JP2003214813A - Laser interferometer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable microminiature laser interferometer in which steps of assembling and regulating individual components can be reduced, a cost can be decreased, a mass productivity can be improved, and an influence of an environmental change can be hardly received. <P>SOLUTION: The laser interferometer comprises a semiconductor laser 5 of a light emitting element, a photodiode 6a of a photodetector, an optical waveguide 3, a polarized beam splitter 7, a quarter-wavelength plate 8, and a beam splitter 8 formed or fixed on a semiconductor substrate 4. A light from the laser 5 is collimated in a horizontal direction by a parabolic shape total reflection mirror 14 on the way of the waveguide 3 and emitted toward an external mirror through the splitter 7, the plate 8 and a beam splitter 9. The reflected light from the mirror 14 and the reflected light from the splitter are reflected by the splitter 7 and received by the laser 5. The displacement of the mirror 14 is measured. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser interferometer, and more particularly, to a displacement sensor for detecting displacement of a movable part which is incorporated in a small displacement sensor incorporated in a micro stage or the like and used for positioning, a micro accelerometer or a micro strain sensor or the like. The present invention relates to a non-contact small integrated laser interferometer that utilizes light, such as a sensor.

[0002]

2. Description of the Related Art FIG. 11 shows an example of a conventional laser interferometer. In the figure, a lens 21, a beam splitter 22, a phase shifter 23, and a mirror 24 are provided on a silicon substrate 20 having a quartz optical waveguide, and a semiconductor laser 25 and a photodiode 26 are externally adhesively mounted on the silicon substrate 20. (Papers: J. Lizet, P. Gidon, S. Val
ette, Integrated Optics Displacement Sensor Achiev
ed on Silicon Substrate, Proceedings of the Fourth
European Conference on Integrated Optics ECIO87,
pp. 210-212, Glasgow, Scotland, May 11th-13th, 198
7). In practice, it also implements an external lens, as described in the above paper. This interferometer measures the distance from the interferometer to the measurement target mirror 27 by the principle of the Michelson interferometer. That is, the light from the semiconductor laser 25 is collimated (collimated) by the lens 21 and divided into the reference light 28 and the signal light 29 by the beam splitter 22.
Is reflected by the mirror 24 and returns to the beam splitter 22, and the signal light 29 is reflected by the mirror 27 to be measured and returns to the beam splitter 22. The two lights interfere with each other, pass through the beam splitter 30, and are passed through the photodiode 26. To be measured. A part of the reference light 28 has a phase different from that of the other part by the phase shifter 23, and these two parts are respectively
By interfering with the signal light 29, separated by the beam splitter 30, separately measured by the photodiode 26, and the two electric signals obtained as a result are subjected to signal processing, the distance from the interferometer to the mirror 27 to be measured is measured. Desired.

FIG. 12 shows a laser interferometer in which a DBR laser, a detector, and a waveguide are monolithically manufactured, and an external lens (GRIN lens) is externally mounted on this interferometer. Also in this interferometer, the distance from the interferometer to the mirror to be measured (shown as a half mirror in the figure) is measured by the principle of the Michelson interferometer (reference: D. Hofstetter, HP Zappe, and R. Dae
ndliker, A Monolithically Integrated Double Michel
son Interferometer for Optical Displacement Measur
ement with Direction Determination, IEEE Photonics
Technology Letters, Vol. 8, No. 10, pp. 1370-137
2, 1996).

FIG. 13 shows a laser interferometer in which a semiconductor laser, a detector, and a waveguide are monolithically manufactured. Also in this interferometer, the principle of the Michelson interferometer is used.
The distance from the interferometer to the mirror to be measured is measured (Japanese Patent Laid-Open No. 09-318323, Sawada, Higurashi, Oguchi, Tsubamoto, Laser length measuring device and its manufacturing method, and reference: R.
Sawada, E. Higurashi, T. Ito, M. Tsubamoto, and
O. Ohguchi, Integrated micro-laser displacement se
nsor, Proc. IEEE Micro Electro Mechanical Systems
See '97, Nagoya, 19-24 (1997)).

