JPH11248955A - Optical waveguide, method for aligning lens and optical waveguide, device for aligning lens and optical waveguide, wireless optical communication equipment and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the method and device capable of precisely aligning the lens and optical waveguide. SOLUTION: The beam spot 106 which is converged by a condenser lens 104 and travels toward the projection end surface of an optical waveguide layer 102 is picked up by a CCD 103. In its image pattern, interference fringes are observed which are different in cycle with the distance between the beam spot 106 and the top surface of a substrate 101. Namely, this results from that when the beam spot 106 is above the top surface of the optical waveguide, the interference fringes are observed owing to the interference between light made incident directly on the CCD 103 and light reflected by the top surface of the optical waveguide. For the purpose, the condenser lens 102 is moved along a Y axis over a look at the screen of a monitor 107 to position the interference fringes along the Y axis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of optical communication such as wireless optical communication and sensors using light, and more particularly to the field of coupling light from space used in this kind of field. A program corresponding to a control procedure for positioning an optical waveguide having a lens, an alignment method of a lens and an optical waveguide, an alignment device of a lens and an optical waveguide, a wireless optical communication device, and a lens and an optical waveguide is stored. Recording media.

[0002]

2. Description of the Related Art As an example of an optical coupling method from a space to an optical waveguide, there is known an "edge coupling method" described on page 236 of "Optical Integrated Circuit" by Hiroshi Nishihara et al. ing. This end face coupling method is a method of irradiating the end face of the optical waveguide with an incident wave having a mode distribution substantially matching the mode distribution of the optical waveguide, and has an advantage that highly efficient optical coupling is possible.

In general, when light is guided to a single mode waveguide by using this end face coupling method, as shown in FIG. 12, a condensing lens 2 disposed on an incident end face side of an optical waveguide 1 is used.
It is necessary to align the position of irradiation of the incident wave with the incident end face 1a of the optical waveguide by performing alignment with the optical waveguide 1 and thus the optical waveguide 1 can be moved in the XYZ three-dimensional direction. Is placed on top.

As shown in FIG. 1, an optical power meter 4 for observing a guided light power of light transmitted through the optical waveguide 1 is disposed on an emission end face side of the optical waveguide 1. The alignment with the optical waveguide 1 is performed by the optical power meter 4.
This is performed by the operator finely adjusting the manual stage in the XYZ directions so that the guided light power observed by the operator becomes maximum.

[0005]

By the way, optical waveguides used in the field of optical communication and the like are often single mode waveguides. In this case, the size of the optical waveguide layer (or core layer) is usually 2 to 3 μm square. Therefore, it is difficult for the operator to adjust the irradiation position of the incident wave by the above-described alignment method. For example, the wavelength of the incident wave is 0.8 μm as the oscillation wavelength of a commonly used semiconductor laser, the numerical aperture of the condenser lens for condensing the incident wave on the end face of the optical waveguide is 0.2, and the cross-sectional size of the optical waveguide is 2 μm. In the case of the angle, the minimum beam width of the incident wave is 2.6 μm, and the beam width of the propagation mode of the optical waveguide is also about 2.
6 μm.

In addition, in wireless optical communication in which the direction of an incident wave changes every moment, a condenser lens is moved,
Although the position of the beam spot is changed and optically coupled to the optical waveguide, a method of scanning the beam position at the end face of the waveguide is not efficient, and a method of predicting the beam position in advance is indispensable.

Further, as described above, the beam spot is set at 2.
When the position is as small as 6 μm, the position is 1.3 μm from the optimum value.
A shift of m degrades the coupling efficiency by 4.3 dB. Therefore, the relative position between the lens and the optical waveguide must always be adjusted with an accuracy of 1 μm or less.

However, at present, an optical coupling technology that enables such high-precision positioning has not been developed.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and is an alignment method capable of accurately aligning an optical waveguide and a lens with the optical waveguide suitable for the field of optical communication and the like. And an alignment device used for the implementation.

Another object of the present invention is to provide a positioning apparatus capable of automatically performing positioning between a lens and an optical waveguide, and a program used for implementing the apparatus and corresponding to a control procedure for positioning. It is an object of the present invention to provide a recorded medium.

Another object of the present invention is to provide a wireless optical communication apparatus using an optical waveguide device comprising a combination of a lens and an optical waveguide as described above as a receiver.

[0012]

An optical waveguide according to the present invention is an optical waveguide in which an optical waveguide layer is formed on a substrate, and has a flat upper surface, and the surface roughness of the upper surface is transmitted. , Which achieves the above object.

An optical waveguide according to the present invention is an optical waveguide having an optical waveguide layer formed on a substrate, having a projection on an upper surface, and transmitting the surface roughness of the upper surface excluding the projection. The wavelength is equal to or less than the wavelength of light, thereby achieving the above object.

[0014] Preferably, a light receiving element is integrated with the emission end side of the optical waveguide.

According to a second aspect of the present invention, there is provided a method for aligning a lens and an optical waveguide, the method comprising the steps of: providing an optical waveguide according to any one of claims 1 to 3; A converging lens, a Z-axis direction corresponding to the direction of contact and separation between the optical waveguide and the lens, an X-axis direction orthogonal to the Z-axis direction, and a lateral direction of the optical waveguide, and the Z-axis. The lens and the optical waveguide of the optical waveguide device are provided with a moving means that is orthogonal to the direction and the X-axis direction and that is relatively movable in the Y-axis direction corresponding to the height direction of the optical waveguide. Imaging a beam spot converged by the lens and heading toward the exit end face of the optical waveguide,
Obtaining an image pattern in which interference fringes having different periods according to the distance between the beam spot and the upper surface of the optical waveguide are obtained; and using the image pattern, the center of the beam spot coincides with the upper surface. To drive the moving means to
A step of performing temporary alignment in the axial direction, and a step of performing the alignment in the Y-axis direction by driving the moving means by a distance between the known upper surface and the center of the optical waveguide layer,
Thereby, the above object is achieved.

