JPS6171689A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To enable the temperature of a semiconductor laser to be kept constant even when the ambient temperature varies largely, by a method wherein the current and polarity supplied to an electronic cooling element are controlled by the output of a temperature detection element led out of a hermetic sealed terminal. CONSTITUTION:A semiconductor laser 1 is mounted on a stem 2 made of a substance of high thermal conductivity, together with a thermistor 3 which is a kind of temperature detection element, and the stem 2 is fixed in low terminal resistance on a Peltier effect element 6 which has been fixed to a stem 5 in low thermal resistance. A cap 8 having a hermetic window 7 through which the radiated light of the semiconductor laser 1 is led out is welded to the stem 5, and the container is sealed in the state of dry nitrogen atmosphere. In this device, the variation in resistance value caused by temperature changes is grasped as the variation in voltage by impressing constant current on the thermistor 3, and the polarity of the current supplied to the Peltier effect element 6 is inverted so that this variation may reduce to zero, i.e. temperature may become constant; thereby, the temperature of the semiconductor laser 1 is controlled constant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an optically available semiconductor laser device with improved stabilization of an oscillation wavelength.

[Background of the invention]

It is known that the oscillation wavelength of a Fabry-Perot cavity type semiconductor laser, which generally uses a cleavage plane as a resonator, changes depending on the temperature.

For example, in the case of IrbGcLAsP laser, 0.4 to 0.
This results in a wavelength change of 5rLm10C.

Changes in wavelength due to temperature, transmission loss, changes in pulse spread9 and transmission band due to changes in fiber dispersion, or
In the case of wavelength division multiplexing transmission, transmission characteristics are seriously affected, such as an increase in the amount of crosstalk.

Therefore, in single-mode fiber high-speed transmission and dense wavelength multiplexing transmission, which are greatly affected by fluctuations in the oscillation wavelength, it is necessary to take particular measures to stabilize the oscillation wavelength.

As a way to stabilize the oscillation wavelength, distributed feedback lasers and distributed reflection lasers have been developed that use a wavelength-selective diffraction grating in the resonator of a semiconductor laser.
The wavelength change due to temperature is also 0. It was possible to reduce the amount of O5nm to 100g.

However, in the above-mentioned distributed feedback lasers and distributed reflection lasers, the oscillation wavelength is fixed by the diffraction grating, so the energy gap of the semiconductor changes with temperature changes, and the gain spectrum changes from the resonance spectrum of the diffraction grating. If it exceeds this range, it will no longer oscillate.

For this reason, the temperature range that can be excavated is much narrower than that of ordinary Fabry-Perot resonant talking lasers79), and it is not practical to stabilize the oscillation wavelength against temperature changes, and the 311 laser beams are The reality is that

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a semiconductor laser device with improved stabilization of the oscillation wavelength.

[Summary of the invention]

That is, the present invention solves the problem by eliminating the temperature change of the semiconductor laser, which is the direct cause of the change in oscillation growth. Alternatively, in distributed feedback formation, a distributed reflection type semiconductor laser is mounted together with a temperature detection element, a radiator is provided in the high temperature part of the electronic cooling element, and this electronic cooling element, the semiconductor laser element, and the temperature sensing element are connected to the semiconductor laser beam. Hermetically sealed in a container with an airtight window for taking out the air, the inside of this container is filled with dry nitrogen, and the airtight terminal provided on the wall of the container is connected to the high temperature side of the electronic cooling element. The present invention is characterized in that the temperature of the semiconductor laser is kept constant by controlling the current and polarity supplied to the electronic cooling element based on the output of the temperature detection element.

[Embodiments of the invention]

An embodiment of the present invention will be described in detail below. The inventors suppressed changes in the gain spectrum of the semiconductor laser by controlling the temperature of the semiconductor laser to a constant value, and in the case of a Fabry-Perot cavity laser. conducted an experiment to try to stabilize the oscillation wavelength by directly stabilizing the oscillation wavelength and preventing the gain spectrum from going outside the resonance spectrum in distributed feedback and distributed reflection lasers.

The first device is a device that controls the temperature of the semiconductor laser at a constant level.
It is shown and explained in the figure.

In the figure, a semiconductor laser (in this case, a Fabry-Perot cavity laser is used) 1 has a stem 2 made of a material with high thermal conductivity (in this experiment, oxygen-free steel is used), and one temperature detection element is attached to the stem 2. It is installed together with the thermistor 3.

On the other hand, this stem 2 is fixed with low thermal resistance on a Bertier effect element 6 fixed with low thermal resistance to a stem 5 provided with radiation fins 4.

8 is a cap having an airtight window 7 for taking out the emitted light from the semiconductor laser 1 to the outside;
are welded in a dry nitrogen atmosphere to form a sealed container, and therefore the inside of this container is sealed in a dry nitrogen atmosphere.

Reference numeral 9 denotes a hermetically sealed terminal that is provided by penetrating the stem 5 in a hermetically sealed manner, and this penetrating portion corresponds to the high temperature side of the Beltier effect element 6. Through this hermetically sealed terminal 9, power is supplied to the semiconductor laser 1 and the Bertier effect element 6, and the output of the thermistor 3 is derived. Moreover, this hermetically sealed terminal 9 and the semiconductor laser 1. The thermistor 3 is a wire 10 with high thermal resistance.
This reduces the flow of heat from the outside conducted through the hermetically sealed terminal 9.

