JPH01300579A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To provide a semiconductor laser device having simple construction with a decreased number of components and still capable of stabilizing oscillating wavelength of laser beam form the semiconductor laser device without using output light form a semiconductor laser by connecting a semiconductor laser whose output wavelength is dependent on an ambient temperature and driving current in series with a resistance element whose resistance value is dependent on the ambient temperature. CONSTITUTION:A semiconductor laser device comprises a semiconductor laser 1 outputting laser light whose wavelength is dependent on an ambient temperature and driving current, and a resistance element 14 whose resistance value is dependent on the ambient temperature. The semiconductor laser 1 and the resistance element 14 are connected in series. Variation of ambient temperature is detected as variation of resistance value of the resistance element 14 and driving current conducted through the resistance element 14 is controlled based on the detection, so that variation in wavelength of the laser light outputted from the semiconductor laser 1 is decreased. In this manner, oscillation wavelength of the semiconductor laser can be stabilized by means of a single compensating element, and therefore the device as a whole can be manufactured at a low cost. Further, since the device is constructed merely with electric wiring without using output light from the semiconductor laser, the device is more resistive to external variation such as vibration or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor laser device that generates a laser beam.

[Conventional technology]

Conventionally, there has been a device of this type as shown in FIG. This diagram shows ELECTRONIC5I, ETTER5
Vol.

16, No., 18 P, 709, in the figure, 1 is a semiconductor laser, 2 is a Fabry-Bello resonator, 3 is a half mirror, 4 is a mirror, 5 is a light receiving element A,
6 is a light receiving element B, 7 is a differential amplifier, 8 is a constant current drive circuit, L is the semiconductor laser output light, L is the output light of the Fabry-Bello resonator, L is the light that does not pass through the Fabry-Bello resonator, 10 is a semiconductor laser drive current supply line, and l is a current feedback line. Note that the semiconductor laser 1 has a constant current IL.
is driven through a current line 10 by a constant current drive circuit 8 that supplies . The output light of the semiconductor laser 1 is divided into two parts by a half mirror 3, one of which is applied to the Fabry-Bello resonator 2, and the other part of the light is reflected by the mirror 4 and input to the light receiving element B6. The light input to the Fabry-Perot resonator 2 is output after being attenuated in intensity according to the wavelength by the Fabry-Perot resonator 2, and the output light LT is transmitted to the light receiving element A.
Enter 5. In the light receiving element A5, a current Ia proportional to the intensity of the input light is generated and input to the differential amplifier 7.

In the light receiving element B6, a current 1 proportional to the intensity of the input light L+ is generated and input to the differential amplifier 7. The differential amplifier 7 amplifies and outputs the difference between these two currents IA and . If the amplification factor of the differential amplifier 7 is α, the output current of the differential amplifier 7 is α(IA-11), and this feedback current α(I
A −Im ) is passed through the current feedback line l and merged into the current supply line 10 , added to the constant drive current TL, and injected into the semiconductor laser 1 .

Since the conventional semiconductor laser device is configured as described above, it operates as follows.

Semiconductor lasers have the property that their oscillation wavelength changes and their refractive index changes due to changes in injection current and ambient temperature. Therefore, even if the injection current is kept constant, the oscillation wavelength of the laser beam of the semiconductor laser 1 changes if the ambient temperature changes.

Assume that the oscillation wavelength of the semiconductor laser 1 is λ when the injection current is a constant current ① and the ambient temperature is T ('C). Half of the output light from the semiconductor laser 1 is input to the Fabry-Perot resonator 2 . FIG. 4 shows the transmission characteristics of the Fabry-Perot resonator 2 with respect to the wavelength of incident light. The Fabry-Perot resonator 2 is adjusted so that the center of the negative slope region of the transmission curve is at wavelength λ. Therefore, the intensity of the output light 10 of the Fabry-Perot resonator 2 remains unchanged if the oscillation wavelength of the semiconductor laser 1 is constant at λ, but changes accordingly when the oscillation wavelength changes. For example, when the ambient temperature decreases from T, the oscillation wavelength of the semiconductor laser 1 becomes λ,
Suppose that it decreases from λLl to λLl. At this time, as shown in FIG. 4, the intensity of the output light LA of the Fabry-Bello resonator 2 increases. Conversely, when the ambient temperature increases from T, the intensity of the output light LT decreases. Therefore, the current (4) flowing through the light-receiving element A5 that receives the output light LA varies in accordance with the variation in the oscillation wavelength of the semiconductor laser 1. On the other hand, among the semiconductor laser output light, the light Ll that does not pass through the Fabry-Perot resonator 2
is constant regardless of fluctuations in the oscillation wavelength of the semiconductor laser 1. Therefore, the current 1B flowing through the light receiving element B6 is constant. The differential amplifier 7 amplifies the difference between the current (4) which fluctuates according to the fluctuation of the oscillation wavelength of the semiconductor laser 1 and the current (1) which does not fluctuate by α times.

