JPH10209552A - Wavelength variable semiconductor laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavelength variable semiconductor laser which can be easily integrated to the same semiconductor substrate of all constituent elements and can be microminiaturized by simplifying its structure unnecessitating the adjustment of an optical axis. SOLUTION: An external resonance mirror 3, on which one end 3c of the mirror 3 in its longitudinal direction is fixed to a prescribed part of a semiconductor substrate 2, an oscillation semiconductor laser 4, which irradiates one surface 3a of the external resonance mirror 3 with a resonance light A, and a bending excitation semiconductor laser 5, which irradiates the other side 3b of the external resonance mirror 3 with a heatable bending excitation light B, are integrated on the semiconductor substrate 2. An oscillation semiconductor laser 4 and a bending oscillation semiconductor laser 5 are formed on both sides of a groove 6 leaving the prescribed interval by providing the groove 6 on the upper surface 2c of the semiconductor substrate 2, and one end 3c in longitudinal direction of the external resonance mirror 3 is fixed to a protruding part 7 provided on the bottom face 6c of the recessed groove 6 in such a manner that both faces 3a and 3b of the external resonance mirror 3 face each other leaving the prescribed interval against the oscillation semiconductor laser 4 and the bending oscillation semiconductor laser 5 and that the longitudinal direction of the external oscillation mirror 3 becomes in parallel with the longitudinal direction of the recessed groove 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength tunable semiconductor laser used for optical communication and optical measurement.

[0002]

2. Description of the Related Art As is well known, in a semiconductor laser, the oscillation wavelength changes due to a change in temperature or a change in injection current. However, in these methods, the response speed is slow, and the optical output also changes with the change in the oscillation wavelength. And the like. As conventional wavelength tunable semiconductor lasers which have solved such a defect, for example, there are (a) a multi-electrode semiconductor laser, (b) a remote external resonance semiconductor laser, and (c) a proximity external resonance semiconductor laser.

[0003]

However, in the multi-electrode semiconductor laser of (a), the electrodes are divided in the direction of the resonator, and a change in the refractive index or the like caused by a current flowing through each electrode is converted into a change in the oscillation wavelength. Therefore, there is a problem that the operation is complicated (for example, Hidemi Tsuchida: “Tunable semiconductor laser”, Optical Technology Contact, 32, 2, pp81-89, 1994).

In the remote type external resonance semiconductor laser shown in FIG. 1B, the oscillation wavelength of the semiconductor laser is changed by the phase of the return light from the external resonator. There is a problem that the size becomes large as a whole because of the necessity of a diffraction grating serving as a device and its rotation drive mechanism. In addition, since the components are not completely integrated, it is necessary to adjust the component alignment. In addition, for example, when the length of the external resonator is lengthened and the mode interval is narrowed, the wavelength jump due to the mode hop which causes noise is performed. There is a problem that the operation is unstable, for example, the operation becomes unstable.

In order to solve these problems, the proximity type external cavity semiconductor laser shown in FIG. 1 (c) is manufactured by using an external resonator by using micromachining technology, and the external resonator length is reduced by a few minutes when the external resonator is manufactured. μm, which is extremely short. As this type of close proximity type external resonance semiconductor laser, for example, (c-
1) Edge-emitting type (for example, Y.Uenishi, M.Tsugai and MM
ehregany, Hybrid-integrated laser-diode micro-exte
rnal mirror fabricated by (110) silicon micromachin
ing, Electronics Letters 31, 12, pp965-966,1995)
Or (c-2) surface-emitting type (for example, MCLarson, B. Pezeshki
and JSHarris, Verticak Coupled-Cavity Microinte
rferometer on GaAs with Deformable-Membrane Top Mi
rror, IEEE Photonics Tech. Lett. 7, 4, pp382-384, 1
995) has been proposed.