In this device, temperature control of the semiconductor laser 1 is performed by changing the current and polarity of the Beltier effect element 6 and cooling or heating it in accordance with the temperature of the semiconductor laser 1 detected by the thermistor 5 via the stem 2. It will be done.

To explain in more detail, FIG. 2 (α) shows the thermistor 3
This is a diagram showing the characteristics of the thermistor 3. Taking advantage of this property that the resistance value changes with temperature change, a constant current is applied to the thermistor 3 in a range that keeps the amount of self-heating sufficiently small. Temperature is detected by capturing changes in thermistor resistance as voltage changes. Temperature control is performed by controlling the current supplied to the Beltier effect element 6 so that this change in voltage becomes zero, that is, so that the temperature remains constant.

The Beltier effect element 6 can reverse the fixed side of the stem 2 from the low temperature side to the high temperature side (from cooling to heating operation) by reversing the polarity of the current as shown in Figure 2. As shown in the figure, when the ambient temperature becomes lower than the set temperature, the polarity of the current supplied to the Beltier effect element is reversed, and the cooling operation is reversed to the heating operation, thereby reducing the humidity of the semiconductor laser 1. Constant control - Using the apparatus of this embodiment configured as described above, the results of an experiment are shown in FIG. 4 and will be explained.

In the figure, the ambient temperature of the semiconductor laser device is -40°C.
The actual measured values of the thermistor resistance value (temperature of the semiconductor laser 1) and oscillation wavelength when the temperature of the semiconductor laser 1 is controlled to +25'O by changing the temperature in the range of ~+70°C are shown.

(This figure) Week 9, the ambient temperature is -40°C to +70°
At C, the resistance value of thermistor 3 is 5,0KO corresponding to the temperature 25°0, and the wavelength 1302n corresponding to the temperature 25°C.
m is kept stable.

From the figure, when the ambient temperature is above +65℃, some changes in the resistance value and oscillation wave length of Namister 3 are observed, but this is due to
This is because the heat dissipation characteristics of the heat dissipation fins 4, which dissipate the Joule heat generated by the Beriche effect element and the amount of heat absorbed by cooling, have become saturated, and can be improved by increasing the heat dissipation area of the heat dissipation fins 4 or by forced cooling.

In the case of this experiment, the Beltier effect element 6 is a single unit, and when there is one Beltier 'Itd, the temperature difference between the low temperature side and the high temperature side is 4.
6℃, and after mounting, when using heat radiation fins with a heat radiation area of 500 d, natural resistance fil
A temperature difference of 40° C. was obtained at c, and it was possible to control the temperature of the semiconductor laser 1 to +25° C. up to an ambient temperature of 65° C.

In this experiment, the temperature of the semiconductor laser was kept constant and the cause of the instability of the oscillation wavelength was fundamentally described, so a similar module structure in which the semiconductor laser 1 and the original fiber were optically coupled was Effects can be obtained.

〔Effect of the invention〕

As detailed above, according to the semiconductor laser device of the present invention, the semiconductor laser and the temperature detection element are both mounted in the low temperature part of the cooling element, housed in a sealed container filled with dry nitrogen, and the high temperature part of the cooling element is mounted. A radiator is installed in the radiator, and the temperature of the semiconductor laser is controlled by controlling the current and polarity supplied to the electronic cooling element using the output of the temperature detection element derived from the hermetically sealed terminal.
1N, the temperature of the semiconductor laser can be kept constant even if the ambient temperature changes significantly, the stability of the oscillation wavelength is reliably maintained, and the transmission characteristics are significantly improved. I was able to hit it.

In addition, since semiconductor lasers have a property that the lower the operating temperature, the longer the lifespan, the present invention suppresses the increase in semiconductor laser temperature even under high temperatures. (It can also bring about effects such as).

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a semiconductor laser device, which is an embodiment of the present invention. FIG. 2 (α) is a diagram showing the temperature characteristics of the thermistor, and the second factor) is a diagram showing the characteristics of the Beltier effect element. FIG. 3 is an explanatory diagram showing the principle of temperature control of the present invention. FIG. 4 is a diagram showing experimentally measured values of ambient temperature, thermistor resistance value, and oscillation wavelength. 1... Semiconductor L hoop 2... Stem 3... Thermistor (temperature detection element) 4...
...Radiation fin (radiator) 5 ... Stem 6 ... Bertier effect element (cooling element) 7 ...
...Airtight window 9...Hermetically sealed terminal

Claims (1)

[Claims] A Fabry-Bello resonator type semiconductor laser or a distributed reflection type semiconductor laser with distributed feedback formation is mounted together with a temperature detection element in the low temperature part of the thermoelectric cooling element, and a radiator is provided in the high temperature part of the thermoelectric cooling element to connect the thermoelectric cooling element and the above. The semiconductor laser element and the temperature detection element are hermetically sealed in a container having an airtight window for taking out the semiconductor laser light, the inside of the container is filled with dry nitrogen, and the temperature detection element is provided on the wall of the container on the high temperature side of the electronic cooling element. A semiconductor laser device provided with a hermetically sealed terminal for controlling the current and polarity supplied to the electronic cooling element based on the output of the temperature detection element to keep the temperature of the semiconductor laser constant.