JP2001108447A - Semiconductor device, semiconductor laser, gyro and its operation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gyro and its operation method capable of lowering a coupling loss generated when laser light is introduced into a light detector and a noise caused by returning light to a laser from external reflection points. SOLUTION: The gyro has a ring resonance type semiconductor laser where lights circumferentially transmit mutually reversely to each other, terminals detecting beat signal and a ring shape active layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a gyro and a method for operating the gyro. More specifically, an optical gyro and its operation capable of reducing the coupling loss caused when the laser light is incident on the photodetector and the noise generated by the return light from the external reflection point to the laser. About the method.

[0002]

2. Description of the Related Art Conventionally, as a gyro used for detecting an angular velocity of a moving object, a mechanical gyro having a rotor and a vibrator and an optical gyro are known. In particular, the optical gyro is capable of instantaneous activation and has a wide dynamic range, and is thus innovating in the gyro technical field. The optical gyro includes a ring resonator type laser gyro, an optical fiber gyro, and a passive type ring resonator type gyro. Of these, the first to be developed is a ring resonator type laser gyro using a gas laser, which has already been put to practical use in aircraft applications and the like. Recently, a small and high-precision ring resonator type laser gyro has also been proposed.
-288556.

[0003]

However, the conventional ring resonator type laser gyro emits clockwise laser light and counterclockwise laser light from the laser to the outside of the laser once, and detects both laser lights. And received electrical beats as signals. For this reason, coupling loss has been present when the laser light is incident on the photodetector. In addition, since noise is generated by light returning to the laser from a reflection point outside the laser, it is necessary to use an optical isolator to avoid the noise.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a gyro having no or very few problems such as coupling loss and return light noise, and a method of operating the gyro. Still another object of the present invention is to reduce the driving power of the semiconductor ring laser. Still another object of the present invention is to stabilize the oscillation wavelength of a semiconductor ring laser.

A gyro according to the present invention has a ring resonator type semiconductor laser in which light propagates in a counterclockwise direction and detects a beat signal generated by rotation applied to the ring resonator type semiconductor laser. And a structure in which a current does not easily flow in the central region of the ring resonator type semiconductor laser.

A gyro according to the present invention has a ring resonator type semiconductor laser in which light propagates in a counterclockwise circular shape, a terminal for detecting a beat signal, and an active layer of the semiconductor laser having a ring. It is characterized by the shape.

In particular, according to the present invention, the active layer is sandwiched between low refractive index layers having a lower refractive index than the active layer, and both the active layer and the low refractive index layer have a cylindrical structure. It is characterized by doing.

Further, the present invention is characterized in that the beat signal is detected as a change in current, voltage or impedance.

A gyro according to the present invention has a ring resonator type semiconductor laser in which light propagates in a counterclockwise circular shape, and has means for detecting a beat signal generated by rotation applied to the semiconductor laser. The semiconductor laser is characterized in that the active layer is ring-shaped.

The beat signal detecting means includes a voltage detecting circuit,
It is characterized by including at least one of a current detection circuit, an impedance detection circuit, a frequency-voltage conversion circuit, and a frequency counter circuit.

A gyro according to the present invention has a ring resonator type semiconductor laser in which light propagates in a counter-rotating circular shape, has a terminal for detecting a beat signal, and has at least a semiconductor laser central region. It is characterized in that the resistance is partially increased.

A gyro according to the present invention includes a ring resonator type semiconductor laser in which light propagates in a counterclockwise circular shape, and includes means for detecting a beat signal generated by rotation applied to the semiconductor laser. In addition, at least a part of the central portion of the semiconductor laser has a high resistance.

[0013] A semiconductor device according to the present invention includes a ring resonator type semiconductor laser including a ring-shaped active layer, in which light propagates in a counterclockwise circular shape, and a terminal for detecting a beat signal. I do.

A semiconductor laser according to the present invention is a semiconductor laser including an active layer and a low refractive index layer located on the active layer and having a lower refractive index than the active layer. The central region of at least one of the layers has a high resistance by ion implantation.

First, a method for detecting an angular velocity using a semiconductor laser according to the present invention will be described with reference to FIG.

In FIG. 1, reference numeral 100 denotes a semiconductor laser, 101 denotes an active layer, 102 denotes a substrate, 103 denotes an anode, and 104 denotes a cathode. 105 is an electric terminal. Note that the active layer 101 is sandwiched between cladding layers. When a current is injected from the anode 103, a resonance mode guided in a ring shape is selectively amplified, and a laser oscillation occurs when the resonance mode exceeds a threshold.

In the ring resonator type laser having the above configuration, light propagates in a circular shape. That is, clockwise light,
There is counterclockwise light. When the ring resonator type laser is stationary, the respective oscillation frequencies are equal, but when the laser is rotated, a difference occurs between the oscillation frequencies of the clockwise laser light and the counterclockwise laser light, and the difference Δf is , Given by:

Δf = (4S / λL) Ω (1) where S is a closed area surrounded by an optical path, λ is an oscillation wavelength of laser light, L is an optical path length, and Ω is an angular velocity of rotation. For example,
In the case of a laser such as a gas laser or a semiconductor laser that causes a current to flow, there is a one-to-one correspondence between the population inversion and the impedance of the laser. If light interferes in the laser, the population inversion changes accordingly, and as a result, the impedance between the electrodes of the laser changes. The state of this change appears as a change in the current flowing through the laser when a constant voltage source is used as the drive power supply, and as a change in the terminal voltage when a constant current source is used. The state of light interference can be extracted as a signal. When a constant voltage source is used, a battery can be used, so that the drive system can be reduced in size and weight.

Of course, it is also possible to directly measure a change in impedance with an impedance meter. In this case, unlike the case where the terminal voltage or the current flowing through the element is measured, the influence of the noise of the driving power supply is reduced.

When it is necessary to prevent surge noise or the like from entering the semiconductor laser from the detection terminal for detecting a change in the terminal voltage of the semiconductor laser, a circuit for measuring the voltage change and the detection terminal are connected. It is preferable to provide a protection circuit in the device. As a result, deterioration and destruction of the semiconductor laser due to surge noise or the like can be prevented.

As described above, the semiconductor ring laser generates the current caused by the beat generated by the interference of the laser beams traveling in opposite directions inside the semiconductor ring laser,
By detecting a change in voltage or impedance, a beat signal corresponding to rotation can be extracted.
More specifically, the beat signal is extracted as a change in frequency such as current or voltage. Therefore, it is possible to obtain a gyro that can omit a photodetector and an optical system for optical coupling, which are essential in the conventional optical gyro.

In addition, by providing a means for preventing current from flowing to the central region of the semiconductor laser or a means for injecting current into the peripheral active layer region, a gain can be mainly given only to the circulating light.

Since the laser light inside the semiconductor laser affects the population inversion, it is not necessary to extract the laser light outside the semiconductor laser. Therefore, the semiconductor laser can be configured to have a total reflection surface on the side surface of the semiconductor laser. As a result of this total reflection surface, the mirror loss is reduced, and as a result, the laser oscillation threshold value is also reduced.

Further, the gyro according to the present invention is characterized in that the total reflection surface reflector is not provided within an exudation distance range of the evanescent light generated from the ring resonator type laser. If a reflector is present within the distance of the evanescent light seeping out, the reflector and the laser will be optically coupled to each other, causing not only loss when viewed from the laser, but also return light from the reflector to the laser and noise. Source.

Conversely, if there is no reflector within the exudation distance of the evanescent light of the laser as in the present invention, the laser becomes optically independent of other reflectors and is affected by external influences of the laser. In addition to eliminating loss, there is no return optical noise, so that loss due to coupling and return optical noise can be significantly improved.

In the gyro operating method according to the present invention, in the gyro having the above-described configuration, the change in the current, voltage or impedance detected from the terminal is determined by the magnitude of the angular velocity applied to the ring resonator type laser. It is characterized in that it is used as a signal for obtaining the degree. According to this configuration, a photodetector and an optical system for optical coupling, which are indispensable in the conventional optical gyro, are not required, so that problems of coupling loss and return optical noise caused by these components can be solved. , Gyro operation method can be provided.

In the above-mentioned operation method, it is also preferable that the voltage or current for driving the ring resonator type laser is modulated at a frequency different from the frequency band of the signal due to a change in terminal voltage, current, impedance or the like caused by a beat. It is.

In the gyro having the above configuration,
When the gyro is rotated, a difference appears in the oscillation frequency between the clockwise laser light and the counterclockwise laser light, and the difference Δf is given by Expression (1). When the difference Δf in the oscillation frequencies is small, Due to the non-linearity of the laser medium, the oscillation frequency is pulled in, so that a phenomenon called lock-in, in which Δf = 0, may occur.

However, as shown in the above configuration, the lock-in phenomenon can be avoided if the oscillation frequency difference Δf is constantly changed.

Conventionally, a method of applying dither (micro vibration) has been used as a method of avoiding the lock-in phenomenon, which corresponds to the modulation of the angular velocity Ω in the equation (1).

