JP3154870B2 - Optical waveguide device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide device,
In particular, the present invention relates to an optical waveguide device capable of constructing an optical interference system by forming a light reflection portion in an optical waveguide and measuring displacement, distance, and the like using high-precision optical wave interference measurement such as optical heterodyne interference measurement.

[0002]

2. Description of the Related Art Light wave interference measurement is a highly accurate measurement method using laser light having high coherence, and is attracting attention together with the need for a measurement method for ultra-precision positioning in a super LSI or the like. It is a measurement method that is coming. In particular, the heterodyne interferometry has a very high measurement accuracy of 1/100 or more of the wavelength, and is considered to be a measurement method that will be widely used in the future. For heterodyne interferometry, see, for example, Kobayashi et al., IEICE technical research materials, OQE
87-154 (1988) 65-71, and realizes highly accurate measurement using a semiconductor laser and an optical element such as a beam splitter. However, in the case of an interferometer in which an optical element is incorporated in the unit, the material of the unit thermally expands or contracts in response to a change in environmental temperature, and the measurement accuracy is degraded due to a change in the optical path length inside the interferometer due to the change. Therefore, there is a problem that the temperature of the system needs to be controlled.

As an example of a measure for solving this problem, there is a method using a waveguide type interferometer. When this method is employed, alignment is not required for the optical system due to the use of a waveguide, and a great effect is exhibited, such as improvement in stability against vibration. Further, as a substrate for forming a waveguide, for example, in the case of a unit made of aluminum and in the case of a waveguide on a silicon substrate, the linear expansion coefficient of the material of silicon is smaller by about one digit, so that the ambient temperature is lower. The stability of the measurement accuracy with respect to the change is improved.

FIG. 6 shows an example of a waveguide device having a waveguide formed on a silicon substrate, which is a system capable of measuring a distance to an object in a non-contact manner with high accuracy. In this waveguide device, SiO ₂ / Si ₃ N ₄ / Si is formed on a silicon substrate 101.
A waveguide having a three-layer structure of O ₂ is formed to form a waveguide type optical circuit. The laser light emitted from the semiconductor laser 102 is shaped into parallel light by the waveguide lens 103 and split by the beam splitter 104, and the straight component is further split by the beam splitter 105. .

[0005] The component that has traveled straight through the beam splitter 105 is reflected by an end mirror 106, a part of which is reflected by the beam splitter 105 to reach a grating 109, and a part of the component is radiated to the substrate side.
Photodetector 112 formed on silicon substrate 101 immediately below
Is detected by This component is referred to as reference light. On the other hand, the reflected component of the light split by the beam splitter 105 reaches the end face 110 and is emitted toward the object. The light reflected back from the target object is the end face 1
At 10, the component that is coupled back to the waveguide and passes straight through the beam splitter 105 is graded 109.
, And is multiplexed with the above-described reference light in the photodetector 112. Here, since the injection current of the semiconductor laser 102 is obtained by applying a modulation of a triangular wave on a DC bias, the wavelength of the output light is temporally modulated in synchronization with the triangular wave.

Now, one of the two lights multiplexed by the photodetector 112 has passed through the waveguide, while the other has returned to the object after passing through the space and then returned again.
The wavelength and phase differ by the difference in the path length. Therefore, the photodetector 112 detects a beat signal according to the difference in wavelength. Since this wavelength difference corresponds to the difference in path length, the distance to the object can be determined by reading the frequency of the beat signal.

On the other hand, the oscillation wavelength of the semiconductor laser 102 fluctuates depending on the environmental temperature. In this example, another interference system is incorporated for correction. This correction reference system is an interference system composed of an end mirror 106 and an end mirror 107. The light reflected by the respective mirrors 106 and 107 is radiated by the grating 108 to the silicon substrate 101 side, and the light is detected. The signals are multiplexed by the unit 111. Therefore, the photodetector 111 detects a beat signal corresponding to the difference in path length between the two paths. In this case, since the path length of the reference system hardly changes in response to a temperature change, a change in the oscillation wavelength of the semiconductor laser can be confirmed by this reference system.
A measurement error due to a change in the environmental temperature can be corrected.

