JPS59112677A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To produce a detecting light without light loss and to reduce the size and weight of a semiconductor laser device by arranging a photolead unit at one light emitting side of a semiconductor laser element for emitting lights in bidirections. CONSTITUTION:A thermoelectric cooling element 12 is mounted on a heat sink fin 13, and a copper heat sink 8 is secured onto the element through an insulating layer 11 and a metal plate 10. Then, when photolead units each of which has a semiconductor laser element 1 of GaAsAlGaAs double hetero structure and a photodetector 5 made of a solar battery or the like are aligned and arranged on the sink 8, a difference is formed on the surface, on which the photodetector 5 is placed, and the placing surface of the element 1 is projected. In other words, the photodetector 5 in which an insulating layer 9 is covered on the bottom and the side of the element 1 is disposed at the side of the light 4 of the laser lights 3, 4 emitted from the active layer 2 of the element 1 in bidirections, the output from there is amplified by an amplifier 6 as a detecting light. In this manner, the monitoring light can be produced without loss.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an injection type semiconductor laser, in particular a continuous or nearly continuous tutee ratio (DuT) at room temperature or near room temperature.
ty Ratio).

[Background of the invention]

As the temperature of the semiconductor laser device increases, the oscillation threshold current also increases. For example, I Hayashi (1, H
ayashi) and several others are authors of the American academic journal ``Journal of Applied Physics'' (Jou
rnal of Applied physics)
Paper I submitted to Volume 42, Page 1929 (1971)
As reported in ``GaAs - AtX ()a I-x AS Double Heterojunction Injected Laser'', when a semiconductor laser is driven with a constant current, the laser output changes as the ambient temperature changes. do.

In other words, the temperature change of the threshold current "Jth" is J + h
= Jo eXp(T,/To) −
--(1) (Tat, Jo, and 'ro are all parameters that determine the change in 'threshold current' with respect to temperature, and are determined depending on the element.) Double heterojunction structure GaAS- Consider the case where an AtQaAs laser is operated. When the temperature T of the semiconductor laser element changes by ΔT, the threshold current II J , h is obtained from equation (1). Operation of the semiconductor laser element If the current is J, then the change ΔP in the laser output P due to the temperature change of the element is as follows.

If we set J=(1+ε)Jtb (where ε is a parameter that determines the operating point of the half-four-body laser element).

When ε=Qyl, T, =120', the following equation holds.When the temperature of the element rises by 6c from the operating point, the laser output is halved. Of course, if the device is used with a large ε, the rate of change in laser output with respect to temperature changes will decrease, but on the other hand, the rate of deterioration of semiconductor laser devices will increase as the operating current increases. ``It is desirable to operate it nearby.

As mentioned above, the optical output of a semiconductor laser is easily influenced by the temperature of the element, so under normal conditions where no means of maintaining a constant temperature is taken, other methods are required to maintain the laser output at a steady state. A means of doing so is required.

Conventionally, semiconductor laser devices equipped with such means have not been commercially available, but in the field of gas lasers, a portion of the laser light is separated by a beam splitter.
The extracted laser light is extracted using an optical system such as a 5 splitter), and the extracted laser light is detected by an appropriate photodetector. If the laser output changes, the detected output is returned to the gas gas laser excitation power source, and the gas gas laser is Means are employed to maintain a constant laser output by controlling the supply input to the laser.

The same method can be used to combine semiconductor lasers, but introducing an optical system such as a beam splitter into a semiconductor laser device, which is designed to be small and lightweight, will make the device larger. Moreover, large optical losses occur at the beam splitter. Since a semiconductor laser has a lower optical output than a gas laser, such light loss becomes a big problem. In theory, sufficient optical output can be obtained by increasing the operating current by Jfa, but increasing the operating current accelerates deterioration of the semiconductor laser device, which is detrimental to the life of the device.