For example, in a semiconductor laser, it is known that the oscillation wavelength varies depending on the magnitude of the current. This is because the refractive index of the semiconductor changes according to the current.

Therefore, by modulating the current of the semiconductor laser, λ of the equation (1) can be modulated.
As a result, a state in which Δf always fluctuates can be created.

Moreover, by modulating the signal at a frequency in a band different from the signal frequency, lock-in can be avoided without affecting the signal.

Of course, even if the voltage is modulated via the series resistor, the current flowing through the semiconductor laser is modulated, so that
The same effect is obtained.

Also, in the case of a gas laser, by modulating the current or the voltage, the Q value of the resonator fluctuates, so that the oscillation wavelength is modulated. This is because the oscillation wavelength of a gas laser is determined by the Q value of the resonance transition of an atom, a molecule, or an ion and the Q value of a resonator, and this phenomenon is known as attraction of the oscillation wavelength.

In the operating method, vibration is applied to a gyro having the ring resonator type laser at a frequency different from the frequency band of the signal, and a signal is detected from the terminal in synchronization with the vibration. It is possible to establish a correspondence between the direction of vibration and the magnitude of the terminal voltage. For example,
When a vibration is applied in the clockwise rotation direction, the terminal voltage increases when the gyro receives clockwise rotation, and conversely, decreases when the gyro receives counterclockwise rotation. Therefore, it is possible to identify whether the gyro is rotating clockwise or counterclockwise. Moreover, by modulating the signal at a frequency in a band different from the signal frequency, the direction of rotation can be detected without adversely affecting the signal.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration and operation of a gyro according to the present invention and its operating method will be described below with reference to the drawings.

(First Embodiment) FIG. 2 is a schematic perspective view showing an example of a gyro provided with a ring resonator type laser in which light propagates in a circular shape according to the present invention. In the present embodiment, at least a part of the substantially central region of the semiconductor laser 200 is formed into a cylindrical shape 209. In the figure, reference numeral 201 denotes an active layer. A layer including a clad layer is formed above and below the layer. 202 denotes a substrate on which a semiconductor laser is mounted, 203 denotes an anode and wiring connected to the anode, 204 denotes a cathode, and 205 denotes an electric terminal.

Of course, it is also preferable to provide a light guide layer between the active layer and the cladding layer in order to increase the optical binding coefficient in the active layer.

The positions, structures, etc. of the electrodes are not limited to those shown in FIG. 2, but may have a configuration as shown in FIG.

FIG. 4 shows the semiconductor laser having the cylindrical structure shown in FIG. 3 as viewed from above.

FIG. 5 schematically shows an example of a cross-sectional view between XX ′ of the semiconductor laser shown in FIG. 300 is a semiconductor laser, 301 is an active layer, 302 is a substrate, 303 is an anode, 304 is a cathode, 306 is an upper cladding layer, and 307 is a lower cladding layer.

As described above, at least the upper cladding layer 306
By forming the structure (cylindrical shape) 309 in which the central region of the semiconductor laser is hollowed out, it becomes difficult for current to flow in the central region of the semiconductor laser. Therefore, since a gain can be generated only in the light that mainly circulates, an ineffective current can be reduced. In particular, when the single transverse mode is realized, the beat frequency becomes very stable.

Although the light guide layer and the cap layer are not particularly shown in FIG. 5, even when such a layer is present, it is sufficient that at least the central portion of the upper cladding layer 306 has a hollow structure.

FIG. 6 shows an example. 321 is a cap layer,
322 and 323 are light guide layers.

It is also possible to form the electrode in a cylindrical shape while keeping the shape of the upper cladding layer, the cap layer and the like.

It is also preferable to form a part of the active layer 301 or the active layer itself as shown in FIG. 7, or to form a part of the lower clad layer 307 as shown in FIG. Things. When a part of the active layer is also formed in a cylindrical shape, the volume of the active layer is reduced, so that the threshold current can be more effectively reduced.

In particular, it is preferable to have a cylindrical shape within a range where the laser light is distributed (for example, l in FIG. 8). That is, the active layer is preferably ring-shaped (donut-shaped).

For example, when the active layer is 0.1 μm, FIG.
1 in the figure is 1 μm.

When the thickness of the active layer is constant, it has a ring-like structure within 1 in FIG. 8, that is, light confinement with respect to the active layer within a seepage distance perpendicular to the active layer surface. The larger the coefficient, the more suitable low-current driving becomes possible, and the more stable the oscillation frequency. Of course, as shown in FIG. 9, the entire semiconductor laser 300 may have a cylindrical shape (ring-shaped ridge type structure).

In FIG. 8, the light exudation distance l
Are described as being located in the cladding layers 306 and 307, but of course, depending on conditions such as the refractive index and thickness of the cladding layer, light may seep beyond the cladding layer. In such a case, the portion corresponding to the light exudation distance 1 preferably has a cylindrical shape. Also,
When the light guide layer between the active layer and the clad layer or the substrate 302 is exuded, it is preferable that a part of the optical guide layer and the substrate corresponding to the exudation distance have a cylindrical shape.

When low current or low voltage driving is required to prevent loss of light, the low refractive index layers 306 and
It is desirable to reduce the light loss at 07.

FIG. 59 is an enlarged view of the area 350 of FIG. When driving with low power, the low refractive index layer side surface,
The angles θ ₁ , θ ₂ (FIG. 59) formed by the active layer surface are 75 ° ≦ θ ₁ , θ ₂ ≦ 105 °, preferably 80 ° ≦ θ ₁ , θ ₂ ≦ 100 °, more preferably 85 ° ≦ θ. It is desirable to manufacture the element so that ₁ , θ ₂ ≦ 95 °.

By satisfying such conditions, the loss of the light (evanescent light) seeping into the low refractive index layers 306 and 307 can be prevented, so that the semiconductor laser can be driven with a lower current (or lower voltage). It becomes possible.

Of course, it is also preferable that the side surface of the semiconductor laser is a total reflection surface. It is preferable that the angle formed by 90% or more of the light exuding region on the total reflection surface with the active layer surface is within the above range.

Further, the side surface over the entire circumference of the low refractive index layer is
It is also preferable that the above conditions of θ ₁ and θ ₂ are satisfied. In the case of a cylindrical shape such as a cylindrical shape, it is more preferable that the inner side surface of the laser also satisfies the above conditions of θ ₁ and θ ₂ .

The surface accuracy (surface roughness) of the side surface of the low refractive index layer sandwiching the active layer 301 is not more than half of the wavelength in the medium (wavelength in vacuum / equivalent refractive index of the medium) in the active layer. , More preferably less than 1/3. Specifically, in the case of an InP system (wavelength: 1.55 μm, equivalent refractive index of the medium: 3.6), it is about 0.22 μm or less, preferably 0.14 μm or less.

In the case of a GaAs system (wavelength 0.85 μm, equivalent refractive index of the medium 3.6), about 0.12 μm or less,
Preferably, it is 0.08 μm or less.

The "surface accuracy" indicates the flatness of the side surface of the layer. If the semiconductor laser is circular, it can be considered as a deviation from a perfect circle. Of course, it is desirable that not only the side surface of the low refractive index layer but also the side surface of the active layer be in the above range.

(Filling of cylindrical portion) At least a part of the cylindrical portion (cylindrical structure portion) is provided with an insulating material (dielectric thin film).
Is also preferable. Of course, if desired characteristics can be obtained, it is not limited to an insulating material, and it is not necessary to completely fill the hollow portion.

The dielectric thin film is not particularly limited as long as its specific resistance is higher than that of the cladding layer, but amorphous Si, SiO ₂ , MgO, and SiN are preferably used. The filler may form a total reflection surface inside the cylindrical shape. As shown in FIG. 10, one type of material 330 may be filled, or a mixture may be used. In addition, as shown in FIG. 11, it is preferable that at least one of the inner side and the outer side of the active layer or the like is covered with the thin film 311. In this case, deterioration of device characteristics due to exposure to an external atmosphere can be prevented, and material can be saved compared to a case where the device is completely filled. FIG. 11 shows a single-layer coating film, but it goes without saying that a plurality of layers may be used.

When a plurality of dielectric thin films are used, Si
It is also preferable to provide several layers of pairs of O ₂ and Si. Of course, if the desired properties are obtained, it is not necessary to completely fill.

Hereinafter, another example of filling will be described.

In FIG. 12, reference numeral 330 denotes an insulating film. As described above, it is also preferable to have the insulating film region 330 in the central portion under the anode 303. It becomes difficult for the current to flow in the center of the semiconductor laser element, the ineffective current is reduced, and the single transverse mode is easily generated. This is useful when it is desired to form the anode electrode structure flat.

Although the cap layer, the light guide layer and the like are not shown, they may be formed if necessary.

When the upper cladding layer 306 is a P-type, a PNP-type conductive material 330 is used instead of the insulating film 330.
, The central region of the laser has a PNPN thyristor structure, which makes it difficult for current to flow.