[0006] In the edge emitting proximity type external cavity semiconductor laser of (c-1), an edge emitting laser is arranged close to a vibrator manufactured by micromachining, and static electricity is applied by applying a voltage to a nearby electrode. The oscillation wavelength of the semiconductor laser can be changed by changing the length of the external resonator by bending the oscillator with electric power. When the intrinsic wavelength of the semiconductor laser is 850 nm, the variable width of the oscillation wavelength is 3 nm. However, it is difficult to mount the vibrator and the semiconductor laser in units of micron units, and furthermore, an electrode for displacing the vibrator with electrostatic force is required, and the variable width of the oscillation wavelength is small as described above. There is a problem.

[0007] In the surface-emitting type proximity external cavity semiconductor laser of (c-2), a thin-film mirror is integrated into the surface-emitting laser by micromachining, and static electricity is applied by applying a voltage between the upper surface of the surface-emitting laser and the thin-film mirror. The oscillation wavelength of the semiconductor laser can be changed by changing the external resonator length by bending the thin film mirror with electric power. When the intrinsic wavelength of the semiconductor laser is 920 nm, the variable width of the oscillation wavelength is 20 nm and the line width is about 3 nm. However, since the materials of the electrostatically driven thin-film mirror and the semiconductor laser are different, there is a problem that the integration process on the same substrate is complicated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is possible to easily integrate all the constituent elements on the same semiconductor substrate, to simplify the structure and to make the structure very small. It is an object of the present invention to provide a wavelength tunable semiconductor laser that does not require optical axis adjustment.

[0009]

Means for achieving the above object are as follows. First, an external resonant mirror whose one end in the longitudinal direction is fixed to a predetermined portion of a semiconductor substrate;
An oscillation semiconductor laser that irradiates one surface of the external resonance mirror with resonance light; and a bending excitation semiconductor laser that irradiates another surface of the external resonance mirror with bending excitation light capable of heating the other surface. It is integrated on a semiconductor substrate.

Second, the semiconductor laser for oscillation and the semiconductor laser for bending excitation are formed at predetermined intervals on both sides of the groove by providing a groove on the upper surface of the semiconductor substrate. One end in the longitudinal direction of the external resonance mirror is opposed to the protruding portion protruding from the bottom surface of the groove at predetermined intervals with respect to the oscillation semiconductor laser and the bending excitation semiconductor laser. The longitudinal direction is fixed so as to be parallel to the longitudinal direction of the groove.

Third, a bending displacement enlarging thin film having a larger thermal expansion coefficient than the external resonance mirror is laminated on the other surface of the external resonance mirror.

Fourth, a bending promoting thin film having a smaller thermal expansion coefficient than the external resonance mirror and the bending displacement enlarging thin film is interposed between the other surface of the external resonance mirror and the bending displacement enlarging thin film. It is in.

Fifth, an anti-reflection film is fixed to one end face of the oscillation semiconductor laser on the side of the external resonance mirror.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the wavelength tunable semiconductor laser 1 according to the first embodiment includes an external resonance mirror 3 having one end 3c in a longitudinal direction fixed to a predetermined portion of a semiconductor substrate 2, and one surface of the external resonance mirror 3. 3a shows resonance light A
And a bending excitation semiconductor laser 5 for irradiating the other surface 3b of the external resonance mirror 3 with bending excitation light B capable of heating the other surface 3b side to the semiconductor substrate 2. It is integrated.

In this embodiment, for example, the oscillation semiconductor laser 4 and the bending excitation semiconductor laser 5 are
By providing a concave groove 6 on the upper surface 2c of the semiconductor substrate 2, the groove 6 is formed at a predetermined interval on both sides of the concave groove 6, and a protrusion 7 protruding from a bottom surface 6c of the concave groove 6 is provided with the external groove. One end 3c in the longitudinal direction of the resonance mirror 3 is
a and 3b are opposed to the oscillation semiconductor laser 4 and the bending excitation semiconductor laser 5 at predetermined intervals, respectively, and the longitudinal direction thereof is parallel to the longitudinal direction of the concave groove 6. Fixed.

The semiconductor substrate 2 is formed, for example, in a rectangular plate shape, and the concave groove 6 is formed on an upper surface 2c substantially at the center in the longitudinal direction.
Is provided. That is, the semiconductor laser 4 for oscillation and the semiconductor laser 5 for bending excitation are formed on the one side 2a and the other side 2b in the longitudinal direction of the semiconductor substrate 2 at predetermined intervals by the concave grooves 6, respectively.