The current α (■4−■m) output from the differential amplifier 7 is
This current corresponds only to the wavelength fluctuation component of the semiconductor laser 1, and decreases as the wavelength becomes longer, and increases as the wavelength becomes shorter. This current α (IA −1, +) is the current feedback line l
The current flows through the semiconductor laser drive current supply line 10, is added to the drive current (2), and is injected into the semiconductor laser 1. When the oscillation wavelength of the semiconductor laser 1 increases due to a rise in ambient temperature, the feedback current α (IA-I
3) decreases, and the current injected into the semiconductor laser l also decreases. At this time, the oscillation wavelength of the semiconductor laser becomes shorter as the injection current decreases, canceling out the lengthening of the oscillation wavelength due to the above-mentioned increase in ambient temperature. Furthermore, when the oscillation wavelength of the semiconductor laser 1 becomes shorter due to a decrease in the ambient temperature, the feedback current α(rA-In) increases, and the current injected into the semiconductor laser 1 also increases. At this time, the semiconductor laser 1
The oscillation wavelength becomes longer as the injection current increases, canceling out the shortening of the oscillation wavelength due to the above-mentioned decrease in ambient temperature.

[Problem to be solved by the invention]

Since the conventional semiconductor laser device is configured as described above, a Fabry-Perot resonator is used as a component to stabilize the oscillation wavelength of the semiconductor laser.

Requires light receiving elements A and B and a differential amplifier. It is also necessary to couple the output light of the semiconductor laser to these components. Therefore, there is a problem in that the entire device becomes large in size. Additionally, there is a problem in that optical axis alignment is required to couple light between each component. In addition, since the entire system has a complicated structure, it is susceptible to external fluctuations such as vibrations.

This invention was made to solve the above-mentioned problems, and it is possible to stabilize the oscillation wavelength of a laser beam of a semiconductor laser device with a simple configuration with a small number of parts without using the output light of a semiconductor laser. The purpose is to obtain a semiconductor laser device.

[Means to solve the problem]

The present invention includes a semiconductor laser 1 whose output wavelength of laser light is determined by the environmental temperature and drive current, and a resistor element 14 whose resistance value is determined by the environmental temperature, and these are connected in series.

[Effect]

Fluctuations in the environmental temperature are interpreted as fluctuations in the resistance value of the resistor element 14, and the drive current flowing through the resistor element 14 is controlled to reduce fluctuations in the wavelength of the laser light output by the semiconductor laser 1.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram showing one embodiment of the present invention, in which 1 is a semiconductor laser, 14 is a compensation element as a resistance element, and 15 is a configuration diagram showing an embodiment of the present invention.
is a constant voltage supply circuit. Note that the semiconductor laser l and the compensation element 14 are installed adjacent to each other and are electrically connected in series. A constant voltage supply circuit 15 is connected to both ends of the semiconductor laser 1 and the compensation element 14 which are connected in series.

In the device configured as described above, the semiconductor laser 1
IL is the current flowing through the constant voltage supply circuit 15, V o is the output voltage of the constant voltage supply circuit 15, and RL% is the resistance of the semiconductor laser 1.
When the resistance of is R2, the current IL is expressed by equation (11).

I L = Vo / (Rt + Rp)
-(11 The above current IL flows through the semiconductor laser 1, and it oscillates at the oscillation wavelength λ.) When the ambient temperature changes, the oscillation wavelength of the laser beam of the semiconductor laser 1 changes from λ, and its refraction At this time, when the ambient temperature rises, the wavelength of the laser beam from the semiconductor laser 1 becomes longer and the refractive index increases. Conversely, when the ambient temperature falls, the wavelength of the laser beam from the semiconductor laser 1 becomes shorter and the refractive index increases. On the other hand, when the ambient temperature changes, the electrical resistance value R2 of the compensation element 14 changes.At this time, when the ambient temperature rises, the electrical resistance value R, of the compensation element 14 increases, and when the ambient temperature falls, the electrical resistance value R2 of the compensation element 14 increases. The electrical resistance value R1 of the compensation element 14 decreases.When the electrical resistance value R, of the compensation element 14 changes, the (1)
The current IL flowing through the semiconductor laser 1 varies according to the formula. According to equation (1), the current 1L decreases as the electrical resistance value R2 of the compensation element 14 increases, and increases as the electric resistance value R2 decreases.

When the current (1) flowing through the semiconductor laser 1 changes, the refractive index of the laser beam of the semiconductor laser 1 changes accordingly. At this time, when the current IL decreases, the oscillation wavelength decreases and the refractive index decreases. Furthermore, as the current IL increases, the oscillation wavelength increases and the refractive index increases.

