JPS62119992A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To obtain a required polarization mode by a small apparatus which is easy to assemble by a method wherein a structural anisotropic medium, composed of alternately laminated media with different specific inductive capacities, is provided at the emitting end surface or in the waveguide region of a semiconductor laser. CONSTITUTION:A structural anisotropic medium 7 is formed by arranging medium 1 and medium 2 which have specific inductive capacities different from each other alternately at the emitting end surface of or inside a semiconductor laser (LD). The boundary surfaces 8 between the media 1 and 2 are inclined to have an angle of 45 deg. relative to the junction surface of the LD. With this constitution, the laser oscillation is induced by using the boundary surface between the LD and the medium 7 as a reflective surface of a resonator and the output light is oscillated with a polarization mode which is determined by the thickness T of the medium 7, the widths t1 and t2 of the media 1 and 2. Therefore, by selecting those parameters, a required polarization mode can be obtained and an optical system can be assembled easily in a small size. Moreover, by providing the media 7 on both ends of the LD, clockwise or counterclockwise circular polarization can be obtained.

Description

[Detailed Description of the Invention] [Summary] A structurally anisotropic medium made by alternately laminating media with different dielectric constants is provided in the optical path of a semiconductor laser, and laser light is output through the structurally anisotropic medium. This makes it possible to integrate the polarization function with the semiconductor laser.

゛ [Industrial Application Field] Semiconductor lasers usually oscillate only with TE polarization, but when using the output light for homodyne or heterodyne measurements, it is better if the output light is circularly polarized light or dual polarized light of TE and TM. Often advantageous. The present invention relates to a semiconductor laser capable of extracting circularly polarized light, TE polarized light, TM polarized light, etc. as output light in response to such uses.

[Conventional technology]

Since semiconductor lasers only generate TE polarized light, the
174 wavelength plate 3 in front of the semiconductor laser LD as shown in b).
As shown in (b), a 172 wavelength plate 4 is placed in front of the semiconductor laser LD to generate TM polarized light.

The 1/4 wavelength plate 3 and the 1/2 wavelength plate 4 are made by polishing crystal or other birefringent material.

The actual arrangement of the wave plates is as shown in FIG.

That is, in front of the semiconductor laser LD, a lens 51, a wavelength plate 3 or 4, a lens 52, a light receiving optical fiber 6, etc. are arranged in this order. In this polarization plane control means using a wave plate, the wave plate 3.4 must be placed in a space, so there is a drawback that it requires a large space, and it is difficult to align the optical system. There are problems such as increased thickness and angle errors.

As a small device capable of solving these problems, Japanese Patent Application Laid-Open No. 104609/1983 proposes the use of a structurally anisotropic medium. FIG. 8 is a perspective view illustrating the principle of a structurally anisotropic medium. 1 is a medium with a dielectric constant of 61, and 2 is a medium with a dielectric constant of 82. In this way, two types of media 1 and 2 having different dielectric constants are arranged alternately.

t is the thickness of medium 1, and tz is the thickness of medium 2, which are each sufficiently smaller than the optical wavelength λ.

Now, when the light 7 propagates in the X or y direction, the effective permittivity in the Xy plane is εI-CttGt +tzEz)/(tt (-tz
) Also, the effective permittivity in the z-axis direction is EL -Ctt +f, z)εt';-z/(de f
+ tzF"t), and Qtt -EL-fttzcGt -Qz>7CttE
z + b9t) (ft + f-z), resulting in a propagation shift between the orthogonal polarization components of the light.

This is the same effect as when light passes through a birefringent material. Therefore, by placing this structurally anisotropic medium between the lens 51 and the optical fiber 6 in FIG. 7, the plane of polarization can be controlled.

[Problem that the invention seeks to solve]

However, even if the polarization plane control element can be miniaturized in this way,
If they are arranged in space, the effect of reducing the size of the device as a whole is small, and since it is difficult to adjust the position and orientation of the polarization plane control element, the assembly of the entire device remains complicated. Accordingly, the present invention aims to facilitate the assembly of an optical system and reduce the installation space of the device by directly forming a film of this structurally anisotropic medium on a semiconductor laser.

[Means for solving problems]

FIG. 1 is a perspective view illustrating the basic principle of a semiconductor laser device according to the present invention. LD is a semiconductor laser, and a structurally anisotropic medium 7 is placed in its optical path. The structurally anisotropic medium 7 has a structure in which media 1 and 2 having different dielectric constants are alternately arranged. The boundary surface 8 between adjacent media 1.2 is formed at an angle of 45 degrees with respect to the junction surface 9 of the semiconductor laser LD.

The structurally anisotropic medium 7 may be arranged not at the emission end facet of the semiconductor laser LD but in the waveguide region inside the semiconductor laser LD.

[Effect]

In the case of the present invention, the semiconductor laser LD includes a structurally anisotropic medium 7
oscillates with the boundary surface as the reflection surface of the resonator. The output light 10 from the structurally anisotropic medium 7 is
It oscillates in the polarization mode determined by −ε. That is, if (ε〃-ε,L)・T=(2m+1), then the output light is circularly polarized λ (ε〃−ε)・T=2rn−4, then the output light is linearly polarized.

Therefore, when manufacturing a semiconductor laser, the medium 1.
By selecting the thickness T of 2 and the film thicknesses t1 and tz of each medium 1.2, a desired polarization mode can be obtained.