FIG. 13 is a sectional view of a semiconductor laser having a columnar shape. 340 is, for example, a Fe-doped high-resistance layer. By using such a high resistance layer, a structure in which a current does not easily flow in the center of the semiconductor laser device can be realized.

(Cylindrical Portion Size) The cylindrical portion 309 (for example, FIG. 9) of the active layer of the semiconductor laser may be located approximately at the center. A state in which no waveguide mode exists is called a cutoff. In order to stabilize a transverse mode, it is preferable that the waveguide be formed so as to satisfy a cutoff condition for a higher-order mode. Further, it is desirable that the diameter d (FIG. 5) of the cylindrical portion is also defined so as to satisfy the cutoff condition for the higher-order mode.

By satisfying the cut-off condition for the higher-order mode, the transverse mode becomes only the basic mode and becomes stable.

(Cylindrical Shape) The shape of the cylindrical portion is not necessarily limited to a circular shape. The cut-off condition of the higher-order mode is satisfied as much as possible, and only a single guided mode exists (single mode). It is preferable that the cylindrical shape is such that one horizontal mode is achieved.

(Production of Cylindrical Part) A semiconductor laser having a cylindrical shape is formed by using a mask or the like when depositing a semiconductor film to be an active layer, a light guide layer, a clad layer, etc. on a substrate. It may be deposited in a shape. Alternatively, the active layer, the light guide layer, the clad layer, and the like may be deposited in a cylindrical shape, and then may be hollowed out by etching or the like so as to form a cylindrical shape.

The etching method for forming the cylindrical portion includes wet etching, gas etching, plasma etching, sputter etching, reactive ion etching (RIE), and reactive ion beam etching (RIB).
E) and the like can be used as appropriate.

(Active Layer, etc.) As the material of the active layer applicable to this embodiment, GaAs, InP, ZnSe, AlGaAs, InGaAs
P, InGaAlP, InGaAsP, GaAsP, InGaAsSb, AlGaAsSb, In
AsSbP, PbSnTe, GaN, GaAlN, InGaN, InAlGaN, GaInP,
GaInAs, SiGe type, and the like.

As the clad layer, those applicable to the above-mentioned active layer can be used.

As the combination of the active layer and the cladding layer, for example, PbSnTe (active layer) / PbSeTe (cladding layer), PbSnSeTe (active layer) / PbSeTe (cladding layer), Pb
EuSeTe (active layer) / PbEuSeTe, PbEuSeTe (active layer) / Pb
Te (cladding layer), InGaAsSb (active layer) / GaSb (cladding layer), AlInAsSb (active layer) / GaSb (cladding layer), In
GaAsP (active layer) / InP (cladding layer), AlGaAs (active layer) / AlGaAs (cladding layer), AlGaInP (active layer) / AlG
aInP (active layer) or the like can be used.

Further, the structure of the semiconductor laser is not limited to the active layer having a bulk structure, but may be a single quantum well structure (SQ).
W) and a multiple quantum well structure (MQW).

When a quantum well laser is used, it is preferable to adopt a strained quantum well structure. For example, 8 layers of InGaAsP quantum well with about 1% compression strain and InG
An active layer is formed by a barrier layer of aAsP. Of course, an MIS structure can also be used.

(Substrate) The substrate may be any substrate on which a desired material can be grown, and may be a GaAs substrate, an InP
Substrate, GaSb substrate, InAs substrate, PbTe substrate, GaN substrate, ZnSe
Substrate, compound semiconductor such as ZnS substrate, SiC substrate, 4H-Si
C substrate, 6H-SiC substrate, sapphire substrate, silicon substrate,
An SOI substrate or the like can be used.

(Formation method) For forming an active layer of a semiconductor laser, a liquid phase epitaxy (LPE method), a molecular beam epitaxy (MBE method), a metal organic chemical vapor deposition method (MOCVD method, MOVPE method)
Method, an atomic layer growth method (ALE method), an organometallic molecular beam epitaxy (MOMBE), a chemical beam epitaxy (CBE), or the like.

(Electrode material) As the anode electrode, Cr /
Au, Ti / Pt / Au, AuZn / Ti / Pt / Au and the like can be used. AuGe / Ni / Au or AuSn / Mo as cathode electrode
/ Au or the like can be used.

Of course, the present invention is not limited to these.

The arrangement of the electrodes can be appropriately reversed from that shown in the drawings according to the conductivity of the substrate, the active layer, and the like. The same applies to other embodiments.

It is also preferable to form a cap layer (contact layer) for reducing contact resistance with an electrode on the clad layer, and then form the above electrode material on the cap layer.

For example, the structure is InGaAsP (active layer) / P-type InP (cladding layer) / P-type InGaAsP (cap layer) / electrode.

Although the cathode electrode is shown below the substrate in the drawings, the arrangement of the anode and the cathode may be reversed depending on the type of the substrate.

(Others) It is preferable to mount a semiconductor laser chip on a heat radiating material (heat sink) in order to prevent the semiconductor laser from affecting the heat. Heat sink materials include Cu, Si, and Si
C, AlN, diamond and the like can be used. Of course, it is not limited to these. Further, if necessary, a Peltier element can be used for temperature control.

In order to ensure that the semiconductor laser becomes a total reflection surface or to prevent deterioration, an insulating film (coating film) is provided on the side surface (side surface of the region where light exists) of the semiconductor laser. The formation is also preferable. The coating materials include SiO ₂ , SiN, Al
Insulating films such as ₂ O ₃ and Si ₃ N ₄ and amorphous silicon (α-
Si) or the like can be used.

Using the method described in the present embodiment, a current flowing through the laser, a voltage applied to the laser, or a frequency change of the impedance of the laser itself is detected as a beat signal, thereby functioning as a gyro.

(Second Embodiment) FIG. 14 is a schematic perspective view showing another example of a gyro provided with a ring resonator type laser in which light propagates in a circular shape according to the present invention. The difference from the first embodiment (FIG. 2) is that the semiconductor laser has a quadrangular prism shape.

In FIG. 14, reference numeral 1100 denotes a semiconductor laser;
1101 denotes an active layer, 1102 denotes a substrate, 1103 denotes an anode, 1104 denotes a cathode, and 1105 denotes an electric terminal.

By adopting such a configuration, the same effect as that of the first embodiment can be obtained, and the number of propagation modes is smaller than that of the first embodiment. S / N is improved as compared with the embodiment.

The structure of the positions of the electrodes and the like are not limited to those shown in FIG. 14, and a structure as shown in FIG. 15 may be employed.

FIG. 16 schematically shows the semiconductor laser of FIG. 15 as viewed from above.

FIG. 17 shows XX 'of the semiconductor laser shown in FIG.
FIG. 1 schematically shows an example of a cross-sectional view taken between them. 1100
Is a semiconductor laser, 1101 is an active layer, 1102 is a substrate, 1103 is an anode, 1104 is a cathode, 1106 is an upper cladding layer, 11
07 Lower clad layer.

As described above, at least the upper cladding layer 1106
By forming a structure (tubular structure) 1109 in which the central region of the semiconductor laser is hollowed out, it becomes difficult for current to flow in the central region of the semiconductor laser. Therefore, since a gain can be generated only in the light that mainly circulates, an ineffective current can be reduced. In particular, when the single transverse mode is realized, the beat frequency becomes very stable.

Although the light guide layer and the cap layer are not particularly shown in FIG. 17, even when those layers are provided, it is sufficient that at least the center portion of the upper cladding layer 1106 has a hollow structure. FIG. 18 shows an example. 1121 is a cap layer, and 1122 and 1123 are light guide layers.

It is also possible to form the electrode in a cylindrical shape while keeping the shape of the upper cladding layer, the cap layer, and the like.

It is also preferable that a part of the active layer 1101 be cylindrical as shown in FIG. 19, and that a part of the lower cladding layer 1107 be hollow as shown in FIG. is there. When a part of the active layer is also formed in a cylindrical shape, the volume of the active layer is reduced, so that the threshold current can be more effectively reduced.

In particular, the exudation distance of light (for example, FIG.
In the range of l) in 20, it is preferable to have a cylindrical shape. That is, the active layer is preferably ring-shaped (donut-shaped).

Specifically, the light exudation distance 1 in the case of an ordinary semiconductor laser is about 1 μm.

When the light seeping distance has a cylindrical structure, that is, the light confining coefficient with respect to the active layer becomes larger as the light seeping distance becomes perpendicular to the active layer surface. More preferably, low current driving is possible, and the oscillation frequency is stabilized. (Single transverse mode is realized) Of course, as shown in FIG. 21, the entire semiconductor laser 1100 may have a hollow shape.

In FIG. 20, the light seeping distance is shown.
Although l is described as being located in the cladding layers 1106 and 1107, of course, depending on conditions such as the thickness of the cladding layer, light may seep beyond the cladding layer. In such a case, it is preferable that the portion corresponding to the light exudation distance 1 has a cylindrical structure. Also,
When the light guide layer between the active layer and the clad layer or the substrate 1102 is exuded, it is preferable that a part of the optical guide layer and the substrate corresponding to the exudation distance have a cylindrical structure.