[Purpose of the invention]

In view of this point, the present invention makes it possible to extract light for one output without causing any loss to the output light extracted from the semiconductor laser element, and without compromising the advantages of small size and light weight of the semiconductor laser element. It is possible to efficiently extract the above output light with a simple structure. i! The purpose is to provide a J-integrated laser device.

[Summary of the invention]

The semiconductor laser device of the present invention includes a semiconductor laser system element, a light receiving system element, and a support for arranging the two elements in a positional relationship such that the two elements enter one optical path of the laser light bidirectionally transmitted from the semiconductor laser. By arranging a light guide body near the semiconductor laser element so as to output the other laser light from the semiconductor laser element as output light *υ, there is no loss in the output light. The light for monitoring can be taken out without any noise, and the above-mentioned output source can be taken out efficiently through the light guiding body.

[Embodiments of the invention]

The present invention will be explained below using examples.

FIG. 1 is a diagram schematically showing the configuration of an embodiment of a semiconductor laser device according to the present invention. This semiconductor laser device (directly) consists of a semiconductor laser element 1, a steel heat sink 8, a heat dissipating cooling element 12, a heat dissipation fin/13, and a photodetector 5, 6 an amplifier for the output of the photodetector, 7 The semiconductor laser device 1 is an ()aAS-AtGaAs double heterostructure laser, which is equipped with a power supply 14 and a load resistor. When an electric current th greater than the "threshold current" is passed through 15=i, laser oscillation occurs, and laser beams 3 and 4 are emitted from the two cleavage planes (i.e., reflective surfaces) at both ends of the active vehicle 2, respectively. The laser beam 3 can be used as a light source for optical communication, optical information processing, spectrometer, etc.
The laser beam 4 emitted from the laser beam 4 is irradiated onto 1 ml of light received by a photodetector 5 placed close to the laser element 1. As this photodetector 5, for example, an aAS semi-floating laser (within the range of about 7,500 to 9,000 people),
Sensitivity 1 for 1-inch hot water battery made of Si, PIN source detector, etc.
, Akira F! Cities are better in terms of characteristics. In this embodiment, the photodetector 5 operates in short-circuit DC mode, which is relatively stable with respect to temperature.
cost. The photodetector 5 is electrically isolated from the heat sink 8 by a thin insulating layer 9. The temperature T of the active layer 2 of the semiconductor laser system f1 is determined by the electric power supplied to the laser system I, the ambient temperature T1, and the current flowing through the thermoelectric cooling system 12. Laser, (Tun IJ-1i flow exposed to Rokuko is V and 1 respectively, 1MAIhL of heat sink 8 is Th, then T1=Th+θV'I...
・(5) and Ith=IoeXl)(Tj/'J,'o) ・-
・−・−(6) There are threads around one turn. Here, θ is the heat t(l; hole) of the laser element l and the heat sink 8, and Lh is t/
- The threshold current of the system element 1. The optical output P of the laser is
P=η(I-Lb) ・・・・・・(7
) is given by a). Here, η is a constant of proportionality θ. From the above equation (3), the laser output can be determined as a function of direct current and heat sink temperature. Figure 2 is a performance diagram schematically showing the calculation results, and the vertical axis is the laser output P.
, the horizontal axis represents the current ■, and the parameter is the temperature Th of the heat // T h a > T h + > T b 2
It is. From FIG. 2, it can be seen that there are various combinations of @, flow, and heat tank temperature necessary to obtain the laser output P1. When the heat sink 1iiAK is fixed, the current value 1 required to obtain the laser output P1 is 20%, but of course lower frost and current values are preferable. Sakae: When the heat sink is equipped with the thermoelectric cooling element 12 as in the embodiment 151 of FIG. 1, the temperature of the heat sink can be selected within a considerable range. Now, if the heat sink temperature is T h H, the required current is 1. From the viewpoint of obtaining the necessary laser output with as small a current as possible, it is preferable to select the heat sink temperature Thl lower than the ambient temperature T, that is, Th =T, -ΔT ・・・・・・・・・
(8). Here, ΔT is the temperature difference maintained by the thermoelectric cooling element 12, and is determined by the current flowing into the thermoelectric element. Now, if the ambient temperature is 1゛1, for some reason θT
, and the heat sink temperature becomes Th3 (Sa T b
1+θT), and if the direct current supplied to the thermoelectric cooling system does not change, the laser output decreases from the predetermined laser output 1 direct P+ to P3. In the embodiment shown in FIG. 1, the signal 1g, which is proportional to the laser output 4 monitored by the photodetector 5, is amplified by the amplifier 6 and then converted to a reference value (i.e., a predetermined laser output value in this embodiment). P1
The current supplied from the power supply 7 to the thermoelectric cooling element 12 is changed so that the variation from the reference value approaches zero. In the above case, the variation aT in the ambient temperature is canceled out. Thus, the temperature difference ΔT maintained by the thermoelectric cooling system is changed to ΔT10T.

