JPH05288556A - Semiconductor laser gyroscope - Google Patents

Abstract

PURPOSE:To provide a small-sized, high-precision semiconductor laser gyroscope reducing the deterioration of the positional precision of optical components by the aging change. CONSTITUTION:A ring-like gain wave guide path 11 having the function of a ring resonator is formed on a p-n junction semiconductor substrate 10, a current is fed via an electrode 22, and a carrier is injected into the gain wave guide path 11 to generate a laser oscillation. Laser beams propagated clockwise and counterclockwise in the gain wave guide path 11 are partially extracted from light output faces 13, 14 to interfere with each other in a light absorption region 17, and the coherent light intensity is extracted via an electrode 23 as a photoelectric current. Optical components are integrally formed on the same semiconductor substrate 10, they can be integrated, the positional precision of the optical components can be strictly set, and a small-sized, high-precision gyroscope can be constituted 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 gyro, and more particularly to a small-sized, highly accurate and inexpensive semiconductor laser gyro integrated on a semiconductor substrate.

[0002]

2. Description of the Related Art Conventionally, as a gyro for detecting the angular velocity of a moving object, a mechanical gyro having a rotor and an optical fiber gyro using an optical fiber are known. In particular, the optical fiber gyro has been energetically developed because it has the advantage of being lightweight.

An optical fiber gyro is, as shown in FIG.
Basically, it comprises a laser light source 1, a half mirror 2, a fiber ring interferometer 3, and a photodetector 4. The laser light 5 emitted from the laser light source 1 is branched into two directions in the half mirror 2 and is incident from two opposite directions of the fiber ring interferometer 3. The laser light propagated in the clockwise and counterclockwise directions through the fiber ring interferometer 3 is emitted from the fiber ring interferometer 3 and then added again by the half mirror 2 to cause interference at the position of the photodetector 4. Be done. At this time, when the fiber ring interferometer 3 receives a rotational movement, the fiber ring interferometer 3 rotates clockwise in the fiber ring.
And the respective laser lights propagating in the counterclockwise direction,
A phase difference occurs after propagation due to the Sagnac effect. This phase difference appears as the shift amount Z of the interference fringe 6, and the phase difference increases as the angular velocity of the rotary motion increases,
It is measured as the shift amount Z increases. Actually, the shift amount can be calculated from the intensity change of the signal output from the photodetector 4 arranged on the interference surface, and the movement of the object to which this optical fiber gyro is attached can be detected.

[0004]

However, in the above-mentioned conventional optical fiber gyro, it is required that optical components such as a laser light source, a half mirror, an optical fiber, and a photodetector be arranged with high positional accuracy. As a result, it was large and expensive. In addition, the deterioration of the positional accuracy of the optical component due to changes over time has been a problem.

In view of the above problems, it is an object of the present invention to provide a semiconductor laser gyro which reduces deterioration in the positional accuracy of optical components due to changes over time, and further to provide a small and highly accurate semiconductor laser gyro. It is in.

[0006]

To achieve the above object, the present invention provides, in claim 1, a semiconductor laser gyro for detecting an angular velocity of a moving object, which is a ring-shaped resonator structure. Forming a semiconductor gain waveguide, carrier injection means for injecting carriers into the semiconductor gain waveguide, and outputting a part of light propagating in the semiconductor gain waveguide in the clockwise and counterclockwise directions, respectively. Light detection means for outputting electric signals corresponding to the received light intensity at a position where lights propagating in the clockwise and counterclockwise directions emitted from the light output means are overlapped with each other. We propose a semiconductor laser gyro equipped with a heater.

According to a second aspect, in the semiconductor laser gyro according to the first aspect, the ring-shaped semiconductor gain waveguide, carrier injection means, light output means, and photodetector are formed on the same semiconductor substrate. We propose a semiconductor laser gyro.

According to a third aspect, in the semiconductor laser gyro according to the first or second aspect, the light output means is
A semiconductor laser gyro composed of a partially transmissive mirror formed in the semiconductor gain waveguide is proposed.

Further, a fourth aspect of the present invention proposes the semiconductor laser gyro according to the first or second aspect, wherein the light output means is a directional coupler.

[0010]

According to the first aspect of the present invention, carriers are injected by the carrier injection means into the ring-shaped semiconductor gain waveguide. As a result, laser oscillation occurs in the semiconductor gain waveguide, and the laser light propagates in the clockwise and counterclockwise directions in the semiconductor gain waveguide. As a result, a semiconductor ring resonator laser in which the light source and the ring interferometer in the conventional optical fiber gyro are integrated is constructed. Further, the light output means extracts a part of each of the laser lights propagating in the semiconductor gain waveguide in opposite directions as output light. These output lights interfere at the position where the photodetector is configured, and an electric signal corresponding to the intensity of the interference light is output by the photodetector.