(Filling of cylindrical portion) It is preferable that at least a part of the hollow portion is filled with an insulating material (dielectric thin film). Of course, if desired characteristics can be obtained, it is not limited to an insulating material, and it is not necessary to completely fill the hollow portion.

The dielectric thin film is not particularly limited as long as it has a higher specific resistance than the cladding layer, but amorphous Si, SiO2, MgO, and SiN are preferably used. The filler may form a total reflection surface inside the cylindrical shape. As shown in FIG. 22, one type of material 1130 may be filled, or a mixture may be used. In addition, as shown in FIG. 23, it is preferable that at least one of the inner side and the outer side surface of the active layer or the like is covered with the thin film 1111. In this case, deterioration of device characteristics due to exposure to an external atmosphere can be prevented, and material can be saved compared to a case where the device is completely filled. FIG. 23 shows a single-layer coating film, but it goes without saying that a plurality of layers may be used.

When a plurality of dielectric thin films are used, Si
It is also preferable to provide several layers of pairs of O2 and Si. Of course, if the desired properties are obtained, it is not necessary to completely fill.

The following is an application example of filling.

In FIG. 24, reference numeral 1130 denotes an insulating film. As described above, it is also preferable to have the insulating film region 1130 in the lower central portion of the anode 1103. It becomes difficult for the current to flow in the center of the semiconductor laser element, the ineffective current is reduced, and the single transverse mode is easily generated. This is useful when it is desired to form the anode electrode structure flat.

Although the cap layer, the light guide layer and the like are not shown, they may be formed if necessary.

In the structure shown in FIG. 24, when the upper cladding layer 1106 is of a P-type, a PNP-type conductive substance 1130 is filled instead of the insulating film 1130, so that the laser central region is formed of a PNPN-type. With the thyristor structure, it is possible to make the current hardly flow.

Further, a configuration as shown in FIG. 25 can be adopted. Reference numeral 1140 denotes an Fe-doped high resistance layer. By using such a high resistance layer, a structure in which a current does not easily flow in the center of the semiconductor laser device can be realized.

(Cylindrical portion size) The cylindrical portion 1109 of the active layer of the semiconductor laser may be approximately at the center. The state where there is no guided mode is called cut-off. In order to stabilize the transverse mode, it is preferable that the cut-off condition is formed so as to satisfy the cut-off condition for a higher-order mode. Further, it is desirable that the diameter d of the cylindrical portion (FIG. 17) is also defined so as to satisfy the cutoff condition for the higher-order mode. By meeting the cut-off condition for higher order modes,
The horizontal mode becomes only the basic mode and becomes stable.

(Cylindrical Shape) The cylindrical structure is not necessarily limited to a quadrangle, but it satisfies the cut-off condition of the higher-order mode as much as possible and has only a single guided mode (single lateral mode). It is preferable to have a cylindrical shape that can be used as a mode.

(Preparation of Cylindrical Structure) A semiconductor laser having a hollow shape is formed by using a mask or the like when depositing a semiconductor film to be an active layer, a light guide layer clad layer, etc. on a substrate. May be deposited. Alternatively, the active layer, the light guide layer, the cladding layer, and the like may be deposited in a quadrangular prism shape and then hollowed out in a cylindrical shape.

As an etching method for forming the cylindrical structure, the method described in the first embodiment or the like can be used.

Also in this embodiment, the active layer and the like described in the first embodiment can be applied. Also,
As for the structure of the semiconductor laser, the structure described in the first embodiment can be used.

The substrate described in the first embodiment can be used as the substrate.

For forming an active layer and the like of a semiconductor laser, those described in the first embodiment can be used.

As the anode and the cathode, those described in the first embodiment can be used.

As the heat sink material, the materials described in the first embodiment can be used.

(Third Embodiment) FIG. 26 is a schematic perspective view showing another example of a gyro provided with a ring resonator type laser in which light propagates in a circular shape according to the present invention.
The point that a triangular prism shape is used as the shape of the semiconductor laser is mainly different from the first and second embodiments.

By adopting such a configuration, the same effect as that of the first embodiment can be obtained, and since the number of propagation modes is smaller than that of the first embodiment, the number of oscillation modes is reduced. S / N is improved as compared with the embodiment.

Regarding the point that the central region has a hollow cylindrical structure, its shape, position, depth, filling of the hollow portion, etc., the items described in the first and second embodiments are applied. can do.

(Fourth Embodiment) FIG. 27 is a schematic perspective view showing another example of a gyro provided with a ring resonator type laser in which light propagates in a circular shape according to the present invention.
2300 is a semiconductor laser, 2301 is an active layer, 2302 is a substrate, 23
03 is an anode, 2304 is a cathode, and 2305 is an electric terminal. Although not particularly numbered, at least a low refractive index layer (cladding layer) is formed above and below the active layer 2301. Reference numeral 2309 indicates that the resistance has been increased by ion implantation. In FIG. 27, the light guide layer, the cap layer, and the like are omitted as appropriate, but a light guide layer (optical waveguide layer) may be formed between the active layer and the clad layer.
It is also preferable to form a cap layer as a buffer layer between the clad layer and the electrode. Figure 27
Describes that the anode 2303 is formed in a ring shape and the region 2309 with high resistance is exposed, but the entire surface of the region 2309 may be covered with the anode 2303. Also, the positions of the electrodes and the like are not limited to those shown in FIG. 27, and the electrodes may be arranged as shown in FIG.

FIG. 29 is a schematic diagram when the semiconductor laser shown in FIG. 28 is viewed from the upper surface side.

FIG. 30 is a schematic view showing an example of a cross-sectional view taken along the line XX ′.

Reference numeral 2301 denotes an active layer, 2302 denotes a substrate, 2303 denotes an anode, 2304 denotes a cathode, 2306 denotes an upper clad layer, 2307 denotes a lower clad layer, and 2309 denotes a region whose resistance is increased by ion implantation. With such a configuration, the current is less likely to flow in the central region, and a gain can be given mainly to only the circulating light.

In FIG. 30, the high resistance region 2309 is shown.
Are clearly shown, but actually there is some spread at the interface. Of course, FIG.
As shown in FIG. 6, it is also preferable that the ion implantation is performed so that the projection range at the time of the ion implantation mainly comes to the active layer.

Although FIG. 30 shows that at least a part of the upper cladding layer has a high resistance,
As long as the structure is such that current does not easily flow in the central region, the resistance may be increased to a part of the active layer region 2301 or to at least a part of the lower cladding layer 2307. Of course, the entire central region of the semiconductor laser may have a higher resistance.

In particular, when the central region of the active layer 2301 has a high resistance, the volume of the active layer is substantially reduced, and the drive current can be further reduced.

Of course, it is also possible to perform ion implantation so as to have a projection range at a depth near the active layer, and to increase the resistance around the depth.

In FIG. 30, the anode 2303 is
Although the structure is arranged around the semiconductor laser, it may be arranged on the entire upper surface of the laser.

An optical guide layer, a cap layer, and the like can be formed as appropriate.

Regarding the increase in the resistance according to the present invention, the specific resistance in the ion-implanted region is approximately 100 Ω · cm to 10 ⁵ Ω · cm, preferably 5 × 10 ³ Ω · cm, although it depends on the type of the active layer. And 1 × 10 ⁵ Ω · cm.

Examples of the ion-implanted species include protons and boron.

It is also preferable to perform ion implantation so that the projection range Rp of the ion implantation is at the center of the active layer.
The accelerating voltage in that case is a cladding layer on the active layer,
Considering the material and thickness of the light guide layer, etc., 10 KeV to 1 Me
It is preferable to perform the treatment appropriately in the range of V.

The ion implantation dose ranges from 1 × 10 ¹³ cm ⁻² to 1 × 10 ¹⁵
It can be performed within the range of cm- ² .

The substrate temperature at the time of ion implantation may be room temperature.

The ion implantation region does not need to be strictly at the center of the semiconductor laser, but is preferably implanted approximately at the center so as to satisfy the cut-off condition for higher-order modes.

It is desirable that the diameter d of the implantation region is also defined so as to satisfy the cutoff condition for the higher-order mode.

The shape of the injection region is not necessarily limited to a circle, but satisfies the cutoff condition of a higher-order mode as much as possible, and only a single waveguide mode (single transverse mode) exists. It is preferable to make it into such a shape.

It is also preferable to perform an annealing process after the implantation in order to reduce the damage caused during the ion implantation. The annealing temperature is 200 ℃
To 500 ° C, preferably 300 ° C to 400 ° C. As an atmosphere for annealing, an atmosphere containing hydrogen or the like can be used.

In this embodiment, the active layer and the like described in the first embodiment can be applied. Also,
As for the structure of the semiconductor laser, the structure described in the first embodiment can be used.

As the substrate, the substrate described in the first embodiment can be used.

