JPH0766383A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To obtain high resolution in a lighweight device at a low cost, by constituting a plurality of lasers different in light emission direction and photodetectors on the same semiconductor substrate. CONSTITUTION:A laser array region 1 and a diffraction grating region 2 are formed on a semiconductor substrate 6. Five semiconductor lasers 3 having the same structure are formed in the laser array region 1. Diffraction gratings 2 (5a-5e) having different periods are formed in the diffraction grating region 2. A semiconductor thin film 10 composed of a plurality of layers is grown on the semiconductor substrate 6. This thin film 10 is composed of an active layer 7, an upper clad layer 8, and a lower clad layer 9. One end of the active layer 7 is a cleavage face 11 acting as a reflecting mirror surface. A first diffraction grating 4 and a second diffraction grating 5 are formed on the upper clad layer 8. The first diffraction grating acts as a DBR and constitutes a resonator together with the cleavage face 11. Thereby high resolution can be obtained in a lightweight device at a low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser which emits laser beams of the same wavelength in a plurality of directions and a semiconductor laser radar using the same.

[0002]

2. Description of the Related Art As a conventional semiconductor laser device which emits laser light in different directions, there is one shown in FIG. In the figure, 15 is an outgoing beam, 16 is a laser chip, and 17 is a printed circuit board. In this semiconductor laser, it is necessary to form a Fabry-Perot resonator,
A cleaved surface of a semiconductor crystal or the like is used for the reflecting surface. However, since the direction in which cleavage is easy is limited, the direction in which laser light is emitted is also limited. For example, the substrate (10
0) With a GaAs crystal, the cleavage plane occurs on the {110} plane. There is also a method of forming a reflecting surface by etching without using a cleaved surface, but it is possible to etch in a direction perpendicular to the surface, and since only the {100} surface can be used as a reflecting surface, light is emitted in any direction. (See Resources Proceedings of the Seventh Conference on Solid State Devices, Pro
ceeding of the 7th conference on Solid State Devic
es, 1975, pp. 293). Therefore, in order to emit light in a plurality of directions, a discrete structure as shown in FIG. 8 has been used. Specifically, a required number of laser chips 16 are prepared, and they are mounted on a printed circuit board 17 or the like in advance with an angle difference in the laser emission direction.

[0003]

However, in such a conventional semiconductor laser device, (1) the cost and weight increase due to the discrete structure, (2) it is difficult to set the angle accurately, and it is difficult to set the angle. Takes a lot of time,
(3) To increase the angular resolution, a large number of laser chips and optical systems are required, which is a problem. The present invention does not have the above-mentioned conventional problems, and is lightweight, inexpensive,
An object of the present invention is to provide a semiconductor laser device which requires a small number of assembling steps and has a sufficient angular resolution.

[0004]

In order to solve the above-mentioned problems, according to the present invention, the light emitting directions are not parallel to the main plane of the same semiconductor substrate but are different from each other and all are the same. A plurality of semiconductor lasers for emitting laser light of a wavelength, a light-receiving element having a sensitivity region for the wavelength of the laser light, and means for sequentially operating the semiconductor lasers to sequentially change the emission direction of light are provided. , A plurality of semiconductor laser light emitting directions different from each other, respectively, depending on the time between the time of emission and the time of detecting the scattered light from the object irradiated by the laser light, We decided to provide a distance counting circuit that measures and outputs the distance. Further, as a specific means for relatively easily realizing a plurality of laser light sources in which the emission directions of the laser light are different from each other, a plurality of semiconductor lasers that emit laser light of the same wavelength are provided on the same semiconductor substrate. A plurality of diffraction gratings that are combined with the formed semiconductor laser region and each of the above semiconductor lasers to form a pair and that emit laser light in mutually different directions due to the first-order diffraction effect are formed. The diffraction grating region thus formed is provided.

[0005]

By adopting the above means, a plurality of semiconductor lasers emitting laser light of the same wavelength in different directions, a light receiving element having a sensitivity region at the wavelength of the laser light, and the semiconductor laser are sequentially operated. Since the means for sequentially changing the light emission direction can be formed on the same semiconductor substrate and integrated into one chip, it is lightweight, inexpensive, and has a small number of assembly steps despite having sufficient angular resolution. A desired semiconductor laser device can be obtained.

[0006]

FIG. 1 is a diagram showing a first embodiment of the present invention. In this embodiment, as shown in FIG. 1, five semiconductor lasers are integrated. The semiconductor substrate 6 has a laser array region 1
And two areas of the diffraction grating area 2 are formed. Five laser diodes 3 having the same structure are formed in the laser array region 1. Diffraction gratings 2 (5a, 5b, 5c, 5d, 5e) having different periods are formed in the diffraction grating region 2. The individual configuration will be described with reference to FIG.