On the silicon substrate 101, in addition to the photodetectors 111 and 112, a semiconductor laser drive circuit 12
0, an amplifier circuit 121 for amplifying the output signal of the photodetector, a waveform shaping circuit 122 for shaping the output signal of the amplifier circuit, and a frequency counter 123 for counting the frequency of the beat signal are formed using a normal IC process. I have.

[0009]

By the way, the interference system of the waveguide device has a light reflecting portion in principle.
Effective feedback of light is a condition for ensuring stable operation.

However, in the conventional waveguide device, the mirror formed on the end surface for reflecting light is formed by cleavage of the silicon substrate. However, the waveguide portion on the surface is mirror-shaped like the crystal of the substrate. In addition, it is very difficult to cleave uniformly, and even if it is formed by dry etching such as RIE or RIBE, the mirror has many minute irregularities, so this effect is even greater. As a result, the disorder of the surface state of the light reflecting part causes the phase disorder at the time of reflection, which causes a measurement error. Further, since this measurement error occurs, there is a problem in yield.

The present invention has been made to solve the above-mentioned conventional problems, and it is possible to obtain a sufficiently stable light feedback even by using cleavage or dry etching, and to perform a stable operation.
An object is to provide an optical waveguide device with a good yield.

[0012]

According to the present invention, there is provided an optical waveguide device, comprising: a first waveguide for reflecting light from a semiconductor laser incident from one end by a light reflecting portion on the other end; A second waveguide that intersects with the waveguide, propagates light whose direction has been changed from the first waveguide, and emits the light from one of the emission end faces; and an intersection between the first waveguide and the second waveguide. A first beam splitter, which is provided in the first section and changes a direction of a part of light propagating through the first waveguide and guides the light to a second waveguide;
A third waveguide that intersects the first waveguide, propagates light whose direction has been changed from the first waveguide, and has one end serving as a light reflecting portion; and A second beam splitter, which is provided at an intersection with the waveguide and changes the direction of a part of light propagating through the first waveguide and guides the light to a third waveguide, is provided on the substrate; The light reflecting portion on the other end of the waveguide and the third
The light reflection part on one end side of the waveguide is a light reflection part of the light interference system, and the horizontal electric field of light propagating through the waveguide part near at least one of the light reflection parts of the light interference system. Since the full width at half maximum of the distribution is configured to be smaller than the full width at half maximum of the lateral electric field distribution of light in the main region of the waveguide, the above object can be achieved.

In this optical waveguide device, the light reflecting portion of the light interference system can be formed by cleaving the substrate crystal.

The angle (θ ₂ ) between the normal to the waveguide end face other than the light reflecting portion of the optical interference system and the traveling direction of the guided light reaching the waveguide end face is 1 / cos (2θ _2). ) ≧
wi (1 is the distance between the end face of the waveguide and the optical circuit closest to the end face of the waveguide), and the normal to the end face of the waveguide of the light reflecting portion of the optical interference system and the end face of the waveguide. The angle (θ ₁ ) with the traveling direction of the arriving guided light is 1 / co
It is preferable to satisfy s (2θ ₁ ) <wi.

Further, the light reflecting portion of the light interference system can be a waveguide end face formed by etching. The end face of the waveguide can be formed by dry etching. Reactive ion etching (RI
E) or reactive ion beam etching (RIB)
E) can be used. Also in this case, the angle (θ) between the normal to the end face of the waveguide other than the light reflecting portion of the optical interference system and the traveling direction of the guided light reaching the end face of the waveguide.
₂ ) satisfies 1 / cos (2θ ₂ ) ≧ wi, and forms a normal line at a waveguide end face of a light reflection portion of the optical interference system with a traveling direction of guided light reaching the waveguide end face. Angle (θ
₁ ) preferably satisfies ₁ / cos (2θ ₁ ) <wi.

