JPH0738202A - High-output-power semiconductor laser - Google Patents

Abstract

PURPOSE:To prevent the occurrence of noises casued by returning light and the fluctuation in output in high-output broad-area lasers, phased-array lasers or MOPA-type semiconductor lasers. CONSTITUTION:A part of a laser beam 13, which is emitted from a high-output- power semiconductor laser 10 such as an MOPA-type semiconductor laser, is diffracted at a grating 15 and fed back into the semiconductor laser 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser, and more particularly to a high output broad area laser, a phased array laser and a master oscillator / power amplifier type semiconductor laser.

[0002]

2. Description of the Related Art Broad area lasers, phased array lasers, and master oscillator / power amplifier type semiconductor lasers have been known as high-power semiconductor lasers. Especially Elect
ronics Letters Vol.
28 No.21 pp 2011-2013 As shown in Master Oscillator Power Amplifier (Maste
r Oscillator Power Amplifier (MOPA) type semiconductor laser is composed of the Master Oscillator part and the TWA (T
Power Amplifier consisting of raveling Wave Amplifier)
It has a fier part and is capable of obtaining a high-power laser beam with a narrow spectral width in a single longitudinal mode.

[0003]

However, in these high-power semiconductor lasers, the amount of return light from the external optical system is particularly large due to the large oscillation power, and therefore the return light seen in many other semiconductor lasers is used. Noise and output fluctuations are likely to occur.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a high-power semiconductor laser capable of preventing the occurrence of noise due to the returning light and the fluctuation of the output. is there.

[0005]

A high-power semiconductor laser according to the present invention is combined with a grating that diffracts a part of a laser beam emitted from the laser and returns it to the semiconductor laser, and the semiconductor laser and the grating are simultaneously heated. It is characterized by being adjusted.

[0006]

When the laser beam diffracted by the above grating returns to the high power semiconductor laser,
Since so-called optical feedback is applied and the oscillation wavelength (frequency) is locked, it is possible to prevent generation of noise and fluctuation of output due to the returning light.

In particular, in a MOPA type semiconductor laser, the feedback light is usually amplified by about 20 dB by the power amplifier part, so that the oscillation wavelength locking effect due to the optical feedback becomes particularly remarkable, and this semiconductor laser is effective against the return light. Will be particularly strong.

An external resonator is constituted by the above-mentioned grating. Since the external resonator is temperature-controlled simultaneously with the semiconductor laser, the wavelength of the semiconductor laser is almost perfect to the wavelength determined by the external resonator. It will be locked to and you will not be able to mode hop.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the embodiments shown in the drawings. FIG. 1 shows a high power semiconductor laser according to the first embodiment of the present invention, and FIG. 2 shows a MOPA type semiconductor laser 10 used therein. This MOPA type semiconductor laser 10 is as shown in FIG.
It has an active region 10a, a single mode optical waveguide 10b, a master oscillator portion 10c and a power amplifier portion 10d. The above master oscillator part
10c is generally composed of a DFB (distributed feedback type) laser, but in the present invention, since optical feedback as described later is applied, it is not limited to the DFB laser and may be composed of a normal single longitudinal / transverse mode laser. I do not care.

As shown in FIG. 1, the semiconductor laser 10 having the above structure is fixed on a mount 12 made of Invar alloy or the like, which is housed in a case 11. A laser beam in a divergent light state emitted from this semiconductor laser 10.
The collimator lens 14 collimates the light 13.
This collimated laser beam 13 is a grating
Diffracted at 15 and this diffracted laser beam 13 (0th order light)
Goes out of the case through the transparent window 16 attached to the case 11.

The collimator lens 14 and the grating 15 are also fixed on the mount 12.
12 is mounted on a Peltier device 17 fixed to the case 11. Then, the thermistor 18 is arranged on the mount 12, and the Peltier element 17 is driven by a temperature control circuit (not shown) that receives the temperature detection signal,
The semiconductor laser 10, the collimator lens 14, and the grating 15 are kept at a predetermined temperature.

