JPH07283475A - Frequency stabilizing semiconductor laser light source - Google Patents

Abstract

PURPOSE:To prevent the oscillation frequency of a semiconductor laser from being exerted the effect of an ambient temperature even in the case where a thermal resistance between the semiconductor laser and a temperature detector is high by a method wherein the ambient temperature is detected, the value of this detected temperature is converted into a change component of the temperature of the laser and the temperature of the laser is controlled on the basis of the value of the converted change component. CONSTITUTION:As a variation component 'TA2-TA0' of an ambient temperature is converted as a variation component 'TLD2-TLD0' of the temperature of a semiconductor laser 1 and the converted variation component 'TLD2-TLD0' is added to the temperature of the laser 1 by an adder, which is constituted of resistors 15, 19, 21 and 22 and an operational amplifier 23, a control circuit 24 controls the temperature of the laser 1 so as to drop to the 'TCD0' anticipating that the temperature of the laser 1 rises to the 'TLD2'. As a result, the ambient temperature is detected by a temperature detector 11 and the value of this detected temperature is converted into a change component of the temperature of the laser 1 to control the temperature of the laser 1 by the circuit 24. Thereby, the temperature of the laser 1 is prevented from being exerted the effect of the ambient temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency-stabilized semiconductor laser light source, and more particularly to a frequency-stabilized semiconductor laser light source capable of compensating the influence of ambient temperature.

[0002]

2. Description of the Related Art In a conventional frequency-stabilized semiconductor laser light source, the oscillation frequency is stabilized by controlling the oscillation frequency of the semiconductor laser with an absorption line of a standard substance.

FIG. 3 is a block diagram showing an example of such a conventional frequency-stabilized semiconductor laser light source. Figure 3
1 is a semiconductor laser, 2 is a beam splitter, 3
Is an absorption cell containing a standard substance such as C ₂ H ₂ molecule,
4 is a photodetector, 5 is an oscillator, 6 is a synchronous detection circuit, 7 is a current control circuit, 8 is a temperature detector, 9 is a temperature control circuit, and 10 is a temperature control circuit.
Is a constant temperature bath, and 100 is output light. Further, 2 to 7 constitute the frequency control means 50.

The output light of the semiconductor laser 1 is incident on the beam splitter 2, a part of the incident light is output as the output light 100, and the rest of the incident light is reflected and enters the absorption cell 3.

The transmitted light of the absorption cell 3 is incident on the photodetector 4, the output of the photodetector 4 is connected to one input terminal of the synchronous detection circuit 6, and the other input terminal of the synchronous detection circuit 6 is an oscillator. 5 outputs are connected.

The output of the synchronous detection circuit 6 is connected to one input terminal of the current control circuit 7, and the output signal of the oscillator 5 is connected to the other input terminal of the current control circuit 7. The output of the current control circuit 7 supplies a driving current to the semiconductor laser 1.

On the other hand, the semiconductor laser 1 and the temperature detector 8 are provided inside the thermostatic chamber 10, the output of the temperature detector 8 is connected to the temperature control circuit 9, and the control signal of the temperature control circuit 9 is sent to the semiconductor laser 1. Connected.

The operation of the conventional example shown in FIG. 3 will be described. The detailed operation is described in Japanese Patent Application No. 3-106390 filed by the applicant of the present application, and only the basic part will be described.

The light transmitted through the absorption cell 3 is absorbed by the standard substance enclosed in the absorption cell 3 at a specific frequency and is incident on the photodetector 4 to be converted into an electric signal. A differential waveform is obtained by synchronously detecting the electric signal based on the output signal of the oscillator 5 having the current modulation frequency in the synchronous detection circuit 6.

By controlling the oscillation frequency of the semiconductor laser 1 at the inflection point of this differential waveform, the oscillation frequency is controlled to the center line of the absorption line of the standard substance, and the frequency is stabilized.

Further, in general, the oscillation frequency of the semiconductor laser 1 is easily affected by temperature, and as can be seen from the characteristic curve diagram showing the relationship between the temperature and the oscillation frequency of the semiconductor laser 1 of FIG.
The oscillation frequency of the semiconductor laser 1 also changes as the temperature of the semiconductor laser 1 changes.

For example, if the temperature of the semiconductor laser 1 is "TLD"
When changing from 0 "to" TLD2 ", the semiconductor laser 1
Oscillation frequency changes from "FLD0" to "FLD2".

Therefore, the semiconductor laser 1 is provided in the constant temperature chamber 10, the temperature of the constant temperature chamber 10 is detected by the temperature detector 8, and the temperature of the semiconductor laser 1 is controlled based on the detected temperature to obtain the oscillation frequency. It is possible to obtain more stabilized output light.