Further, the light reflecting portion of the optical interference system can be formed of an optical element formed at a portion other than the end face of the waveguide.

Further, a waveguide lens can be provided to reduce the optical diameter of the guided light at the light reflecting portion of the interference system.
As the waveguide lens, a mode index lens such as a Luneburg lens and a step index lens,
Alternatively, a geodesic lens or one of diffractive lenses such as a Fresnel lens and a grating lens can be used.

[0018]

According to the present invention, the full width at half maximum of the horizontal electric field distribution of light propagating in the waveguide portion near at least one of the light reflecting portions of the optical interference system is the half value of the horizontal electric field distribution of light. It is configured to be smaller than the full width. Therefore, the ratio of the light reflecting portion of the optical interference system affected by the disturbance of the surface state is significantly reduced.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 shows an example of an optical waveguide device according to the present embodiment. This optical waveguide device has a waveguide 170 having a three-layer structure and a semiconductor laser 102 formed on a silicon substrate 101. The waveguide 170 intersects the first waveguide 171 that receives light from the semiconductor laser 102 from one end side and reflects the light from the end face mirror 106 that is a light reflection part on the other end side. A second waveguide 172 that propagates the light whose direction has been changed from the first waveguide 171 and emits the light from the light emission end face 110 that is one of the emission end faces, and intersects the first waveguide 171; And a third waveguide 173 having one end serving as an end face mirror 107 which is a light reflection portion. The end face mirror 107 and the end face mirror 106 on the other end side of the first waveguide 171 constitute a light reflecting portion of an optical interference system.

The first waveguide 171 and the second waveguide 1
72, a beam splitter 105 that changes the direction of a part of the light propagating through the first waveguide 171 and guides it to the second waveguide 172 is provided.
At the intersection of the first and third waveguides 173, there is provided a beam splitter 104 that changes the direction of a part of the light propagating through the first waveguide 171 and guides the light to the third waveguide 173.

The waveguide 170 having such a three-layer structure includes a first SiO ₂ layer and a second Si ₃ layer from the silicon substrate 101 side.
An N ₄ layer and a third SiO ₂ layer are formed.
Optical circuit components are provided at various locations 70 and various locations on the silicon substrate 101. Specifically, in the first waveguide 171, the waveguide lens 103 is located at a position closer to the semiconductor laser 102 side of the beam splitter 104.
However, a waveguide lens 130 is provided at a position close to the end face mirror 106 side of the beam splitter 104. In the second waveguide 172, the light emitting end face 110
A grating 109 is formed on the end surface opposite to the side of the silicon substrate 1 below the grating 109.
A photodetector 112 is formed on the surface layer of the photodetector 01. In the third waveguide 173, the beam splitter 104
The waveguide lens 1 is located at a position closer to the end face mirror 107 side.
A grating 108 is formed on an end surface portion opposite to the end surface mirror 107, and a photodetector 111 is formed on a surface layer portion of the silicon substrate 101 below the grating 108. In this example, a step index lens was used as the waveguide lenses 103, 130, and 131.

In a region of the silicon substrate 101 surrounded by the first waveguide 171 and the third waveguide 173,
A semiconductor laser drive circuit 120 and a signal amplifier circuit 121 are provided, and a signal waveform shaping circuit 122 and a frequency counter 123 are provided in a region surrounded by the first waveguide 171 and the second waveguide 172. ing.

Next, a description will be given of a manufacturing process of the optical waveguide device thus configured.

First, on a silicon substrate 101, an ordinary I
A semiconductor laser driving circuit 120 using a C process;
Two photodetectors 111 and 112 and a signal amplifying circuit 1
21, a waveform shaping circuit 122, and a frequency counter 123
And formed.