According to a third aspect of the present invention, there is provided a method for aligning a lens and an optical waveguide, comprising: an optical waveguide according to claim 3; a lens for condensing incident light from an external space on an incident end face of the optical waveguide; The wave path and the lens are arranged in the Z-axis direction corresponding to the direction of contact and separation between the two, the X-axis direction orthogonal to the Z-axis direction, the X-axis direction corresponding to the lateral direction of the optical waveguide, and both the Z-axis direction and the X-axis direction. A method of performing alignment between a lens of an optical waveguide device and an optical waveguide, comprising a moving unit that is orthogonal and relatively movable in a Y-axis direction corresponding to a height direction of the optical waveguide. Condensed, receiving a beam spot toward the emission end face side of the optical waveguide by the light receiving element, and performing the alignment in the Y-axis direction so that the received light current is maximized. Thereby, the above object is achieved.

Preferably, the temporary alignment step in the Y-axis direction and the alignment step in the Y-axis direction are performed automatically or manually.

Preferably, the method includes a step of performing the positioning in the X-axis direction after the positioning in the Y-axis direction is completed, and a step of performing the positioning in the Z-axis direction after that. .

Preferably, the positioning step in the X-axis direction is performed by adjusting the guided light power of the beam spot to be maximum, and the positioning step in the Z-axis direction is performed in the Y-axis direction. Alternatively, the method is performed by shifting the X-axis direction by a predetermined amount, detecting the guided light power of the guided light guided through the optical waveguide in this state, and adjusting the guided light power to be a minimum.

Preferably, the positioning step in the X-axis direction is performed by adjusting the light-receiving current generated in the light-receiving element to be maximum, and the positioning step in the Z-axis direction is performed in the Y-axis direction. Alternatively, the method is performed by shifting the X-axis direction by a predetermined amount and adjusting the light receiving current generated in the light receiving element in this state so as to be minimized.

According to a second aspect of the present invention, there is provided an apparatus for aligning a lens and an optical waveguide, comprising: an optical waveguide according to any one of claims 1 to 3; A converging lens, a Z-axis direction corresponding to the direction of contact and separation between the optical waveguide and the lens, an X-axis direction orthogonal to the Z-axis direction, and a lateral direction of the optical waveguide, and the Z-axis. And a moving means which is orthogonal to both the X-axis direction and the X-axis direction and is relatively movable in the Y-axis direction corresponding to the height direction of the optical waveguide. An image pattern in which a beam spot focused by the lens and heading toward the emission end face side of the optical waveguide is imaged, and interference fringes having different periods depending on the distance between the beam spot and the upper surface of the optical waveguide is observed. Imaging means for imaging, and the imaging means Therefore and a control means for controlling the movement of the said Y-axis direction of the moving means based on the image pattern that is captured, the objects can be achieved.

Preferably, the control means includes a storage means for storing a reference image pattern, an operation means for comparing an image pattern taken by the imaging means with the reference image pattern, and outputting a comparison result; A drive control unit that drives the moving unit in accordance with the comparison output of the arithmetic unit and performs positioning in the Y-axis direction.

In addition, an apparatus for aligning a lens and an optical waveguide according to the present invention comprises: an optical waveguide according to claim 3; a lens for condensing incident light from an external space on an incident end face of the optical waveguide; The wave path and the lens are arranged in the Z-axis direction corresponding to the direction of contact and separation between the two, the X-axis direction orthogonal to the Z-axis direction, the X-axis direction corresponding to the lateral direction of the optical waveguide, and both the Z-axis direction and the X-axis direction. At right angles, in the alignment device of the optical waveguide device and the lens of the optical waveguide device having a moving means capable of relatively moving in the Y-axis direction corresponding to the height direction of the optical waveguide, the light is collected by the lens, The light receiving element for receiving a beam spot heading toward the emission end face side of the optical waveguide, and control means for controlling movement of the moving means in the Y-axis direction so that a light receiving current generated in the light receiving element is maximized. Have the above purpose It is achieved.

Preferably, means for performing the alignment in the X-axis direction so that the light-receiving current generated in the light-receiving element is maximized, and the position in the Z-axis direction such that the light-receiving current generated in the light-receiving element is minimized. And a means for performing alignment.

Further, the wireless optical communication device of the present invention comprises:
The positioning device for a lens and an optical waveguide according to any one of claims 10 to 13 is used as a receiver,
Thereby, the above object is achieved.

Further, the recording medium of the present invention is characterized in that:
A program corresponding to a control procedure used in the apparatus for aligning a lens and an optical waveguide according to claim 13 is stored, whereby the object is achieved.

The operation of the present invention will be described below.

In the present invention, as an example, a beam spot condensed by a lens and heading toward the emission end face side of the optical waveguide is imaged by an image pickup means, and alignment in the Y-axis direction is performed using the imaged image pattern. ing.

Here, this image pattern is an image pattern in which interference fringes having different periods according to the distance between the beam spot and the upper surface of the optical waveguide are observed. That is, when the beam spot is located above the upper surface of the optical waveguide, interference fringes are observed due to interference between light directly incident on the imaging means and light reflected by the upper surface of the optical waveguide.

As shown in FIGS. 2 to 4, which will be described later, the period of the interference fringes differs depending on the distance between the beam spot and the upper surface of the optical waveguide, and can be understood by comparing FIGS. 2 and 3. In addition, the shorter the distance, the longer the period of the interference fringes. Then, when the center of the beam spot substantially coincides with the upper surface of the optical waveguide (the distance at this time is assumed to be Y = 0), an image pattern as shown in FIG. 4 is observed. That is, an image pattern without interference fringes is observed.