Here, a part of the laser beam 13 incident on the grating 15 is diffracted there, and the diffracted laser beam 13 (−1st order light) returns to the semiconductor laser 10 through the collimator lens 14. The light quantity of this -1st order light is
The amount of light of the laser beam 13 incident on the grating 15 is, for example, about 0.1%. Grating in this way 15
Since the wavelength of the laser beam 13 diffracted by is selected by the grating 15, the frequency width (wavelength width) is sufficiently narrowed to, for example, about 1 MHz.

A part of the laser beam 13 is, for example, a transparent window 16
It may be reflected by an optical element such as a lens after that or the like, and the reflected light may be returned light and enter the semiconductor laser 10. However, as described above, the laser beam 13 (-1
Since the oscillation wavelength of the semiconductor laser 10 is locked by feeding back the (second light) to the semiconductor laser 10, it is possible to prevent noise or fluctuation of the output due to the returning light.

Particularly in the MOPA type semiconductor laser, the laser beam 13 diffracted by the grating 15 is
Power amplifier part 10d of semiconductor laser 10
After being amplified about 20 dB at the master oscillator part
Since it is incident on 10c, the effect of preventing the generation of return light noise and the prevention of output fluctuation due to the optical feedback becomes particularly remarkable.

Further, in this embodiment, since the semiconductor laser 10, the collimator lens 14 and the grating 15 on the mount 12 are simultaneously temperature-controlled, the optical distance between these elements can be kept constant. Therefore, it is possible to suppress the mode hop due to the change of these optical distances.

Next, a high power semiconductor laser according to a second embodiment of the present invention will be described with reference to FIG. The device of the second embodiment is different from the device of the first embodiment shown in FIG. 1 in that a broad area laser 20 is used in place of the MOPA type semiconductor laser 10.
Hereinafter, differences from the first embodiment will be mainly described.

In general, the broad area laser is different from the above-mentioned MOPA type semiconductor laser in that its longitudinal mode is a single mode. Therefore, the light (-1st-order light) diffracted by the grating 15 is broad area laser.
By returning to 20, the number of longitudinal modes can be suppressed. As a result, the number of longitudinal modes is suppressed and the temperature of the broad area laser 20, collimator lens 14 and grating 15 is controlled simultaneously, so the optical distance between these elements can be kept constant and the broad area laser 20 can oscillate in a stable longitudinal mode. It also becomes possible to suppress mode hopping due to the change in the optical distance. As a result, it is possible to prevent noise from occurring due to the returning light and fluctuation of the output.

Also, when a phased array laser is used instead of the MOPA type semiconductor laser 10 shown in FIG. 1, the same effect as in the second embodiment can be obtained.

As the collimator lens 14, a general spherical lens or a combination of cylindrical lenses can be appropriately selected and used. Further, a beam shaping function by an anamorphic prism can be used. Those provided may be used.

[Brief description of drawings]

FIG. 1 is a partially cutaway side view of an apparatus according to a first embodiment of the present invention.

2 is a schematic perspective view of a MOPA type semiconductor laser used in the device shown in FIG.

FIG. 3 is a partially cutaway side view of a second embodiment device of the present invention.

[Explanation of symbols]

 10 MOPA type semiconductor laser 12 Mount 13 Laser beam 14 Collimator lens 15 Grating 17 Peltier element 18 Thermistor 20 Broad area laser

Claims (1)

[Claims] 1. A high-power semiconductor laser selected from a broad area laser, a phased array laser, and a master oscillator / power amplifier type laser, wherein a grating for diffracting a part of a laser beam emitted therefrom and returning the same to the semiconductor laser is provided. A high output semiconductor laser, characterized in that the temperature of the semiconductor laser and the grating are simultaneously adjusted while being combined.