JPS60117695A - Semiconductor laser light source device - Google Patents

Abstract

PURPOSE:To obtain easily a laser light source, in which the change of oscillation wavelength is very small, by a method wherein the output of a semiconductor laser is controlled constantly by a light detector, and the oscillation wave length of the semiconductor laser is made constant by an interference filter, a light detector and a Peltier element. CONSTITUTION:Light is radiated from both end surface of the semiconductor laser of the type of a Fabry-Perot resonant device, and the light from one side is used as the light source. A part of the light which is radiated from another end surface of the resonant device directly shines into a light detector 2 for controlling the driving electric current, and the remnant part of the light shines into the light detector 5 for controlling the oscillation wave length after passing through an interference filter. The light volume which entered the light detector 2 is transformed to the electric signal, and is introduced to a constant output circuit 3 which is the circuit to supply the driving current to the semiconductor laser 1. The electric signal from the light detector 2 becomes the feedback signal to make the output of the semiconductor laser 1 constant. The light entered in the light detector 5 is transformed to the electric signal, and is inputted to a Peltier element driving circuit 6, and the output from said circuit 6 is inputted to a Peltier element 7 connected to the semiconductor laser 1.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a light source device using a wavelength-controlled semiconductor laser.

<Prior Art> Recently, with the development of measurement technology using light, measurement technology using wavelength as a medium has come to be regarded as important. Semiconductor lasers with stabilized wavelengths are required for measurement technology that uses wavelength as a medium.

In a typical semiconductor laser device, the oscillation wavelength fluctuates greatly due to changes in ambient temperature, etc., making it difficult to use it as a constant wavelength output light source. Therefore, as a light source with the above-mentioned wavelength stabilized, DBR (Distributed Brgg
Reflection) W (Bragg reflection type) laser and DFB (Distributed FeedBac)
A type k (distributed feedback) laser or the like having a structure in which the wavelength is determined using a diffraction grating is used.

However, these semiconductor laser devices have a complicated structure, and are difficult to manufacture because they require continuous formation of fine diffraction gratings with a constant pitch in the active region, resulting in low yields and very high costs. There is a problem.

<Object of the Invention> The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a light source device with a stable wavelength using a semiconductor laser having a relatively simple structure.

<Embodiment> FIG. 1 is a schematic configuration diagram of a light source device showing an embodiment of the present invention. Reference numeral 1 denotes a normal fiber bellows resonator type semiconductor laser, and one of the lights emitted from both end faces of the resonator is used as a light source.

Further, a part of the light emitted from the other resonator end face is directly incident on the photodetector 2 for controlling the drive current, and the remaining part passes through the interference filter 4 and then controls the oscillation wavelength. The light is incident on the photodetector 5. The amount of light incident on the photodetector 2 is converted into an electrical signal and guided to a constant output circuit 3. The constant output circuit 3 is a circuit 3 that supplies a driving current to the semiconductor laser 1, and the electric signal from the photodetector 2 serves as a feedback signal to keep the output of the semiconductor laser 1 constant. The light incident on the photodetector 5 is converted into an electrical signal and input to the Vertier element drive circuit 6. The output from the Beltier element drive circuit 6 is input to the Beltier element 7 connected to the semiconductor laser 1.

Next, the relationship between the transmission characteristics of the interference filter 4 and the wavelength λ of the semiconductor laser 1 is shown in FIG. In the example shown in FIG. 2, the semiconductor laser 1 is an AlGaAs laser diode,
A laser element was manufactured so that the wavelength λ was 7 sooA at a room temperature of 25°C. The interference filter 4 is 5if2/
Ti1t system was selected as the filling material, and the wavelength was 78.
We designed and manufactured a short wavelength transmission filter whose transmittance changes most steeply from maximum to minimum at 00λ. When a multilayer film consisting of 50 layers of the above filter material thin films was successively deposited with an electron beam with a film thickness accuracy of 1%, the transmittance was close to 100% at λ < 780 OA ~ and the transmittance was low at λ > 8000 A. An interference filter having a transmission characteristic as shown in FIG. 2 close to 0% was obtained. When this interference filter 4 was irradiated with the output light of the semiconductor laser 1, the temperature change in transmittance /6λ at a wavelength of 7800λ was ΔT/co=8−5%/λ.

△ If the change in transmittance with respect to wavelength is large as described above, when the oscillation wavelength of the semiconductor laser 1 is set, the ambient temperature T
When the oscillation wavelength changes due to a change in the amount of light passing through the interference filter 4, the amount of light passing through the interference filter 4 changes significantly. Therefore, the change in the oscillation wavelength can be electrically detected as a change in the amount of light incident on the photodetector 5. By feeding this back to the Bertier element driving circuit 6, the output from the Bertier element driving circuit 6 makes the amount of light incident on the photodetector 5 constant, that is, the semiconductor laser 1
The stem temperature of the semiconductor laser 1 can be changed by driving the Vertier element 7 so that the oscillation wavelength of the semiconductor laser 1 remains constant. The Bertier element 7 is an element that can control heat generation and cooling in response to current, and is directly connected to the stem on which the semiconductor laser 1 is mounted. Therefore, the Beltier element drive circuit 6
Heating and cooling of the stem can be controlled by the output from.

To summarize the above, the output light of the semiconductor laser 1 can be controlled to be constant by the photodetector 2, and the oscillation wavelength of the semiconductor laser 1 can be kept constant by the interference filter 4, the photodetector 5, and the Vertier element 7. When the ambient temperature of the laser light source device shown in FIG. 1 was varied from 0° C. to 50° C., the oscillation wavelength of the semiconductor laser I varied by 2 Å or less.

<Effects of the Invention> As detailed above, according to the present invention, a laser light source with extremely small change in oscillation wavelength can be easily obtained.
In particular, the value of use in the fields of measurement technology and communication technology is extremely large. In the above embodiment, G is used as the material of the semiconductor laser.
Although an aAlAs system is used, a similar semiconductor laser device can be constructed using a quaternary system such as an InGaAsP system or other materials. Furthermore, the material of the interference filter is not limited to the 5if2/Ti1t system, but may include Altos, Ba205jYxαB, Ta
, O, and various other materials can be used.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a semiconductor laser light source device showing one embodiment of the present invention. FIG. 2 is an explanatory diagram showing the variation and dependence of the transmittance of the interference filter shown in FIG. 1 and the oscillation wavelength of the semiconductor laser (room temperature 25° C.). DESCRIPTION OF SYMBOLS 1... Semiconductor laser, 2... Photodetector, 3... Constant output circuit, 4... Interference filter, 5... Photodetector, 6... Vertier element drive circuit, 7...・Beltier element.

Claims (1)

[Claims] 1. An interference filter that transmits the output light of a semiconductor laser in accordance with the wavelength, a photodetector that detects the amount of light transmitted through the interference filter, and a temperature-controlled device in response to the output of the photodetector. A semiconductor laser light source device, characterized in that the temperature of the semiconductor laser is controlled by heating and cooling the Vertier element in accordance with the output light wavelength of the semiconductor laser. . 2. The semiconductor laser light source device according to claim 1, wherein the semiconductor laser is driven and controlled by a constant output drive circuit that detects the output light intensity and keeps the output light constant.