Here, since the distance between the center of the optical waveguide layer and the upper surface of the optical waveguide is known, the alignment in the Y-axis direction can be performed by using this distance. That is, if the lens is moved in the Y-axis direction by that distance, positioning in the Y-axis direction can be performed.

If the surface roughness of the upper surface of the optical waveguide is equal to or less than the wavelength of transmitted light, good interference fringes can be obtained.

When the positioning in the Y-axis direction is completed, the positioning in the X-axis direction is performed next. In the state where the alignment in the X-axis direction is performed, the image pattern captured by the imaging unit becomes a beam spot. For example, when an operator manually adjusts the position, the image on the monitor screen connected to the imaging unit is displayed. By operating the moving means in the X-axis direction and moving the lens in the same direction so that the guided light power (brightness) is maximized while observing the beam spot, alignment in the X-axis direction can be easily performed. be able to.

For positioning in the Z-axis direction, the adjustment in the Y-axis direction is performed again until the image pattern becomes as shown in FIG. 4, and in this state, the guided light power guided through the optical waveguide layer is measured. For this measurement, the peak value of only the portion of the spot-shaped guided light in the image picked up by the image pickup means may be read through the monitor screen.

The peak value is read while adjusting the position of the lens with respect to the optical waveguide layer in the Z-axis direction, and the lens is positioned at a position where the peak value is minimized.

Finally, the positioning in the Y-axis direction is performed again. Thereby, the alignment between the lens and the optical waveguide can be optimally performed.

When the positioning in the Z-axis direction is performed by shifting the position in the Y-axis direction in advance, as shown in FIG. 5 described later, the contrast of the guided light intensity due to the positional shift in the Z-axis direction is large. Therefore, there is an advantage that the position can be easily adjusted.

Since such positioning can be automatically performed by using a control system including a microcomputer or the like, it is particularly preferable in a field where the direction of an incident wave changes every moment, such as wireless communication. Become something.

As an example, such a control system includes a storage unit that stores a reference image pattern, a calculation unit that compares an image pattern captured by an imaging unit with a reference image pattern, and outputs a comparison result. This can be achieved by a configuration including a drive control unit that drives the moving unit in accordance with the comparison output of the arithmetic unit and performs positioning in the Y-axis direction.

If a program corresponding to such a control procedure is stored in a recording medium such as a ROM constituting the storage means, the positioning can be automatically performed.

[0041]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings.

(Embodiment 1 of Positioning Method and Positioning Apparatus) FIGS. 1 to 5 show Embodiment 1 of a method of positioning a lens and an optical waveguide of the present invention and a positioning apparatus used for carrying out the method. FIG. 1 shows a part of an optical receiver used in wireless optical communication. This optical receiver is a receiver used to perform optical transmission between buildings,
An optical waveguide 101 made of a Si substrate having a rectangular parallelepiped shape and formed with an optical waveguide layer 102, a condenser lens 104 disposed in front of the optical waveguide 101, that is, on a light incident side, and the condenser lens 104 Spring movable table (actuator) 10 movable in the axial, Y-axis, and Z-axis directions
5, a CCD 103 disposed on the rear surface side of the optical waveguide 101, that is, on the light emission side, for capturing incident light;
And a monitor 107 for displaying a captured image.

Note that, in the present invention, the Z-axis direction corresponds to FIG.
As shown in (1), the direction in which the condenser lens 104 and the optical waveguide 102 move toward and away from each other, the Y-axis direction is the vertical direction, and the X-axis direction is the horizontal direction.

As described above, since this system is used for optical transmission between buildings, the relative position of the transceiver does not shift after the installation, and The position of the condenser lens 104 and the position of the optical waveguide layer 102 may be adjusted so that the incident light 111 is efficiently optically coupled to the optical waveguide layer 102.

Here, the numerical aperture NA of the condenser lens 104 is 0.2. The optical waveguide layer 102 is formed by embedding SiO ₂ in a Si substrate 101 and has a size of 2 μm.
It is a μm square and the length is 1 mm. The material of the optical waveguide layer 102 is not limited to the above. Further, the Si substrate 1 is positioned from the center of the optical waveguide layer 102.
01 is 3 μm. Note that the surface roughness of the upper surface of the Si substrate 101, that is, the upper surface of the optical waveguide is set to be equal to or less than the wavelength of transmitted light.

Next, the condenser lens 102 and the optical waveguide layer 10
2 will be described. In the above configuration, the incident light (signal light) 111 arriving from the external space
A beam spot 106 is generally formed on the incident end face of the optical waveguide layer 102 by a condensing lens 102 having an NA of 0.2 attached to a spring-type movable base 105.

Here, when the beam spot 106 is above the Si substrate 101, the image picked up by the CCD 103 is composed of light directly incident on the CCD 103 and the Si substrate 1.
Interference fringes are observed due to interference with light reflected on the upper surface of the light emitting device 01.

The period of the interference fringes differs depending on the distance between the beam spot 106 and the upper surface of the optical waveguide 101. As an example, FIG. 2 shows an image pattern when the distance is 10 μm (image pattern on the screen of the monitor 107), and FIG. 3 shows an image pattern when the distance is 20 μm. As can be seen by comparing FIGS. 2 and 3, the shorter the distance, the longer the period of the interference fringes. Then, when the center of the incident beam spot substantially coincides with the upper surface of the optical waveguide 101 (the distance at this time is assumed to be Y = 0), an image pattern as shown in FIG. 4 is observed. That is, an image pattern without interference fringes is observed.

Here, since the distance between the center of the optical waveguide layer 102 and the upper surface of the optical waveguide 101 is known, the alignment in the Y-axis direction can be performed by using this distance. That is, if the condenser lens 104 is moved by the distance in the Y-axis direction, the alignment in the Y-axis direction can be performed. Note that these image patterns are hardly affected by the condensing position in the Z-axis direction,
A similar image pattern is captured even when there is a displacement of about m.

