JPS6384185A - Semiconductor laser module with optical isolator - Google Patents

Abstract

PURPOSE:To form a highly reliable, stable power source, by using a magnetooptic crystal for the material of the light emitting window of an airtight sealing cap, and arranging the end surface of the crystal at a specified slant angle with respect to the emitting light from a semiconductor laser element. CONSTITUTION:The end surface of a magnetooptic crystal 5 is arranged at a specified slant angle with respect to emitting light from a semiconductor laser element 1. The emitting light from the element 1 is emitted through the light emitting window of a cap 11. Thereafter, the light is coupled with optical fiber 7 through a lens 2 and an analyzer 6. As reflected returning light to the element 1, only the light reflected at the end surface of the magnetooptic crystal 5, which is used for the material of the window, on the side of the semiconductor element is considered. Then the reflected returning light can be made very little. Only the light having the extinction ratio of the magnetooptic element of, e.g., -40 dB, is returned to the element 1, with respect to the light, which is reflected by optical parts such as the lens and the like that are located at points further than the crystal 5 from the element 1. Since a semiconductor laser module having an optical isolator is sealed in an airtight manner in this way, high reliability is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a semiconductor laser module with an optical isolator used as a light source for optical communication, optical measurement, optical recording, etc.

2. Description of the Related Art A conventional semiconductor laser module with an optical inulator is disclosed in Japanese Patent Application Laid-Open No. 132925/1983. As shown in FIG.
After the light is focused by the polarizer 4. It passed through a magneto-optic crystal 5 and an analyzer 6 and was coupled to an optical fiber 7. Also, 1981 IEICE General National Conference 2322
The semiconductor laser module with an optical isolator announced in 2003 used a magneto-optic crystal that was processed into a spherical shape and had a lens function.

In addition, in conventional semiconductor laser devices, in order to prevent end face deterioration, N
It was used in an airtight seal with two gases.

Problems to be Solved by the Invention Optical isolators are intended to prevent reflected light from the ends of optical components, connectors, etc. after passing through the magneto-optic crystal from returning to the semiconductor laser element. If there is an optical component such as a lens closer to the semiconductor laser element than the optical crystal, near-end reflection from the end face of the optical component may return to the semiconductor laser element, causing noise in the semiconductor laser element and deteriorating the oscillation characteristics. there were. Furthermore, in order to maintain high reliability, semiconductor laser devices are generally filled with N2 gas and hermetically sealed, so even if the magneto-optic crystal has a lens function, the hermetic seal on the side of the semiconductor laser device is The reflected light from both the front and back end faces of the light exit window of the cap returns to the semiconductor laser probe, causing noise.
The custom-made transmission sometimes deteriorated.

Means for Solving the Problems The present invention solves the above problems and solves the above problems by minimizing the near-end reflected return light to the semiconductor laser device, in which the light emitted from the light emitting end of the semiconductor laser device first enters the magneto-optic crystal. A semiconductor laser module with an optical isolator is obtained.

Function: If the LD module with optical isolator of the present invention is used,
Since the light emitted from the semiconductor laser element first enters the magneto-optic crystal, the light reflected from the end face of the optical component after passing through the magneto-optic crystal does not return to the semiconductor laser element. With this configuration, the reflected light that returns to the semiconductor laser element is only from the end face of the magneto-optic crystal on the semiconductor laser element side, and according to the present invention,
Since the end face of the magneto-optic crystal is inclined with respect to the light emitted from the semiconductor laser element, the light reflected from the end face does not return to the semiconductor laser. Therefore, a module with low noise and good oscillation characteristics can be obtained. Furthermore, since the semiconductor laser element is hermetically sealed, the reliability of the semiconductor laser element is also high.

Embodiment A block diagram of an embodiment of the present invention is shown in FIG. The magneto-optic crystal 6 is used as the window material for the light exit window of the hermetic sealing cap 11, and the end face of the magneto-optic crystal 6 is inclined by 8 degrees with respect to the light emitted from the semiconductor laser element 1. The emitted light from the semiconductor laser element 1 is emitted from the light exit window of the cap 11, passes through the lens 2 and the analyzer 6, and is coupled to the optical fiber.

If the semiconductor laser module with optical isolator of this example is used, the reflected light returning to the semiconductor laser element will be:
It is only necessary to consider the reflected light at the end face of the magneto-optic crystal 5 used as the window material on the semiconductor laser element side, and (BiLuGd)5Fe50,2 with a refractive index of 2.3 is used as the magneto-optic crystal.
When using an anti-reflection film, if the distance between the semiconductor laser element and the window end face is approximately 100 μm, the reflected return light will be -110 dB, and if an anti-reflection film is further applied, the distance between the semiconductor laser element and the window end face will be -1110 dB. Even when the distances were the same, the reflected return light was -125 dB, which was a very small value.

In reality, the distance between the semiconductor laser element and the window end face is much longer, about 30,071 m, so the reflected return light was a negligible value. The reflected light from an optical component such as a lens which is located farther from the semiconductor laser element 1 than the magneto-optic crystal 6 returns to the semiconductor laser element only at an extinction ratio of -40 dB of the magneto-optic element. Furthermore, since the semiconductor laser module with optical inulator of this embodiment is hermetically sealed, high reliability can be obtained.

Therefore, according to this example, a highly reliable and stable light source with very little noise due to reflected return light was obtained.

Note that the present invention does not only refer to a case where a magneto-optic crystal is used as the window material of the hermetic sealing cap as shown in this embodiment, but also to a case where the emitted light from a semiconductor laser element first enters the magneto-optic crystal. Any configuration may be used as long as it does so. Further, the magneto-optic crystal may be made of any material and may have any shape, and may form a waveguide, for example.

Effects of the Invention According to the present invention, a highly reliable and stable light source with very little noise due to reflected return light was obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a semiconductor laser module with an optical isolator according to an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional module. DESCRIPTION OF SYMBOLS 1... Semiconductor laser element, 2... Lens, 5... Magneto-optic crystal, 7... Optical fiber.

Claims (3)

[Claims] (1) A semiconductor laser module with an optical isolator, characterized in that light emitted from a light emitting end of a semiconductor laser element first enters a magneto-optic crystal. (2) A semiconductor laser module with an optical isolator according to claim 1, wherein the semiconductor laser element is hermetically sealed. (3) A semiconductor laser module with an optical isolator according to claim 1, wherein the entrance surface of the magneto-optic crystal is arranged at an angle with respect to the light emitted from the semiconductor laser element.