For forming an active layer and the like of a semiconductor laser,
The one described in the first embodiment can be used.

The anode and cathode described in the first embodiment can be used. The materials described in the first embodiment can be used as the heat sink material and the like.

In this embodiment, an example in which ion implantation is used to increase the resistance has been described. However, by selectively oxidizing a portion to be increased in resistance, the resistance can be increased. Is also good.

(Fifth Embodiment) FIG. 31 is a schematic perspective view showing another example of an optical gyro provided with a ring resonator type laser in which light propagates in a circular shape according to the present invention. . 2600 is a semiconductor laser, 2601 is an active layer, 2602 is a substrate, 2603 is an anode, 2604 is a cathode, and 2605 is an electric terminal. Although not particularly numbered, at least a low refractive index layer (cladding layer) is formed above and below the active layer 2601. 2609 indicates that the resistance is increased by ion implantation. In FIG. 31, the light guide layer, the cap layer, and the like are appropriately omitted, but a light guide layer (optical waveguide layer) may be formed between the active layer and the clad layer, and further, the gap between the clad layer and the electrode may be formed. It is also preferable to form a cap layer as a buffer layer in advance.
Although FIG. 31 shows that the anode 2603 is formed in a ring shape and the region 2609 with high resistance is exposed, the region 2609 may be entirely covered with the anode 2603. Absent. Also, the positions of the electrodes and the like are not limited to those shown in FIG. 31, and the electrodes may be arranged as shown in FIG.

FIG. 33 is a schematic diagram when the semiconductor laser shown in FIG. 32 is viewed from above.

FIG. 34 is a schematic diagram showing an example of a cross-sectional view taken along the line XX ′.

Reference numeral 2601 denotes an active layer, 2602 denotes a substrate, 2603 denotes an anode, 2604 denotes a cathode, 2606 denotes an upper clad layer, 2607 denotes a lower clad layer, and 2609 denotes a region whose resistance is increased by ion implantation. With such a configuration, the current is less likely to flow in the central region, and a gain can be given mainly to only the circulating light.

In FIG. 34, a high resistance region 2309 is shown.
Are clearly shown, but actually there is some spread at the interface. Further, the anode 2603 may be formed on the entire surface including the high resistance region of 2609. The same applies to FIG.

In FIG. 34, it is described that at least a part of the upper cladding layer has a high resistance.
As long as the structure is such that current does not easily flow in the central region, the resistance may be increased to a part of the active layer region 2601 or to at least a part of the lower cladding layer 2607. Of course, the entire central region of the semiconductor laser may have a higher resistance.

In particular, if the central region of the active layer 2601 has a high resistance, the volume of the active layer is substantially reduced, and the drive current can be further reduced.

Of course, it is also possible to carry out ion implantation so as to have a projection range at a depth near the active layer, and to increase the resistance around the depth.

In FIG. 34, the anode 2603 is
Although the structure is arranged around the semiconductor laser, it may be arranged on the entire upper surface of the laser.

It is also possible to appropriately form a light guide layer, a cap layer, and the like.

Also in the present embodiment, the one described in the first embodiment can be applied.

Further, regarding the structure of the semiconductor laser,
The one described in the first embodiment can be used.

The substrate described in the first embodiment can be used as the substrate.

For forming an active layer and the like of a semiconductor laser,
The one described in the first embodiment can be used.

As the anode and the cathode, those described in the first embodiment can be used.

As the heat sink material, the materials described in the first embodiment can be used.

(Sixth Embodiment) FIG. 35 is a schematic perspective view showing another example of a gyro provided with a ring resonator type laser in which light propagates in a circular shape according to the present invention.
The point that a triangular prism shape is used as the shape of the semiconductor laser is mainly different from the fourth and fifth embodiments.

By adopting such a configuration, the same effect as that of the fourth embodiment can be obtained, and the number of propagation modes is smaller than that of the fourth embodiment. S / N is improved as compared with the embodiment.

In FIG. 35, the anode 2903 is formed in a ring shape, and the region 2909 having a high resistance is shown as being exposed.
It can be covered with 2903. Also, the positions of the electrodes and the like are not limited to those shown in FIG.

Regarding the position, depth, forming method, etc. of the high resistance region, active layer, substrate, electrode material, etc.
Alternatively, a configuration similar to that of 5 can be adopted.

In the embodiment, the ring laser has been described as having a cylindrical, quadrangular, or triangular prism shape. However, the present invention is not limited to these shapes. As long as the laser beam and the counterclockwise laser beam have the same path,
The shape of the path may be a shape having a polygon such as a pentagon, a hexagon, as well as a circle, a quadrangle, and a triangle.

Embodiment 1 FIG. 2 is a schematic perspective view showing another example of an optical gyro provided with a ring resonator type laser in which light propagates in a circular shape according to the present invention. This shows a case where a semiconductor laser having a circular waveguide and a cylindrical structure is used. In FIG. 2, 205 is an electric terminal, 203 is an anode, 204 is a cathode, 200 is a cylindrical semiconductor laser having a hollow shape, 201 is an active layer constituting the semiconductor laser, and 202 is a substrate on which the semiconductor laser is mounted. .

In the above configuration, a current is injected from the anode 203 into the semiconductor laser. Active layer 201 is 1.55μ
m of InGaAsP, and 1.3 μm above and below
An InGaAsP light guide layer having a composition, and an InP clad layer are formed so as to sandwich these. Since a semiconductor and air have different refractive indexes, reflection occurs at the interface. Assuming that the refractive index of the semiconductor is 3.5, total reflection occurs when the angle between the normal to the interface and the laser beam is 16.6 degrees or more.
In the mode that receives total reflection, the oscillation threshold value can be reduced by the amount corresponding to the absence of the mirror loss as compared with the other modes, so that oscillation starts at a low injection current level. Moreover, since the gain is concentrated in this oscillation mode, oscillation in other modes is suppressed. The radius of the element consisting of the semiconductor laser 200 is 10μ
m and the thickness of the active layer is 0.1 μm, the oscillation threshold current is 0.2 mA. When the driving current is 0.5 mA, when the camera shakes or the vehicle rotates 30 degrees per second, which is about the vibration of the automobile, a signal having a voltage amplitude of 100 mV and a frequency of 23.6 Hz is obtained from the electrode terminal 1.

For comparison, FIG. 1 does not have a hollow shape.
In the case of the configuration shown in Fig. 5, the oscillation threshold value is 0.8 mA, so that it is possible to drive at a constant current as compared with the columnar shape, that is, it is possible to obtain a gyro having a small oscillation threshold current.

When total reflection occurs, there is evanescent light traveling along the interface. When the oscillation wavelength is 1.55 μm, the exudation distance of the evanescent light is 0.074 μm. The intensity of the evanescent light attenuates exponentially.
If it is 10 μm away from a reflector that can be considered with a margin, the effect of the return light can be neglected. That is, the above configuration example is the semiconductor laser 200
This is an example in which no reflector is present within 10 μm from the interface of the column, and is not affected by return light noise.

Further, by modulating the injection current with an amplitude of 0.1 mA and a frequency of 2 kHz, the beat frequency becomes 1
A gyro that does not cause a lock-in phenomenon even when rotating according to a small frequency such as less than Hz can be configured. In addition, since the signal is modulated at a frequency in a band different from the signal frequency, the signal is not adversely affected.

Note that here, InG is used as the semiconductor material.
aAsP type was used, but GaAs type, ZnSe type
Any material system such as a system, an InGaN system, and an AlGaN system may be used.

As a ring resonator type laser, FIG.
The gyro can also be configured using a ring resonator type gas laser shown in FIG. 7 or FIG.

In FIGS. 57 and 58, 1 is an electric terminal,
Reference numeral 10 denotes a quartz tube produced by hollowing out quartz, 11 denotes a mirror, and 21 and 22 denote discharge electrodes. For example, 21 is an anode and 22 is a cathode. Reference numeral 31 denotes clockwise laser light, and reference numeral 32 denotes counterclockwise laser light.

In the above configuration, when helium gas and neon gas are put in the quartz tube 10 and a voltage is applied between the anode 21 and the cathode 22, discharge starts and a current flows.

When the quartz tube 10 is stationary, the oscillation frequencies of the clockwise laser light and the counterclockwise laser light are exactly the same, 4.73 × 10 ¹⁴ Hz, and the oscillation wavelength λ is 63.
It is 2.8 nm. For example, if the quartz tube 10 functioning as a resonator receives a rotation of 180 degrees per second and the length of one side of the quartz tube 10 is 10 cm, the beat frequency is 496.5 kHz. At this time, if the power supply current is adjusted to be constant and the terminal voltage is monitored from the electric terminal 1, a signal having an amplitude of 100 mV and a frequency of 496.5 kHz is obtained.

Embodiment 2 FIG. 36 is a schematic diagram of a gyro provided with a ring resonator type laser 3000 in which light propagates in a circular shape when viewed from above. It has a rectangular waveguide structure and a hollow structure according to the present invention. FIG. 38 shows a cross-sectional view taken along XX ′.