When the positioning in the Y-axis direction is completed, the positioning in the X-axis direction is performed next. The positioning in the X-axis direction can be easily performed as follows. That is, in the state where the alignment in the X-axis direction is performed, the image pattern captured by the CCD 103 becomes a beam spot, so that the operator observes the beam spot on the monitor 107 and the guided light power (luminance) is maximized. If the condensing lens 104 is moved in the same direction by operating the spring-type movable base 105 in the X-axis direction, the alignment in the X-axis direction can be easily performed.

Next, positioning in the Z-axis direction will be described. The adjustment in the Y-axis direction is performed again until the image pattern becomes as shown in FIG. 4, and in this state, the power of the guided light guided through the optical waveguide layer 102 is measured. This measurement is based on CCD 10
The peak value of only the portion of the spot-shaped waveguide light in the image picked up in 3 may be read through the monitor 107.

Then, the optical waveguide layer 1 of the condenser lens 104
The peak value is read while adjusting the position in the Z-axis direction with respect to 02, and the condenser lens 104 is positioned at a position where the peak value is minimized.

Finally, the alignment in the Y-axis direction is performed again. Thereby, the position of the condenser lens 104 can be optimized.

Next, the positioning effect of the present embodiment will be described. Positioning in the Y-axis direction is performed using interference fringes as described above. Y-axis alignment
This is performed after the axial alignment has been performed. This allows
High-speed alignment is possible without blindly scanning the beam spot on the incident end face of the optical waveguide layer 102.
In order to perform highly accurate alignment in the Y-axis direction, the actually guided waveguide light is imaged by the CCD 103, the peak value of the captured image is read through the monitor 107, and the Y value is set so that the peak value becomes maximum. The alignment in the axial direction may be performed.

As described above, the alignment in the Z-axis direction is performed as follows.
By shifting the position in the Y-axis direction in advance, the CCD
Positioning is performed so that the peak value of the guided light imaged at 103 takes the minimum value. At this time, the amount of displacement △ y
Depending on the magnitude of / σy (where σy is the incident beam waist), the guided light power (relative value) changes as shown in FIG. As can be seen from FIG. 5, if the position in the Y-axis direction is shifted in advance, the contrast of the intensity of the guided light due to the position shift in the Z-axis direction is increased, so that there is an advantage that the position can be easily adjusted accordingly.

In the present embodiment, the positional displacement is caused in the Y-axis direction in advance, and the positioning in the Z-axis direction is performed. However, for the purpose of enhancing the contrast of the intensity of the guided light with respect to the positional displacement in the Z-axis direction, The same effect can be expected even if the position is shifted in the X-axis direction after the alignment in the X-axis direction. Therefore, the positioning in the Z-axis direction may be performed in a state where the position is shifted in the X-axis direction in advance.

In the present embodiment, when substantially parallel light is incident on the condenser lens 104, the alignment is performed so that the light is focused on the incident end face of the optical waveguide layer 102. This allows
Even when the angle of the signal light arriving from the outside is shifted, the beam spot 106 can be formed on the incident end face of the optical waveguide layer 102.

In this embodiment, the condenser lens 104 is used.
The alignment is performed with the movable side, but the Si substrate 1
It is also possible to perform positioning by making the 01 side movable.

(Embodiment 2 of Positioning Method and Positioning Apparatus) FIGS. 6 to 9 show a second embodiment of a method for positioning a lens and an optical waveguide of the present invention and a positioning apparatus used for implementing the method. First, the system configuration of the second embodiment will be described with reference to FIG. The parts corresponding to those in the first embodiment are denoted by the same reference numerals.

The receiver according to the second embodiment includes an optical waveguide 200
And a light receiving section (light receiving element) 201 are integrally formed. First, a method for manufacturing the optical waveguide 200 and the light receiving unit 201 will be described. On a n-type GaAs substrate 101 ′, Al is formed by a usual metal organic chemical vapor deposition (MOCVD) method.
_0.25 Ga _0.75 As Lower cladding layer 112, Al _0.2 Ga _0.8
An As optical waveguide layer 102 and an Al _0.25 Ga _0.75 As upper cladding layer 113 are sequentially laminated. These layers are stacked non-doped so that light absorption does not occur.

Next, a part of the n-type GaAs substrate 101 'is partially etched by ion beam etching, and the n-type Al _0.75 Ga _0.25 A is again formed by MOCVD.
s layer 114, undoped GaAs light absorbing layer 115 and p
A type Al _0.75 Ga _0.25 As layer 116 is laminated.

Next, in order to form the three-dimensional optical waveguide 200, the side surface of the optical waveguide 200 is etched partway in the lower cladding layer 112 by the above-described ion beam etching. Subsequently, an Al _0.25 Ga _0.75 As side cladding 119 is laminated on the etched portion by MOCVD. Here, the optical waveguide 200 and the side cladding 119 are used.
MOCV so that the heights of
Method D was used. This was successfully performed up to a mixed crystal ratio of Al of 0.3 in the semiconductor layer to be laminated. Thus, the optical waveguide 200 having almost the same height was formed.

Next, the connection between the optical waveguide 200 and the light receiving section 201 was etched by an ion beam etching method. At this time, the etching is performed so that the etching depth reaches the GaAs substrate 101 '. Finally, electrodes 117 and 118 are deposited on the lower surface of the GaAs substrate 101 'and the upper surface of the light receiving section 201. At this time, the optical waveguide 200 and the light receiving unit 201 are designed so that the heights thereof are substantially equal to each other. However, in practice, there is no problem even if there is a height shift of about 10 μm or more.