[0005]

There are some problems in such a laser interferometer.

First, in the laser interferometer shown in FIG. 11, since the semiconductor laser 25 and the photodiode 26 are externally bonded and mounted on the silicon substrate 20,
Since it is necessary to align the semiconductor laser 25 and the photodiode 26 three-dimensionally, and it is difficult to connect the optical waveguide to the semiconductor laser 25 and the photodiode 26, the manufacturing cost becomes large and expensive.
In addition, since an external lens is required, the device becomes large.
The attachment of an external lens also requires three-dimensional optical axis alignment and adjustment.

In the laser interferometer shown in FIG. 12,
Since the DBR laser, the detector, and the waveguide are monolithically manufactured interferometers, alignment of individual components is not necessary, but the characteristics of individual optical components are not good.
For example, the threshold of a DBR laser is as high as 30 mA,
The sensitivity of the photodiode is as low as about 0.2 W / A.
In addition, since an external lens is required, the device becomes large.
The attachment of an external lens also requires three-dimensional optical axis alignment and adjustment.

The laser interferometer shown in FIG. 13 has a semiconductor laser 31, a measuring photodiode 43, and an optical waveguide 35.
Since the interferometer is manufactured monolithically, it is not necessary to align individual components, but similarly, the characteristics of individual optical components are not good. For example, the half mirror 39 is realized by forming a groove structure in the optical waveguide 35.
Since the characteristics of 1 are sensitive to the groove width, the element performance varies widely. Further, although the light is collimated in the horizontal direction by the convex end face 34, the beam is expanded in the vertical direction from the emission end face, and therefore the addition of a cylindrical lens (cylindrical lens) is sufficient to achieve complete vertical collimation. You cannot do it.

Further, since all the laser interferometers are of the Michelson type, the reference light and the measurement light pass through different optical paths, so that there is a problem that they are easily affected by environmental changes.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to assemble individual parts, reduce the adjustment process, reduce the cost, and improve the mass productivity. It is an object to provide an ultra-compact laser interferometer that is not easily affected.

[0011]

In order to achieve the above object, the present invention provides a light emitting device as described in claim 1.
A light receiving element, an optical waveguide, a polarization beam splitter, a quarter-wave plate and a beam splitter are formed or fixed on the same semiconductor substrate, and the light emitted from the light emitting element is guided through the optical waveguide, and the optical waveguide is in the middle. Is collimated in the horizontal direction by the parabolic mirror, and is emitted toward the external mirror through the polarization beam splitter, the quarter-wave plate and the beam splitter, and the reflected light from the external mirror and the beam splitter The laser interferometer is characterized in that the displacement of the external mirror is measured by reflecting the reflected light from the above-mentioned polarized beam splitter and receiving it by the above-mentioned light receiving element.

According to the present invention, as described in claim 2, in the laser interferometer according to claim 1, a first rod lens for collimating light in a vertical direction is further fixed on the semiconductor substrate. , The light emitted from the optical waveguide is collimated in the vertical direction by the first rod lens, and emitted toward the external mirror through the polarization beam splitter, the quarter wavelength plate and the beam splitter, By reflecting the reflected light from the external mirror and the reflected light from the beam splitter by the polarization beam splitter, and by receiving the light by the light receiving element,
A laser interferometer is characterized in that the displacement of the external mirror is measured.

Further, according to the present invention, as described in claim 3, in the laser interferometer according to claim 1 or 2,
A second light source for further horizontally converging light on the semiconductor substrate
The rod lens is fixed, and the light emitted from the optical waveguide or the light emitted from the first rod lens is
After passing through the polarization beam splitter, the quarter-wave plate, and the beam splitter, the second rod lens collects the light in the horizontal direction and emits the light toward the external mirror. The laser interferometer is characterized in that the displacement of the external mirror is measured by reflecting the reflected light from the beam splitter by the polarization beam splitter and receiving the light by the light receiving element.