[0014]

However, in the conventional example shown in FIG. 3, although the temperature of the semiconductor laser 1 is controlled to be equal to the temperature detected by the temperature detector 8, the semiconductor laser 1 and the temperature detector are controlled. When the thermal resistance between the semiconductor laser 1 and the semiconductor laser 8 is large, the actual temperature of the semiconductor laser 1 does not match the temperature detected by the temperature detector 8.

That is, the temperature of the semiconductor laser 1, which should have been temperature-controlled, fluctuates as the ambient temperature fluctuates.

For example, FIG. 5 shows the ambient temperature and the semiconductor laser 1.
6 is a characteristic curve diagram showing the relationship with the temperature of the semiconductor laser 1. When the ambient temperature rises from "TA0" to "TA2" as shown in FIG. 5, the temperature of the semiconductor laser 1 also changes from "TLD0" to "TLD0".
LD2 ″, the oscillation frequency of the semiconductor laser 1 also fluctuates as described above, and the frequency cannot be stabilized outside the lock range of the current control. Therefore, the object of the present invention is Another object is to realize a frequency-stabilized semiconductor laser light source with a wide frequency range, in which the oscillation frequency is not affected by the ambient temperature even when the thermal resistance with the temperature detector is large.

[0017]

In order to achieve such an object, according to the present invention, the output light of a semiconductor laser is transmitted through an absorption cell in which a standard substance is enclosed, and the absorption line of the standard substance is changed to the semiconductor laser. A frequency-stabilized semiconductor laser light source for controlling the oscillation frequency of the semiconductor laser,
Frequency control means for controlling the oscillation frequency of the semiconductor laser to the absorption line, a first temperature detector for detecting the temperature of the semiconductor laser, a second temperature detector for detecting ambient temperature, and the first temperature detector. And temperature control means for controlling the temperature of the semiconductor laser based on the output of the second temperature detector.

[0018]

The temperature of the semiconductor laser is controlled by detecting the ambient temperature with the second temperature detector, converting this value into the temperature change of the semiconductor laser, and controlling the temperature of the semiconductor laser based on this value. However, even if the thermal resistance between the semiconductor laser and the first temperature detector is large, the oscillation frequency is not affected by the ambient temperature.

[0019]

The present invention will be described in detail below with reference to the drawings.
FIG. 1 is a configuration block diagram showing an embodiment of a frequency-stabilized semiconductor laser light source according to the present invention. Where 1-8,
10, 50 and 100 are denoted by the same reference numerals as in FIG.

In FIG. 1, 11 is a temperature detector, 12 and 16 are constant current sources, 13, 15, 17, 19, 21, and 2.
2 is a resistor, 14, 18 and 23 are operational amplifiers, 20 is a voltage source, 24 is a control circuit, 110, 111, 112 and 1
13 is a voltage. Further, 12 to 24 are temperature control means 5
Make up one.

The connection relationship between the frequency control means 50 and the constant temperature bath 10 is the same as that shown in FIG. The output of the temperature detector 8 is connected to one end of the constant current source 16, one end of the resistor 17 and the inverting input terminal of the operational amplifier 18, and the output of the operational amplifier 18 is connected to the other end of the resistor 17 and one end of the resistor 19. .

On the other hand, the output of the temperature detector 11 is the constant current source 1
2 is connected to one end of the resistor 13, one end of the resistor 13 and the inverting input terminal of the operational amplifier 14, and the output of the operational amplifier 14 is connected to the other end of the resistor 13 and one end of the resistor 15.

The output of the voltage source 20 is connected to one end of the resistor 21, and the other end of the resistor 21 is connected to the other ends of the resistors 15 and 19, one end of the resistor 22 and the inverting input terminal of the operational amplifier 23, respectively. To be done.

The output of the operational amplifier 23 is connected to the other end of the resistor 22 and the control circuit 24, and the output of the control circuit 24 is connected to the semiconductor laser 1 as a control signal. Further, the other ends of the constant current sources 12 and 16 and the operational amplifiers 14, 18 and 2
The non-inverting input terminal of 3 is grounded.

The operation of the embodiment shown in FIG. 1 will be described with reference to FIG. FIG. 2 is a characteristic curve diagram showing the relationship between the ambient temperature and the temperature of the semiconductor laser 1.

A current corresponding to the detected temperature is output from the temperature detector 8, and the constant current source 16 subtracts the offset current component. This current is transferred to the resistor 17 and the operational amplifier 18.
Is converted into a voltage 111. Similarly, the temperature detected by the temperature detector 11 is also converted into a voltage 112 using 12 to 14.

