JPS58153388A - Monitoring method for semiconductor laser output beam - Google Patents

Abstract

PURPOSE:To enable to perform an accurate and stable monitoring on the laser beam by a method wherein a diffraction grating is provided in front of a semiconductor laser beam and a direct monitoring is performed on the laser beam. CONSTITUTION:The diffraction grading 34 such as a grating lens and the like is arranged on the output beam path (the path of output laser beam to be used directly) located in front of a semiconductor laser 31. The diffracted beam 36 coming from said diffraction grating 34 is picked out to outside for use. On the other hand, among the output beams 35 of the semiconductor layer, the laser beam 37 to be used directly is monitored by providing a light-receiving element 35 so that the zero diffraction beam, which has not received the effect of diffraction of the diffraction grating 34, or a higher diffraction beam can be received. Thus, the intensity of the laser beam used directly is monitored as above, and the monitoring can be performed accurately and stably.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Labor Cost of the Invention The present invention relates to a method for monitoring the oscillation output of a semiconductor laser light source.

[Technical background of the invention and its problems]

A semiconductor laser uses a pair of cleavage planes on a Ga-containing JAs @ 1l-V group compound semiconductor crystal as a resonator for laser oscillation. In the conventional technology, it is assumed that laser oscillation is performed equally from both ends of a pair of cleavage planes, and as shown in FIG.
The amount of light radiated forward was monitored by determining the amount 12 of light radiated backward relative to the amount 13 of light radiated forward with a photodetector 14.

However, the cleavage plane of a semiconductor laser is set at an AJ of 0.05 mm for the purpose of preventing deterioration or increasing the radiation efficiency of laser light. Generally, a thin film of SiN is applied as a protective film. The above-mentioned 5iIIN is formed by a vacuum evaporation method or a sputtering method, but non-uniformity may occur.

In addition, there is also non-uniformity in the characteristics of the semiconductor laser which is generated during driving of the semiconductor laser, or in the case of a semiconductor laser that uses a diffraction grating as a resonator, there is non-uniformity in the laser light emitted in both directions due to the non-uniformity in the formation of the diffraction grating. Uniformity occurs.

Therefore, the conventional method of monitoring based on the intensity of the laser beam emitted backward cannot necessarily be said to be a stable semiconductor laser light output monitor.

Furthermore, in a semiconductor laser, it is known that if there is about 1 to 0.1 inch of return light to the semiconductor laser itself, the laser oscillation will be disturbed and the optical output will become unstable. In the conventional monitor arrangement, the light emitted toward the rear of the semiconductor laser is transmitted to the light receiving element 1.
There is a risk that the reflected light may be reflected by the laser beam 4 or the package 15 and return to the semiconductor laser 11, so care must be taken regarding this returning light.

[Purpose of the invention]

The present invention has been made in view of the above points, and it is possible to accurately and stably monitor the output light of a semiconductor laser by directly monitoring the output of the laser light emitted forward from the semiconductor laser, that is, the output of the laser light used directly. The purpose is to provide a method for monitoring.

[Summary of the invention]

The present invention arranges a diffraction grating such as a grating lens on the front output optical path of a semiconductor laser (output laser optical path used directly), and extracts the diffracted light by this diffraction grating to the outside for use. A light receiving element is arranged to receive zero-order diffraction light or high-order diffraction light that has not been affected by the diffraction effect of the grating, and the light intensity of the laser light used directly is monitored.

[Effect of the invention j According to the present invention, the light intensity of the directly used laser light can be monitored, so it is possible to accurately and stably monitor the light intensity which is affected by the non-uniformity at both ends of the semiconductor laser resonator surface. I can do it.

[Embodiments of the invention]

The present invention will be explained in detail below with reference to the drawings.

FIGS. 2A and 2B illustrate the configuration and basic operation of the grating lens 20 used in the present invention.

A grating lens optically belongs to a type of diffraction grating, and for example, as shown in FIGS. To explain the lens action by taking the cross section A-B inside the grating lens, we can see that the grating lens substrate 20Kfll [#ICIC wavelength light is incident and the direction in which the two representative light rays m and b travel is the lattice interval on the grating lens. Since d is different, the deflection angle θ of the diffracted light changes by -=z81n(λ/d), and the beam bO incident on the small part of the grating spacing d has a larger deflection angle than a. As a result, the diffracted light after passing through the grating lens 20 is condensed and subjected to a convex lens action.