In addition to the above configuration, the system according to the second embodiment includes an A / D converter 110 and a micro computer 120 including a CPU 121, a storage device 122, a signal generator 123, and the like. , CCD1
03 based on the captured image
0, more specifically, the CPU 121
And the optical waveguide layer 102 are automatically aligned. In the second embodiment, the condensing lens 104 is controlled by the control command from the CPU 121 so that the XYZ
It is mounted on an actuator 105 'that can move in three axial directions.

Next, the operation of the above system will be described. When the signal light 111 is attached to the actuator 105 ′, the signal light 111 is condensed on the incident end face of the optical waveguide layer 102 via the condensing lens 104. A lens 103 ′ for forming an image of the light on the terminal surface on the CCD 103 is inserted into the terminal surface of the light receiving unit.

The peak value (image pattern) picked up by the CCD 103 is taken into the CPU 121 of the microcomputer 120 via the A / D converter 110. CPU 12
Numeral 1 performs a comparison operation between a reference image pattern pre-recorded in a storage device 108 composed of a ROM and a captured image pattern, and gives the calculation result to a signal generator 123. The signal generator 123 supplies a control signal corresponding to the calculation result to the actuator 105 '. The actuator 105 'is controlled by this control signal, and positioning in the Y-axis direction can be performed.

In the second embodiment, the positioning in the X-axis direction is performed so that the light-receiving current generated in the light-receiving portion is maximized. Control in the Z-axis direction is performed in the same manner as in the first embodiment. That is, after substantially aligning the Y-axis direction, the Y-axis direction is shifted by a set value, and the Z-axis is aligned so that the photocurrent generated in the light receiving unit is minimized.
Finally, the Y-axis position is returned by the set value.

Next, a control procedure of the CPU 121 in the positioning in each axis direction will be described with reference to FIGS.

When the program for alignment processing stored in the storage device 122 starts, the CPU 1
Reference numeral 21 denotes an image pattern captured by the CCD 103 in step S1, more specifically, a peak value at each pixel of the CCD 103 is read and temporarily stored in the storage device 122. This storage is performed in a state of being arranged for each pixel.

Next, in the routine shown in steps S2 to S6, the CPU 121 sequentially compares all the preset reference image patterns with the read image patterns. Specifically, the peak value generated in the CCD 103 is read, and the sum of the product of each pixel with the peak value of the reference image pattern is calculated. At this time, if the reference image pattern and the captured image pattern are close to each other, the portion where the light intensity is high matches, and the sum of the products increases. In this manner, the reference image pattern in which the amount represented by the expression S shown in step S3 of FIG. 7 is maximum is searched, and the reference image pattern in which S is maximum becomes the pattern shown in FIG. The control in the Y-axis direction is performed until it becomes (Step S7).

At this time, as described above, the beam spot 1
The center of 06 is almost on the upper surface of the optical waveguide 200. Since the distance from the upper surface to the center of the optical waveguide layer 102 is also known in the second embodiment, the control in the Y-axis direction is performed so that the center of the beam spot 106 is located at the height center of the optical waveguide layer 102. (Step S8).

Thereafter, as shown in FIG. 8, the alignment in the X-axis direction is performed so that the guided light power becomes maximum. More specifically, the CPU 121 determines the guided light power from the value of the current flowing through the light receiving unit, and
4 is moved (step S9). Next, the guided light power is determined again and compared with the initially determined guided light power (step S10).

Subsequently, in step S11, the difference dP between the guided light power before and after the movement and the predetermined allowable value EPS are determined.
And if it is determined that | dP | ≧ EPS, the process proceeds to step S12, where it is determined whether dP <0. If dP <0, there is no change in the moving direction (+ X axis direction) of the condenser lens 104 and | dP | ≧
Since it is EPS, the processing after step S10, that is,
The control in the X-axis direction is performed again.

Then, in step S11, | dP
When it is confirmed that | <EPS, it is determined that the alignment in the X-axis direction has been completed, and the process proceeds to step S14, where the condenser lens 104 is moved to a constant value (A) in the Y-axis direction, It is returned by the distance between the upper surface of the waveguide 200 and the center of the optical waveguide layer 102.

When the process of step S14 is completed, the process proceeds to step S15, where a positioning process in the Z-axis direction is performed. This positioning in the Z-axis direction is substantially the same as the above-described positioning in the X-axis direction, and is performed through the processing of steps S15 to S19. However, unlike the positioning in the X-axis direction, the positioning is performed here so that the guided light power is minimized. When it is confirmed in step S17 that | dP | <EPS, Z
It is determined that the axial alignment has been completed, and step S2 is performed.
Then, the focusing lens 104 is returned by a certain value (-A) in the Y-axis direction. Optimum positioning can be performed through the above steps.

In the second embodiment, the storage device 1
22 stores a program corresponding to the above control procedure, and such a recording medium is also an object of the present invention. However, the specific control procedure is shown in FIGS.
However, the present invention is not limited to the flowchart shown in FIG.

In the second embodiment, the positioning in the three-axis direction is performed. However, it is of course possible to apply the present invention to a two-dimensional slab-type waveguide. Waveform replacements are also included in the present invention.

Further, as the number of reference image patterns prepared in advance increases, smoother and faster position adjustment becomes possible. For example, only one image pattern as shown in FIG. 4 is prepared. May be used. In this case, the position adjustment in the height direction is performed so that the image pattern picked up substantially matches the image pattern for reference.

The speed at which the transmission angle of the signal light 111 shifts is a speed that can be sufficiently followed by the CCD 103, but a high-speed light receiving element array may be used instead of the CCD 103 depending on the application. In the second embodiment, the high-speed light receiving element 201 is connected to the optical waveguide 20 so as to be used for high-speed data transmission.
0.