The external resonance mirror 3 is formed, for example, in a rectangular plate shape. One end 3c of the external resonance mirror 3 in the longitudinal direction is attached to an upper edge of a protruding portion 7 protruding in, for example, a pentagonal shape at an end edge of the bottom surface 6c of the concave groove 6, and has both surfaces 3c.
a and 3b are opposed to the oscillation semiconductor laser 4 and the bending excitation semiconductor laser 5 at predetermined intervals, respectively, and the longitudinal direction thereof is parallel to the longitudinal direction of the groove 6. So that it is fixed. The thickness of the external resonance mirror 3 is suitably about 1 to several μm, and the length is suitably about several tens to several hundred μm.

That is, the external resonance mirror 3 is fixed at a distance of an external resonator length L from one end surface 4a of the oscillation semiconductor laser 4 on the side of the external resonance mirror 3, and is fixed. The surface 3a can be irradiated with the resonance light A generated from the surface 4a. The resonance light A is reflected by the one surface 3a of the external resonance mirror 3 to be return light, and is incident again into the oscillation semiconductor laser 4 from the one end surface 4a. Is amplified and emitted at a predetermined oscillation wavelength. The other surface 3b of the external resonance mirror 3 can be irradiated with bending excitation light B generated from the bending excitation semiconductor laser 5. In FIG. 1, reference numeral 8 denotes a ridge corresponding to the optical path of the resonance light A and the bending excitation light B.

In order to integrate the external resonance mirror 3, the semiconductor laser 4 for oscillation, and the semiconductor laser 5 for bending excitation on the semiconductor substrate 2 as described above, for example, micromachining using dry etching, wet etching or the like is used. Technology (eg, Hiroki Ukita: “Micromachining and its application to optical devices”, Optics, 23, 12, pp722-727, 1994)
Can be used. According to this micromachining technology, the external resonance mirror 3 and the oscillating semiconductor laser 4 are provided by providing the concave groove 6 in the upper surface 2c of the semiconductor substrate 2 so that the protrusion 7 and the external resonance mirror 3 remain. In addition, there is an advantage that the bending excitation semiconductor laser 5 can be easily integrated integrally with the same material forming the semiconductor substrate 2. Therefore, if an active layer 9 having a predetermined thickness serving as a light emitting portion is provided in advance on the semiconductor substrate 2,
The oscillation semiconductor laser 4 and the bending excitation semiconductor laser 5
This is convenient because the active layer 9 also remains. In this case, the active layer 9 remains on the protruding portion 7 and the external resonance mirror 3, but this is not a problem.

Next, the operation of the tunable semiconductor laser 1 will be described with reference to FIG. Note that 2 in FIG.
1 is an oscillation power supply, 22 is a bending excitation power supply, 23 is an optical fiber, and 24 is an optical spectrumr.

In order to change the oscillation wavelength of the emitted light C, first, an applied current I4 is supplied from the oscillation power supply 21 to the oscillation semiconductor laser 4 to oscillate at a specific wavelength to generate the resonance light A. As a result, the emitted light C is oscillated.
Next, an electric current I5 is applied from the bending excitation power supply 22 to the bending excitation semiconductor laser 5 to generate bending excitation light B, and irradiates the other surface 3b of the external resonance mirror 3. Since the other surface 3b of the external resonance mirror 3 irradiated with the bending excitation light B is heated and thermally expanded, the external resonance mirror 3 is bent toward the oscillation semiconductor laser 4. as a result,
As the external resonator length L becomes shorter, the oscillation wavelength of the emitted light C changes.

In order to control such a change in the oscillation wavelength of the emitted light C, the length L of the external resonator may be changed. Therefore, the optical output of the bending excitation light B, that is, the bending excitation power supply What is necessary is just to increase / decrease the applied current I5 from 22. For example, in order to continuously change the oscillation wavelength, the applied current I5 may be continuously increased or decreased. The change in the oscillation wavelength can be observed using, for example, an optical spectrumr 24 to which an optical fiber 23 is connected, as shown in FIG.