FIG. 2 is a diagram for explaining the pair of semiconductor lasers and diffraction gratings corresponding to each other shown in FIG.
It is an AA 'line sectional view shown inside. A semiconductor thin film 10 composed of a plurality of layers is grown on the semiconductor substrate 6. The thin film 10 includes an active layer 7 and an upper clad layer 8,
It is composed of the lower clad layer 9. When operating in the near infrared region, a GaAs substrate is used as the semiconductor substrate 6, GaAs is used as the active layer 7, and AlGaAs is used as the cladding layers 8 and 9. Further, one end of the active layer 7 is a cleaved surface 11 which is a reflecting mirror surface, and the other upper clad layer 8 is formed with a first diffraction grating 4 and a second diffraction grating 5. The first diffraction grating 4 is a DBR (Distrib-uted Bragg R
efrecter) and forms a resonator with the cleavage plane 11 described above. In addition, 12 is a cap layer, 13 is an upper electrode, and 14 is a lower electrode. When the period of the first diffraction grating 4 is T ₁ , the refractive index of the medium is n _e, and the first-order diffraction effect is used, oscillation occurs at a wavelength λ ₁ = 2 * n _e * T ₁ . The second diffraction grating 5 is used to guide the laser light upward. When the period is T ₂ , the angle between the wavefront of the diffracted light and the substrate 6 is θ, and the first-order diffraction effect is used, T ₂ = λ ₁ / (n _e *
The light is emitted in the direction in which (1 + sin θ)) (0 <θ ≦ 90 °) is satisfied. Therefore, in order to increase θ, that is, to emit light in a direction parallel to the substrate, the period of the second diffraction grating 5 may be reduced. In FIG. 1, the one with the subscript a is closer to parallel to the substrate, and the one with the subscript e is closer to vertical to the substrate. The situation is shown in FIG. In FIG. 3, 15 is an outgoing beam. The manufacturing method is normal D
The number of steps is almost the same as that of the conventional DBR since the pattern of the second diffraction grating 5 is simply added without any change from the BR laser.

FIG. 4 shows a second embodiment of the present invention. This embodiment is an example of a laser radar in which a light receiving element and a processing circuit are integrated on the same substrate. First, the configuration will be described. At the bottom of the semiconductor substrate 6 in the figure, 10 DFBs (distributed feedback type)
There is a distributed feedback laser 27, a HEMT 26 that drives it, and a second diffraction grating 5 that deflects light.
A drive circuit 21 that sequentially supplies signals to the HEMT 26 to sequentially operate the DFB laser 27, a light receiving element 24 that detects reflected light from an object irradiated on the laser, a preamplifier 23 that amplifies the output signal, a drive circuit 21 and the front. A distance counting circuit 22 for calculating a distance to an object by a signal from the on-amplifier 23,
The power supply circuit 20 and the input / output pad 25 are formed in the remaining part (upper part in the drawing). FIG. 6 is a sectional view taken along the line BB 'shown in FIG. In this embodiment, the high resistance layer 3 is used to integrate the DFB laser 27 and the HEMT 26.
3 is provided for element isolation. Further, the electrical connection to the active layer 7 is made by the diffusion layer 32. Further, 29 is a gate electrode of HEMT, and 31 is an electron transit layer. The isolation between the HEMTs 26 is made in the element isolation region 30 by O + ion implantation or the like. Although not shown, the light receiving element 24 is a photodiode, and the HEMT or the like described above is used for the other circuit portions. Further, in order to prevent the influence of the laser light on the light receiving element 24, the light blocking area 28 shown in FIG. 4 is provided. Light emission is performed as shown in FIG. 5, and switching is performed sequentially. The light emitted in a certain direction is reflected (generally scattered light) upon the object and returns. The light is detected by the light receiving element 24,
It is amplified by the preamplifier 23 and sent to the distance counting circuit 22. In this circuit, the distance information is obtained from the time from the emission of light to the detection of reflected light, the direction information is obtained by determining which laser the light is from, and the information is output. In the second embodiment, the spread of the beam in the direction of the diffraction grating is very small, and so-called fan-beam-shaped light is appropriately spread in the direction perpendicular to it, so that it is very useful when used for laser radar. It ’s convenient, so you do n’t need optics,
Since the light is emitted in the direction perpendicular to the substrate, the light receiving element can be easily integrated.