Further, according to the present invention, as described in claim 4, in the laser interferometer according to any one of claims 1 to 3, the wavelength of light of the light emitting element is provided in one part of the beam splitter. A step difference that causes an optical path length difference that is an odd multiple of ⅛ of the above, or an optical path length difference that is an odd multiple of ¼ of the wavelength of the light of the light emitting element is generated at one end of the optical waveguide emission end face. A two-divided photodiode is used as the light-receiving element to obtain two signals having 90 ° different phases to measure the displacement of the external mirror and detect the displacement direction. Configure a laser interferometer.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a light emitting element, a light receiving element, an optical waveguide, a polarization beam splitter, a quarter wavelength plate, and a beam splitter are formed or fixed on the same semiconductor substrate. The light emitted from the light emitting element propagates through the optical waveguide including the lower clad, the core, and the upper clad, and is collimated (parallelized) in the horizontal direction by a parabolic mirror formed in the optical waveguide. here,
The parabolic shape means a surface shape, a line of intersection of the surface and a surface parallel to the semiconductor substrate surface is a parabola, and a shape of a cylindrical surface having a generatrix perpendicular to the semiconductor substrate surface.

Since the semiconductor laser normally oscillates with TE polarized light, the TE polarized component is transmitted through the polarization beam splitter and converted into circularly polarized light by the quarter wavelength plate. A part of the circularly polarized beam is reflected by the beam splitter, and the remaining component is emitted toward an external mirror, that is, a mirror to be measured, reflected by the external mirror, and returned to the beam splitter. When the reflected light from the beam splitter and the reflected light from the external mirror have the circularly polarized light rotating in the opposite direction before and after the mirror reflection, when they are transmitted through the quarter-wave plate again after the mirror reflection, they are incident. Since it becomes a linearly polarized beam orthogonal to the polarization direction of, it is reflected by the polarizing beam splitter and does not return to the optical waveguide side. That is, the isolator formed by the polarization beam splitter and the quarter-wave plate prevents return light from returning to the semiconductor laser which is a light emitting element.

The reflected light from the beam splitter reflected by the polarization beam splitter and the reflected light from the external mirror interfere with each other and are detected by a photodiode which is a light receiving element, and the displacement of the external mirror is measured from the detection signal. be able to. In this interferometer, the reflected light from the beam splitter (reference light) and the reflected light from the external mirror (measurement light)
Since and propagate coaxially (common path), even if the refractive index or the like changes in the common part, the phase difference does not occur, and it is unlikely to be affected by environmental changes. Note that such an interferometer is called a Fizeau interferometer.

Further, since the light emitted from the optical waveguide spreads in the vertical direction due to the diffraction phenomenon, a rod lens (cylindrical lens) is further fixed on the same semiconductor substrate, and the light emitted from the optical waveguide is converted to this rod. The light is collimated in the vertical direction by a lens and emitted toward an external mirror through a polarizing beam splitter, a quarter-wave plate, and a beam splitter, and the reflected light from the external mirror and the reflected light from the beam splitter are reflected by the polarizing beam splitter. The displacement of the external mirror is measured by reflecting and receiving by the light receiving element. Since the light is also collimated in the vertical direction, the external lens, which was required in the conventional technique, is not required in the present invention.

In the present invention, as a parabolic mirror inside the optical waveguide, for example, a parabolic internal total reflection mirror is formed to collimate the beam in the horizontal direction, so that the exit end face of the optical waveguide becomes a straight line. Therefore, vertical collimation can be realized with only a simple rod lens.

Furthermore, when the mirror to be measured is a movable part of a micromachine or the like and has a small size, a microscopic displacement of the mirror can be achieved by providing a rod lens for converging the beam in the horizontal direction after the beam splitter. Can be measured.

Further, in order to detect the displacement direction of the external mirror, that is, the mirror to be measured, a step difference (this step difference) is generated in one part of the beam splitter, which is an odd multiple of 1/8 of the wavelength of the light of the light emitting element. Is d and the refractive index difference between the surrounding medium and the beam splitter is Δn, d
Is calculated as Δn × d is equal to the optical path length difference).
Or a step (its height is obtained in the same manner as above) that causes an optical path length difference that is an odd multiple of 1/4 of the wavelength of the light of the light emitting element at one end of the optical waveguide emission end face. However, it is possible to measure the displacement of the external mirror and detect the displacement direction by using a two-divided photodiode as a light receiving element to obtain two signals having 90 ° different phases.

