser array in which a large number of semiconductor lasers are integrated. Light emitting element 2, light receiving element 3 formed of an optical fiber array in which a large number of optical fibers are integrated, photoconductor 4 interposed between each light emitting element 2 and light receiving element 3, and light emitting element 2, light receiving element 3, and photoconductor A hologram 5 is formed on the photoconductor 4 by a substrate 5 on which the photoconductor 4 is installed.

In order to manufacture the optical module 1 by optically coupling the light emitting element 2 and the light receiving element 3, ± 5 on the substrate 5 is used.
The light emitting element 2 and the light receiving element 3 are installed with an accuracy of about μm,
A photoconductor 4 is interposed between the light emitting element 2 and the light receiving element 3. Then, the light from the light emitting element 2 may be applied to the photoconductor 4 to form the optimum fluctuation of the refractive index, and the hologram 6 may be formed so as to achieve low loss coupling. Further, in order to form the hologram 6 with lower loss, there is no problem even if the photoconductor 4 is irradiated with light from other than the light emitting element 2, for example,
If the light receiving element 3 is also capable of emitting light, the light may be emitted from the light receiving element 3 or the light may be emitted from an external optical element.

As described above, after the light emitting element 2 and the light receiving element 3 are installed, the photoconductor 4 is irradiated with light under the optimum conditions to form the hologram 6, so that the light emitting element 2 and the light receiving element after the hologram 6 are formed. There is no need to finely adjust the position of the element 3. Further, even if the light emitting elements 2 and the light receiving elements 3 in the form of an array composed of a plurality of optical elements or electro-optical elements are installed as they are, the optical paths between the coupling elements are adjusted simultaneously and independently when the hologram 6 is formed. It is possible,
It is not necessary to perform delicate position adjustment for each individual element, and it is possible to efficiently adjust the position of the arrayed elements collectively.

FIG. 2 is a schematic sectional view showing a second embodiment of an optical coupling method for optical elements or electro-optical elements according to the present invention. As shown in FIG. , An optical fiber fixing part 1 as shown in FIG.
5a and an aspherical lens 15b, a light emitting element 12 and a light receiving element 13 formed by fixing an optical fiber A, an element fixing hole 1
6a, a hologram forming device hole 16b, and a housing 16 having a plate 16c for sealing the portion of the hologram forming device hole 16b. The photoreceptor 16 has a transmission hologram 17 formed inside the housing 16.

Here, the light emitting element 12 transmits the light emitted from the optical fiber A in a spread state until it reaches the aspherical lens 15b, and linearly transmits the light by the aspherical lens 15b. Further, the light receiving element 13 collects the transmitted light by the aspherical lens 15b to collect the transmitted light.
To low loss. In addition, two element fixing holes 16a are provided so as to be located substantially opposite to the center of the housing 16. The photoreceptor 14 is composed of a transparent substrate and a photosensitive material layer, and a transparent hologram 17 is formed on a part thereof.

In order to manufacture the optical module 11 by optically coupling the light emitting element 12 and the light receiving element 13 with each other, as shown in FIG.
As shown in (c), the light emitting element 12 and the light receiving element 13 are installed in the element fixing holes 16a, and the polarizer 18, the transparent substrate 14a, and the transparent substrate 14a on the optical axis between the light emitting element 12 and the light receiving element 13 inside the housing 16. The photosensitive material layer 14b coated on the transparent substrate 14a is placed. Here, the polarizer 18 is provided for receiving the coherent radiation emitted from the light emitting element 12 and converting the coherent radiation into linearly polarized light which is perpendicular to the paper surface.
Further, the photosensitive material layer 14b is such that the intensity of the interference fringes can be recorded therein as a change in the refractive index, and the sensitivity and thickness are sufficient to perform highly efficient diffraction and proper operation within the used spectral region. Use one with resolution. Then, in order to form the transmission hologram 17 on the transparent substrate 14a and the photosensitive material layer 14b, the hologram forming device 19 is inserted through the hologram forming device hole 16b. This hologram forming device 19 includes a light emitting element 12 and a light receiving element 13.
A half mirror 19a tilted by 45 ° on the optical axis between
It is composed of a Faraday rotator 19b and a total reflection mirror 19c that are perpendicular to the optical axis, and a tubular permanent magnet 19d that encloses the Faraday rotator 19b and the total reflection mirror 19c. The Faraday rotator 19c has a plane of polarization which is rotated by a predetermined angle when linearly polarized light is propagated in the direction of the magnetic field. In the present embodiment, the Faraday rotator 19c has a rotation angle of 45 °.