3001 is an active layer, 3022 is a light guide layer, 3002 is a substrate, 3003 is an anode, 3004 is a cathode, 3005 is an electric terminal, 3006 and 3007 are cladding layers, and 3040 is a cap layer.

Hereinafter, a method for producing the present ring laser will be specifically described.

First, a base having the structure shown in FIG. 39 is prepared.

On an n-GaAs substrate 3002, Al _0.3 Ga _0.7 As / GaA
There is an active layer 3001 having a multiple quantum well structure composed of three layers of s
An optical guide layer 3022 of Al _0.3 Ga _0.7 As sandwiches this active layer.
Is provided. In addition, clad layers (30
06 is formed of p-Al _0.5 Ga _0.5 As, and 3007 is formed of n-Al _0.5 Ga _0.5 As). Reference numeral 3015 denotes a buffer layer made of n-GaAs. 3040 is a cap layer made of p-GaAs.

An anode 3003 is formed on the cap layer 3040.
Cr / Au (or Ti / Pt / Au) is formed (FIG. 40).

After applying photoresist 3060,
Pattern as in 41.

Dry etching is performed on anode 3003 using patterned photoresist 3060 as a mask (FIG. 42).

Next, the semiconductor layer is removed by dry etching (FIG. 43), and the photoresist is stripped (FIG. 43).
45).

Here, the anode is annealed in a hydrogen atmosphere to form an alloy.

Next, after polishing the substrate as necessary, AuGeNi /
A cathode 3004 made of Au is deposited (FIG. 46).

Thus, the ring laser shown in FIG. 38 can be formed. When the width of the waveguide is 5 μm and the length of one side is 400 μm, the oscillation threshold is 4 mA. When the drive current is 5 mA and the camera shakes or the car rotates at 30 degrees per second, the voltage amplitude from the electrode terminal 3005 is 100 mV and the frequency is 8
A 60 Hz signal is obtained. Thus, a gyro having a small oscillation threshold current is realized.

The angle α in FIG. 36 is in the range of 45 ° ± 0.01 °, preferably in the range of 45 ° ± 0.001 °. The same applies to the portions corresponding to the other corners. This is a condition necessary for the laser beam to return as close to the starting point as possible when making a round in the optical resonator.

Of course, when a semiconductor ring laser is manufactured by another process, α is preferably within the above range.

FIG. 37 is an enlarged view of the corner 3090 in FIG. 36. The surface roughness r at the corner is less than 500 °.
Preferably it is less than 200 °. This is very important to reduce backscatter and reduce lock-in.

FIG. 44 is an enlarged view of the area 3091 in FIG. As shown in the figure, the angle β between the substrate and the side surface of the semiconductor layer is 75 ° ≦ β ≦ 105 °, preferably 80 ° ≦ β ≦ 100.
°, more preferably, 85 ° ≦ β ≦ 95 °. β
Is closer to 90 °, the transverse mode becomes more stable. of course,
It is preferable that θ ₁ and θ ₂ in the drawing also fall within the range described in the first embodiment.

In addition, the outer side of the side surface of the semiconductor layer has been described, but it is preferable that the above-mentioned range of β is satisfied also on the inner side.

In this embodiment, a ring laser having a rectangular waveguide is described. However, even in the case of a waveguide having another shape (square or triangular), it may fall within the range of β. desirable.

Of course, even when a ring laser is manufactured by another process, the angle β formed between the side surface of the mesa semiconductor layer and the substrate is preferably in the above range.

Further, by providing a protection circuit at the detection terminal of the semiconductor laser, deterioration or destruction of the semiconductor laser can be prevented. FIG. 47 shows an example in which a 4005 voltage follower is connected as a protection circuit. 4000 is a semiconductor laser, 4001 is an electric resistance, 4002 is a current source, and 4006 is a voltage detection circuit.

When a constant voltage source is used as the power supply, the angular velocity of rotation can be measured as a change in current flowing through the semiconductor laser. As shown in FIGS. 48 and 49, when a battery is used as the constant voltage source, the driving system can be reduced in size and weight. In FIG. 48, an electric resistance is connected in series with the semiconductor laser, and a current flowing through the semiconductor laser is measured as a change in voltage across the electric resistance. 4003 is a battery (battery) and 4007 is a voltmeter. Meanwhile, the figure
In 49, an ammeter 4008 is connected in series with the semiconductor laser, and the current flowing through the semiconductor laser is measured directly.

Another circuit configuration for detecting a beat signal will be described.

As shown in FIG. 50, the anode of the ring resonator type gas laser 60 is connected to an operational amplifier 61 for a buffer. Since the signal output from the amplifier 61 has a frequency corresponding to the angular velocity, the signal is converted into a voltage by a known frequency-voltage conversion circuit (FV conversion circuit) to detect rotation. I do. 62 is a power supply.

Of course, if desired characteristics can be obtained, the operational amplifier 61 ("voltage follower") can be omitted.

FIG. 51 shows an example of a circuit diagram for driving the laser at a constant current, reading the change in the anode potential of the laser 60, and detecting the rotation.

The anode of the laser 60 is
Is connected to the output terminal of the operational amplifier 70, and the cathode of the laser 60 is connected to the inverting input terminal of the operational amplifier 70.

The operational amplifier 61 outputs a signal Vout. Since this signal has a beat frequency proportional to the angular velocity, the signal is converted into a voltage by a known frequency-voltage conversion circuit (FV conversion circuit) or the like, and rotation is detected.

FIG. 52 shows a frequency-voltage conversion circuit (FV
Conversion circuit). This circuit consists of a transistor,
The output voltage V _C2 is composed of a diode, a capacitor, and a resistor, and is represented by Expression (2).

[0206]

[Outside 1] Here, E _i is the peak-to-peak value of the input voltage, and f is the beat frequency. C ₂ >> C ₁ , R ₀ C ₂ f <
By designing the circuit parameters to be 1, V _C2 = E _i C ₁ R ₀ f (3) as shown in equation (3), and a voltage output proportional to the beat frequency is obtained. Becomes possible.

FIG. 53 shows an example of a circuit diagram for driving the laser at a constant voltage, reading the change in the anode potential of the laser 60, and detecting the rotation.

[0208] The anode of the laser 60 is connected to the output terminal of the operational amplifier 72 via the resistor 63, and the cathode of the laser 60 is grounded to the reference potential.

When a constant potential (Vin) is applied to the inverting input terminal of the operational amplifier 72 from a microcomputer or the like, a constant voltage drive configuration in which the potential is always applied to the resistor 63 and the laser 60 is provided.

The electric resistance 63 is connected to the operational amplifier 61 for the buffer.

The operational amplifier 61 outputs a signal Vout. Since this signal has a beat frequency proportional to the angular velocity, the signal is converted into a voltage by a known frequency-voltage conversion circuit (FV conversion circuit) or the like, and rotation is detected. Of course, the rotation detection may be performed by directly inputting the signal of the electric resistance and the equipotential portion to the FV conversion circuit. Further, a frequency counter circuit can be used as the beat signal detecting means.

Next, FIG. 60 shows a case where the reference of the signal potential is set to the ground by using the subtraction circuit 75 in addition to the constant voltage drive configuration shown in FIG.

A constant potential V ₁ is applied to the inverting input terminal of the operational amplifier 72 from a microcomputer or the like. 60 is a ring resonator type laser, 61 is a voltage follower, 63 and 76-7
Reference numeral 9 denotes an electric resistance, which makes the resistance values of 76 and 77 and 78 and 79 equal.

The electric potential V ₁ V ₂ at both ends of the electric resistor 63 is connected to the inverting input terminal and the non-inverting input terminal of the amplifier 80 through a voltage follower and resistors 76 and 78 circuits. This makes it possible to detect a change in the voltage V ₂ −V ₁ (= V ₀ ) applied to the electric resistance 63 with the reference potential as the ground. That is, a change in the current flowing through the ring resonator type laser 60 can be detected.

The rotation of the obtained signal is detected through an FV conversion circuit or the like.

[0216] Regardless of the type of power supply, a change in the impedance of the semiconductor laser can be directly measured by the impedance meter 4009. 4004 is
Power supply. In this case, unlike the case where the terminal voltage or the current flowing through the element is measured, the influence of the noise of the driving power supply is reduced. This example is shown in FIG.

(Embodiment 3) FIG. 2 is a schematic perspective view showing another example of an optical gyro provided with a ring resonator type laser in which light propagates in a circular shape according to the present invention. The shape of the semiconductor laser used is cylindrical (Fig. 1)
Instead of a cylindrical shape. Other points were the same as in Example 1.

According to this configuration, since the laser light circulates along the interface of the semiconductor, the semiconductor laser 200
The central part of the element consisting of is not required. Therefore, by making the shape of a cylinder as shown in FIG. 2, a gain can be given only to the circulating light, and the volume of the active layer is reduced, so that the driving current is further reduced.