Here, the material of the wavelength tunable semiconductor laser 1 is
That is, the material of the semiconductor substrate 2 is not particularly limited. For example, an InP-based (long wavelength band) having a multiple quantum well (MQW) structure or a G having a double hetero (DH) structure can be used.
aAs (short wavelength band) and the like.

As described above, if the one end 3c in the longitudinal direction of the external resonance mirror 3 is fixed and the other surface 3b of the external resonance mirror 3 is made to be thermally expandable by the bending excitation light B, the external resonator Since the oscillation wavelength of the emitted light C can be changed by changing the length L, there is an advantage that the configuration of the external resonance mirror 3 and the like can be simplified as compared with the conventional one.

Next, the relationship between the external resonator length L and the oscillation wavelength will be described with reference to FIGS. FIG. 3 is a schematic explanatory view of an apparatus that performs the same operation as the wavelength tunable semiconductor laser 1. In FIG. 3, reference numeral 31 denotes a slider, 32 denotes a photodetector, and 33 denotes a translucent mirror corresponding to the external resonance mirror 3. A disk, 34 is a semiconductor laser corresponding to the oscillation semiconductor laser 4, 35 is an oscilloscope, 36 is a lens,
3 is an optical fiber and 24 is an optical spectrumr.

In this device, a semiconductor laser 34 with a photodetector 32 is mounted on the side end surface 31a of the slider 31, and the semiconductor laser 34 emits resonance light A1 upward. The output of the resonance light A1 is output to an oscilloscope 35 connected to the photodetector 32.
Monitored by As the semiconductor laser 34, an InP-based semiconductor laser having an intrinsic wavelength λ of 1300 nm was used. The translucent disk 33 can float above the slider 31 by rotation, and the external resonator length L changes depending on the rotation speed of the translucent disk 33. The oscillation wavelength of the transmitted light C1 transmitted through the translucent disk 33 is measured by the optical spectrumr 24 through the lens 36 and the optical fiber 23.

As a result of measuring the change in the oscillation wavelength with respect to the change in the external resonator length L using the above-described apparatus, FIG.
As shown in the graph, the oscillation wavelength changed in substantially the same pattern every time the external resonator length L changed by about 650 nm. Also,
The difference between the maximum value and the minimum value of the oscillation wavelength, that is, the variable width is about 9
nm. The above value of 650 nm depends on the used I
Since the wavelength corresponds to １ ／ of the intrinsic wavelength λ (= 1300 nm) of the nP-based semiconductor laser, in order to maximize the variable width of the oscillation wavelength, the external resonator length L, that is, the bending displacement of the external resonance mirror 3 is set. Is desirably λ / 2 (nm) or more.

As shown in FIG. 5, the wavelength tunable semiconductor laser 51 according to the second embodiment differs from the first embodiment in that the other surface 3b of the external resonance mirror 3 has a thermal expansion coefficient higher than that of the external resonance mirror 3. In addition to laminating a large bending displacement enlarging thin film 52, thermal expansion between the other surface 3b of the external resonance mirror 3 and the bending displacement enlarging thin film 52 is performed by the external resonance mirror 3 and the bending displacement enlarging thin film 52. A three-layer thin film vibrator 63 having a three-layer structure is formed by interposing a bending promoting thin film 53 having a small coefficient.

Even when the bending displacement enlarging thin film 52 is laminated on the other surface 3b of the external resonance mirror 3 to form a two-layered two-layer thin film vibrator, the bending displacement enlarging thin film 5
2 is irradiated with the bending excitation light B so that the external resonance mirror 3
Since the thermal expansion is larger, there is an advantage that the bending displacement can be increased as compared with the case where only the external resonance mirror 3 is used. However, as in this embodiment, the other surface 3b of the external resonance mirror 3 is used.
When the three-layer structure is formed by interposing the bending promoting thin film 53 between the thin film 52 and the bending displacement enlarging thin film 52, the bending displacement can be reduced more by the so-called bimorph effect as compared with the above two-layer structure. There is an advantage that it can be expanded.