Here, the process of forming the transmission hologram 17 will be described. Hereafter, the direction from the light emitting element 12 to the light receiving element 13 is the forward direction, and the direction from the light receiving element 13 to the light emitting element 12 is the reverse direction. First, the coherent wavefront emitted from the light emitting element 12 passes through the polarizer 18 to become linearly polarized light which is perpendicular to the paper surface, and after passing through the photosensitive material layer 14b and the transparent substrate 14a, the optical path is vertically bent by the half mirror 19a. When it is bent and passes through the Faraday rotator 19b, the polarization plane is rotated by 45 ° to reach the reflection mirror 19c, and after being reflected by the reflection mirror 19c, the polarization plane is further rotated by 45 ° through the Faraday rotator 19b. In order to
Light incident on the transparent substrate 14a and the photosensitive material layer 14b in the state of being rotated by 90 ° from the plane of polarization in the forward direction, that is, in the state of linearly polarized light parallel to the paper surface is used as reference light. Further, the coherent wave in a state parallel to the paper surface emitted from the light receiving element 13 passes through the half mirror 19a and enters the transparent substrate 14a and the photosensitive material layer 14b as object light. The interference fringes that cause the fluctuation of the refractive index are formed only in the same polarization direction, so that the light emitting element 12
The interference fringes cannot be formed between the light in the forward direction and the object light, but since the reference light and the object light have the same polarization direction, it is possible to form the interference fringes. The transmission hologram 17 can be formed by the object light.

A fiber collimator may be used instead of the aspherical lens 15b. Further, when the distance is such that it is not necessary to prevent the light from spreading, the optical fiber A is directly connected to the light emitting element 12. It may be used as the light receiving element 13. Also, instead of the Faraday rotator 19b, 1 /
There is no problem even if a four-wave plate is used.

As described above, by forming the interference fringes by the reference light and the object light, the light emitted from the light emitting element 12 passes through the transmission hologram 17, and then follows the same optical path as the object light to receive the light receiving element. Since it is incident on 13, the coupling is low loss. In addition, the transmission hologram 17
By using, it is possible to install the light emitting element 12 and the light receiving element 13 in a positional relationship that substantially opposes the central portion of the housing 16, and the optical module 11 can be downsized.

FIG. 3 is a schematic cross-sectional view showing a third embodiment of the optical coupling method for optical elements or electro-optical elements of the present invention. The optical module 21 has one light emitting element 22. On the other hand, two light receiving elements 23a and 23b are installed. In this way, it is possible to couple one light emitting element with a plurality of light receiving elements or couple one light receiving element with a plurality of light emitting elements with low loss.

In order to form the transmission type hologram 27 corresponding to the optical module 21 as shown in FIG. 3, first, the light emitting element 22 and the light receiving element 23a are used, and interference is caused at the wavelength λ1 in the same manner as in the second embodiment. The stripes are formed, and then the light emitting element 22 is formed.
And the light receiving element 23b are used to form interference fringes at the wavelength λ2. When the transmission hologram 27 is formed on the photoconductor 24 in this manner, the optical signal of the wavelength λ1 is received by the light receiving element 23a.
, And the optical signal of wavelength λ2 is combined with the light receiving element 23b, so that the transmission hologram 27 can have a function as a wavelength demultiplexer and can be used for wavelength division multiplexing communication.

FIG. 4 is a schematic diagram showing a fourth embodiment of the optical coupling method for optical elements or electro-optical elements according to the present invention, which is a hologram in which a light emitting element and a light receiving element are coupled with low loss. The case where a computer generated hologram (CGH) is formed in order to form First, FIG.
As shown in (a), a light emitting element 3 made of a semiconductor laser
2 and the light receiving element 33 formed of an optical fiber are aligned and fixed with an accuracy of about ± 5 μm, and an optical spatial modulator 38 capable of forming a hologram by an external computer 37 is provided between the light emitting element 32 and the light receiving element 33. A monitor 39 capable of observing the coupling efficiency with the light emitting element 32 is connected to the light receiving element 33, and light is emitted from the light emitting element 32 or an optical element (not shown) from the outside to the spatial light modulator 38. The conditions for forming the fluctuation of the refractive index are inputted to the spatial light modulator 38 by the monitor 39 and the computer 37 so that the optical path with a low loss is formed, and the computer generated hologram 40 is formed.
Next, as shown in FIG. 4B, a self-developing photoconductor 34 capable of recording a volume phase hologram is brought into close contact with the formed computer-generated hologram 40, and the ultraviolet or natural light source 41 is computer-synthesized. Irradiation is performed from the hologram 40 side, and the hologram shape formed on the computer-generated hologram 40 is transferred to the photoconductor 34 to form the hologram 36 on the photoconductor 34. Then, as shown in FIG. 4C, by installing the photoconductor 34 having the hologram 36 formed in the place where the optical spatial modulator 38 was installed, the optical module 31 with low loss coupling can be obtained. Can be obtained.