(Embodiment 3 of Positioning Method) FIG. 9 shows Embodiment 3 of the positioning method of the lens and the optical waveguide of the present invention.
2A and 2B show an optical waveguide structure used, wherein FIG. 1A shows a ridge-type optical waveguide layer 102, and FIG. 1B shows a high-mesa-type optical waveguide layer. Embodiment 3 relates to an alignment method when the shape of the optical waveguide changes.

The optical waveguide structure of the ridge-type optical waveguide layer 102 and the high-mesa-type optical waveguide layer 102 may be made of any material. For example, when the optical waveguide structure is made of a GaAs semiconductor, the semiconductor is formed by MOCVD. After the layers are stacked, they can be manufactured by ordinary wet etching or ion beam etching. In any of the manufacturing methods,
The portion other than the protruding portion 102a is formed substantially in a mirror surface.

Thus, the first and second embodiments described above are performed.
The alignment with the lens can be performed by the method described in (1). That is, the positioning in the height direction is performed so that the interference pattern shown in FIG. 4 is observed at a portion away from the protrusion 102a. In general, the size of the protrusion 102a is several μm to 1 μm in height.
0 μm and a width of 1 to 3 μm.
It is expected that almost the same interference pattern will be observed even if the light beams overlap each other.

If the incident light is focused on the projection 102a and the height cannot be adjusted, the focusing lens may be moved in the X-axis direction. When the height of the spot of the incident beam is made equal to the height of the mirror surface, the height of the optical waveguide layer 102 is known from the mirror surface portion. To adjust.
After that, the position is adjusted substantially so that the guided light is observed in the X-axis direction, and then the position is adjusted in the Z-axis direction.
Finally, if a fine adjustment is made in the XY plane, it can be adjusted to the optimum position.

According to the third embodiment, FIG.
Even if the optical waveguide structure such as the ridge type or high mesa type shown in FIG. 2B is not uniformly flat, the position of the optical waveguide layer 102 and the condenser lens can be aligned by the method of the present invention. Light from space can be optimally guided to the optical waveguide layer 102.

Here, according to the manufacturing process of the optical waveguide, the upper surface of the optical waveguide becomes almost flat, but in a specific process (for example, wet etching or the like), it becomes a curved mirror surface slightly reflecting the ridge shape or the like. There is also. In each case, the upper surface of the optical waveguide becomes a smooth mirror surface, and good interference fringes can be obtained. On the other hand, a certain value of surface roughness may remain on the upper surface of the substrate. However, it has been confirmed that good interference fringes can be obtained if the in-plane roughness is equal to or less than the wavelength of the transmitted light. Therefore, the method of the present invention can be applied to an optical waveguide whose surface roughness is equal to or less than the wavelength of light to be transmitted.

(Embodiment 4 of Positioning Method) FIG. 10 shows Embodiment 4 of a method of positioning a lens and an optical waveguide according to the present invention. Since the positioning device used in the positioning method of the fourth embodiment is almost the same as the system of the second embodiment, it will be described below with reference to FIG. However, in the fourth embodiment, the CCD 103 is not used, and the CPU 121 is used based on the photocurrent detected by the light receiving unit (light receiving element) 201 in FIG.
Has a configuration in which the position of the condenser lens 104 with respect to the optical waveguide layer 102 is automatically adjusted.

Here, the light receiving element 201 receives the incident light 111
1 according to the position of the beam spot 106 in the Y-axis direction of FIG.
A photocurrent (light receiving current) shown in FIG. In FIG. 10, the reason why the photocurrent value fluctuates in the region of Y ≧ 0 is due to interference fringes generated on the light receiving element 201.
Such a vibration is generated according to the number of light and dark fringes of the interference fringes generated in 01.

Therefore, in the fourth embodiment, the CPU 121
Drives and controls the actuator 105 ′ to collect the condenser lens 1.
04 is moved in the Y-axis direction, and if the CPU 121 monitors a change in the received light current at that time, the positioning in the Y-axis direction can be performed. More specifically, the CPU 121 moves the condenser lens 104 in the Y-axis direction, takes in the photocurrent value that is the current detected by the light receiving element 201 at that time, and moves the condensing lens 104 in the Y-axis direction so that the maximum photocurrent can be obtained. By performing the adjustment, the position in the Y-axis direction can be adjusted.

As described above, in the fourth embodiment, although a single light receiving element 201 is used, it can be said that this is a method of performing alignment using light interference on the upper surface of the optical waveguide.

Here, in FIG. 10, the reason why the photocurrent does not reach the minimum value even when the position of the beam spot 106 is a negative value is that the beam spot 106 is finite (approximately 1-2 μm).
m).

Thereafter, the positioning in the X-axis direction and the Z-axis direction is performed in the same manner as in the second embodiment.

According to the positioning method of the fourth embodiment,
There is an advantage that alignment can be easily performed without using a relatively expensive CCD, and alignment can be performed with a simpler algorithm.

The alignment method according to the fourth embodiment can be applied to a method in which an operator manually performs alignment as in the first embodiment. In this case, by scanning the beam spot 106 in the Y-axis direction and, for example, monitoring the photocurrent displayed on the monitor screen,
06 can be brought almost near the upper surface of the optical waveguide. Thereafter, since the distance between the optical waveguide layer 102 and the upper surface of the optical waveguide is known, if the spring-type movable stage is moved so that the beam spot 106 substantially coincides with the upper surface of the optical waveguide, the spring-type movable stage becomes X A light receiving current due to the guided light is generated in the light receiving element 201 simply by operating in the axial direction.

Therefore, the worker may adjust the X-axis direction while viewing the monitor screen so that the light receiving current is maximized. Adjustment in the Z-axis direction can be performed in the same manner as in the second embodiment.

(Embodiment Using Positioning Apparatus of the Present Invention for Wireless Optical Communication) FIG. 11 shows an embodiment in which a positioning apparatus for a lens and an optical waveguide of the present invention is used for wireless optical communication. That is, FIG. 11 shows a configuration of a coherent optical communication receiver, and uses the positioning device of the present invention.