FIG. 1 is a plan view showing a first embodiment of a laser interferometer according to the present invention, and FIG. 2 is a sectional view taken along the line AA 'in FIG.

As shown in FIG. 1 or 2, a semiconductor laser 5 as a light emitting element and photodiodes 6a and 6b as light receiving elements are formed on a semiconductor substrate 4 on which an electrode 1, a solder film 2 and an optical waveguide 3 are patterned. Are fixed (bonded) with high precision. As the semiconductor laser 5, a DFB laser having a light wavelength of 1.3 μm or 1.55 μm was used. As the photodiodes 6a and 6b, end-face incidence refraction type photodiodes were used. Papers on such photodiodes include:
H. Fukano, Y. Matsuoka, A Low-Cost Edge-Illuminate
d Refracting-Facet Photodiode Module with Large Ba
ndwidth and High Responsivity, J. Lightwave Techno
logy, Vol. 18, No. 1, 79-83 (2000).

Optical elements such as semiconductor lasers and photodiodes may be monolithically formed on a GaAs substrate or InP substrate.

Further, the polarization beam splitter 7, the quarter-wave plate 8 and the beam splitter 9 were bonded (fixed) on the same semiconductor substrate 4. Here, the semiconductor substrate 4
As the substrate, a silicon (Si) substrate was used. Optical waveguide 3
Is the lower clad 3-1, the core 3-2, the upper clad 3-
It is formed from three layers. As the material of the optical waveguide 3, fluorinated polyimide having high heat resistance and chemical resistance was used. This is obtained by applying a polyamic acid solution by spin coating to a desired film thickness, baking and imidizing. This polyimide film was processed by reactive ion etching in an oxygen gas atmosphere using a silicone-based resist obtained by patterning a desired shape by photolithography as an etching mask. The optical waveguide 3 is not limited to an organic type such as polyimide, but it is also possible to use a silica type optical waveguide. In order to make the thickness of the lower clad 3-1 sufficient, the silicon substrate is wet etched by KOH (potassium hydroxide) solution or deep reactive ion etching (Deep Reactive Ion Etch).
ing) dry etching is performed by an apparatus or the like.

The polarization beam splitter 7 and the beam splitter 9 are formed by vapor-depositing a dielectric multilayer film on one surface of a synthetic quartz substrate (thickness: about 300 μm) so as to form the antireflection film 10, and on the other surface, respectively. The dielectric multilayer film 1 is formed so as to serve as the polarization beam splitter 7 and the beam splitter 9.
1 and 12 were vapor-deposited and used. These were cut by dicing and bonded on the semiconductor substrate 4.

The quarter-wave plate 8 is prepared by polishing quartz, a dielectric multilayer film is vapor-deposited on both sides to form the antireflection film 10, and similarly cut by dicing to obtain the semiconductor substrate 4.
Bonded on.

Note that FIG. 2 shows a state before the semiconductor laser 5 is bonded to the semiconductor substrate 4. At the time of bonding, the semiconductor laser 5 descends in the direction of the downward arrow in the figure, and the semiconductor laser 5 Active layer 5
Bonding is performed at a position where the height of -1 and the center of the core 3-2 of the optical waveguide 3 coincide with each other.

This laser interferometer operates as follows. When a current is injected into the semiconductor laser 5, laser oscillation occurs. When oscillating the power as constant as possible, one end face of the semiconductor laser 5 (on the side opposite to the optical waveguide 3)
An output monitor photodiode 6b is installed at the position to monitor the output of the semiconductor laser 5, and the injection current of the semiconductor laser 5 is controlled by a feedback circuit so that the power is always constant. The light emitted from the semiconductor laser 5 propagates in the optical waveguide 3 while confining the light in the vertical direction, and is collimated in the horizontal direction by a parabolic total reflection mirror 13 formed in the optical waveguide 3. Here, the parabolic shape is a surface shape, and a line of intersection between the surface and a surface parallel to the surface of the semiconductor substrate 4 is a parabola, and a cylindrical surface having a generatrix perpendicular to the surface of the semiconductor substrate 4. Means the shape of. When the spread angle of the light totally reflected by the parabolic total reflection mirror 13 was measured, the spread angle was 0.44 ° in full width at half maximum.