The thin film 52 for enlarging bending displacement and the thin film 53 for accelerating bending can be laminated by, for example, a sputter deposition method or the like.
The thickness is desirably about 1 μm or less.

Next, the displacement characteristics of the three-layer thin-film vibrator 63 will be described with reference to FIGS.
The displacement of the three-layer thin film oscillator 63 is calculated by the displacement equation of the two-layer thin film oscillator (WHChu, M. Mehregany and RLMullen, "Analysis of
tip deflection and force of a bimetalliccantileve
r microactuator ", J. Micromech. Microeng. 3, pp4-7,
1993) can be extended as follows.

That is, as shown in FIGS. 6 (a) and 6 (b), a three-layer thin film formed by sequentially laminating the external resonance mirror 3, the bending promoting thin film 53, and the bending displacement enlarging thin film 52. When one end 63c of the vibrator 63 is fixed, the temperature is Δ
The change that occurs at the other end 63d when changed by T ° C. may be obtained. Here, the length of the three-layer thin-film vibrator 63 is 1, the width is b, and the thickness of each of the layers 3, 53, 52 is t1 _,
t _2, t _3, the thermal expansion coefficient of each _{α 1, α 2, α 3} , it is Young's modulus and E _1, E _2, E _3, respectively.

As shown in FIG. 7, as in the case of the two-layer thin film vibrator, the difference in vertical strain due to thermal expansion is
With acts normal stress P _1, P _2, P ₃ to the cross section of the layer thin film oscillator 63, bending assuming moments M _1, M _2, M ₃ occurs, the layers 3,53,52 of this time Assuming that the radii of curvature are r _1, r _{2, and} r ₃ , the vertical strain at the interface between the bending displacement enlarging thin film 52 and the bending promoting thin film 53 and the interface between the bending promoting thin film 53 and the external resonance mirror 3 are equal. , Can be expressed as

[0034]

(Equation 1)

The vertical stress P_1,P_2,P_ThreeAnd the resultant force
Bending moment M_1,M_2,M_ThreeThe resultant force of each is zero
Therefore, it can be expressed as in the following Expression 2. Where h in Equation 2
_1,h _2,h_ThreeIs the center plane of each layer 3, 53, 52 from the neutral plane
Is the distance to

[0036]

(Equation 2)

Assuming that the thicknesses t _1, t _{2, and} t ₃ of the layers 3, 53, and 52 are sufficiently thin, it is assumed that r ₁ = r ₂ = r ₃ = r.
When the several 2 which erases the _{P 1, P 2, P 3} , the curvature (1 /
Since r) can be expressed as in the following Expression 3, the bending displacement d of the three-layer thin-film vibrator 63 can be expressed as in Expression 4.

[0038]

(Equation 3)

[0039]

(Equation 4)

As the external resonance mirror 3, for example, InP
For example, when Al or Au is used for the bending displacement enlarging thin film 52 having a thickness of 0.1 μm and SiO ₂ or Si ₃ N ₄ is used for the bending promoting thin film 53 having a thickness of 0.1 μm, the InP ( FIG. 8 shows the results of calculating the dependence of the displacement of the three-layer thin film vibrator 63 on the thickness of the external resonance mirror 3) (when the temperature rise is 100 ° C.) using the above equation (4).

FIG. 8 shows that the displacement of the three-layer thin-film vibrator 63 decreases as the thickness of InP increases.
When InP is selected as the external resonance mirror 3,
The oscillation semiconductor laser 4 is also made of InP (inherent wavelength 1300).
Therefore, in order to maximize the variable width of the oscillation wavelength in this case, the thickness of the InP film should be set to 0.65 μm as described above.
It is desirable to keep the above range.