The production of the optical waveguide 200 and the light receiving section 201 is performed in substantially the same manner as in the second embodiment. An i-type semiconductor layer is deposited, the light receiving portion is etched, and the light receiving element 132,
1332 is manufactured again. Thereafter, a resist pattern of the cross-shaped optical waveguide is transferred to the waveguide portion (optical waveguide portion), and a cross-shaped ridge optical waveguide is manufactured by wet etching. Finally, using the aforementioned ion beam etching,
The junction between the optical waveguide and the light receiving portion and the intersection of the cross waveguide are etched substantially vertically. Thereby, the groove 131
Is formed, and functions as a waveguide type beam splitter.

Next, the operation of the present system will be described. In this system, the semiconductor laser element 130 is arranged on one incident end face of the waveguide, and the condenser lens 104 and the actuator 105 'are arranged on the other incident end face, and the signal light 111 arriving from the outside is guided to the optical waveguide. . At this time,
In order to efficiently guide the signal light 111 to the optical waveguide, the lens and the CCD 103 are arranged at a position facing the condenser lens 104, and the alignment is performed using an interference fringe pattern generated on the CCD 103.

In this system, the waveguide is of a tenu type and has a step on the upper surface of the waveguide. However, the step is not more than 10 μm, which is not a practical problem.

In coherent optical communication, signal transmission and local oscillation light are superimposed at the optical stage and heterodyne detection is performed, so that data transmission with a high signal-to-noise ratio using weak signal light becomes possible. For this reason, superposition of light in an optical waveguide is important, but in the case of wireless optical communication, there has been no method to guide signal light to the waveguide with high efficiency. Further, even if the optical coupling to the optical waveguide is performed, if the relative position between the transmitting side and the receiving side changes or the temperature changes, communication is interrupted.

However, by using the positioning apparatus of the present invention, it is possible to perform high-precision and high-speed positioning of the condenser lens 104 and the optical waveguide, thereby enabling stable optical communication.

[0101]

According to the present invention described above, the lens can be positioned with high precision manually or automatically with respect to the optical waveguide, and in the case of automatic positioning, the direction of the incident wave changes every moment. A positioning method and a positioning device suitable for communication can be realized.

Further, in the present invention, the alignment in the X-axis direction is performed after the alignment in the Y-axis direction is performed. This eliminates the need to scan the beam spot on the incident end face of the optical waveguide unnecessarily. , High-speed alignment can be realized.

When the positioning in the Z-axis direction is performed in a state where a positional shift has occurred in the Y-axis direction or the X-axis direction in advance, the contrast of the intensity of the guided light can be increased. In addition, there is an advantage that it can be performed with high accuracy.

When the optical waveguide of the present invention is used, the surface roughness of the upper surface of the optical waveguide is equal to or less than the wavelength of the transmitted light, and good interference fringes can be obtained. Can be performed with high accuracy.

When the XYZ three-axis alignment is performed automatically, a program corresponding to such a control procedure is stored in a recording medium such as a ROM, and is read by a CPU or the like. Since it can be performed automatically, high-accuracy and high-accuracy positioning can be performed accordingly.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing a first embodiment of a positioning device for a lens and an optical waveguide of the present invention.

FIG. 2 is a diagram illustrating an example of an image pattern captured by a CCD.

FIG. 3 is a diagram showing another example of an image pattern picked up by a CCD.

FIG. 4 is a diagram showing still another example of an image pattern captured by a CCD.

FIG. 5 is a graph showing the relationship between the amount of displacement in the Z-axis direction and the guided light power.

FIG. 6 is a system configuration diagram showing a second embodiment of a positioning device for a lens and an optical waveguide according to the present invention.

FIG. 7 is a flowchart showing a control procedure of the CPU in the positioning process up to a certain point.

FIG. 8 is a flowchart showing a continuation of FIG. 7;

9A is a perspective view showing a ridge-type optical waveguide structure used in Embodiment 3 of the method for aligning a lens and an optical waveguide of the present invention, and FIG. 9B is a high-mesa-type optical waveguide structure. Perspective view.

FIG. 10 is a graph showing a light receiving current in a light receiving element.

FIG. 11 is a system configuration diagram showing a fifth embodiment of a device for positioning a lens and an optical waveguide according to the present invention.

FIG. 12 is a system configuration diagram of a system used in a conventional optical coupling method.

[Explanation of symbols]

 101, 101 ′ Substrate 102 Optical Waveguide Layer 103 CCD 104 Condenser Lens 105 Spring-Movable Stand 105 ′ Actuator 106 Beam Spot 107 Monitor 110 A / D Converter 111 Signal Light 112 Lower Cladding Layer 113 Upper Cladding Layer 114 p-type AlGaAs Layer 115 GaAs light absorption layer 116 n-type AlGaAs layer 117, 118 electrode part 119 side cladding layer 120 microcomputer 121 CPU 122 storage device 123 signal generator 130 semiconductor laser 131 groove (beam splitter) 132, 133 light receiving element 200 optical waveguide 201 Light receiving element

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04B 10/22

Claims (15)

