JPH03132619A - Semiconductor laser device and its manufacture - Google Patents

Abstract

PURPOSE:To eliminate return light and to prevent a noise occurring by mounting a light absorber on a surface irradiated with light except for a coupling lens. CONSTITUTION:Most of the light emitted from a semiconductor laser 1 is converged on the coupling lens 2, however, the light emitted at an angle larger than the diameter of the lens 2 is reflected on a lens supporting tool 20 which fixes the lens 2, and goes to the return light of the semiconductor laser 1. To prevent such light occurring, light absorbing resin 9 which absorbs unrequired light is applied in the periphery of the coupling lens 2 of the lens supporting tool 20. Thereby, it is possible to disturb the light out of emitting light from the semiconductor laser 1 reflected on a part that is not a regular path and going to the return light to the samiconductor laser, and to prevent the noise occurring, and also, to reduce a distortion component.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a semiconductor laser device used as a light source for optical signal transmission in optical communication or optical measurement.

BACKGROUND OF THE INVENTION A conventional semiconductor laser device has a configuration as shown in FIG. 4, for example, as shown in IEICE Semiconductor and Materials Division National Encyclopedia No. 319, 1986. In other words, the plate has a coupling system in which the light emitted from the semiconductor laser 3° is converted into diffused light close to parallel light by the second lens 31, and is condensed to the optical fiber 37 by the second lens 32. Furthermore, the second lens 31 and the second Between the lens 32 and the polarizer 33
, an optical isolator composed of an analyzer 34, a magneto-optic crystal 35, and a magnet 36 is arranged. This means that it will not return to .

Each surface of each optical component through which the semiconductor laser light passes is coated with a non-reflective coating to prevent reflected light from occurring. Furthermore, the entire optical system ζ is constructed on a thermoelectric cooling element 38 and is kept at a constant temperature without being affected by the outside temperature.

However, in such a configuration, the light emitted from the second lens 31 is a diffused light close to parallel light, and if the distance between the second lens 31 and the second lens 32 is increased, the second lens 32
This makes it difficult to condense all the light onto the optical fiber 37, causing deterioration in coupling efficiency. This is particularly noticeable when attempting to install a plurality of optical isolators between lenses. In addition, in the case of a semiconductor laser that generally uses a lens with a small diameter and has a large divergence angle, a portion of the emitted light is diffusely reflected by the microscopic irregularities 60 inside the support, as shown in Figure 5, and the light beam path is 51a and the semiconductor laser 30 through a path such as ray path 52b.
You will end up going back to . In addition, since the polarizer 33ζ which constitutes the optical isolator bends the traveling direction of the light in orthogonal polarization directions by 90 degrees and emits it to the magnet 36 side, the light is reflected from the side of the polarizer 33. The emitted light efficiently returns to the semiconductor laser 30 along a nearly parallel beam path 53c.

When the returning light enters the semiconductor laser in this way, not only does the semiconductor laser itself generate noise, but also distortion components increase. This is especially a problem in analog transmission systems that transmit signals depending on the strength of the light.

In addition, when assembling a semiconductor laser device, conventionally, an optical isolator was assembled by sequentially adjusting the angle and position of the polarizer 33, analyzer 34, magneto-optic crystal 35, and magnet 36, but this required a large number of assembly steps and resulted in an increase in manufacturing costs. Means for Solving Nine Problems Contributing to the Invention The present invention (friends) In order to solve the above problems, the first means is to provide polarized light constituting a support around a lens into which light emitted from a semiconductor laser enters and an optical isolator. The side surfaces of the laser beam are covered with a material that has a shielding effect (to prevent light from returning to the semiconductor laser).As a second means, the present invention also uses a polarizer to minimize transmission loss and return light. , Analyzer, Magneto-Optical Crystal A method is provided in which magnets are assembled as an optical isolator and the optical isolator is temporarily fixed using the attractive force of the optical isolator's own magnet.

