JPH0532917B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor laser device that can reduce wavelength fluctuations of light emitted from a semiconductor laser element.

Semiconductor laser elements not only experience fluctuations in optical output due to changes in ambient temperature, but also shifts in laser oscillation wavelength.

For these reasons, when a semiconductor laser element is used for image recording or the like, the wavelength dependence of the sensitivity of the photoreceptor used in the device becomes a major problem.

Conventionally, semiconductor laser elements have been widely used as light sources in fields such as optical communications.
In such cases, Auto Power Control (hereinafter referred to as
(called APC) is often adopted.

The photodetector used for such APC is
Semiconductor photoelectric conversion elements are often used due to their ease of use, but when a semiconductor photodetector is used, the characteristics of the photodetector itself change with temperature, which hinders accurate control.

Particularly in the infrared light region emitted by a semiconductor laser, the detection sensitivity changes significantly depending on the temperature of the photodetector. Therefore, in order to control the amount of light with high precision, it is preferable to control the temperature of the photodetector itself by placing it in a constant temperature bath.

However, when a temperature control circuit that controls the temperature control element according to the temperature detected by the temperature sensing element is used to adjust the temperature of a semiconductor laser element that is easily affected by temperature, the temperature may become abnormal due to runaway of the circuit. becomes high,
There was a risk that the life of the semiconductor laser device would be significantly shortened, and furthermore, the semiconductor laser device would be destroyed.

Furthermore, when temperature is adjusted using a temperature control circuit, a temperature ripple, that is, a phenomenon in which the temperature changes in an impulse manner, often occurs. The temperature ripple may cause the emission wavelength of the temperature-sensitive semiconductor laser device to change rapidly, or in extreme cases, the semiconductor laser device may be destroyed. Furthermore, when attempting to construct a temperature control circuit with less temperature ripple, the circuit configuration became complicated and expensive.

In addition, in order to make a part of the output light of the semiconductor laser element enter the photodetector, an optical device such as a half mirror is required to split the output light, so if the above control is performed separately, the semiconductor laser The device configuration becomes complicated.

The present invention provides a semiconductor laser device with good temperature characteristics without using such a complicated structure.

Hereinafter, a semiconductor laser device according to an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view of an embodiment of the present invention in which a semiconductor laser element is housed in a metal can type IC case, and lead wires of each element are omitted for convenience of drawing.

1 is a metal can type IC case, and this case 1 consists of a base part 2 made of metal and a cylindrical part 3 provided integrally with the base part 2. One end of the cylindrical portion 3 is sealed with a glass 4, and the cylindrical portion 3, the base portion 2, and the glass 4 are sealed.
This creates a closed space.

A heat insulating block 5 whose part is fixed to the cylindrical part 3 and the base part 2 is provided in this sealed space, and a heat generating element 7 is fixed onto this heat insulating block 5. As the heating element 7, a self-temperature-controlled heating element such as a positive temperature coefficient thermistor is used.

Therefore, the heating element 7 is shielded from heat from the outside world by the heat insulating block 5, and the current value is controlled so that it maintains a constant temperature by itself.
It becomes possible to maintain a more stable temperature. On the other hand, a thermally conductive material 9 is closely fixed on the heating element 7, and a semiconductor laser element 10 is mounted and fixed thereon. For example, as shown in FIG. 2, such a semiconductor laser element 10 has a positive electrode contact 11, P
It is constructed by laminating a layer 12, an N layer 13, and a negative electrode contact 14, and the contact 1
By applying power between 1 and 14, laser beams L ₁ and L ₂ are emitted.

In FIG. 1, the semiconductor laser element 10 is fixed so that the laser beam L ₁ is emitted toward the glass 4, but there is no space on the optical path of the laser beam L ₂ on the thermally conductive material 9. A photodetector ₁ , such as a photodiode, for receiving laser light L2
Place 1. Reference numeral 13-1 indicates a pin for connecting an element housed in the case 1 to an external circuit. However, connection lines connecting the elements inside the case and the pins are not shown in order to avoid complication of the drawings.

FIG. 3 shows the control circuit of the semiconductor laser device as described above, and 14-1 indicates the detection signal detected by the photodetector 11.
This is a light amount control circuit that controls the driving power source for driving the semiconductor laser element 10 so that the laser beams L ₁ and L ₂ are always constant.

Reference numeral 15 denotes a power source for the heating element 7, which supplies a substantially constant voltage from the power source. As a result, the current is controlled so that the heating element 7 maintains a constant temperature by itself.

According to the above configuration, the output laser beam _L1 can always have a constant output and a constant oscillation wavelength regardless of changes in ambient temperature or aging of the semiconductor laser element, and the photodetector can be kept at a constant oscillation wavelength regardless of changes in ambient temperature or aging of the semiconductor laser element. By placing it on the element, it can be controlled extremely accurately.

Note that this embodiment does not necessarily need to use a case as shown in FIG. 1, but in the configuration shown in FIG. 1, the entire case can be used as a heat dissipation surface. Furthermore, if the inside of the case is vacuum sealed, it is effective in preventing dew condensation on the glass surface.