[Claims] 1. An optical waveguide having an optical waveguide layer formed on a substrate, wherein the optical waveguide has a flat upper surface and the surface roughness of the upper surface is equal to or less than the wavelength of transmitted light. 2. An optical waveguide in which an optical waveguide layer is formed on a substrate, the optical waveguide having a projection on an upper surface, and a surface roughness of the upper surface excluding the projection is equal to or less than a wavelength of light to be transmitted. Wave path. 3. The optical waveguide according to claim 1, wherein a light receiving element is integrated with an emission end side of the optical waveguide. 4. The optical waveguide according to claim 1, a lens for converging incident light from an external space on an incident end face of the optical waveguide, and the optical waveguide and the lens. A Z-axis direction corresponding to the contact and separation direction of the two, an X-axis direction orthogonal to the Z-axis direction, an X-axis direction corresponding to a lateral direction of the optical waveguide, and both the Z-axis direction and the X-axis direction orthogonal to each other; A method for aligning a lens of an optical waveguide device and an optical waveguide, comprising a moving means capable of relatively moving in the Y-axis direction corresponding to the height direction of the optical waveguide, wherein the light is condensed by the lens, Imaging a beam spot heading toward the emission end face side of the waveguide, and obtaining an image pattern in which interference fringes having different periods are observed in accordance with the distance between the beam spot and the upper surface of the optical waveguide; and using the image pattern. , The center of the beam spot coincides with the upper surface Driving the moving means to perform the temporary alignment in the Y-axis direction, and driving the moving means by a known distance between the upper surface and the center of the optical waveguide layer to position in the Y-axis direction. A method of aligning a lens and an optical waveguide, the method including a step of performing alignment. 5. The optical waveguide according to claim 3, a lens for condensing incident light from an external space on an incident end face of the optical waveguide, and the optical waveguide and the lens correspond to the directions of contact and separation between the two. Z-axis direction, an X-axis direction orthogonal to the Z-axis direction, corresponding to the lateral direction of the optical waveguide, and a Y-axis orthogonal to the Z-axis direction and the X-axis direction, both corresponding to the height direction of the optical waveguide. What is claimed is: 1. A method for aligning a lens of an optical waveguide device and an optical waveguide, comprising a moving means capable of relatively moving in an axial direction, wherein the beam is condensed by the lens and heads toward an emission end face side of the optical waveguide. Receiving a spot by the light receiving element;
A method for aligning a lens and an optical waveguide, comprising the step of performing alignment in the Y-axis direction so that the light receiving current is maximized. 6. The method for positioning a lens and an optical waveguide according to claim 4, wherein the temporary positioning step in the Y-axis direction and the positioning step in the Y-axis direction are performed automatically or manually. 7. The method according to claim 4, further comprising the steps of: performing the alignment in the X-axis direction after the completion of the alignment in the Y-axis direction; and subsequently performing the alignment in the Z-axis direction. 7. A method for aligning a lens and an optical waveguide according to any one of 6. 8. The positioning process in the X-axis direction is performed by adjusting the guided light power of the beam spot to be maximum, and the positioning process in the Z-axis direction is performed by:
By shifting the Y-axis direction or the X-axis direction by a predetermined amount, detecting the guided light power of the guided light guided through the optical waveguide in this state, and adjusting the guided light power so as to minimize the guided light power. A method for positioning a lens and an optical waveguide according to claim 7. 9. The positioning process in the X-axis direction is performed by adjusting the light-receiving current generated in the light-receiving element to be maximum, and the positioning process in the Z-axis direction is performed in the Y-axis direction or the X-axis direction. 8. The method for positioning a lens and an optical waveguide according to claim 7, wherein the method is performed by shifting the axial direction by a predetermined amount and adjusting the light receiving current generated in the light receiving element in this state to be a minimum. 10. The optical waveguide according to claim 1, a lens for condensing incident light from an external space on an incident end face of the optical waveguide, and the optical waveguide and the lens. A Z-axis direction corresponding to the contact and separation direction of the two, an X-axis direction orthogonal to the Z-axis direction, an X-axis direction corresponding to a lateral direction of the optical waveguide, and both the Z-axis direction and the X-axis direction orthogonal to each other; An alignment device for a lens and an optical waveguide of an optical waveguide device, comprising a moving means capable of relatively moving in the Y-axis direction corresponding to the height direction of the optical waveguide. Imaging means for imaging a beam spot directed to the side, and an image pattern for observing interference fringes having different periods according to the distance between the beam spot and the upper surface of the optical waveguide; and an image captured by the imaging means. Moving means based on the pattern The alignment device between the lens and the optical waveguide and a control means for controlling the movement of the said Y-axis direction. 11. The control unit includes: a storage unit configured to store a reference image pattern; a calculation unit configured to compare an image pattern captured by the imaging unit with the reference image pattern and output a comparison result; Driving the moving means according to the comparison output of the calculating means,
11. The apparatus for positioning a lens and an optical waveguide according to claim 10, further comprising a drive control unit for performing the positioning in the Y-axis direction. 12. The optical waveguide according to claim 3, a lens for converging light incident from an external space on an incident end face of the optical waveguide, and the optical waveguide and the lens correspond to the directions of contact and separation between the two. Z-axis direction, an X-axis direction orthogonal to the Z-axis direction, corresponding to the lateral direction of the optical waveguide, and a Y-axis orthogonal to the Z-axis direction and the X-axis direction, both corresponding to the height direction of the optical waveguide. In a positioning device for a lens and an optical waveguide of an optical waveguide device provided with a moving means capable of relatively moving in an axial direction, a light spot condensed by the lens and directed toward an emission end face side of the optical waveguide is received. An alignment device for a lens and an optical waveguide, comprising: the light receiving element; and control means for controlling movement of the moving means in the Y-axis direction so that a light receiving current generated in the light receiving element is maximized. 13. A means for performing positioning in the X-axis direction so as to maximize a light-receiving current generated in the light-receiving element, and positioning in the Z-axis direction so as to minimize a light-receiving current generated in the light-receiving element. The apparatus for positioning a lens and an optical waveguide according to any one of claims 10 to 12, further comprising means for performing: 14. A wireless optical communication device using the device for positioning a lens and an optical waveguide according to claim 10 as a receiver. 15. A recording medium storing a program corresponding to a control procedure used in the apparatus for positioning a lens and an optical waveguide according to claim 10. Description: