JP2001050753A - Semiconductor laser gyro - Google Patents

Abstract

(57) [Problem] To provide a semiconductor laser gyro that can be miniaturized without sacrificing measurement accuracy. SOLUTION: A multi-circular ring resonator 22 composed of a plurality of circular optical paths (waveguides) having different sizes is formed on a semiconductor substrate 21, and a voltage is applied to a carrier injection electrode 23 provided on the resonator 22. The laser is oscillated by the application, and the frequency difference between the clockwise and counterclockwise oscillation modes is obtained as a voltage change from the voltage detection terminal 24 or from the beam multiplexing prism 25 and the light receiving device 26, whereby the rotation applied from the outside is obtained. Measure the angular velocity.

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 semiconductor laser gyro that can be reduced in size without sacrificing size-dependent measurement accuracy.

[0002]

2. Description of the Related Art Currently, gyroscopes put into practical use include a mechanical gyroscope, an optical gyroscope, and a vibration gyroscope. Each of these has advantages and disadvantages in price, accuracy, size, etc., and models are selected according to the application.

A coma gyro whose main part is a machine is:
Since it is difficult to reduce the size and is susceptible to acceleration, etc., it has recently been on a downward trend. Active ring laser gyros are the most accurate and stable, but are expensive, and are therefore limitedly used in aircraft and space development. For consumer use, passive optical fiber gyros and vibrating gyroscopes are mainly used. Vibrating gyroscopes are used frequently because they are small and inexpensive, measuring several centimeters square, while having low measurement accuracy.

Conventionally, various methods for forming a small sensor using a semiconductor laser have been studied. Considerations have also begun on gyro sensors. In particular, the use of a semiconductor laser has a wider range of applications because it is easier to reduce the size than conventional products.

[0005]

SUMMARY OF THE INVENTION An optical fiber gyro has been realized for consumer use in order to reduce the size and cost of the ring laser gyro. However, in terms of price,
It is not easy to improve the size and performance more than the current situation. In addition, since there is a process of assembling optical components, in a construction site or the like where strong vibration occurs, a desired performance cannot be often obtained due to a minute displacement of each component. Further, the measurement accuracy of the gyro sensor is related to the size. Therefore, if the measurement accuracy is reduced unnecessarily, the measurement accuracy is reduced, and the gyro sensor cannot be used as a practical product.

[0006] The vibrating gyroscope is still of the mechanical type, and there is a limit to miniaturization of about several centimeters square. Attention must be paid to acceleration and vibration as external force. The fact that the object to be detected is the vibration itself also has an effect, and the object to be measured needs to be careful because it is different from the optical fiber gyro.

Regardless of which method is used, a gyro sensor which is smaller and has no decrease in measurement accuracy has been difficult to realize even if desired.

An object of the present invention is to provide a semiconductor laser gyro that can be miniaturized without sacrificing measurement accuracy.

[0009]

FIG. 1 shows the configuration of a typical ring laser gyro using a He-Ne laser, in which 1 is a He-Ne laser, 2 and 3 are total reflection mirrors, 4 is an output mirror, 5 is a half mirror, 6 is a beam combining prism, and 7 is a light receiver.

The rotational angular velocity measured by the ring laser gyro is obtained from the frequency difference (beat signal) between the clockwise and counterclockwise oscillation modes of the ring laser. Since the length of the resonator sensed by each of the left and right modes changes due to the rotational motion (Sagnac effect), a relational expression such as Δf = 4AΩ / λL is established. Here, Δf is the beat (Sagnac beat) frequency between the oscillation modes of light traveling left and right through the ring resonator, A is the area of the ring, L is the length of the ring, Ω is the rotational angular velocity, and λ is the laser output light. The oscillation wavelength.

In order to manufacture a ring laser gyro using a semiconductor laser, FIGS.
It is common to use a triangular, square or circular waveguide structure 11, 12, 13 as a ring resonator as shown in FIG.
Twelve reflecting surfaces. ). Of course, the shapes of the ring resonators are not limited to these shapes, but practically simple shapes are desirable. Therefore, only these shapes will be described here.

At present, a triangular or square waveguide having an optical path of 10 μm to several cm or a circular waveguide having a diameter of 10 μm to several cm can be relatively easily manufactured. Therefore, the production of such a ring laser gyro is easy.