As described above, when the ambient temperature rises and the oscillation wavelength λ1 of the semiconductor laser 1 becomes longer, the electric resistance value R7 of the compensation element 14 increases, the current 2 flowing through the semiconductor laser 1 decreases, and the semiconductor laser 1 As the wavelength of the laser beam becomes shorter, the refractive index decreases, thereby canceling out the longer oscillation wavelength. Conversely, when the ambient temperature decreases and the oscillation wavelength λL of the laser beam of the semiconductor laser 1 becomes shorter, the electrical resistance value RP of the compensation element 14 decreases, the current flowing through the semiconductor laser 1 increases, and the semiconductor laser As the wavelength of the laser beam 1 becomes longer, the refractive index increases, thereby canceling out the above shortening of the oscillation wavelength.

In this case, an element or the like which quantitatively corrects the phase characteristics of the resistance element 14 and the temperature characteristic of the semiconductor laser 1 is found experimentally and connected to each other.

FIG. 2 shows another embodiment of the present invention, in which 18 is a storage block for a semiconductor laser, 14 is a compensation element, 15 is a constant voltage supply circuit, 16 is an active layer of the semiconductor laser, and 17 is an electrode of the semiconductor laser. It is.

The compensation element 14 is formed within the block of the semiconductor laser 1 and is electrically connected in series with the electrodes of the semiconductor laser. With this configuration, temperature fluctuations in the active layer 16 of the semiconductor laser are instantaneously transmitted to the compensation element 14 through the storage block 18, so that the refraction due to wavelength fluctuations of the laser beam of the semiconductor laser is reduced by the process described above. This has the effect of instantly suppressing rate fluctuations. In this way, a laser beam of a constant wavelength can always be obtained stably.

〔Effect of the invention〕

As described above, the present invention includes a semiconductor laser whose output wavelength of laser light is determined by the environmental temperature and drive current, and a resistive element whose resistance value is determined by the environmental temperature, and which are connected in series. Since only one compensation element is required for stabilizing the oscillation wavelength of the semiconductor laser, the device can be easily assembled. Another advantage is that the device can be made smaller and cheaper. Further, according to the present invention, since the device is configured only with electrical wiring without using the output light of a semiconductor laser, it is possible to obtain a device with high reliability and resistance to external fluctuations such as vibration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a semiconductor laser device of the present invention, FIG. 2 is a block diagram showing the structure of another embodiment of the present invention, and FIG. 3 is a block diagram of a conventional laser device. FIG. 4 is a diagram showing transmission characteristics of a laser beam. 1... Semiconductor laser, 14... Compensation element, 15...
- Constant voltage supply circuit, 16... active layer, 17... electrode, 18... storage block. Agent Masu Oiwa M (2 idiots) 1st ward b 1 Shi-za-hitsu fake bribe net 14: λkame I 1■ Prefectural hand 15: Shiba Ryu Pressure Urei-dou boasting procedure amendment (self-motivated) fpe 7 years. Month 2, 2, Name of the invention: Semiconductor laser device 3, Person making the amendment Representative Moriya Shiki 4, Agent 5 Column for detailed explanation of the invention to be amended. G. Contents of the amendment (1) On page 1, line 11 of the specification, the phrase ``This invention generates a laser beam'' has been changed to ``This invention generates a laser beam with a constant oscillation wavelength regardless of fluctuations in ambient temperature.''"Yes," he corrected. (2) On page 3, line 7 of the same book, the phrase ``The oscillation wavelength changes and the refractive index changes'' is corrected to ``The refractive index changes, which causes the oscillation wavelength to change.'' (3) On page 8 of the same book, lines 1 to 6, the phrase ``The refractive index of the semiconductor laser 1 decreases'' was replaced with ``The refractive index of the semiconductor laser 1 fluctuates. The oscillation wavelength varies from and the oscillation wavelength becomes shorter.'' (4) Same book, page 8, lines 16 to 20 [Accordingly, the refractive index increases. "The refractive index of the semiconductor laser 1 changes accordingly. At this time, as the current , decreases, the refractive index decreases and the oscillation wavelength decreases. Also, as the current , increases, the refractive index increases. Therefore, the oscillation wavelength increases.'' (5) On page 9 of the same book, lines 4 and 5, the phrase ``The refractive index of the semiconductor laser 1 decreases,'' was replaced with ``The refractive index of the semiconductor laser 1 decreases, and the oscillation wavelength becomes shorter,” he corrects. (6) The same book, page 9, lines 10 to 11, “The wavelength of the laser beam of the semiconductor laser 1 becomes longer and the refractive index increases,
J is corrected to read, "The refractive index of the semiconductor laser 1 increases and the oscillation wavelength becomes longer." (7) On page 10 of the same book, lines 6 and 7, "The refractive index variation due to the wavelength variation of the laser beam of a semiconductor laser" is replaced with "The wavelength variation due to the refractive index variation of the semiconductor laser"
and correct it. that's all

Claims (1)

[Claims] A semiconductor laser device includes a semiconductor laser whose output wavelength of laser light is determined by environmental temperature and drive current, and a resistive element whose resistance value is determined by the environmental temperature, and these two elements are connected in series.