Next, a bending promoting thin film 5 having a thickness of 0.1 μm
InP (external resonance mirror 3) using Si ₃ N ₄ as 3
The results of calculating the displacement of the three-layer thin-film vibrator 63 (when the temperature rise is 100 ° C.) using the above equation (4) when the film thickness is 2.0 μm are shown by contour lines in FIG. FIG. 9 shows the displacement of the three-layer thin-film vibrator 63 when various materials such as Al are used as the thin film for bending displacement expansion 52 having a thickness of 0.1 μm. Table 1 shows the Young's modulus and coefficient of thermal expansion of each material.

[0043]

[Table 1]

FIG. 9 shows that a metal such as Al or Au can be preferably used as the bending displacement enlarging thin film 52. The bending promoting thin film 53 is made of the above Si ₃
In addition to N ₄ , a dielectric such as SiO ₂ can be suitably used.

As shown in FIG. 10, the wavelength tunable semiconductor laser 71 according to the third embodiment differs from the second embodiment in that
An anti-reflection film 72 is fixed to one end face 4 a of the oscillation semiconductor laser 4 on the side of the external resonance mirror 3.

As described above, if the antireflection film 72 is fixed, the return light reflected by the one surface 3a of the external resonance mirror 3 can be prevented from being reflected when entering the oscillation semiconductor laser 4. There is an advantage that the oscillation wavelength of the output light C can be changed more greatly.

The anti-reflection film 72 is made of, for example, (SiO ₂ ) _x (S
i ₃ N ₄₎ can consist _1-x or the like, so-called ion beam sputtering, the one side end face _{4a (SiO 2) x (Si} 3 N 4) can be secured by forming the _1-x layer (For example,
Y.Katagiri and H.Ukita: "Ion beam sputtered (SiO ₂ ) _x
(Si ₃ N ₄ ) _1-x antireflection coating on laser facets
produced using O ₂ -N ₂ discharges ", Appl.Opt. 29, 3
4, pp5074-5079, 1990).

Next, the relationship between the external resonator length L and the oscillation wavelength when the antireflection film 72 is used will be described with reference to FIG. FIG. 11 shows the result of measuring the change of the oscillation wavelength with respect to the change of the external resonator length L by using the same device as in FIG. 3 and fixing the antireflection film 72 on the side end face of the semiconductor laser 34. As described above, when the antireflection film 72 shown in FIG. 4 was not used, the variable width of the oscillation wavelength was 9 nm.
In the case of using No. 2, it can be seen that it is greatly improved to 23 nm.

[0049]

As described above, according to the first aspect of the present invention, one end of the external resonance mirror in the longitudinal direction is fixed, and the other surface of the external resonance mirror can be thermally expanded by the bending excitation light. Since the oscillation wavelength of the emitted light can be changed by changing the length of the external resonator, there is an advantage that the configuration of the external resonance mirror and the like can be simplified as compared with the conventional one. Therefore, there is also an advantage that the wavelength tunable semiconductor laser can be configured to be very small.

According to the second aspect of the present invention, since the micromachining technology can be used, the oscillation semiconductor laser, the external resonance mirror, and the bending excitation semiconductor laser are integrally formed of the same material forming the semiconductor substrate. In addition, there is an advantage that the optical axis can be easily integrated and the optical axis adjustment or the like is not required. Therefore, there is an advantage that the wavelength tunable semiconductor laser can be manufactured at low cost.

According to the third aspect of the present invention, the bending displacement enlarging thin film having a larger thermal expansion coefficient than the external resonance mirror is laminated on the other surface of the external resonance mirror. By irradiating the bending excitation light, thermal expansion can be made larger than that of the external resonance mirror, and therefore, there is an advantage that bending displacement can be further increased as compared with the case of using only the external resonance mirror.

According to the invention of claim 4, between the other surface of the external resonance mirror and the bending displacement enlarging thin film, a bending promoting thin film having a smaller thermal expansion coefficient than those of the external resonance mirror and the bending displacement enlarging thin film. , The bending displacement can be further increased by the so-called bimorph effect as compared with the above-described two-layer structure.