Next, the silicon substrate 101 in this state was introduced into a plasma CVD apparatus, and a waveguide 170 having a three-layer structure was formed at a substrate temperature of 250 ° C. The thickness of each layer is as follows. The first SiO ₂ layer has a thickness of 1 μm, the second Si ₃ N ₄ layer has a thickness of 0.16 μm, and the third SiO ₂ layer has a thickness of 0.3 μm.

Thereafter, the beam splitters 104 and 105 and the waveguide lenses 103, 130,
The optical circuit components 131 and the gratings 108 and 109 were formed, and unnecessary portions of the surrounding waveguide were removed as shown in the figure. Here, regarding the method of forming the optical circuit component,
For example, Valette and others, IEEE PROCEEE
DINGS Vol. 131, Pt. H, 325, OC
TOBER 1984. For example, the waveguide lens 103 and the like, the beam splitter 104 and the like can be formed by removing the outermost SiO ₂ layer in a desired shape. In this embodiment, the optical circuit component is formed using RIE, but the formation of the optical circuit component is not limited to RIE, and for example, RIBE or the like may be used.

Next, the cleavage of the end face mirror 10 is performed.
6, 107 and the light emitting surface 110 were formed, and the semiconductor laser 102 was fixed using a brazing material.

Finally, wiring (not shown) was performed between the semiconductor laser 102 and its driving circuit 120, and between the photodetectors 111 and 112 and the signal amplifier 121.

In the optical waveguide device manufactured as described above, for example, as a result of an experiment of distance measurement, the smoothness of the surfaces of the end mirrors 106 and 107 formed by cleavage is equal to that of the conventional example. Despite this, the ratio of the light reaching the end mirrors 106 and 107 affected by the non-uniform portions on the mirror surface is reduced, and the probability of obtaining good light interference is 95%, which is about 20% of the conventional value. 4 times or more improvement as compared with the above, distance measurement can be stably and accurately performed.

In this embodiment, the end mirrors 106 and 107 are used.
Although the waveguide lenses 130 and 131 are provided in the vicinity of both of them, they may be formed only for those who particularly want to increase the amount of feedback of light. In addition, a step index lens was adopted as the waveguide lens, but this may be another mode index lens such as a Luneburg lens, or a geosick lens, a Fresnel lens, or a diffractive lens such as a grating lens. Similar effects can be obtained.

(Embodiment 2) FIG. 2 is an example of an optical waveguide device showing a second embodiment of the present invention, and the same parts as those in FIG. 1 are denoted by the same reference numerals. In this optical waveguide device, the etched mirror 1 is located on the side of the first waveguide 171 opposite to the beam splitter 105 of the waveguide lens 130.
40, and an etched mirror 141 is formed on the third waveguide 173 on the side of the waveguide lens 131 opposite to the beam splitter 104.

Next, the manufacturing process of the optical waveguide device having such a configuration will be described. First, a semiconductor laser driving circuit 120, two photodetectors 111 and 112, a signal amplifying circuit 121, and a waveform shaping circuit 12 are formed on a silicon substrate 101 by using an ordinary IC process as in the first embodiment.
2 and a frequency counter 123, and then Si
A waveguide 170 having a three-layer structure of O ₂ / Si ₃ N ₄ / SiO ₂ was formed. The thickness of each layer was the same as in the first embodiment.

Thereafter, circuit components such as beam splitters 104 and 105, step index lenses 103, 130 and 131 as waveguide lenses, and gratings 108 and 109 were formed by RIE.

Next, the etched mirrors 140 and 141 were formed by RIE using vertical etching until reaching the silicon substrate 101 through the three layers forming the waveguide 170. Here, etched mirror 1
40, 141 are step index lenses 130,
The focus 131 was formed so as to be focused on the mirror surfaces of the etched mirrors 140 and 141.

Thereafter, an optical waveguide device was manufactured through the same process as in the first embodiment.