Temperature control using thermoelectric cooling system has a fast response (less than 1 second)
Also, it has the advantage of being able to make the temperature higher or lower than the ambient temperature depending on the polarity of the direct current, so it has the advantage of being able to keep the laser output constant even in environments where the ambient temperature fluctuates wildly. be. - For example, if the ambient temperature is between 110C and 45C, the output fluctuation will be reduced by 5C.
It can be kept within %. Furthermore, another advantage of this embodiment is that the laser beam 4 for monitoring is provided independently of the laser beam 3 to be used. That is, since the laser beams 3 and 4 are emitted from the same optical cavity, their outputs are proportional to each other, so by controlling the laser output 4 to keep it constant, the amount of laser beam 3 to be used can be reduced. This allows the output to be kept constant.

As described above, in this embodiment, since a monitoring optical system is not required, an optical fiber or the like is placed close to the laser system element 1 and the laser beam 3 is directly introduced into the fiber. In this case, the semiconductor laser system and the photodetector are arranged on a heat sink, and it is only necessary to align the laser beam 3 and the optical fiber, so it is preferable. If the reflectances of the two reflective surfaces are equal, the magnitudes of the laser outputs 3 and 4 are equal, but the output 4 for monitoring is not affected by small stones, so
Output 4? It is preferable that the reflective surface to be taken out be coated with an insulating film and a metal coating film to increase the reflectance. By increasing the reflectance of one of the reflective surfaces, the oscillation threshold current llI! This is because it can be made smaller.

Moreover, since the photodetector 5 is installed on the same heat sink 8 as the semiconductor laser element F1, the temperature of the photodetector 5 is also kept almost constant, and therefore the photodetector The sensitivity of the device also has the advantage of being less affected by ambient temperature. Note that if the output of the semiconductor laser element is directly modulated, it is necessary to incorporate a low-pass filter into the amplifier 6. At this time, the time average of the radar output is kept constant. Furthermore, in the implementation flJ shown in FIG.
Since the photodetector is also kept at a substantially constant temperature, there is an advantage that the sensitivity of the seven-color detector is also kept substantially constant.

FIG. 3 shows a schematic configuration diagram of an embodiment of a semiconductor laser device according to the present invention. In FIG. 3, of the laser beams emitted from two reflective surfaces of the semiconductor laser device 1, four laser beams are irradiated onto a photodetector 5 mounted on a heat sink.