(Embodiment 4) FIG. 27 is a schematic perspective view showing another example of a gyro provided with a ring resonator type laser in which light propagates in a circular shape according to the present invention, and is used as a laser. The central part of a cylindrical semiconductor laser (Fig. 2
7 (cross hatched portion) is made high in resistance by ion implantation. Ions use protons and the dose is 5 × 1
0 ¹⁴ cm ^-2 , the accelerating voltage is 100 keV. Although laser light is distributed also in the proton injection region, annealing is performed at 350 ° C. for 15 minutes in order to reduce absorption loss of light in this region. Other points were the same as in Example 1.

According to this configuration, the same effect as that of the third embodiment, that is, a gain can be given only to the circulating light, and the drive current can be further reduced because the volume of the active layer is reduced. can get.

(Embodiment 5) FIG. 14 is a schematic perspective view showing another example of a gyro provided with a ring resonator type laser in which light propagates in a circular shape according to the present invention, and is used as a laser. The difference from the third embodiment (FIG. 2) is that the semiconductor laser has a quadrangular prism shape. Other points were the same as in Example 3.

According to this configuration, since the number of propagation modes is smaller than that of the third embodiment, the number of oscillation modes is reduced, and an optical gyro having better S / N than that of the third embodiment can be obtained.

(Embodiment 6) FIG. 31 is a schematic perspective view showing another example of a gyro provided with a ring resonator type laser in which light propagates in a circular shape according to the present invention, and is used as a laser. The difference from the fourth embodiment (FIG. 27) is that the semiconductor laser has a quadrangular prism shape. Other points are described in Example 4.
The same as above.

According to this configuration, the number of oscillation modes is further reduced as compared with the fourth embodiment, so that a gyro with a better S / N can be obtained.

(Embodiment 7) FIG. 26 is a schematic perspective view showing another example of a gyro provided with a ring resonator type laser in which light propagates in a circular shape according to the present invention, and is used as a laser. The difference from the fifth embodiment (FIG. 14) is that the semiconductor laser has a triangular prism shape.

The other points were the same as in the fifth embodiment.

According to this configuration, since the number of propagation modes is smaller than in the fifth embodiment, the number of oscillation modes is reduced, and a gyro having better S / N than in the fifth embodiment can be obtained.

(Embodiment 8) FIG. 35 is a schematic perspective view showing another example of a gyro provided with a ring resonator type laser in which light propagates in a circular shape according to the present invention, and is used as a laser. The difference from the sixth embodiment (FIG. 31) is that the semiconductor laser has a triangular prism shape.

The other points were the same as in the sixth embodiment.

According to this configuration, the number of oscillation modes is further reduced as compared with the sixth embodiment, so that a gyro having an even better S / N can be provided.

(Embodiment 9) FIG. 55 is a schematic perspective view showing another example of a gyro provided with a ring resonator type laser in which light propagates in a circular shape according to the present invention, and is used as a laser. Substrate 5000 with semiconductor laser
Example 1 (FIG. 32) in that a piezoelectric element 5100 was provided.
And different. Other points were the same as in Example 1.

According to the above configuration, by applying a voltage of 20 kHz to the piezoelectric element 5100, the clockwise and counterclockwise rotation can be given to the semiconductor laser 5000 constituting the optical gyro. By detecting a signal synchronized with the voltage applied to the piezoelectric element 5100 from the terminal 5005, clockwise rotation and counterclockwise rotation can be distinguished. For example, when vibration is applied in the clockwise direction, the terminal voltage increases when the semiconductor laser 5000 receives clockwise rotation, and conversely, decreases when the semiconductor laser 5000 receives counterclockwise rotation. . Moreover, by modulating the signal at a frequency in a band different from the signal frequency, the direction of rotation can be detected without adversely affecting the signal. Although the case where a circular waveguide is provided has been described, it is needless to say that the piezoelectric element can be applied to a waveguide shape such as a square or a triangle (FIGS. 14 and 26).

[0233]

As described above, according to the gyro according to the present invention, a ring resonator type laser in which light propagates in a circular shape is generated by the interference of laser light traveling in opposite directions inside the laser. Current caused by beats,
By detecting changes in voltage or impedance,
Since a beat signal corresponding to the rotation can be extracted from the terminal, it is possible to provide a gyro that can omit a photodetector and an optical system for optical coupling, which are essential in the conventional optical gyro. In addition, the drive power can be reduced by substantially reducing the volume of the active layer.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a method of detecting an angular velocity using a ring resonator type semiconductor laser according to the present invention.

FIG. 2 is a schematic perspective view showing an example of a gyro provided with the ring resonator type semiconductor laser according to the first embodiment of the present invention.

FIG. 3 is a schematic perspective view showing an example of a gyro provided with the ring resonator type semiconductor laser according to the first embodiment of the present invention.

FIG. 4 is a schematic diagram of the ring resonator type semiconductor laser according to the first embodiment of the present invention as viewed from above.

FIG. 5 is a schematic sectional view of the ring resonator type semiconductor laser according to the first embodiment of the present invention.

FIG. 6 is a schematic sectional view of the ring resonator type semiconductor laser according to the first embodiment of the present invention.

FIG. 7 is a schematic sectional view of the ring resonator type semiconductor laser according to the first embodiment of the present invention.

FIG. 8 is a schematic sectional view of the ring resonator type semiconductor laser according to the first embodiment of the present invention.

FIG. 9 is a schematic sectional view of the ring resonator type semiconductor laser according to the first embodiment of the present invention.

FIG. 10 is a schematic sectional view of the ring resonator type semiconductor laser according to the first embodiment of the present invention.

FIG. 11 is a schematic sectional view of a ring resonator type semiconductor laser according to the first embodiment of the present invention.

FIG. 12 is a schematic sectional view of the ring resonator type semiconductor laser according to the first embodiment of the present invention.

FIG. 13 is a schematic sectional view of the ring resonator type semiconductor laser according to the first embodiment of the present invention.

FIG. 14 is a schematic perspective view showing an example of a gyro provided with a ring resonator type semiconductor laser according to a second embodiment of the present invention.

FIG. 15 is a schematic perspective view showing an example of a gyro provided with a ring resonator type semiconductor laser according to a second embodiment of the present invention.

FIG. 16 is a schematic diagram of a ring resonator type semiconductor laser according to a second embodiment of the present invention as viewed from above.

FIG. 17 is a schematic sectional view of a ring resonator type semiconductor laser according to a second embodiment of the present invention.

FIG. 18 is a schematic sectional view of a ring resonator type semiconductor laser according to a second embodiment of the present invention.

FIG. 19 is a schematic sectional view of a ring resonator type semiconductor laser according to a second embodiment of the present invention.

FIG. 20 is a schematic sectional view of a ring resonator type semiconductor laser according to a second embodiment of the present invention.

FIG. 21 is a schematic sectional view of a ring resonator type semiconductor laser according to a second embodiment of the present invention.

FIG. 22 is a schematic sectional view of a ring resonator type semiconductor laser according to a second embodiment of the present invention.

FIG. 23 is a schematic sectional view of a ring resonator type semiconductor laser according to a second embodiment of the present invention.

FIG. 24 is a schematic sectional view of a ring resonator type semiconductor laser according to a second embodiment of the present invention.

FIG. 25 is a schematic sectional view of a ring resonator type semiconductor laser according to a second embodiment of the present invention.

FIG. 26 is a schematic perspective view showing an example of a gyro provided with a ring resonator type semiconductor laser according to a third embodiment of the present invention.

FIG. 27 is a schematic perspective view showing an example of a gyro provided with a ring resonator type semiconductor laser according to a fourth embodiment of the present invention.

FIG. 28 is a schematic perspective view showing an example of a gyro provided with a ring resonator type semiconductor laser according to a fourth embodiment of the present invention.

FIG. 29 is a schematic view of a ring resonator type semiconductor laser according to a fourth embodiment of the present invention as viewed from above.

FIG. 30 is a schematic sectional view of a ring resonator type semiconductor laser according to a fourth embodiment of the present invention.

FIG. 31 is a schematic perspective view showing an example of a gyro provided with a ring resonator type semiconductor laser according to a fifth embodiment of the present invention.

FIG. 32 is a schematic perspective view showing an example of a gyro provided with a ring resonator type semiconductor laser according to a fifth embodiment of the present invention.

FIG. 33 is a schematic view of a ring resonator type semiconductor laser according to a fifth embodiment of the present invention as viewed from above.

FIG. 34 is a schematic sectional view of a ring resonator type semiconductor laser according to a fifth embodiment of the present invention.

FIG. 35 is a schematic perspective view showing an example of a gyro provided with a ring resonator type semiconductor laser according to a sixth embodiment of the present invention.

FIG. 36 is a schematic diagram of a gyro provided with a ring resonator type laser according to the present invention when viewed from above.

FIG. 37 is an enlarged view of a partial area of a schematic view when a gyro provided with the ring resonator type laser according to the present invention is viewed from above.

FIG. 38 is a schematic sectional view of a ring resonator type semiconductor laser according to the present invention.