Effects According to the above-described first means of the present invention, it is possible to prevent the emitted light from the semiconductor laser from being reflected by a portion other than the original path and returning to the semiconductor laser. By covering the lens with a material that absorbs the light that cannot enter the lens (for example, by covering it with a material that absorbs the light so that it is not reflected by the support for fixing the lens), it is possible to prevent the light from returning.In addition, an optical isolator is ideal. Components of light whose direction is bent by 90 degrees by the polarizer due to the structure of the polarizer (i. It becomes possible.

Further, according to the second method described above, the optical isolator is assembled in advance so that the isolation ratio is at the maximum and the reflected light is at the minimum. By doing this, it is only necessary to adjust the approximate position and angle of the installation between the semiconductor laser and the optical fiber. Furthermore, by using a material containing iron or the like for the support for attaching the optical isolator, the optical isolator can be temporarily fixed by the magnetic force of the magnets that constitute the optical isolator.

Embodiment An embodiment of the present invention, as shown in FIG. A polarizer 3, an analyzer 4, a magneto-optic crystal 5
, and a magnet 6, and efficiently enters the optical fiber 7, which is obliquely polished so that the reflected light does not return to the semiconductor laser 1. The semiconductor laser 1 is mounted on a thermoelectric cooling element 8 so that its temperature can be controlled. Most of the light emitted from the semiconductor laser l is focused by the ζ-table coupling lens (the light emitted at an angle larger than the diameter of the lens is focused by the lens support 2 that fixes the lens).
0 and becomes the return light of the semiconductor laser 1. To prevent this, a light-absorbing resin 9 that absorbs unnecessary light is applied around the coupling lens 2 of the lens support 20.

Furthermore, the light incident on the optical isolator is such that the TE mode light, which is parallel to the active layer of the semiconductor laser 1, is transmitted through the polarizer 3.The TM mode light whose polarization plane differs by 90 degrees and the optical isolator are generated due to angular misalignment. A part of the light in the TE mode (Table) The direction of light is bent by 90 degrees by the polarizer and travels to the side of the polarizer 3. The applied force (adhesive etc. used to fix the polarizer 3) eliminates the effect of the frosted glass processing and reflects the light.The reflected light is again bent in its traveling direction by the polarizer 3 and is emitted by the semiconductor laser. 1 (ray path 53c in Figure 5).Therefore, as shown in Figures 1 and 2, a light absorbing resin 1 is placed on the side of the polarizer 3.
By fixing the optical isolator using 0, reflection on the side surface of the polarizer 3 can be suppressed, and the amount of light returning to the semiconductor laser 1 can be reduced. This is particularly true for analog AM systems, such as analog RF multiplexed optical transmission systems, where second and third harmonic distortion due to the influence of reflected light appears conspicuously in the deterioration of the characteristics of the transmitted signal.
This is effective in optical transmission systems that employ modulation.

Next The optical isolator is manufactured in advance using a predetermined method to maximize the isolation ratio and minimize the reflected light.

Assembling procedure (as shown in Figure 3 (a, d), the polarizer 3
is fixed in a polarizer holder 51 via a light absorption layer 10. Further, a magneto-optical crystal 5 fixed in the cylinder of a cylindrical samarium cobalt magnet 6 is attached to a polarizer holder 51.
(b). Thereafter, the analyzer 4 is fixed in the analyzer holder 52 and fixed while adjusting its rotation so that the backlight 55 is minimized (c, e). At this time, front light 5
By measuring 6, you can measure the transmission loss of the optical isolator.
The ratio between the forward light 56 and the backlight 55 is the isolation ratio. In this way, an optical isolator with clear characteristics such as isolation ratio can be fixed by simply adjusting the angle to match the dove wave front of the emitted light from the semiconductor laser so that the loss in the forward direction is minimized (f).

A semiconductor laser device with a built-in optical isolator that is easy to manufacture and of high quality can be realized.