According to a second aspect, the ring-shaped semiconductor gain waveguide, carrier injection means, light output means,
And the photodetector are formed on the same semiconductor substrate.

According to a third aspect of the present invention, the light output means is constituted by a partial transmission mirror formed in the semiconductor gain waveguide, and the semiconductor gain waveguide is rotated in the clockwise direction and the counterclockwise direction in the semiconductor gain waveguide. A part of each of the propagating laser light is extracted as output light through the partial transmission mirror.

Further, according to a fourth aspect of the present invention, the light output means is constituted by a directional coupler, and each of the laser lights propagating in the semiconductor gain waveguide in the clockwise rotation direction and the counterclockwise rotation direction. The part is taken out as output light through the directional coupler.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 is a plan view showing the configuration of an embodiment of the present invention,
FIG. 3 is a perspective view showing the structure of the partial transmission mirror in one embodiment. In the figure, 10 is a semiconductor substrate having a pn junction, on which a rectangular semiconductor gain waveguide (hereinafter, referred to as gain waveguide) 11 having a width of 4 μm and a side length of 600 μm is formed. There is. This gain waveguide 11 has the function of a ring resonator, and at the four corners thereof, surfaces 12 having an angle of 45 degrees with respect to the optical axes of the intersecting waveguides are formed, and the base of the gain waveguide 11 is Below pn junction 1
This surface 12 is made to act as a reflecting mirror by processing by reactive ion beam etching until it becomes μm.

Further, as shown in FIG. 3, the reflection angle propagates in the gain waveguide 11 in a part of regions of two adjacent surfaces (reflecting mirrors) 12 of the four corners of the gain waveguide 11. A surface 1 having an angle equal to or less than the total reflection angle with respect to the optical axis of light
3 and surface 14 are provided as light output surfaces. With such a structure, the surface 1 having the surfaces 13 and 14 is formed.
The reflecting mirror constituted by 2 is operated as a partial transmitting mirror. That is, the light output surface 13 emits a part of the light 15 propagating in the gain waveguide 11 in the clockwise direction as the output light 18, and the light output surface 14 propagates in the gain waveguide 11 in the counterclockwise direction. A part of the light 16 is emitted as the output light 19.

Lights 18 and 19 emitted from the two light output surfaces 13 and 14, respectively, are superposed at the position of a light absorption region (photodetector) 17 provided on the semiconductor substrate 10. The light absorption region 17 is made of a material having the same composition as the gain waveguide 11. Furthermore, the gain waveguide 1
1 and the light absorption region 17 have independent electrodes 22 and 2 respectively.
3 is provided, and carriers are injected into the gain waveguide 11 by causing a current to flow through the gain waveguide 11 via the electrode 22, and laser oscillation is generated in the gain waveguide 11. Further, by providing the electrode 23 in the light absorption region 17, a known photodetector is configured, and the interference light intensity of the light emitted from the two light output surfaces 13 and 14 described above is monitored as an electric signal. You can

In the element having the above structure, when the semiconductor substrate 10 is rotated at various angular velocities while the current is flowing in the gain waveguide 11, the current flowing in the light absorption region 17 corresponds to those rotational angular velocities. The frequency is shown. This is because the laser light propagating in the clockwise direction and the counterclockwise direction in the ring resonator formed by the gain waveguide 11 undergoes the Sagnac effect due to the rotation of the element, which causes a laser oscillation frequency shift, This is because the beat frequency due to the interference of these laser lights is measured as the frequency of the photocurrent in the light absorption region 17.

Generally, the beat frequency fr is defined by the optical path length L of the ring resonator, the area surrounded by the optical path A, the wavelength of light λ, the angle between the normal of the ring surface and the rotation axis Φ, and the rotation angular velocity ω. , Fr = 4A ω cos Φ / λL. In the element described above, the length of one side is 600 μm, the oscillation wavelength of the laser is 1.0 μm, and fr = 360 KHz is observed when rotated in the state of Φ = 0 degree, and from this, the rotational angular velocity ω = 600 sec It turns out to be ^-1 .

As described above, according to this embodiment, laser oscillation occurs in the ring-shaped gain waveguide 11, and the laser light can be propagated in the clockwise and counterclockwise directions in the gain waveguide 11. In addition, since the light source and the ring interferometer in the conventional optical fiber gyro can be integrated, it is possible to save the labor of highly accurate alignment work of the conventional light source and the ring interferometer, and to change with time. It is possible to eliminate the deterioration of the positional accuracy of the optical parts. Furthermore, each optical component in the conventional example is replaced with the gain waveguide 1.
Since the 1 and the light absorption region 17 are integrally formed on the same semiconductor substrate 10, it is possible to configure a gyro that is small in size and high in accuracy, and can be supplied at a low cost.

In the present embodiment, the gain waveguide 11
Although the ring resonator structure has a quadrangular shape, it is clear that the same effect can be obtained by a ring resonator structure having a polygonal shape such as a circular shape or a triangular shape in view of the principle of operation.