The grating lens having the diffraction grating pattern shown in FIG. 2 can condense parallel light rays to almost one point.

FIG. 3 is a diagram for explaining a basic monitoring method of the present invention using such a grating lens. It is provided on a semiconductor laser package 33 via a submount substrate 32. Then, on the optical path of the forward output light of this semiconductor laser 31, a grating lens 34 having a concentric diffraction grating pattern 22 carved on its surface as shown in FIG. 314C are arranged to face each other.

Note that the diffraction grating spacing d is summed so that it gradually becomes wider toward the top of the drawing. In such a configuration, when the semiconductor laser 31 is placed at the focal position of the grating lens 34, the semiconductor laser output light 35 is directed to the grating lens 34.
The diffracted light 36 becomes parallel light rays and is taken out to the outside.
Can be used directly. On the other hand, the zero-order diffracted light of the semiconductor laser output light 35 that is not affected by the diffraction effect by the grating lens 34 travels straight, so in the present invention,
A light receiving element 38 is arranged on an extension of a line connecting the semiconductor laser 31 and the approximate center of the crating lens 34 to receive this zero-order diffracted light, and monitors this zero-order diffracted light.

According to such a configuration, the light intensity of the directly used laser output light can be monitored without interfering with the progress of the directly used laser output light.

Next, a variant embodiment of the present invention will be described.

BK-7 glass with a thickness of l- is used as the grating lens substrate, the range of the diffraction grating turns is set to 2-×2 holes, and the grating spacing is dmm x = I on the A side where the grating spacing is wide.
L 9 voice 01. do = 3.1/' in the center
A grating lens 34 was fabricated by forming a grating lens of d B w L G μm on the s B side using a photoetching technique. The focal position of the grating lens 34 for the laser beam having an oscillation wavelength of 800 fim is a position 5 degrees diagonally upward in the direction of 15° in FIG. 3 from the center of the lens. Therefore, the oscillation wavelength is 800n
M O semiconductor laser chip 31 is mounted on a submount substrate 32
The diffracted light by the grating lens 34 is fixed to the above position of the front and rear package 33 and is emitted forward as a parallel beam.

In order to receive the zero-order diffracted light 37, the position of the light receiving element 38 is a position extending from the center of the semiconductor laser 131 and the grating lens 34, that is, 2.5 to 2.5 mm from the grating lens substrate.
3I fix it on the package 33 that went outside.

The semiconductor laser assembled using the above design is parallel! Since a beam is obtained and appropriate angles are set between each component, if the surface of the substrate without a diffraction grating pattern is coated with anti-reflection coating, the semiconductor laser will have almost no return light and can be used as a stable laser light source. .

In the embodiment, the light-receiving element is provided at a position where it receives the zero-order diffracted light from the grating lens, but it is also possible to provide it at a position where it receives the higher-order diffracted light for monitoring. Of course, it is possible to place a photoelectric conversion element directly as a light receiving element at the monitor position, but it is also possible to place an optical transmission medium as a light receiving element at the monitor position and transmit the laser light guided by this optical transmission medium to the photoelectric conversion element. It is also possible to monitor by

[Brief explanation of drawings]

Fig. 1 is a diagram for explaining a conventional semiconductor laser output light monitoring method, Fig. 2 is a diagram for explaining the configuration of the grating lens used in the present invention and its basic operation, and Fig. 3 is a diagram for explaining the structure of the grating lens used in the present invention. FIG. 2 is a rounded diagram illustrating a method of monitoring semiconductor laser output light based on the implementation of FIG. 11.31...Semiconductor laser 14,38...
Light receiving element 2G, $4...Grating lens 22
... Diffraction Grating Nokuturn Agent Patent Attorney Kensuke Chika (and 1 other person) 1st
Figure 2

Claims (2)

[Claims] (1) A diffraction grating is placed on the output optical path of the semiconductor laser, and the diffracted light by this diffraction grating is taken out to the outside, and the zero-order diffraction light or higher-order diffraction light that has not been affected by the diffraction effect of the diffraction grating is received. 1. A method for monitoring output light without using a hand conductor, characterized in that a light receiving element is arranged so as to monitor the light intensity of the output light of the semiconductor laser. (2) A grating lens was used as a diffraction grating, a semiconductor laser was placed at the focal point of the grating lens, and a light receiving element was placed on an extension of a line connecting the semiconductor laser and the center of the grating lens. A method for monitoring a semiconductor laser output light according to claim 1, wherein the amount is $4.11.