The difference in thickness between the optical spatial modulator 38 and the photoconductor 34, the phase delay of the optical fiber, and the like are considered as conditions for forming the computer-generated hologram 40 in the computer 37, so that the It is possible to form the hologram 36 that results in lossless coupling. Also, without transferring to the photoconductor 34,
The spatial light modulator 38 may be installed as it is. In this case, it is possible to combine a large number of light emitting elements 32 and light receiving elements 33 by giving the computer generated hologram 40 a lens effect to focus light or add a deflection function.

In the above embodiment, as the coupling between the light emitting element 32 and the light receiving element 33, only the coupling between the semiconductor laser and the optical fiber or the coupling between the optical fibers has been described.
The optical coupling between other optical elements or electro-optical elements can be similarly performed.

[0020]

As described above, according to the optical coupling method of the optical element or the electro-optical element of the present invention, the photoconductor is arranged between the optical element or the electro-optical element, and the element or the external optical element is provided. By irradiating light from the above, a hologram or a transmission hologram is formed on the photoconductor, or an optical spatial modulator is arranged between the elements and a computer-generated hologram (CGH) is formed on the optical spatial modulator. After the optical element or the electro-optical element is installed and the hologram is formed, there is no need to make a fine position adjustment of the optical element or the electro-optical element. In addition, an array-shaped element composed of a plurality of optical elements or electro-optical elements can be easily made into a low-loss optical coupling with respect to all the optical elements or electro-optical elements. .

[Brief description of drawings]

FIG. 1 is a schematic view showing a first embodiment of an optical coupling method for optical elements or electro-optical elements of the present invention.

FIG. 2 is a schematic cross-sectional view showing a second embodiment of an optical coupling method for optical elements or electro-optical elements of the present invention.

FIG. 3 is a schematic cross-sectional view showing a third embodiment of the optical coupling method for optical elements or electro-optical elements of the present invention.

FIG. 4 is a schematic view showing a fourth embodiment of the optical coupling method of optical elements or electro-optical elements of the present invention.

[Explanation of symbols]

 1, 11, 21, 31: Optical module 2, 12, 22, 32: Light emitting element 3, 13, 23a, 23b, 33: Light receiving element 4, 14, 24, 34: Photoconductor 5: Substrate 6, 36: Hologram 14a: Transparent substrate 14b: Photosensitive material layer 15a: Optical fiber fixing part 15b: Aspherical lens 16: Housing 16a: Element fixing hole 16b: Hologram forming device hole 16c: Plate 17, 27: Transmission hologram 18: Polarizer 19: Hologram forming device 19a: Half mirror 19b: Faraday rotator 19c: Total reflection mirror 19d: Permanent magnet 37: Computer 38: Optical spatial modulator 39: Monitor 40: Computer-generated hologram 41: Ultraviolet or natural light source A: Optical fiber

Claims (3)

[Claims] 1. A method of optically coupling an optical element or an electro-optical element for transmitting and receiving an optical signal with a hologram interposed therebetween, wherein a photoconductor is disposed between the elements, and the element or an external optical element. An optical coupling method between optical elements or electro-optical elements, characterized in that a hologram is formed on the photoconductor by irradiating light from the optical element. 2. The method of optically coupling by interposing a hologram between an optical element or an electro-optical element for transmitting and receiving an optical signal, wherein the hologram is a transmission type hologram. Optical coupling method between optical elements or electro-optical elements of. 3. A method of optically coupling by interposing a hologram between optical elements or electro-optical elements for transmitting and receiving optical signals, wherein an optical spatial modulator is provided between the elements,
By irradiation with light from the element or an external optical element, a computer generated hologram (CG
H) is formed, which is an optical coupling method between optical elements or electro-optical elements.