Incidentally, the measurement of the rotational angular velocity using an optical fiber gyro having a passive configuration is obtained from the phase difference of light traveling right and left, which is represented by Δφ = 8πnNAΩ / λc (2). Here, Δφ is the phase difference, N is the number of turns of the optical fiber, n is the refractive index, and c is the speed of light.

A comparison of measurement sensitivity between an active ring laser gyro and a passive optical fiber gyro shows that:
From both (1) and (2), it can be seen that the ring laser gyroscope is more advantageous in terms of the scale factor.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

[0016]

Embodiment 1 In a semiconductor laser gyro, the upper limit of the maximum ring size is determined depending on the wafer size used at the time of fabrication. Therefore, in comparison with a conventional ring laser gyro using a He-Ne laser, the semiconductor laser gyro is generally disadvantageous in terms of measurement accuracy in terms of a scale factor as shown in Expression (1).

This is because, in contrast to a He-Ne ring laser gyro using a triangle or a quadrangle having a side of several tens of cm as a ring resonator, the current semiconductor laser has a full wafer of about 2 to 3 inches. This is because a semiconductor ring resonator is manufactured in order to form a gyro.

However, it is easy to fabricate multi-turn structures having different sizes as shown in FIGS. 3A and 3B by using a semiconductor process. However, it is easy to fabricate a conventional ring laser gyro (He-Ne). With a configuration using a gas laser such as a laser), it is almost impossible to realize such a multi-turn structure in a very small area.

FIGS. 3A and 3B are schematic views of a semiconductor laser multi-turn ring resonator used in the present invention. FIG. 3A shows a square multi-turn structure, and FIG. 3B shows a circular multi-turn structure. The orbital structure is shown.

In order for the clockwise and clockwise oscillation modes to run independently of each other in a ring resonator having a multi-turn structure having different sizes, a rectangular shape shown in FIG. The ring is more advantageous than the circular ring of FIG. 3B because crosstalk is smaller. In fact, in the case of a circular ring, crosstalk occurred at the intersection, and improvement in measurement accuracy could not be realized.

In the rectangular ring shown in FIG. 3A, the apex portion excluding the portion where the light circulating in the left and right directions intersects is a total reflection surface formed by using reactive etching or the like. The assumed structure is shown. However, this portion may have a structure having a curvature as shown in FIG.

FIG. 4 is an explanatory view of a multi-circular ring resonator in a semiconductor laser gyro according to the present invention. FIG. 4 (a) shows an example of a structure in which a rectangular vertex where there is no crossing of circular light becomes a total reflection surface. FIG. 2B shows an example of a structure in which a portion where there is no intersection of the circulating lights has a curvature.

When a gyro sensor is constructed using light output, for example, the upper left apex portion is etched as shown in FIG.
The light circulating in the left and right directions may be multiplexed by installing a waveguide pickup as shown in No. 4088 or extracting a partial output.

As shown in FIG. 4A, a Sagnac effect of light that circulates independently in the left and right directions in a rectangular ring resonator having multiple circulating structures having different sizes has a side of a ₀ , a ₁ , a. _2, a _3, ........., square one apex portion of the a _n-1, a _n is equal to the effect of light feel orbiting the deformed rectangular ring waveguides missing as a square of a side b.

Therefore, one side is a _k−1 to a _k (k = 0,
1, 2, 3, 4,..., N−1, n) at the junction where the rectangular waveguide is changed,
It becomes ² . From these, a _k is _represented by a _k = a _{k -1} + 2b = a ₀ +2 kb (3)

Considering the number of multiple orbiting ring resonators contained in a square with one side d, h = Int ｛(d−a ₀ ) / b｝ +1... (4) You can see it exists. Therefore, the total circuit length L of the multiple circuit ring resonator is

[0027]

(Equation 1)

## EQU1 ##

The total sum A of the area S _i surrounded by the orbiting ring resonator is

[0030]

(Equation 2)

It can be expressed by

Therefore, the parameter A / L for determining the measurement accuracy of the gyro is A / L = [4b ² h ³ + 6b (b + a ₀ ) h ² + {6a ₀ b−b ² +3 (a ₀ ) ² } h + 3 (A ₀ ) ² ] / 12 (bh + a ₀ ) (h + 1) (8)

With the given a ₀ and b, h, which gives the maximum value of A / L, indicates the number of orbits giving the optimum path of the multi-turn ring resonator, which is the figure of measurement accuracy. The merit (F≡A / L) is given by equation (8)
It means being given by itself.