Since the semiconductor laser normally oscillates with TE polarization, the TE polarization component passes through the polarization beam splitter 7 and is converted into circular polarization by the quarter wavelength plate 8. Part of the circularly polarized light is reflected by the beam splitter 9 (becomes reference light), and the remaining component is emitted toward an external measurement target mirror and is reflected by an external mirror, that is, the measurement target mirror 14 (becomes measurement light), Return to the beam splitter 9. The reflected light (reference light) from the beam splitter 9 and the reflected light (measurement light) from the external mirror, that is, the mirror 14 to be measured have their rotation directions of circularly polarized light reversed before and after reflection, and thus are again quadrant. After passing through the one-wave plate 8, the light becomes a linearly polarized light which is orthogonal to the polarization direction of the incident light, is reflected by the polarization beam splitter 7, and is received by the photodiode 6a. In this way, the reflected light (reference light) from the beam splitter 9 and the external mirror, that is, the measurement target mirror 1
The reflected light (measurement light) from 4 interferes, is reflected by the polarization beam splitter 7, and is detected by the photodiode 6a.
When the external mirror, that is, the measurement target mirror 14 is driven by a piezo element, an interference signal having a cycle of ½ wavelength is obtained,
It was found that it is possible to measure the displacement of the measurement target mirror from this signal.

FIG. 3 is a plan view showing a second embodiment of the laser interferometer according to the present invention, and FIG. 4 is a sectional view taken along the line BB 'of FIG. Since the light emitted from the optical waveguide 3 spreads in the vertical direction due to the diffraction phenomenon, the rod lens 15a is further bonded (fixed) to the tip of the optical waveguide 3. Here, the rod lens means a cylindrical lens. The light emitted from the optical waveguide 3 was also collimated in the vertical direction by the rod lens 15a. In the present invention, since the parabolic total reflection mirror 13 is formed inside the optical waveguide 3 to collimate the beam in the horizontal direction, the exit end face of the optical waveguide 3 becomes a straight line, so that only the simple rod lens 15a is provided. It was possible to achieve vertical collimation. The rod lens 15a used here is a gradient index type rod lens having a diameter of 60 μm to 500 μm. The operating principle is the same as that of the first embodiment.

FIG. 5 is a plan view showing a third embodiment of the laser interferometer according to the present invention. After the beam splitter in the diagram showing the second embodiment, a rod lens 15b for converging the beam in the horizontal direction is provided. It was possible to measure a minute displacement when the measurement target mirror 14 is a movable part of a micromachine or the like. The operating principle is the same as that of the first embodiment.

FIGS. 6 and 7 are plan views showing a fourth embodiment of the laser interferometer according to the present invention. An optical path length difference (Δn × d, Δn × d,) equal to an odd multiple of λ / 8 (where λ is the wavelength of the light from the light source) is applied to one part of the beam splitter 9.
Where Δn is the refractive index difference between the surrounding medium and the beam splitter, and d is the height of the step) 9-1
Is formed (FIG. 6), or a step 3-4 that gives an optical path length difference equal to an odd multiple of λ / 4 is formed on one part of the emission end face of the optical waveguide 3 (FIG. 7). By doing so, a phase difference of 90 ° is generated between the light that has passed through one portion and the light that has passed through the other portion of the light that is incident on the photodiode 6a that is the light receiving element. As a photodiode 6a which is a
If two lights having different phases are received separately, two signals are obtained. Therefore, it is possible to measure the displacement of the external mirror, that is, the mirror 14 to be measured and detect the displacement direction by using these signals. Become.