According to the fifth aspect of the present invention, since the anti-reflection film is fixed to the end face of the oscillation semiconductor laser on the side of the external resonance mirror, the return light reflected on one surface of the external resonance mirror is oscillated. There is an advantage that the reflection at the time of entering the semiconductor laser for use can be prevented, so that the oscillation wavelength of the emitted light can be changed more greatly.

[Brief description of the drawings]

FIG. 1 is a perspective view of a wavelength tunable semiconductor laser according to a first embodiment.

FIG. 2 is a schematic explanatory view showing how the wavelength tunable semiconductor laser of FIG. 1 operates.

FIG. 3 is a schematic explanatory view of an apparatus that performs the same operation as the wavelength tunable semiconductor laser of FIG. 1;

FIG. 4 is a graph showing a relationship between an external resonator length and an oscillation wavelength measured by the apparatus shown in FIG. 3;

FIG. 5 is a perspective view of a wavelength tunable semiconductor laser according to a second embodiment.

6A is a plan view of a three-layer thin-film vibrator, and FIG. 6B is a front view of the three-layer thin-film vibrator.

FIG. 7 is an explanatory diagram showing a state in which a three-layer thin film vibrator is bent.

FIG. 8 is a graph showing the relationship between the thickness of InP (external resonance mirror) and the displacement of a three-layer thin film vibrator when the temperature rise is 100 ° C.

FIG. 9 shows a thin film for promoting bending having a thickness of 0.1 μm formed of Si ₃
With N _4, 2 the thickness of the InP (external cavity mirror 3).
7 is a graph showing the displacement of a three-layer thin-film vibrator when the temperature rise is 100 ° C. when the thickness is set to 0 μm.

FIG. 10 is a perspective view of a wavelength tunable semiconductor laser according to a third embodiment.

FIG. 11 is a graph showing a relationship between an external resonator length and an oscillation wavelength when an antireflection film is used.

[Explanation of symbols]

 1, 51, 71 Wavelength tunable semiconductor laser 2 Semiconductor substrate 2c Top surface 3 External resonance mirror 3a One surface 3b Other surface 3c One end 4 Oscillation semiconductor laser A Resonance light 4a One end surface 5 Bend excitation semiconductor laser B Bend excitation light 6 Groove 6c Bottom surface 7 Projection 52 Thin film for bending displacement enlargement 53 Thin film for bending promotion 72 Anti-reflection film

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yoichiro Masuda 1-1-1 Nojihigashi, Kusatsu-shi, Shiga Prefecture Ritsumeikan University Biwako-Kusatsu Campus Faculty of Science and Technology

Claims (5)

[Claims] An external resonance mirror having one end in a longitudinal direction fixed to a predetermined portion of a semiconductor substrate; an oscillation semiconductor laser for irradiating one surface of the external resonance mirror with resonance light; A wavelength tunable semiconductor laser, wherein a semiconductor laser for bending excitation that irradiates the surface with bending excitation light capable of heating the other surface is integrated on the semiconductor substrate. 2. The semiconductor laser for oscillation and the semiconductor laser for bending excitation are formed at predetermined intervals on both sides of the groove by providing a groove on an upper surface of the semiconductor substrate. One end in the longitudinal direction of the external resonance mirror is opposed to the projecting portion provided on the bottom surface at predetermined intervals with respect to the oscillation semiconductor laser and the bending excitation semiconductor laser, and both surfaces thereof are opposed to each other. 2. The wavelength tunable semiconductor laser according to claim 1, wherein said laser beam is fixed so as to be parallel to a longitudinal direction of said groove. 3. The wavelength tunable semiconductor laser according to claim 1, wherein a thin film for bending displacement expansion having a larger thermal expansion coefficient than the external resonance mirror is laminated on the other surface of the external resonance mirror. 4. A bending promoting thin film having a smaller thermal expansion coefficient than the external resonance mirror and the bending displacement enlarging thin film is interposed between the other surface of the external resonance mirror and the bending displacement enlarging thin film. The tunable semiconductor laser according to claim 3, wherein 5. The wavelength tunable semiconductor laser according to claim 1, wherein an antireflection film is fixed to one end face of the oscillation semiconductor laser on the side of an external resonance mirror.