In the case of a ₀ ≫b, simplification is possible, and F≡A / L ≒ ｛4b ² h ² +2 (b + 3a ₀ ) bh + 3 (a ₀ ) ² } / 12 (bh + a ₀ ) (9) ).

For example, a₀= 0.2 mm, b = 0.03
mm, a ring resonator that fits within 1 mm square
Assuming that L = 3.15 cm, A = 7.86 mm^TwoWhen
F≡A / L is about five times that of a single ring.
You. Under these conditions, a ring resonator that fits within 10 mm
L = 334cm, A = 5570mm ^Two
Becomes In this case, F is about 33 times that of a single ring
And a rectangular ring laser gyro with a side of 33 cm
Performance can be achieved with a size of 1 cm square.

When h> 10, dF / dh> 0, and F is monotonically increased under this condition. For this reason, it can be seen that if accumulation and loss of minute effects determined by the superiority of the manufacturing technology can be ignored, F can be simply improved by increasing the multiplicity.

The Sagnac effect, which is the heart of the gyro operation, can be detected in the same manner by using the interference output of the left and right independently transmitted light or by detecting the change in the voltage in the ring resonator. Can be.

FIG. 5 is a plan view and a side view showing an embodiment of a semiconductor laser gyro according to the present invention. Here, the variety of light source portions is shown. Here, (a) of the figure shows an example in which the entire semiconductor laser gyro of the present invention is realized only by a semiconductor gain medium. In the figure, 21 is a semiconductor substrate, and 22 is a multiplex formed on the semiconductor substrate 21. The orbiting ring resonator 23 is a carrier injection means (electrode) formed over almost the entire surface of the multiple orbiting ring resonator 22, 24 is a voltage detection terminal formed on a part of the multiple orbiting ring resonator 22, 25 Is a beam combining prism, and 26 is a light receiver.

In the case of using the interference output of light, for example, a part of the light is extracted from the reflection surface 27 at the upper left of the multiple orbiting ring resonator 22, and each light is separated by a half mirror, a prism, a waveguide, an optical fiber, or the like. After causing interference using the coupler used, detection may be performed by the light receiver 26 (in this case,
The voltage detection terminal 24 may be omitted. ). FIG. 5A shows an example in which the beam combining prism 25 is used, but the illustration is omitted in the other examples of FIG. However, it goes without saying that other examples can be similarly applied.

When the Sagnac effect is detected by measuring a change in voltage in the ring resonator,
The operation is performed by extracting a voltage from the voltage detection terminal 24.

FIG. 5 (b) shows an example in which the semiconductor laser gyro of the present invention is constituted by a gain medium portion and a waveguide portion each having a different composition, a different structure, and a different material. An example having a semiconductor laser having a ring resonator or a semiconductor optical amplifier manufactured by applying an AR coat (anti-reflection coat) is shown below.
That is, in the figure, reference numeral 31 denotes a multi-turn ring resonator, 32 denotes a ring laser or a semiconductor optical amplifier provided at the innermost portion of the multi-turn ring resonator 31, and the ring laser or the semiconductor optical amplifier 32 is multiplexed. An AR coating (anti-reflection coating) 33 is applied to a boundary surface with the orbiting ring resonator 31. Reference numeral 34 denotes a carrier injection electrode, and reference numeral 35 denotes a voltage detection terminal.

FIG. 5 (c) is basically the same as FIG. 5 (b), except that a semiconductor laser or an AR coat (anti-reflection coat) having no ring resonator in the multi-turn ring resonator is used here. An example having a semiconductor optical amplifier manufactured by applying the method is described below. That is, in the drawing, reference numeral 36 denotes a fabric provided at the innermost portion of the multi-turn ring resonator 31.
A Perot (FP) type laser or FP type semiconductor optical amplifier, and a semiconductor laser is oscillated by a multi-turn ring resonator on both end surfaces of the FP type laser or FP type semiconductor optical amplifier 36. Therefore, an AR coat 37 is provided. Reference numeral 38 denotes a carrier injection electrode that also serves as a voltage detection terminal.