As a result of a distance measurement experiment using the optical waveguide device manufactured as described above, it was found that the smoothness of the surface of the etched mirror formed by RIE was equal to that of the conventional example. Also, the ratio of being affected by the unevenness is reduced, and the probability of obtaining good light interference is 95%, which is more than 6 times higher than the conventional 15%, and the distance can be stably and accurately determined. Measurement has become possible.

In the second embodiment, the etched mirror 140,
Although the step index lenses 130 and 131 are provided as waveguide lenses near both of them 141, they may be formed especially only for those who want to increase the amount of light feedback. Also, a step index lens was adopted as the waveguide lens, but this may be another mode index lens, such as a Luneburg lens, or a diffractive lens such as a geodesic lens, a Fresnel lens, or a grating lens. The effect of is obtained. In this embodiment, the etched mirrors 140 and 141 are RIE
Although it was formed by using, dry etching such as RIBE may be used, and the same effect can be obtained in such a case. Needless to say, one of the two etched mirrors 140 and 141 may be formed by cleavage and the other may be an etched mirror.

(Embodiment 3) FIG. 3 is an example of an optical waveguide device showing another embodiment of the present invention, and the same parts as those in FIG. 1 are denoted by the same reference numerals. In this optical waveguide device, a light reflection portion 160 is formed on the side of the first waveguide 171 opposite to the beam splitter 105 of the waveguide lens 130, and the waveguide lens 13 of the third waveguide 173 is formed.
The light reflecting portion 16 is located on the side opposite to the first beam splitter 104.
1 is formed.

The manufacturing process of the optical waveguide device having such a configuration will be described below. First, trapezoidal patterns 150 and 151 as shown in FIG. 4 were formed on the silicon substrate 101.

Thereafter, the semiconductor laser driving circuit 120 and the semiconductor laser driving circuit 120 are used in the same manner as in the first embodiment by using a normal IC process.
Photodetectors 111 and 112 and a signal amplifying circuit 121
, A waveform shaping circuit 122, and a frequency counter 123.

Next, the wafer was introduced into a plasma CVD apparatus, and a waveguide 170 having a three-layer structure was formed at a substrate temperature of 250 ° C. The thickness of each layer is as follows. First layer: Si
O ₂ 1 μm, second layer: Si ₃ N ₄ 0.16 μm, third
Layer: 0.3 μm of SiO ₂ . Here, since the plasma CVD apparatus has very good step coverage, the waveguide portions on the trapezoidal patterns 150 and 151 have a bent shape as shown in FIG. Therefore, the effective refractive index of the waveguide 170 changes at this portion, and in this embodiment, it functions as a reflection mirror.

Thereafter, an optical waveguide device was manufactured through the same process as in the first and second embodiments.

In this embodiment, the trapezoidal pattern 1 shown in FIG.
50 and 151 are employed, but the present invention is not limited to this shape. For example, a ridge shape having no flat portion on the surface may be used. If it can be formed, it can be adopted.

When the distance was measured using the optical waveguide device manufactured by the above process, the same good measurement was realized as in the first embodiment, and the yield and the yield were compared with the case where the conventional technique was used. It was confirmed that the stability was improved.

In the above-described first to third embodiments, an example is described in which the waveguide 170 having a three-layer structure of SiO ₂ / Si ₃ N ₄ / SiO ₂ is formed on a silicon substrate. Is not limited to this. For example, a waveguide of ZnS may be formed on the glass substrate 101, or an epoxy film may be formed on the glass substrate 101. In addition, a three-layer waveguide composed of As ₂ S ₃ / SiO ₂ / Si, a three-layer waveguide composed of glass / SiO ₂ / Si, a one-layer waveguide composed of LiNbO ₃ , etc. The present invention is applicable to all the waveguides of the above. However, it is preferable to use a silicon substrate as the substrate so that the optical circuit portion can be formed using an IC process.