The voltage 110 from the voltage source 20 and the voltages 112 and 111 from the operational amplifiers 14 and 18 are the resistor 15,
The voltage 113 of the addition result is input to the adder composed of 19, 21, and 22 and the operational amplifier 23, and the control circuit 24
Entered in.

The output voltage 110 of the voltage source 20 corresponds to the set temperature, and if the temperature of the semiconductor laser 1 changes, the voltage value of the voltage 111 changes and the voltage 113 as the addition result also changes. Here, the control circuit 24 controls the temperature of the semiconductor laser 1 by the voltage 113 so that the voltage 111 becomes equal to the voltage 110.

On the other hand, when the ambient temperature changes, the voltage value of the voltage 112 changes, and the voltage 113 as the addition result also changes. At this time, the control circuit 24 considers that the temperature of the semiconductor laser 1 has changed and controls the temperature of the semiconductor laser 1.

For example, in FIG. 2, the ambient temperature is "TA
Consider the case where it rises from 0 ”to“ TA2. ”At this time,
When the thermal resistance between the semiconductor laser 1 and the temperature detector 8 is large, the temperatures of the semiconductor laser 1 and the temperature detector 8 are different as described above, and the actual temperature of the semiconductor laser 1 is shown in FIG. As shown in "a", "TLD0" is not "T"
It rises to LD2 ".

On the other hand, the temperature detector 11 detects the change in the ambient temperature, and the circuit composed of 12 to 14 detects the voltage 1
12 is generated.

[0032] Here, when the resistance value of the resistor 15 and the resistor 19 were respectively "R _15" and _{"R 19", R 19 /} R 15 = (TLD2-TLD0) / (TA2-TA0) and (1) To be set.

That is, by the adder composed of the resistors 15, 19, 21 and 22 and the operational amplifier 23, the variation "TA2-TA0" of the ambient temperature is converted into the variation "TLD2-TLD0" of the temperature of the semiconductor laser 1. Therefore, the control circuit 24 considers that the temperature of the semiconductor laser 1 has become “TLD2”, and the semiconductor laser 1 is thus added.
The temperature of is controlled to be "TLD0".

As a result, the ambient temperature is detected by the temperature detector 11, this value is converted into a temperature change amount of the semiconductor laser 1, and the temperature of the semiconductor laser 1 is controlled by the control circuit 24. The temperature is not affected by the ambient temperature as shown by "B" in FIG. That is, the oscillation frequency is not affected by the ambient temperature.

[0035]

As is apparent from the above description,
The present invention has the following effects. By detecting the ambient temperature with the second temperature detector and converting this value into the temperature change of the semiconductor laser to control the temperature of the semiconductor laser, the temperature of the semiconductor laser becomes constant with respect to the ambient temperature, It is possible to realize a frequency-stabilized semiconductor laser light source with a wide frequency lock range in which the oscillation frequency is not affected by the ambient temperature even if the thermal resistance between the laser and the first temperature detector is large.

[Brief description of drawings]

FIG. 1 is a configuration block diagram showing an embodiment of a frequency-stabilized semiconductor laser light source according to the present invention.

FIG. 2 is a characteristic curve diagram showing a relationship between ambient temperature and semiconductor laser temperature.

FIG. 3 is a configuration block diagram showing an example of a conventional frequency-stabilized semiconductor laser light source.

FIG. 4 is a characteristic curve diagram showing the relationship between the temperature of the semiconductor laser and the oscillation frequency.

FIG. 5 is a characteristic curve diagram showing a relationship between ambient temperature and semiconductor laser temperature.

[Explanation of symbols]

 1 Semiconductor Laser 2 Beam Splitter 3 Absorption Cell 4 Photodetector 5 Oscillator 6 Synchronous Detection Circuit 7 Current Control Circuit 8, 11 Temperature Detector 9 Temperature Control Circuit 10 Constant Temperature Chamber 12, 16 Constant Current Source 13, 15, 17, 19, 21,22 Resistance 14,18,23 Operational amplifier 20 Voltage source 24 Control circuit 50 Frequency control means 51 Temperature control means 100 Output light 110,111,112,113 Voltage

Claims (1)

[Claims] 1. A frequency-stabilized semiconductor laser light source, wherein an output light of a semiconductor laser is transmitted through an absorption cell in which a standard substance is encapsulated, and an oscillation frequency of the semiconductor laser is controlled by an absorption line of the standard substance. A frequency control unit that controls the oscillation frequency of the semiconductor laser to the absorption line; a first temperature detector that detects the temperature of the semiconductor laser; a second temperature detector that detects an ambient temperature; 1. A frequency-stabilized semiconductor laser light source, comprising: temperature control means for controlling the temperature of the semiconductor laser based on the outputs of the first and second temperature detectors.