The carrier injection electrode and the voltage detection terminal
It is better to be independent from the viewpoint of improving S / N, but the measurement itself is possible without dividing.

[0044]

[Embodiment 2] FIG. 6 is a plan view showing an embodiment of a semiconductor laser gyro according to the present invention, and here shows the variety of waveguide portions. In particular, here, portions not described in the first embodiment will be described.

FIG. 6A shows an example in which the semiconductor laser gyro of the present invention is realized only by a semiconductor gain medium. In the figure, reference numeral 41 denotes a semiconductor substrate, reference numeral 42 denotes a multi-turn ring resonator, and reference numeral 43 denotes carrier injection. The electrode 44 is a voltage detection terminal.

This figure shows an example in which a semiconductor laser gyro can be realized by the configuration of a semiconductor laser itself having a multiple orbiting ring resonator provided with a carrier injection electrode and a voltage detection terminal. Since it is the same as FIG. 5A except that the measurement is not shown, detailed description is omitted.

FIG. 6B shows an example in which the semiconductor laser gyro of the present invention is constituted by a semiconductor gain medium section and a semiconductor waveguide section having the same composition and the same structure. A carrier injection electrode 46 is provided corresponding to only the innermost portion of the resonator 42, and a bias application electrode 46 is provided corresponding to a portion other than the carrier injection electrode 45 of the multi-turn ring resonator 42.

The injection currents to the carrier injection electrode 45 and the bias application electrode 46 are individually adjusted, so that the semiconductor gain medium of the multi-circular ring resonator 42 includes an active light source portion and a passive waveguide portion. It is designed to share two roles.

According to this configuration, it is possible to suppress the reflection at the boundary between active / passive, simplify the fabrication of the device, improve the yield of the device, reduce the injection current, and reduce the power consumption. Further, it is convenient to suppress the temperature rise of the element.

[0050]

Third Embodiment FIG. 6C shows an example in which the semiconductor laser gyro of the present invention is constituted by a semiconductor gain medium portion and a semiconductor waveguide portion having different compositions and structures, respectively. 1B and 1B, there is shown an example in which a semiconductor structure in which a semiconductor gain medium portion serving as an active light source and a passive semiconductor waveguide portion have a structure that can be clearly distinguished is used. That is, in the drawing, reference numeral 47 denotes a multiple orbiting ring resonator, which comprises a semiconductor gain medium portion 47a and a semiconductor waveguide portion 47b having different compositions and structures.

When the gain medium portion is made of GaAs, InP or a compound containing these, as well as when the composition is changed between the gain medium portion and the waveguide portion, the passive waveguide portion is made of Si, Ge, or a compound thereof. There is also a method of carrying it. Of course, not only the aforementioned III-V group, but also Zn, C
A group II-VI such as d or Se or a nitride may be used.

Unlike the case shown in FIG. 6B, the carrier injection electrode 45 is provided in the gain medium portion 47a serving as an active light source, and the voltage detection terminal 44 is provided in a part of the passive waveguide portion 47b. Has become. As in the case of FIG. 6B, a bias application electrode may be provided on the waveguide portion 47b to inject a different amount of carriers from the gain medium portion 47a. Incidentally, it is better to apply an AR coating to the boundary between the gain medium portion and the waveguide portion.

[0053]

Fourth Embodiment FIG. 6D shows an example in which the semiconductor laser gyro of the present invention is constituted by a gain medium portion and a waveguide portion made of different media, and FIGS. 6A to 6C show the same. Unlike the above, the gain medium portion serving as the active light source is made of a semiconductor, but the passive waveguide portion may be made of a material different from the semiconductor. That is, in the figure, reference numeral 48 denotes a multi-turn ring resonator, which includes a gain medium portion 48a formed of a semiconductor and a waveguide formed of a glass waveguide or an optical fiber regardless of the presence or absence of an amplification function or a doping material. And a wave path portion 48b. 49 is a carrier injection electrode, and 50 is a voltage detection terminal. The passive waveguide portion depends on the wavelength used, but especially on the long wavelength side, Si
Also available.