In the first to third embodiments,
Although no lens was provided near the light emitting end face 110,
This is because if reflection occurs at this end face, interference due to the reflection will occur and cause measurement errors. Therefore, no lens is provided here to suppress reflection. Further, for the purpose of suppressing reflection, the light emitting end face 110 is angled so as not to be orthogonal to the traveling direction of the guided light. The reason is described below. FIG. 5 shows a normal line at a light emitting end face 110 which is a waveguide end face other than the light reflecting portion of the optical interference system;
FIG. 3 is a diagram schematically illustrating how the guided light propagates when the traveling direction of the guided light reaching the light emitting end face 110 is shifted. In this figure, 201 is the light emitting end face 110
7 shows the position of the wavefront at the exit of the optical circuit that is closest to the optical circuit, and can be regarded as the position of the beam splitter 105 in the first to third embodiments.
The shaded portion 202 in the drawing represents the guided light traveling toward the light emitting end face 110, and its width wi represents the spread of the electric field distribution of the guided light. Also,
The other shaded portion 203 indicates the guided light reflected by the light emitting end face 110.

Here, assuming that the angle between the normal line at the light emitting end face 110 and the traveling direction of the guided light reaching the light emitting end face 110 is θ, when the wavefront of the reflected light reaches the position 201. The amount of shift δ of the guided light in the horizontal direction can be expressed by the following equation.

Δ = l / cos (2θ) where l is the distance between the light emitting end face 110 and the optical circuit closest to it.

Now, assuming that δ> wi, the reflected light propagates almost without interfering with the original light except for the vicinity of the light emitting end face 110. Therefore, for interference suppression, 1 /
It can be seen that cos (2θ) ≧ wi should be satisfied.

On the other hand, the relationship between the end face forming the optical interference system and the traveling direction of the guided light may be such that 1 / cos (2θ) <wi.

Accordingly, reflection can be suppressed by doing in this way.

[0053]

As described above, in the case of the optical waveguide device of the present invention, even if cleavage or dry etching is used, it is hard to be affected by the non-uniformity of the light reflecting portion. In comparison, the stability of the interference system was remarkably improved, and it was possible to manufacture the interference system with a high yield.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a configuration of an optical waveguide device according to a first embodiment of the present invention.

FIG. 2 is a perspective view illustrating a configuration of an optical waveguide device according to a second embodiment of the present invention.

FIG. 3 is a perspective view illustrating a configuration of an optical waveguide device according to a third embodiment of the present invention.

FIG. 4 is a perspective view showing a shape of a silicon substrate before forming a waveguide in an optical waveguide device according to a third embodiment.

FIG. 5 is a schematic diagram showing how the guided light propagates when the traveling direction of the guided light and the light emitting end face deviate from an orthogonal relationship.

FIG. 6 is a perspective view showing a configuration of a conventional optical waveguide device.

[Explanation of symbols]

Reference Signs List 101 silicon substrate 102 semiconductor laser 103 waveguide lens 104/105 waveguide type beam splitter 108/109 grating 110 light emitting end face 111/112 photodetector 120 semiconductor laser driving circuit 121 signal amplifying circuit 122 signal waveform shaping circuit 123 frequency counter 130 · 131 Waveguide lens 106 · 107 End face mirror 140 · 141 Etched mirror 150 · 151 Trapezoidal pattern 160 · 161 Light reflection part θ 90 ° of the angle formed by the light emitting end face and the traveling direction of the guided light
201 Position of the wavefront of the guided light at the exit of the optical circuit closest to the light exit end face l Shortest distance between the light exit end face and the exit of the optical circuit closest to the light exit end face wi The lateral electric field distribution of the guided light Spread (full width at half maximum) 202 Guided light toward the light emitting end face 203 Guided light reflected at the light emitting end face and returned into the waveguide device

