Semiconductor laser device, and method and program for driving the same

1. A semiconductor laser device, comprising:

a semiconductor laser element:

a temperature control part to perform a temperature control of the semiconductor laser element;

a temperature sensor to detect a temperature of the temperature control part; and

a temperature control device to control a supply signal to the temperature control part so that the detected temperature obtained from the temperature sensor reaches a predetermined target temperature, wherein

the temperature control device changes the predetermined target temperature for the temperature control part depending on the supply signal to the temperature control part,

the temperature control device comprises:

a relationship data storage part configured to store therein relationship data indicating a relationship between the supply signal to the temperature control part and the predetermined target temperature for the temperature control part when an oscillation wavelength of the semiconductor laser element is constant,

a supply signal acquisition part configured to acquire the supply signal to the temperature control part, and

a supply control part configured to, when the acquired supply signal is changed, acquire the predetermined target temperature for the temperature control part from the relationship data depending on the acquired supply signal, and further configured to control the supply signal to the temperature control part so as to achieve the predetermined target temperature thus acquired,

the supply control part is further configured to, when a change in the supply signal due to a change in ambient temperature is detected in a state in which the supply signal to the temperature control part is controlled so that the temperature detected by the temperature sensor becomes the predetermined target temperature, change the target temperature of the temperature control part from the supply signal and the relationship data according to a variation of the supply signal so that the oscillation wavelength of the semiconductor laser element is constant, and control the supply signal to the temperature control part so that the detected temperature detected by the temperature sensor becomes the changed target temperature.

2. The semiconductor laser device according to claim 1 , wherein the supply control part acquires the predetermined target temperature for the temperature control part from the relationship data depending on an average value of the supply signal thus obtained, per predetermined period.

3. The semiconductor laser device according to claim 1 , wherein the supply control part does not change the predetermined target temperature for the temperature control part if a variation of an average value of the supply signal thus obtained is less than a predetermined value.

4. The semiconductor laser device according to claim 1 , wherein the relationship data indicates the relationship between the supply signal to the temperature control part and the predetermined target temperature for the temperature control part per oscillation wavelength of the semiconductor laser.

5. The semiconductor laser device according to claim 1 , wherein the semiconductor laser element is composed of a multi quantum well structure including a plurality of well layers subjected to multistage connection, and the semiconductor laser element is designed to emit a light by optical transition between subbands formed in the plurality of well layers.

6. A gas analyzer to analyze a measurement target component included in gas, the gas analyzer comprising:

a measurement cell to permit introduction of the gas,

a semiconductor laser device according to claim 1 designed to emit a laser light to the measurement cell,

an optical detector to detect a laser light after passing through the measurement cell, and

an analysis part to analyze the measurement target component by using a detection signal obtained from the optical detector.

7. The semiconductor laser device according to claim 1 , wherein the supply control part is configured to, only when the acquired supply signal is changed, acquire the predetermined target temperature for the temperature control part from the relationship data depending on the acquired supply signal, and further configured to control the supply signal to the temperature control part so as to achieve the predetermined target temperature thus acquired.

8. A method for driving a semiconductor laser device, the semiconductor laser device comprising a semiconductor laser element, a temperature control part to perform a temperature control of the semiconductor laser element, and a temperature sensor to detect a temperature of the temperature control part, the method comprising:

storing a relationship data indicating a relationship between a supply signal to the temperature control part and a predetermined target temperature for the temperature control part when an oscillation wavelength of the semiconductor laser element is constant;

acquiring the supply signal to the temperature control part;

when the acquired supply signal is changed, acquiring the predetermined target temperature for the temperature control part from the relationship data depending on the acquired supply signal, and further configured to control the supply signal to the temperature control part so as to achieve the predetermined target temperature thus acquired;

when a change in the supply signal due to a change in ambient temperature is detected in a state in which the supply signal to the temperature control part is controlled so that the temperature detected by the temperature sensor becomes the predetermined target temperature, changing the target temperature of the temperature control part from the supply signal and the relationship data according to a variation of the supply signal so that the oscillation wavelength of the semiconductor laser element is constant, and control the supply signal to the temperature control part so that the temperature detected by the temperature sensor becomes the changed target temperature,

controlling the supply signal to the temperature control part so that the detected temperature obtained from the temperature sensor reaches the predetermined target temperature;

changing the predetermined target temperature for the temperature control part depending on the supply signal to the temperature control part.

9. A non-transitory computer readable medium storing a driving program used for a semiconductor laser device comprising a semiconductor laser element, a temperature control part to perform a temperature control of the semiconductor laser element, a temperature sensor to detect a temperature of the temperature control part, a control device to control a supply signal to the temperature control part so that the detected temperature obtained from the temperature sensor reaches a predetermined target temperature, wherein

the driving program is executable to cause the control device to store therein relationship data indicating a relationship between the supply signal to the temperature control part and the predetermined target temperature for the temperature control part when an oscillation wavelength of the semiconductor laser element is constant,

the driving program is executable to cause the control device to acquire the supply signal to the temperature control part,

the driving program is executable to cause the control device to, when the acquired supply signal is changed, acquire the predetermined target temperature for the temperature control part from the relationship data depending on the acquired supply signal, and further configured to control the supply signal to the temperature control part so as to achieve the predetermined target temperature thus acquired,

the driving program is executable to cause the control device to, when a change in the supply signal due to a change in ambient temperature is detected in a state in which the supply signal to the temperature control part is controlled so that the temperature detected by the temperature sensor becomes the predetermined target temperature, change the target temperature of the temperature control part from the supply signal and the relationship data according to a variation of the supply signal so that the oscillation wavelength of the semiconductor laser element is constant, and control the supply signal to the temperature control part so that the temperature detected by the temperature sensor becomes the changed target temperature, and

the driving program is executable to cause the control device to perform a function of changing the predetermined target temperature for the temperature control part depending on the supply signal to the temperature control part.