The solid material constituting the waveguide portion 48b other than the solid material described above, regardless of the presence or absence of a doping material,
In addition to inorganic substances such as sapphire, YAG, and LiNb ₃ , an organic waveguide such as polyimide can be used. Incidentally, it is better to apply an AR coating to the boundary between the gain medium portion and the waveguide portion.

[0055]

Embodiment 5 In the case where a laser gyro is constituted by using a semiconductor laser or a semiconductor optical amplifier as a light emitting section, the terminal voltage (noise) of either clockwise or counterclockwise output light is measured, so that the Sagnac beat can be reduced. can get. This operation can be obtained, for example, by removing the beam combining prism 25 at the upper left of FIG. 5A and simply detecting a part of the output light with the light receiver 26 as it is. This is because the Sagnac effect felt by the light circling in each of the left and right directions is detected as a Sagnac beat as a voltage change, and at the same time, is equivalently input to the carrier injection electrode of the laser. This is because mixing of the Sagnac beat occurs.

[0056]

As described above, according to the present invention,
It is possible to realize downsizing that is impossible with the prior art without impairing the measurement accuracy.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of a conventional ring laser gyro;

FIG. 2 is an explanatory diagram of a shape of a semiconductor laser ring resonator.

FIG. 3 is a schematic view of a semiconductor laser multi-turn ring resonator used in the present invention.

FIG. 4 is an explanatory view of a multi-turn ring resonator in the semiconductor laser gyro of the present invention.

FIG. 5 is a configuration diagram of an embodiment showing the diversity of light source portions of the semiconductor laser gyro of the present invention.

FIG. 6 is a configuration diagram of an embodiment showing the diversity of the waveguide section of the semiconductor laser gyro of the present invention.

[Explanation of symbols]

1: He-Ne laser, 2, 3: total reflection mirror, 4: output mirror, 5: half mirror, 6, 25: beam combining prism, 7, 26: light receiver, 11, 12, 13: waveguide, 14, 15, 27: reflection surface, 21, 41: semiconductor substrate, 22, 31, 42, 47, 48: multiple orbital ring resonators, 23, 34, 43, 45, 49: carrier injection electrodes, 24, 35, 44, 50: voltage detection terminal, 32:
Ring laser or semiconductor optical amplifier, 33, 37: A
R coat, 36: FP type laser or FP type semiconductor optical amplifier, 38: carrier injection electrode also serving as voltage detection terminal, 46: bias application electrode.

Claims (7)

[Claims] 1. A semiconductor laser gyro having a ring resonator, a semiconductor laser disposed in a ring resonator, or a semiconductor laser gyro including a semiconductor optical amplifier disposed in a ring resonator. Is constituted by a plurality of orbiting optical paths (waveguides) having different sizes. 2. The semiconductor optical device according to claim 1, further comprising: a carrier injecting means for injecting carriers into the semiconductor gain medium, and a means for measuring a voltage change in the ring resonator. The semiconductor laser gyro according to claim 1. 3. A carrier injection means having the same composition and the same structure for the entire orbiting optical path and provided independently of the orbiting optical path and capable of individually adjusting the amount of injected carriers, and a voltage change in the ring resonator. 2. A semiconductor laser gyro according to claim 1, further comprising: 4. A circulating circuit comprising a semiconductor gain medium section, a semiconductor waveguide section having a different composition and structure, a carrier injection means for injecting carriers into the semiconductor gain medium section, and a voltage in a ring resonator. 2. The semiconductor laser gyro according to claim 1, further comprising means for measuring a change. 5. A circulating circuit comprising a gain medium part, a waveguide part made of a material different from the gain medium part, carrier injection means for injecting carriers into the gain medium part, and means for measuring a voltage change in the ring resonator. The semiconductor laser gyro according to claim 1, further comprising: 6. Instead of a means for measuring a voltage change in a ring resonator, output lights circulating in left and right directions extracted from the ring resonator are multiplexed, and a photodetector such as a photodiode is used. 6. The semiconductor laser gyro according to claim 1, further comprising a light receiving unit. 7. A semiconductor laser gyro having a semiconductor light source or a semiconductor optical amplifier, by receiving a part of one of optical outputs circulating in left and right directions or receiving leaked light, or circulating in left and right directions. A semiconductor laser gyro utilizing a beat signal obtained by independently receiving light output or leaked light.