FIG. 8 is a plan view showing a fifth embodiment of the laser interferometer according to the present invention. A semiconductor laser 5 as a light emitting element, a photodiode 6a as a light receiving element,
The alignment mark 17 is provided on the polarization beam splitter 7, the quarter-wave plate 8, the beam splitter 9, and the semiconductor substrate 4, and these elements are precisely bonded on the semiconductor substrate by alignment using the alignment mark 17. did. This drawing shows an example in which the end faces of the polarization beam splitter 7, the quarter-wave plate 8 and the beam splitter 9 are aligned with the alignment mark 17 formed on the semiconductor substrate 4.

A sixth embodiment of the laser interferometer according to the present invention will be described with reference to FIG. FIG. 4 shows B- of FIG.
It is a B'sectional view. Silicon is used as the semiconductor substrate 4, the concave portion 18 is precisely formed by anisotropic wet etching, and the active layer 5-1 of the semiconductor laser 5 as a light emitting element is formed.
The semiconductor laser 5, which is a light emitting element, is bonded with the height (not shown) substantially aligned with the center of the core 3-2 of the optical waveguide 3 and the center of the rod lens 15a. A laser interferometer was produced by precisely disposing the respective elements of the wave plate 8, the beam splitter 9 and the rod lens 15a on the silicon substrate 4. A KOH solution was used as the etching solution.

FIG. 9 is a plan view showing a seventh embodiment of the laser interferometer according to the present invention, and FIG. 10 is CC 'of FIG.
FIG. A positioning part 19 is provided on the semiconductor substrate 4 by using the same material as the optical waveguide 3, and each element of the polarization beam splitter 7, the quarter-wave plate 8 and the beam splitter 9 is positioned by using the positioning part 19. A laser interferometer was produced by precisely positioning on the semiconductor substrate 4 and fixing each element with an ultraviolet curing resin.

As described above, in the laser interferometer according to the present invention, the light emitting element, the light receiving element, the lens, the polarization beam splitter, the quarter wavelength plate, and the beam splitter are formed or fixed (bonding) on the same semiconductor substrate. By doing so, an ultra-compact and lightweight laser interferometer can be realized at a significantly reduced cost. Since each element can be assembled into a hybrid, an interferometer with a long life can be realized by using an element with good characteristics. Further, in the manufacturing process of the interferometer, since each element is formed or fixed on the same substrate, formation or fixation of each element may be two-dimensional positioning and active three-dimensional alignment (positioning). I don't need it, so
Significant cost reduction can be realized.

[0038]

By implementing the present invention, it is possible to assemble individual parts, reduce adjustment steps, reduce costs, and improve mass productivity. The laser interference is highly reliable and is not easily affected by environmental changes. A total can be provided.

[Brief description of drawings]

FIG. 1 is a plan view of a laser interferometer showing a first embodiment of the present invention.

2 is a cross-sectional view taken along the line A-A 'in FIG.

FIG. 3 is a plan view of a laser interferometer showing a second embodiment of the present invention.

4 is a cross-sectional view taken along the line B-B 'in FIG.

FIG. 5 is a plan view of a laser interferometer showing a third embodiment of the present invention.

FIG. 6 is a plan view of a laser interferometer showing a fourth embodiment of the present invention.

FIG. 7 is a plan view of a laser interferometer showing a fourth embodiment of the present invention.

FIG. 8 is a plan view of a laser interferometer showing a fifth embodiment of the present invention.

FIG. 9 is a plan view of a laser interferometer showing a seventh embodiment of the present invention.

10 is a cross-sectional view taken along the line C-C ′ of FIG.

FIG. 11 is a diagram showing a conventional laser interferometer.

FIG. 12 is a diagram showing a conventional laser interferometer.

FIG. 13 is a diagram showing a conventional laser interferometer.

