JP2000215503A - Optically integrated device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain integration by a process for producing a semiconductor substrate and to easily produce an optically integrated device for an optical pickup device at a reduced production cost while miniaturizing the entire device, enhancing effective utilization efficiency of light quantity and effectively making good use of existing resources. SOLUTION: An aluminum light shielding layer 23, a buffer layer 26, an optical waveguide 27 and a grating 28 are successively formed on a semiconductor substrate 20 by a process for producing a semiconductor and a propagation loss reducing film 29, having a higher refractive index than the optical waveguide 27, is formed in a prescribed thickness on the optical waveguide 27 corresponding to a region with the aluminum light shielding layer 23 in the same process as the process for forming the grating 28.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a CD (Compact Diode).
sc), an optical integrated device used for an optical pickup device for optically reproducing information recorded on a recording medium such as an LVD (Laser Vision Disc), a DVD, or optically recording information on a recording medium. It belongs to

[0002]

2. Description of the Related Art Conventionally, as an optical pickup device as described above, as disclosed in Japanese Patent Application Laid-Open No. 4-89634, a semiconductor laser is provided as a light emitting means on a semiconductor substrate, and a semiconductor laser is provided in the semiconductor substrate. There is a type in which a phase film layer, a polarizing film layer, a diffraction grating, an optical waveguide, and a first light receiving unit are formed in a stacked manner, and further, a second light receiving unit is provided at an end of the optical waveguide.

In this optical pickup device, when a semiconductor laser irradiates the phase film layer with laser light at a predetermined depression angle, the laser light transmits through the phase film layer and is reflected on the surface of the polarizing film layer. The light is condensed and projected on the information surface of the optical disk. Then, the laser light diffracted and reflected on the information surface of the optical disk passes through the phase film layer and the polarizing film layer and enters the diffraction grating. Most of the reflected laser light is transmitted through this diffraction grating and travels downward from the substrate, and the rest is guided light propagated by the optical waveguide. The transmitted light is received by a first light receiving unit, and the first light receiving unit generates a tracking error signal, an RF signal, and the like. The guided light is received by a second light receiving portion formed at an end of the optical waveguide, and a focus color signal is generated by the second light receiving portion.

According to this optical pickup device, since the respective components are integrated in the manufacturing process of the semiconductor substrate, it is possible to reduce the size of the entire device and to improve the efficiency of effectively using the amount of light.

[0005]

However, in the conventional optical pickup device, an aluminum wiring layer for a light receiving portion or an amplifier portion for generating a predetermined signal from the light receiving portion is provided below the optical waveguide. An aluminum light-shielding layer for shielding light is provided, and guided light propagated by the optical waveguide is absorbed by the aluminum wiring layer or the aluminum light-shielding layer, so that the electromagnetic field distribution is asymmetric in the optical waveguide, and the propagation loss is reduced. There was a problem of increasing.

Accordingly, the present invention can solve such a problem, not only can achieve the integration by the manufacturing process of the semiconductor substrate, can reduce the size of the whole device, but also can improve the effective use efficiency of the light quantity. An object of the present invention is to provide an optical integrated device for an optical pickup device that can reduce propagation loss due to an optical waveguide.

[0007]

According to a first aspect of the present invention, there is provided an optical integrated device, comprising: an optical information recording medium on which recording information is recorded; An optical integrated device used for an optical pickup device for irradiating and receiving the reflected light reflected by the optical information recording carrier and laminated on a semiconductor substrate, wherein the optical waveguide propagates guided light; A light wave coupling unit that is stacked on a wave path, and that forms a coupler together with the optical waveguide to couple the guided light that propagates the reflected light to the optical waveguide and the transmitted light that passes through the optical waveguide; and And a propagation loss reducing film having a refractive index different from that of the optical waveguide and laminated on the optical waveguide outside the region where the optical waveguide is formed.

