JPS60262481A - Optical feedback type semiconductor laser device - Google Patents

Abstract

PURPOSE:To enable optical and electrical effective feedback control by simple constitution by feeding back only primary diffracted beams to a laser element by a diffraction grating having a reflection function while other order beams are received and feedback-controlling a laser driving power supply. CONSTITUTION:Laser luminous flux 12 projected from the end surface of a semiconductor laser element 10 is reflected and diffracted by a diffraction grating 15 having a reflection function. Positive primary diffracted beams 16 are fed back to the element 10 again and optical feedback is conducted, reflected zero-order beams 17 are received by a photodetector 18, detected as monitor beams and converted into electric signals, and a driving power supply for the element 10 is feedback-controlled electrically through an optical output stabilizing control circuit 20. Accordingly, optical and electrical effective feedback control is conducted by simple constitution, reflected noises from the laser element are inhibited, and single mode oscillation is conducted while an optical output is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a semiconductor laser device that can be used as a light source for optical fiber communications.

Conventional Structure and Problems When using a semiconductor laser as a light source for optical communication, it is desirable that the semiconductor laser oscillate in a single longitudinal mode.

However, it is difficult to achieve complete single-longitudinal mode oscillation with a single semiconductor laser, and several submodes often oscillate simultaneously. Furthermore, when coupled with an optical fiber, a part of the emitted light from the semiconductor laser is reflected from the end face of the optical fiber and returns to the semiconductor laser, causing an increase in noise in the semiconductor laser element and a change in the longitudinal mode spectrum. This is one of the obstacles to stabilizing and improving the quality of semiconductor laser devices.One way to solve this problem is to use a so-called complex system that actively utilizes the feedback light to the semiconductor laser element, as shown in Figure 1. There is a semiconductor laser device with a resonator configuration. Laser light 3 emitted from the cavity end face 2 of the semiconductor laser device 1 passes through the lens 4 and is reflected by the 1/3 Beno projector 5, and the reflected light 6 passes through the lens 4 again and enters the semiconductor laser device 1. . Laser light 8 emitted from the other resonator end face 7 is coupled to optical fiber 9 .

In such a configuration, reflection noise is suppressed by optical feedback, and at the same time complete single-longitudinal mode oscillation is possible.If a diffraction grating is used as a reflector, the oscillation wavelength can be selected; In some cases, the optical output intensity fluctuates greatly due to the environment, for example, temperature changes, which poses a practical problem in terms of stability.

OBJECT OF THE INVENTION The present invention solves the above-mentioned conventional problems by suppressing reflection noise of a semiconductor laser element by optical feedback, simultaneously achieving single-longitudinal mode oscillation, and further stabilizing optical output by electrical feedback. The purpose is to provide a semiconductor laser device suitable for a light source for optical communications.

Structure of the Invention The present invention provides a first aspect of the present invention, in which a convergent light transmitting body is disposed opposite to one output end face of a semiconductor laser element, and a first convergent light transmitting body of the convergent light transmitting body
A second end face has a diffraction grating having a reflection function, and is reflected and diffracted by the second end face, and the diffracted positive first-order diffracted light is coupled to the semiconductor laser element. The reflected or diffracted light of orders other than the positive first-order diffracted light is received by a photodetector disposed on the first end surface, and the received light output is sent to a drive power supply circuit for the semiconductor laser element. Electrical feedback is applied to couple the light emitted from the other output end face of the semiconductor laser element with an optical fiber.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. Second
In the figure, a laser beam 12 emitted from an emission end face 11 of a semiconductor laser element 10 is transmitted to a convergent optical transmission body 1 having a refractive index distribution that gradually decreases from a central axis 13 toward the periphery.
4 and is reflected and diffracted by the diffraction grating 16. Then, the positive first-order diffracted light 16 is returned to the semiconductor laser element 10 again, and the reflected zero-order light 17 is transmitted to the photodetector 1.
8, it is detected as 5 peno semiconductor laser output monitor light and electrical signal 1
9 and sent to the optical output stabilization control circuit 2°.

In this way, a semiconductor laser device with a composite resonator configuration using the diffraction grating 15 as an external resonator and a power servo mechanism is obtained, reflection noise is suppressed, and at the same time, single-longitudinal mode oscillation is realized. , the optical output is stabilized.

In this example, zero-order light was used as the semiconductor laser output monitoring light, but any order light other than the positive first-order diffracted light may be used, and as long as it satisfies the diffraction grating equation, By setting the placement position of the semiconductor laser element on the first end face of the focusing optical transmission body and the placement angle of the diffraction grating, it is possible to select the monitor light, and only the light of the desired wavelength can be returned. It is also possible to select the oscillation wavelength by

Effects of the Invention As described above, the present invention suppresses reflection noise and simultaneously achieves single-longitudinal mode oscillation by optical feedback to the semiconductor laser element, and also enables selection of the oscillation wavelength67, which enables optical detection. Electrical feedback from the device to the driving power source of the semiconductor laser makes it possible to stabilize the optical output, and by providing the focusing optical transmitter with reflection and diffraction functions, the feedback light to the semiconductor laser element and the output can be stabilized. Monitor light can be obtained simultaneously, optical and electrical feedback can be achieved with a simple configuration, and an optical feedback semiconductor laser device can be realized which is extremely advantageous when used as a light source for optical communications or a light source for optical fiber sensors. It is something.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a conventional optical feedback semiconductor laser device, and FIG. 2 is a schematic configuration diagram of an optical feedback semiconductor laser device according to an embodiment of the present invention. 1o... Semiconductor laser element, 11...
Laser light emitting end face, 12... Laser light, 13.
...--Central axis, 14... Focusing light transmission body,
16...Diffraction grating, 16...--order diffracted light, 17...Reflected zero-order light, 18...Photodetector, 19...・Electrical signal, 20...
Optical output stabilization control circuit.

Claims (1)

[Claims] A focusing light transmitting body is arranged opposite to one emission end face of the semiconductor laser element, a first end face of the focusing light transmitting body is coupled to the semiconductor laser element, and a second end face has a reflection function. It has a diffraction grating, the light incident from the first end face is reflected and diffracted by the second end face, the diffracted positive first-order diffracted light is returned to the semiconductor laser element, and the reflected or diffracted light is reflected and diffracted by the second end face. The light of orders other than the first-order diffracted light of the pressure is received by a photodetector disposed on the first end surface, and the output of the received light is electrically fed back to the drive power circuit of the semiconductor laser element, and the front-body laser is Device.