[Explanation of symbols]

1 ... Electrode, 2 ... Solder film, 3 ... Optical waveguide, 3-1 ... Lower cladding, 3-2 ... Core, 3-3 ... Upper cladding, 3-4
... step, 4 ... semiconductor substrate, 5 ... semiconductor laser, 5-1 ...
Active layer, 6a, 6b ... Photodiode, 7 ... Polarization beam splitter, 8 ... Quarter wave plate, 9 ... Beam splitter, 9-1 ... Step, 10 ... Antireflection film, 11, 12 ...
Dielectric multilayer film, 13 ... Parabolic shape total reflection mirror, 14 ... Measurement target mirror, 15a, 15b ... Rod lens, 17 ...
Alignment mark, 18 ... Recessed portion, 19 ... Positioning portion, 20 ...
Silicon substrate, 21 ... Lens, 22 ... Beam splitter, 23 ... Phase shifter, 24 ... Mirror, 25 ... Semiconductor laser, 26 ... Photodiode, 27 ... Measuring mirror, 28 ... Reference light, 29 ... Signal light, 30 ... Beam Divider, 31 ... Semiconductor laser, 32 ... Electrode, 33 ... Phase shifter, 34 ... Convex end face, 35 ... Fluorinated polyimide optical waveguide, 36 ... Monitor photodiode, 37 ... Mirror to be measured, 38 ... GaAs substrate, 39 … Half mirror, 4
0 ... Signal light, 41 ... Monitor photodiode, 42 ...
Reference light, 43 ... Photodiode for measurement.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2F064 AA03 AA04 BB01 BB05 CC01                       EE05 FF01 GG06 GG12 GG20                       GG23 GG24 GG33 GG34 GG38                       GG39 GG45 HH01 HH05 JJ11                 2F065 AA01 AA06 AA20 AA31 BB01                       BB25 DD02 DD11 FF52 FF61                       GG06 HH04 HH08 HH13 JJ01                       JJ18 LL00 LL04 LL12 LL19                       LL35 LL36 LL37

Claims (4)

[Claims] 1. A light emitting device, a light receiving device, an optical waveguide, a polarization beam splitter, a quarter-wave plate and a beam splitter are formed or fixed on the same semiconductor substrate, and light emitted from the light emitting device is passed through the optical waveguide. And is collimated in the horizontal direction by a parabolic mirror in the middle of the optical waveguide, and emitted toward an external mirror through the polarization beam splitter, the quarter wavelength plate and the beam splitter, and the external mirror. The reflected light from and the reflected light from the beam splitter is reflected by the polarizing beam splitter, and is received by the light receiving element,
A laser interferometer characterized by measuring the displacement of the external mirror. 2. The laser interferometer according to claim 1, wherein
A first rod lens for collimating light in the vertical direction is further fixed on the semiconductor substrate, and the light emitted from the optical waveguide is collimated in the vertical direction by the first rod lens to obtain the polarization beam splitter, The light is emitted toward the external mirror through the quarter-wave plate and the beam splitter, the reflected light from the external mirror and the reflected light from the beam splitter are reflected by the polarization beam splitter, and the light is received by the light receiving element. A laser interferometer characterized by measuring the displacement of the external mirror by receiving light. 3. The laser interferometer according to claim 1 or 2, wherein a second rod lens for converging light in the horizontal direction is further fixed on the semiconductor substrate, and light emitted from the optical waveguide, or The light emitted from the first rod lens passes through the polarization beam splitter, the quarter-wave plate, and the beam splitter, and then passes through the second beam.
Is horizontally condensed by the rod lens of and is emitted toward the external mirror, and the reflected light from the external mirror and the reflected light from the beam splitter are reflected by the polarization beam splitter, and are reflected by the light receiving element. A laser interferometer characterized by measuring the displacement of the external mirror by receiving light. 4. The laser interferometer according to any one of claims 1 to 3, wherein an optical path length difference that is an odd multiple of ⅛ of a wavelength of light of the light emitting element is generated in one part of the beam splitter. Or a step that causes an optical path length difference that is an odd multiple of 1/4 of the wavelength of the light of the light emitting element is formed in one part of the light emitting surface of the optical waveguide, and the light receiving element is divided into two parts. A laser interferometer characterized in that it uses a photodiode to obtain two signals having 90 ° different phases to measure the displacement of the external mirror and detect the displacement direction.