FIG. 4 shows another embodiment, in which a photodetector with relatively little temperature dependence is used.
This shows an example in which only a semiconductor laser element is placed and fixed on the end of a heat generating element.

It is a cross-sectional view of a semiconductor laser element housed in a metal can type IC case, and lead wires of each element are omitted for convenience of drawing. Reference numeral 19 indicates a metal can type IC case, and this case 19 is composed of a base portion 22 made of metal and a cylindrical portion 23 provided integrally with the base portion 22. One end of the cylindrical portion 23 is sealed with a glass 24, and the cylindrical portion 23, the base portion 22, and the glass 24 form a sealed space. A portion of the sealed space includes the cylindrical portion 23 and the base portion 22.
A heat insulating block 25 is fixed to the heat insulating block 25, and a heating element 27 is fixed on the heat insulating block 25. As this heating element, a self-temperature control heating element such as a positive temperature coefficient thermistor is used, which controls its own current so that a constant temperature is maintained when a constant voltage is applied. The heat conductive material 29 is the heating element 27
A semiconductor laser element 20 is mounted on the semiconductor laser element 20.
Place and fix.

A photodetector 21 such as a photodiode for receiving the light L ₂ emitted from the semiconductor laser element is placed on a substrate 30 placed on the base 22 .

According to this method, the heating element 27 only needs to heat the semiconductor laser element 20, which requires less heat generation energy and can also reduce the heat capacity, making it possible to control the temperature with good response.

As described above, according to this embodiment, the laser light has a substantially constant wavelength without being affected by the ambient temperature or by aging.

As explained above, according to this embodiment, the semiconductor laser element and the self-heating control type heating element are
By arranging it on a heat insulating block, the following remarkable effects can be obtained.

(a) Efficient temperature control can be achieved by reducing the influence of temperature changes applied from the outside through the sealed container and preventing the heat generated from the heating element from dissipating to the outside.

As explained above, according to the present invention, the following remarkable effects can be obtained by using a self-temperature-controlled heating element to control the temperature of a semiconductor laser element.

(b) To adjust the temperature of semiconductor laser elements that are easily affected by temperature, depending on the temperature detected by the temperature sensing element,
If a temperature control circuit is used to control the temperature control element, the temperature may become abnormally high due to runaway of the circuit, which may significantly shorten the life of the semiconductor laser element or even destroy the semiconductor laser element. It was hot. In the present invention, since a self-temperature-controlled heating element that does not require a temperature control circuit is used, the semiconductor laser element is free from the risk of deterioration or destruction due to abnormally high temperatures caused by runaway circuits as described above. The temperature can be adjusted by simply keeping the heating element in operation at all times.

(c) When temperature is adjusted using a temperature control circuit, a temperature ripple, that is, a phenomenon in which the temperature changes in an impulse manner, often occurs. The temperature ripple may cause the emission wavelength of the temperature-sensitive semiconductor laser device to change rapidly, or in extreme cases, the semiconductor laser device may be destroyed. Furthermore, if an attempt is made to configure a temperature control circuit with less temperature ripple, the circuit configuration will be complicated and expensive. In contrast, the present invention uses a self-temperature-controlled heating element that has a unique characteristic of not generating temperature ripples, so it has a simple and inexpensive configuration, and thus the fluctuation of the emission wavelength as described above can be avoided. can be prevented.

As described above, the self-heating controlled heating element is particularly suitable for adjusting the temperature of a semiconductor laser element that is easily affected by temperature.The combination of the self-heating controlled heating element and the semiconductor laser element enables You can get extraordinary effects like this.

[Brief explanation of drawings]

FIG. 1 is a partially cross-sectional perspective view showing a semiconductor laser device according to the present invention, FIG. 2 is a perspective view showing a semiconductor laser element, FIG. 3 is a control circuit diagram of the semiconductor laser device, and FIG. 4 is another embodiment. 1 is a partially cross-sectional perspective view showing a semiconductor laser device according to the present invention. Here, 5 and 25 are heat insulating blocks, 7 and 27 are heating elements, 9 and 29 are heat conductive materials, 10 and 20 are semiconductor laser elements, L ₁ ,
L ₂ is a laser beam, and 11 and 21 are photodetectors.

Claims (1)

[Scope of Claims] 1. A semiconductor laser device in which a semiconductor laser element is housed in a sealed container, comprising: a heat insulating block fixed in the sealed container; and a self-temperature-controlled heat generating device fixed on the block. What is claimed is: 1. A semiconductor laser device comprising: an element; and a thermally conductive material closely fixed on the heating element, the semiconductor laser element being placed and fixed on the thermally conductive material. 2. In a semiconductor laser device in which a semiconductor laser element and a photodetection element that receives light emitted from the semiconductor laser element are built in a sealed container, a heat insulating block fixed in the sealed container and a a self-temperature-controlled heating element fixed to the
A semiconductor laser device comprising: a thermally conductive material closely fixed on the heat generating element; and the semiconductor laser element and the photodetector element are mounted and fixed on the thermally conductive material.