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jun Shimonaka 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (56) References JP-A-6-331314 (JP, A) JP-A-5 JP-A-288509 (JP, A) JP-A-4-321195 (JP, A) JP-A-64-12205 (JP, A) JP-A-62-81506 (JP, A) JP-A-62-5106 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01B 9/00-11/30 G02B 6/122

Claims (10)

(57) [Claims] 1. A first waveguide for reflecting light from a semiconductor laser incident from one end side on a light reflection portion on the other end side, and intersects with the first waveguide and extends from the first waveguide. A second waveguide that propagates the light whose direction has been changed and emits the light from one emission end face, and is provided at an intersection of the first waveguide and the second waveguide;
By changing the direction of a part of the light propagating through the first waveguide, the second
A first beam splitter leading to the first waveguide, a third beam crossing the first waveguide, transmitting light whose direction has been changed from the first waveguide, and having one end serving as a light reflecting portion. A waveguide, provided at the intersection of the first waveguide and the third waveguide;
By changing the direction of a part of the light propagating through the first waveguide,
A second beam splitter for guiding to the first waveguide is provided on the substrate, and a light reflecting portion on the other end of the first waveguide and a light reflecting portion on one end of the third waveguide are formed of an optical interference system. A light reflecting portion, and a full width at half maximum of a horizontal electric field distribution of light propagating in a waveguide portion near at least one of the light reflecting portions of the optical interference system is equal to a lateral width of light in a main region of the waveguide. A two-dimensional slab optical waveguide device configured to be smaller than a full width at half maximum of an electric field distribution in a direction. 2. The optical waveguide device according to claim 1, wherein the light reflecting portion of the optical interference system is a waveguide end face formed by cleaving the substrate crystal. 3. The optical waveguide device according to claim 2, wherein an end face of the waveguide other than the light reflecting portion of the optical interference system is also formed by cleavage, and the end face of the waveguide is not orthogonal to the traveling direction of the guided light. 4. An angle (θ ₂ ) between a normal to the end face of the waveguide other than the light reflection portion of the optical interference system and a traveling direction of the guided light reaching the end face of the waveguide is 1 / cos (2θ). ₂ ) ≧
wi (1 is the distance between the end face of the waveguide and the optical circuit closest to the end face of the waveguide), and the normal to the end face of the waveguide of the light reflecting portion of the optical interference system and the end face of the waveguide. The angle (θ ₁ ) with the traveling direction of the arriving guided light is 1 / co
4. The optical waveguide device according to claim 3, wherein s (2θ ₁ ) <wi is satisfied. 5. The optical waveguide device according to claim 1, wherein the light reflecting portion of the optical interference system is a waveguide end face formed by etching. 6. The optical waveguide device according to claim 5, wherein an end face of the waveguide serving as a light reflection portion of the optical interference system is formed by dry etching. 7. The optical waveguide device according to claim 6, wherein reactive ion etching (RIE) or reactive ion beam etching (RIBE) is used for the dry etching. 8. An angle (θ ₂ ) between a normal to the end face of the waveguide other than the light reflection portion of the optical interference system and the traveling direction of the guided light reaching the end face of the waveguide is 1 / cos (2θ). ₂ ) ≧
wi, and the angle (θ ₁ ) between the normal to the waveguide end face of the light reflecting portion of the optical interference system and the traveling direction of the guided light reaching the waveguide end face is 1 / cos (2θ ₁ ) <
The optical waveguide device according to claim 6, wherein wi is satisfied. 9. The optical waveguide device according to claim 1, wherein the light reflecting portion of the optical interference system comprises an optical element formed at a portion other than an end face of the waveguide. 10. A waveguide lens is provided at the light reflecting portion of the optical interference system to reduce the optical diameter of guided light, and the waveguide lens is a mode index lens such as a Luneburg lens, a step index lens, or the like. 2. The optical waveguide device according to claim 1, wherein the optical waveguide device is one of a geodesic lens and a diffractive lens such as a Fresnel lens and a grating lens.