FIG. 39 is a schematic cross-sectional view for explaining the manufacturing process of the ring resonator type semiconductor laser according to the present invention.

FIG. 40 is a schematic cross-sectional view for explaining the manufacturing process of the ring resonator type semiconductor laser according to the present invention.

FIG. 41 is a schematic cross-sectional view for explaining the manufacturing process of the ring resonator type semiconductor laser according to the present invention.

FIG. 42 is a schematic cross-sectional view for explaining a manufacturing process of the ring resonator type semiconductor laser according to the present invention.

FIG. 43 is a schematic cross-sectional view for explaining a manufacturing process of the ring resonator type semiconductor laser according to the present invention.

FIG. 44 is a schematic cross-sectional view for explaining a ring resonator type semiconductor laser according to the present invention.

FIG. 45 is a schematic cross-sectional view for explaining the manufacturing process of the ring resonator type semiconductor laser according to the present invention.

FIG. 46 is a schematic cross-sectional view for explaining a manufacturing step of the ring resonator type semiconductor laser according to the present invention.

FIG. 47 is a diagram illustrating an example in which a voltage follower is connected as a protection circuit.

FIG. 48 is an example of a circuit diagram for detecting a beat signal.

FIG. 49 is an example of a circuit diagram for detecting a beat signal.

FIG. 50 is an example of a circuit diagram for detecting a beat signal.

FIG. 51 is a schematic perspective view showing another example of the optical gyro provided with the semiconductor laser according to the present invention.

FIG. 52 is a diagram illustrating an example of an FV conversion circuit.

FIG. 53 is an example of a circuit diagram for detecting a beat signal.

FIG. 54 is an example of a circuit diagram for detecting a beat signal.

FIG. 55 is a schematic perspective view showing another example of a gyro provided with the semiconductor laser according to the present invention.

FIG. 56 is a schematic sectional view of a semiconductor laser according to the present invention.

FIG. 57 is a schematic diagram of the ring resonator type laser according to the present invention as viewed from above.

FIG. 58 is a schematic diagram of the ring resonator type laser according to the present invention as viewed from above.

FIG. 59 is a part of a schematic cross-sectional view of a ring resonator type laser according to the present invention.

FIG. 60 is an example of a circuit diagram for detecting a beat signal.

[Explanation of symbols]

 Reference Signs List 100, 200 semiconductor laser 101, 201 active layer 102, 202 substrate 103, 203 anode 104, 204 cathode 105, 205 electric terminal 209 cylindrical structure 2309 high resistance region 5100 piezoelectric element

[Procedure amendment]

[Submission date] October 23, 2000 (2000.10.
23)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

A gyro according to the present invention has a ring resonator type semiconductor laser in which light propagates in a counterclockwise circular shape, has a terminal for detecting a beat signal, and has an active layer of a semiconductor laser having a ring shape. And the drive source of the semiconductor laser is modulated at a frequency in a band different from the frequency of the beat signal.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

A gyro according to the present invention has a ring resonator type semiconductor laser in which light propagates in a counterclockwise circular shape, and has means for detecting a beat signal generated by rotation applied to the semiconductor laser. The active layer of the semiconductor laser is ring-shaped, and the driving source of the semiconductor laser is modulated at a frequency in a band different from the frequency of the beat signal.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction contents]

A gyro according to the present invention has a ring resonator type semiconductor laser in which light propagates in a counterclockwise direction, has a terminal for detecting a beat signal, and has at least a part of the semiconductor laser central region. , And the driving source of the semiconductor laser is modulated at a frequency in a band different from the frequency of the beat signal.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction contents]

A gyro according to the present invention includes a ring resonator type semiconductor laser in which light propagates in a counterclockwise circular shape, and includes means for detecting a beat signal generated by rotation applied to the semiconductor laser. The resistance of at least a part of the central portion of the semiconductor laser is increased, and the driving source of the semiconductor laser is modulated at a frequency in a band different from the frequency of the beat signal.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

A semiconductor device according to the present invention includes a ring resonator type semiconductor laser including a ring-shaped active layer, light propagating in a counterclockwise circular shape, and a terminal for detecting a beat signal. The drive source of the semiconductor laser is modulated at a frequency in a band different from the frequency of the beat signal.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

A semiconductor laser according to the present invention is a semiconductor laser including an active layer and a low refractive index layer located on the active layer and having a lower refractive index than the active layer. The resistance of the central region of at least one layer is increased by ion implantation, and the driving source of the semiconductor laser is modulated at a frequency in a band different from the frequency of the beat signal.

Claims (29)

[Claims] 1. A gyro having a ring resonator type semiconductor laser in which light propagates in a counterclockwise direction, comprising a terminal for detecting a beat signal, and an active layer of the semiconductor laser having a ring shape. A gyro characterized by a certain point. 2. The gyro according to claim 1, wherein said semiconductor laser has a cylindrical structure. 3. The active layer is sandwiched between low refractive index layers having a lower refractive index than the active layer, and both the active layer and the low refractive index layer have a cylindrical structure. The gyro according to claim 1. 4. The gyro according to claim 1, wherein an insulating thin film is provided on at least one of the inside and the outside of the tubular structure. 5. The gyro according to claim 1, wherein the beat signal is detected as a change in current, voltage or impedance. 6. The gyro according to claim 1, wherein the semiconductor laser is driven by a constant voltage or a constant current. 7. A gyro according to claim 1, wherein said semiconductor laser has a triangular, square or circular cylindrical structure. 8. A semiconductor laser comprising GaAs
The gyro according to claim 1, wherein s, InP is used. 9. A gyro having a ring resonator type semiconductor laser in which light propagates in a counter-rotating circular shape, comprising: means for detecting a beat signal generated by rotation applied to the semiconductor laser; and A gyro, wherein the active layer of the semiconductor laser is ring-shaped. 10. The gyro according to claim 9, wherein said beat signal detection means includes at least one of a voltage detection circuit, a current detection circuit, and an impedance detection circuit. 11. The gyro according to claim 9, wherein said beat signal detecting means includes a frequency-voltage conversion circuit. 12. The gyro according to claim 9, wherein said beat signal detecting means includes a frequency counter circuit. 13. A gyro having a ring resonator type semiconductor laser in which light propagates in a counterclockwise direction, comprising a terminal for detecting a beat signal, and at least a part of a central portion of the semiconductor laser. A gyro characterized by high resistance. 14. The gyro according to claim 13, wherein the central region is a central portion when the semiconductor laser is viewed from above. 15. The gyro according to claim 13, wherein the part of the central region having the increased resistance is an active layer constituting the semiconductor laser. 16. The gyro according to claim 13, wherein the part of the central region where the resistance is increased is a cladding layer above the semiconductor laser active layer. 17. The gyro according to claim 13, wherein the increase in the resistance is performed by ion implantation into the semiconductor laser. 18. The method according to claim 1, wherein the increase in resistance is performed by ion implantation of protons into a central portion of the semiconductor laser.
The gyro according to 3. 19. The gyro according to claim 13, wherein said semiconductor laser has a cylindrical, triangular, or quadrangular prism shape. 20. A semiconductor laser comprising:
The gyro according to claim 13, wherein As or InP is used. 21. A gyro having a ring resonator type semiconductor laser in which light propagates in a counter-rotating circular shape, comprising means for detecting a beat signal generated by rotation applied to the semiconductor laser, and A gyro, wherein at least a part of the semiconductor laser central region has a high resistance. 22. The gyro according to claim 21, wherein said beat signal detection means includes at least one of a voltage detection circuit, a current detection circuit, and an impedance detection circuit. 23. A gyro according to claim 21, wherein said beat signal detecting means includes a frequency-voltage conversion circuit. 24. A gyro according to claim 21, wherein said beat signal detecting means includes a frequency counter circuit. 25. A semiconductor device comprising: a ring resonator type semiconductor laser including a ring-shaped active layer, in which light propagates in a counterclockwise circular shape; and a terminal for detecting a beat signal. 26. In a semiconductor laser including an active layer and a low refractive index layer located on the active layer and having a lower refractive index than the active layer, a center of at least one of the active layer and the low refractive index layer. A semiconductor laser characterized in that a region is made high in resistance by ion implantation. 27. A semiconductor laser comprising: GaAs, In
P, ZnSe, AlGaAs, InGaAsP, InG
aAlP, InGaAsP, GaAsP, InGaAs
Sb, AlGaAsSb, InAsSbP, PbSnT
e, GaN, GaAlN, InGaN, InAlGa
The semiconductor laser according to claim 26, wherein at least one of N, GaInP, GaInAs, and SiGe is included in a constituent material. 28. The semiconductor laser according to claim 26, wherein the increase in the resistance is performed by ion implantation of protons. 29. The gyro according to claim 1, wherein a change in a frequency of a current, a voltage, or an impedance detected from the terminal is used as a signal for determining a magnitude of an angular velocity applied to the ring resonator type semiconductor laser. Gyro operation method.