〔Example〕

Next, examples will be used to explain how the semiconductor laser device according to the present invention is actually implemented. FIG. 2 is a perspective view showing a first embodiment of the present invention, and FIG. 3 is a diagram showing a method of manufacturing a semiconductor laser device of the same embodiment. In FIG. 2, the structurally anisotropic medium 7 is formed on the end face of the semiconductor laser LD. In order to manufacture such a semiconductor laser device, the thickness T of the structurally anisotropic medium 7 must be adjusted as shown in FIG.
A step 11 corresponding to the above is formed on the output end surface 2 of the semiconductor laser LD, and a first step is formed on the output end surface 12 as shown in (b).
The medium 1 is laminated by vapor deposition or the like to fill the stepped portion 11.

Then, as shown in (c), a plurality of grooves 13 are formed in the medium 1 at regular intervals in a direction 45 degrees from the bonding surface 9 by a method such as etching. The intervals between the grooves 13... are equal to the width of the first medium 1 in FIG. 2, the width of the grooves 13... is equal to the width of the second medium 2, and then A structurally anisotropic medium 7 as shown in FIG. 2 is obtained by depositing the second medium 2 on the substrate to obtain the structure (d), and then polishing the end face.

For example, by using a vapor deposition method with excellent directivity, such as an ionization vapor deposition method that uses a magnetic lens to deflect and focus, the second
It is also possible to perform the vapor deposition in the direction of the arrow al shown in FIG. At this time, it is necessary to deposit the first medium 1 and the second medium alternately.

FIG. 4 is a plan view showing a second embodiment of the present invention, in which a structurally anisotropic medium is provided inside a semiconductor laser. In this case, after digging a groove in which to embed the structurally anisotropic medium 7 by etching or the like, media 1 and 2 are alternately deposited in the force direction indicated by the arrow a shown in FIG. 3(a). Created with. This method is performed using a vapor deposition method with excellent directivity.

In this device, the width T of the structurally anisotropic medium t7 is determined by the width of the groove formed in advance, so by controlling the medium thicknesses t2 and t2, εl−εヱ can be changed to obtain the desired value. Polarization mode is obtained. Note that polarized light is obtained from the output end face 14 where the structurally anisotropic medium 7 is disposed, but from the output end face 15 that does not have the structurally anisotropic medium 1t7, TE mode laser light that does not receive polarization is obtained. Emits light.

By providing the structurally anisotropic medium 7 at a position in front of the emission end face 14 at the end of the semiconductor laser LD in this manner, there is no need to utilize the emission end face. Therefore, the structurally anisotropic medium can be formed all at once before the output end face is formed by cleaving the semiconductor laser device, so that work efficiency is excellent and the surface precision of the output end face can be maintained by cleaving.

FIG. 5 shows a third embodiment of the present invention, in which the structurally anisotropic medium inside the output end face as shown in FIG. 4 is arranged on both end sides as 71 and 72. In this case, the structurally anisotropic media 171 and 72 on both sides are provided so that the propagation difference between them is 1/4 wavelength, and the reflectance of the end faces 14.15 is increased by coating, so that the resonance of the laser is If this occurs, the laser output light will become two circularly polarized lights in the left and right directions.

Note that the external dimensions of the semiconductor laser LD are approximately 100 μm, and the waveguide region at the junction surface is as small as approximately 5 μm.
It is sufficient that the structurally anisotropic medium 7, 71, 72 is also provided in a small area that can cover this joint surface.

〔Effect of the invention〕

As described above, according to the present invention, at the end of the semiconductor laser LD, the structurally anisotropic medium is provided in a layered structure in the waveguide region at the output end face or in front of the output end face. Therefore, since the structural anisotropic medium for controlling the polarization plane of the emitted light from the semiconductor laser is integrated with the semiconductor laser LD, there is no need for troublesome work such as adjusting the position of the wave plate, and optical Assembling the system becomes easier. Also, by integrating the structurally anisotropic medium, the objective lens 5 in FIG.
2 is unnecessary, so the device can be made smaller.

[Brief explanation of drawings]

゛ Fig. 1 is a perspective view explaining the basic principle of a semiconductor laser device according to the present invention, Fig. 2 is a perspective view showing a first embodiment of the invention, and Fig. 3 shows a method for manufacturing the device of the same embodiment. 4 is a plan view showing a second embodiment of the present invention, FIG. 5 is a plan view showing a third embodiment of the present invention, and FIG. 6 is a side view showing a polarization method using a conventional wave plate. FIG. 7 is a side view showing the arrangement of the wave plate, and FIG. 8 is a perspective view showing the action of the structurally anisotropic medium. In the figure, 1.2 is a medium, LD is a semiconductor laser, 7 is a structurally anisotropic medium, 8 is an interface between media with different dielectric constants, and 9
10 indicates the bonding surface, and 10 indicates the output light. Patent Applicant: Fujitsu Limited Agent, Patent Attorney Minoru Aoyagi Figure 1 1 Ett Branch & Examples Figure 2 LD 3 Good Examples Figure 5 Figure 6 Figure 7 Figure 8

Claims (4)

[Claims] (1) In the optical path at or near the output end face of the semiconductor laser (LD), the boundary face (8) between adjacent media forms an angle of 45 degrees with respect to the junction face (9) of the semiconductor laser. A semiconductor laser device characterized in that a structurally anisotropic medium (7) in which media (1) and (2) having different dielectric constants are alternately laminated is provided as means for controlling the polarization plane of light emitted from a semiconductor laser. (2) A semiconductor laser device according to claim (1), characterized in that the structurally anisotropic medium (7) is provided on the emission end face of the semiconductor laser. (3) A semiconductor laser device characterized in that the structurally anisotropic medium (7) is disposed in a waveguide region within the semiconductor laser in front of the emission end facet. (4) The above-mentioned structurally anisotropic medium is formed on both sides of the semiconductor laser, and has a thickness that causes a phase shift of 1/4 wavelength, so that the oscillation output light is circularly polarized in the right and left directions. Claim No. (3) is characterized in that the structure is as follows.
The semiconductor laser device described in .