In the present embodiment, the gain waveguide 11 is provided with p.
An n-junction is provided to flow a current, and carriers are injected into the gain waveguide 11 to cause laser oscillation. However, the present invention is not limited to this, and the gain waveguide 1 is provided from outside the gain waveguide 11.
1 may be irradiated with light to inject carriers to cause laser oscillation.

Further, although the light output surfaces 13 and 14 are used as the light output means in this embodiment, the present invention is not limited to this. For example, as shown in FIG. 4, two directional couplers 2 are used.
It is also possible to use 0,21. In FIG.
(a) is a plan view, (b) is a cross-sectional view taken along the line AA 'in the plan view. In this case, the ring-shaped gain waveguide 1
A part of the laser beams 15 and 16 propagating in the clockwise direction and the counterclockwise direction in the two 1 are two directional couplers 20 and 2.
The light is extracted as output light 18 and 19 by 1 and guided to the light absorption region 17. Further, by extending the directional couplers 20 and 21 and guiding the output lights 18 and 19 to the light absorption region 17, it is possible to reduce the influence from the outside in the propagation path from the gain waveguide 11 to the light absorption region 17. it can.

In this embodiment, the light emitted from the light output surfaces 13 and 14 is superposed at the position of the photodetector 17 after propagating in the space. It is also possible to form a structure in which an optical waveguide is formed between the photodetectors 17 and the output lights 18 and 19 from the light output surfaces 13 and 14 are propagated in the optical waveguides and made incident on the photodetectors 17. is there.

Further, in this embodiment, the photodetector 1
Although 7 is provided outside the gain waveguide 11, the laser light propagating in the opposite directions causes interference even in the gain waveguide 11. Therefore, the above-mentioned beat frequency is detected by providing a photodetector in the gain waveguide 11, that is, by making a part of the region of the ring-shaped gain waveguide 11 electrically separated from other regions. Is also possible.

[0025]

As described above, according to the first aspect of the present invention, since the light source and the ring interferometer in the conventional optical fiber gyro can be integrated with each other, the height of the conventional light source and the ring interferometer can be increased. It is possible to save the time and labor for the accurate alignment work, and it is possible to eliminate the deterioration of the positional accuracy of the optical component due to a change with time.

Further, according to claim 2, in addition to the above effects, since the respective optical components in the conventional example are formed almost integrally on the same semiconductor substrate, they can be integrated and each optical component can be integrated. Since the positional accuracy of the parts can be set strictly, a small-sized and highly accurate gyro can be constructed and the parts can be supplied at low cost.

Further, according to the third and fourth aspects, in addition to the above effects, a very excellent effect that the output light can be easily extracted from the semiconductor gain waveguide with a simple structure is exerted. is there.

[Brief description of drawings]

FIG. 1 is a plan view showing the configuration of a semiconductor laser gyro using a ring resonator formed of a semiconductor gain waveguide according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a conventional optical fiber gyro.

FIG. 3 is a perspective view showing a configuration of a partial transmission mirror in one embodiment of the present invention.

FIG. 4 is a configuration diagram when a directional coupler is used as a light output unit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Laser light source, 2 ... Half mirror, 3 ... Optical fiber interferometer, 4 ... Photodetector, 5 ... Laser light, 6 ... Interference fringe, 10 ... Semiconductor substrate, 11 ... Ring-shaped semiconductor gain waveguide, 12 ... Reflection Mirrors 13, 14 ... Light output surface, 15 ... Laser light propagating in the clockwise direction, 16 ... Laser light propagating in the counterclockwise direction, 17 ... Light absorbing regions, 18, 19 ...
Output light, 20, 21 ... Directional couplers 22 and 2 for outputting light
3 ... Electrode.

Claims (4)

[Claims] 1. A semiconductor laser gyro for detecting an angular velocity of a moving object, comprising: a semiconductor gain waveguide having a ring-shaped resonator structure; and carrier injection means for injecting carriers into the semiconductor gain waveguide. And a light output means for outputting a part of light propagating in the clockwise direction and the counterclockwise direction in the semiconductor gain waveguide, respectively, and the clockwise rotation emitted from the light output means. A semiconductor laser gyro characterized in that a photodetector that outputs an electric signal corresponding to the received light intensity is provided at a position where lights propagating in the counterclockwise direction and in the counterclockwise direction overlap. 2. The ring-shaped semiconductor gain waveguide, carrier injection means, light output means, and photodetector are formed on the same semiconductor substrate.
The described semiconductor laser gyro. 3. The semiconductor laser gyro according to claim 1, wherein the light output means comprises a partially transmissive mirror formed in the semiconductor gain waveguide. 4. The semiconductor laser gyro according to claim 1, wherein the light output means comprises a directional coupler.