The output obtained by the photodetector 5 is amplified by an amplifier 6 and compared with a value corresponding to a predetermined laser output PL, and the power supply source 14' to the laser beam is adjusted so as to cancel out the corresponding fluctuation.
control. This embodiment differs from the configuration of the embodiment shown in FIG. 1 in that the supply gap to the laser cable is adjusted to cancel out changes in laser output. As can be seen from the characteristic diagram in Figure 2, the maximum value of the laser output that can be obtained under conditions of continuous operation or near-continuous duty ratio is determined by the ambient temperature. Examples are difficult to explain. Furthermore, as is clear from Figure 2, there are operating conditions in which the optical output decreases as the current increases, but it is undesirable to reduce the output to Node 1 under such conditions, and the optical output increases with the current. It should be operated under such conditions. Therefore, in this embodiment, the ambient temperature of the semiconductor laser element is kept almost constant, and the temperature on the heat sink 8 is kept almost constant by a herring-like cooling element, a heat sink, or a four-layer cooling element. In addition, it can be used to precisely control the output. −
As an example, a temperature change of ±3C instead of a room temperature of 25C,
The output stability when it is tilted is ±2 heads. When the laser beam is absorbed, a low-pass filter is provided in the J chamber 6 as in the embodiment shown in FIG.

In addition, a current limiting device r is provided in the first source 14' to prevent the current 15ti, lif flowing through the laser cord from becoming too large and causing an unstable chain reaction in which the laser output decreases as the current increases. is desirable.

In addition, in the case of cleavage shown in Figure 3, we have described a case in which the caviar of a semiconductor laser can be composed of 21 opposing reflecting surfaces, but the amount of reflection is determined by cleaving, polishing, etching, ion etching. In addition to those that utilize flat surfaces obtained by means such as milling, the present invention can also be applied to those that utilize Bragg reflection obtained from a periodic structure provided in the active layer of a laser or in the propagation path of laser light. can do. This is because even in the latter case, it can be assumed that there are 2j white reflective surfaces equimfi.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to achieve the effects described below. That is, (1) Since one of the laser beams bidirectionally emitted from the two reflecting surfaces of the semiconductor laser element is extracted as output light and the other is monitored by the optical output device, the two-way turning power of the semiconductor laser element is reduced. All of the light can be used for >J・υ. On the other hand, if you monitor only with the light between 〃・ra, the 7e and round 吾 will be wiped a little, and you will be unable to do it yourself.

■ In addition, since the light for the 72 is extracted without a structure for each floor, there is no need for an e2 light-≠ system.
・It is not complicated to use and provides stability as a device. As a result, the cost of the device can be reduced and mass productivity is excellent.

■ The semiconductor laser element is generally housed in a package, and the laser beam is extracted by opening the light extraction window to extract the laser beam. However, the positioning for both the output light and the monitor source must be adjusted.・dVCfj) is difficult. In the present invention, the semiconductor laser confectionery and the light receiving element can be housed in one package, and the output light can be taken out to the outside in just one unit, so positioning with the light guiding body is easy. It will be held in

[Brief explanation of the drawing]

FIG. 1 shows disaster relief 1 of the semiconductor Ray V device according to the present invention.
Figure 2 is a diagram showing the relationship between the radar output, current, and temperature of the heat sink of a four-wire generator that operates in coupled operation or at a near-continuous tute ratio. , the third section is a top view of the second implementation column of the semiconductor noser device according to the present invention F and a block diagram of the control circuit. In FIGS. 1 to 3, l...semiconductor laser element, 2...
・Semiconductor laser cleaning layer, 3, 4...Laser light, 5.
・Optical converter, 6... Amplifier, 7... Source for control circuit and thermal cooling element, 8... Heat sink, 9... Insulating layer, 10... Metal plate, 11...・e-en pigeon, 12...
・Thermal cooling element, 13... Radiation fin, 14... Power supply for semiconductor laser, 14'... Control circuit 379- 2nd Fig. 11 r

Claims (1)

[Claims] 1. It has a semiconductor laser element, a light receiving element, and a support body in which the pixel element is arranged in a positional relationship such that it enters one optical path of the laser light bidirectionally transmitted from the semiconductor laser element, and A semiconductor laser device characterized in that a light guide body is disposed near the semiconductor laser element so as to extract the other laser light from the semiconductor laser element as output light.