Furthermore, if the optical isolator (prepared in this way) has an overall cylindrical shape and a recess 22 is formed in the case 21 made of magnetic material as shown in FIG. The optical isolator can be temporarily fixed by the magnetic force of the optical isolator's own magnet while aligned with the recess 22 by the magnetic force of the magnet 6 of the isolator, and the angle can be adjusted in this state. Since the magnetic flux No. 6 forms a closed magnetic path, the effect of the optical isolator is not affected by the magnetic field caused by disturbance from outside the case, and a semiconductor laser device with stable characteristics can be manufactured.

Effects of the Invention According to the present invention, as described above, it is possible to prevent the emitted light from the semiconductor laser from being reflected by a part other than the original path and returning to the semiconductor laser as light. 9 by polarizer
The component of light bent in the 0 degree direction (l, %) is absorbed by the light-shielding absorption layer applied to the side surface of the polarizer itself and does not return to the semiconductor laser. A portion of the emitted light is reflected by the lens support and passes through the semiconductor laser. No more going back to lasers,
Not only can the generation of noise be prevented, but also distortion components can be reduced.

This is particularly effective in analog RF multiplexed optical transmission in which signals are transmitted depending on the strength of light. Also, assemble the optical isolator in advance so that the isolation ratio is maximized and reflected light is minimized. By doing so, it is only necessary to adjust the approximate position and angle of the installation between the semiconductor laser and the optical fiber, reducing assembly man-hours and greatly reducing manufacturing costs. This arrangement greatly contributes to the easy realization of a high-performance semiconductor laser device according to the present invention (i).

[Brief explanation of the drawing]

First factor Figure 2 (friend) is a cross-sectional configuration diagram of a laser device according to an embodiment of the present invention. Figure 1 is a 90-degree side view of Figure 2. (a), (b), and (c) are cross sections @ (d
), (e) are the same as (a), (b). (c) Side dish Fourth factor FIG. 6 is a configuration diagram of the conventional semiconductor laser device with a built-in optical isolator shown in FIG. 5. l...Semiconductor laser beam 2...Coupling lens, 3.
...Polarizer, 4...Analyzer, 5...Magneto-optical detector
6. ・Magnet 7... Optical fiber 9, 10... Light absorption partner 1

Claims (5)

[Claims] (1) A coupling lens is disposed between a semiconductor laser and an optical fiber, the light emitted from the semiconductor laser is incident on the coupling lens, the light emitted from the coupling lens is made into a focused light, and the focused light is A semiconductor laser device characterized in that, in an optical system that guides light to an optical fiber, a light absorbing material is attached to a surface exposed to light outside the coupling lens. (2) A light absorbing material is attached to a support for fixing the coupling lens and a peripheral portion of the support that is exposed to the emitted light from the semiconductor laser, so that a part of the emitted light is absorbed. A semiconductor laser device according to claim 1 (3) An optical isolator is installed between the coupling lens and the optical fiber, and a light absorbing material is attached to the parts of the optical isolator that are exposed to the output light of the semiconductor laser around the polarizer. A semiconductor laser device according to claim 1, which is formed by absorbing a part of emitted light. (4) A coupling lens and an optical isolator are disposed in a case between the semiconductor laser and the optical fiber, and the light emitted from the semiconductor laser is incident on the coupling lens, and the light emitted from the coupling lens is When manufacturing a semiconductor laser device having the optical isolator configured with a polarizer, an analyzer, a magneto-optic crystal, and a magnet on the optical axis of an optical system that converts the focused light into a focused light and guides the focused light to the optical fiber, the polarized light is The analyzer, the magneto-optical crystal, and the magnet are assembled in advance so that the isolation ratio is maximum and the amount of return light is minimized, and the case is made of a magnetic material, and the case is made of a magnetic material. The optical isolator is attracted into the case by its own magnet, temporarily fixed on the optical axis, and rotated to adjust the angle in the wave plane direction of the emitted light of the semiconductor laser. 4. A method of manufacturing a semiconductor laser device according to claim 3, wherein the semiconductor laser device is fixed to a case. (5) The semiconductor laser device according to claim 4, wherein the magnetic flux of the magnet forming the optical isolator forms a closed magnetic path using a ferromagnetic case.