FIG. 7 is a diagram showing a third embodiment of the present invention. This embodiment is an example applied to a vertical cavity type semiconductor laser. First, the configuration will be described. The compound semiconductor thin film 10 and the isotropic etching surface 35 are formed on the semiconductor substrate 6. To form this surface 35, HCl: H ₂ O ₂ : H ₂ O =
An isotropic etching solution such as 80: 4: 1 is used. The semiconductor thin film 10 includes a multilayer reflective film 18, an active layer 7, a cap layer 12, an ohmic contact layer 19, a high resistance layer 33, and an electron supply layer 36. Since the structure of the HEMT 26 portion is the same as that of the second embodiment, its explanation is omitted. Active layer 7
Current is injected to the upper electrode 13 and the lower electrode 14 through a contact hole formed in the insulating layer 34 so that the current flows only in a necessary portion. The light generated in the active layer 7 is reflected between the multilayer reflective film 18 and the upper electrode 13. The laser light passing through the multilayer reflective film 18 is refracted at the isotropic etching surface 35 due to the difference in the refractive index between the substrate 6 and air. According to Snell's law, the angle at that time is n ₁ * sinθ ₁ = n ₂ * sinθ ₂ (n ₁ , n ₂
Are represented by air and the refractive index of the substrate, and θ ₁ and θ ₂ are shown in the figure). Generally, since n ₁ <n ₂ , θ ₁ > θ ₂
Next, it refracts as shown in the figure. Since the incident angle θ ₂ is determined by the relative positional relationship between the laser (that is, the upper electrode 13) and the isotropic etching surface 35, laser light is emitted in multiple directions by appropriately selecting the position as shown in the figure. be able to.

[0010]

As described above, according to the present invention, a plurality of lasers having different light emission directions and a light receiving element having a sensitivity region at the wavelength of laser light are formed on the same semiconductor substrate. Low cost, light weight,
High angular resolution is obtained. Particularly in the case of the second embodiment, since the entire radar that sequentially emits laser light in a plurality of different directions is integrated on the same semiconductor substrate, it is of course small in size and light in weight, and in the end, low cost. It has become.

[Brief description of drawings]

FIG. 1 is a top view of a first embodiment of the present invention.

FIG. 2 is a view for explaining a pair of a pair of semiconductor lasers and diffraction gratings corresponding to each other in the first embodiment, which is indicated by A- in FIG.
It is an A'line sectional view.

FIG. 3 is a diagram schematically showing how the direction of emitted laser light sequentially changes in the first embodiment.

FIG. 4 is a top view of the second embodiment.

FIG. 5 is a diagram schematically showing how the direction of emitted laser light sequentially changes in the second embodiment.

FIG. 6 is a view for explaining a pair of a pair of semiconductor lasers and a diffraction grating corresponding to each other in the second embodiment, which is indicated by B- in FIG.
It is sectional drawing which follows the B'line.

FIG. 7 is a sectional view of a third embodiment using a vertical cavity type semiconductor laser.

FIG. 8 is a plan view showing a conventional example in which a plurality of semiconductor laser devices using Fabry-Perot resonators are arranged in order to emit laser light in different directions.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Laser array area 2 ... Diffraction grating area 3 ... Laser 4 ... First diffraction grating 5 ... Second diffraction grating 6 ... Semiconductor substrate 7 ... Active layer 8 ... Upper clad layer 9 ... Lower clad layer 10 ... Semiconductor thin film 11 ... Cleavage Surface 12 ... Cap layer 13 ... Upper electrode 14 ... Lower electrode 15 ... Emitting beam 16 ... Laser chip 17 ... Printed circuit board 18 ... Multilayer reflective film 19 ... Ohmic contact layer 20 ... Power supply circuit 21 ... Drive circuit 22 ... Distance counting circuit 23 ... Preamplifier 24 ... Light receiving element 25 ... Input / output pad 26 ... HEMT 27 ... DFB laser 28 ... Light blocking area 29 ... Gate electrode 30 ... Element isolation area 31 ... Electron transit layer 32 ... Diffusion layer 33 ... High resistance layer 34 ... Insulation Layer 35 ... Isotropically etched surface 36 ... Electron supply layer

Claims (8)

[Claims] 1. A semiconductor having a plurality of semiconductor lasers in which light emitting directions are different from each other and not parallel to a main plane of a substrate, and a light receiving element having a sensitivity region at the wavelength of the laser light on the same semiconductor substrate. Laser device. 2. The semiconductor laser device according to claim 1, wherein the plurality of semiconductor lasers all emit laser light of the same wavelength. 3. The semiconductor laser device according to claim 1, further comprising means for sequentially changing the emission direction of light by sequentially operating the semiconductor lasers on the same substrate. 4. A distance for measuring and outputting the distance to the object by the time between the time when the semiconductor laser light is emitted and the time when the scattered light from the object irradiated by the laser light is detected. 4. The semiconductor laser device according to claim 1, further comprising a counting circuit. 5. A diffraction grating which forms a pair with a semiconductor laser region having a plurality of semiconductor lasers formed therein, and has a different period from each other and emits laser light in different directions due to a diffraction effect. A semiconductor laser device having a plurality of diffraction grating regions formed on the same semiconductor substrate. 6. The semiconductor laser device according to claim 5, wherein all of the plurality of semiconductor lasers emit laser light of the same wavelength. 7. The semiconductor laser device according to claim 5, wherein the diffraction grating emits laser light in a direction not parallel to the principal plane of the substrate due to the first-order diffraction effect. 8. The semiconductor laser device according to claim 5, wherein the light receiving element having a sensitivity region for the wavelength of the laser light is provided on the same semiconductor substrate.