According to the optical integrated device of the first aspect, the light emitted from the light emitting means and emitted to the optical information recording carrier is reflected by the optical information recording carrier, and the reflected light is reflected by the optical integrated device. Incident on the light wave coupling means. Light wave coupling means,
A coupler is formed together with the optical waveguide, and the incident reflected light is input-coupled to the guided light that propagates through the optical waveguide and the transmitted light that passes through the optical waveguide. The transmitted light passes through the optical waveguide and is received by the light receiving means. Further, the guided light is propagated by the optical waveguide, but a propagation loss reducing film having a refractive index different from that of the optical waveguide is laminated on the optical waveguide outside the region where the coupler is formed. Has a tendency to be shifted toward the propagation loss reducing film side. Therefore, there is an aluminum light-shielding film or wiring layer on the lower layer side of the optical waveguide, and the amplitude distribution of the guided light tends to be shifted toward the aluminum light-shielding film or wiring layer due to the absorption of aluminum. Again, as a whole, a balance will be struck between these two biasing tendencies, and a Gaussian distribution will be maintained which will not be biased on either side. As a result, the propagation loss of the guided light during propagation of the optical waveguide is reduced, and the effective use efficiency of the light amount is improved.

According to a second aspect of the present invention, there is provided an optical integrated device according to the first aspect, wherein the propagation loss reducing film has a refractive index higher than a refractive index of the optical waveguide. It is characterized by having a rate.

According to the optical integrated device of the second aspect, the amplitude distribution of the guided light propagating in the optical waveguide tends to be shifted toward the medium having a high refractive index, and is laminated on the optical waveguide. It tends to be shifted toward the propagation loss reducing film having a higher refractive index than the refractive index. Therefore, there is an aluminum light-shielding film or wiring layer on the lower layer side of the optical waveguide, and the amplitude distribution of the guided light tends to be shifted toward the aluminum light-shielding film or wiring layer due to the absorption of aluminum. However, as a whole, there will be a balance between these two biasing tendencies, and a Gaussian distribution will be maintained which will not be biased on either side. As a result, the propagation loss of the guided light during propagation of the optical waveguide is reduced, and the effective use efficiency of the light amount is improved.

According to a third aspect of the present invention, there is provided an optical integrated device according to the first aspect, wherein the optical waveguide is stacked on a buffer layer.
The propagation loss reducing film has a lower refractive index than the waveguide and has the same refractive index as the buffer layer.

According to the optical integrated device of the third aspect, since the propagation loss reducing film and the buffer layer have the same refractive index, the optical waveguide sandwiched between the propagation loss reducing film and the buffer layer has a refractive index relationship. Becomes symmetrical with respect to the optical waveguide, the vibration of the amplitude distribution of the guided light in the layer thickness direction is suppressed, and even when the light shielding layer or the wiring layer made of aluminum is present in the lower layer, it is hardly affected by the absorption by aluminum. . As a result, the amplitude distribution of the guided light maintains the shape of a Gaussian distribution that is not deviated on either the propagation loss reducing film side or the buffer layer side, and the propagation loss of the guided light during propagation of the optical waveguide is reduced. Therefore, the effective use efficiency of the light amount is improved.

According to a fourth aspect of the present invention, there is provided an optical integrated device as set forth in any one of the first to third aspects, wherein the height of the light wave coupling means is set to one. And a height that saturates the input coupling efficiency and is set to a height corresponding to the thickness of the propagation loss reducing film that obtains a predetermined loss reducing ability.

According to the optical integrated device of the fourth aspect, the height of the light wave coupling means is such that the propagation loss reducing film has a predetermined loss reducing ability while having a height that saturates the input coupling efficiency. It has a height corresponding to the thickness. Therefore, the light wave coupling means and the propagation loss reducing film can be manufactured in the same process, and the manufacturing cost of the optical integrated device is reduced. Further, by manufacturing the light wave coupling means and the propagation loss reducing film in the same process, the input coupling efficiency is saturated, the propagation loss by the propagation loss reducing film is reduced, and the effective use amount of light is improved. .

According to a fifth aspect of the present invention, there is provided an optical integrated device according to any one of the first to fourth aspects, wherein the reflected light is a TM mode laser. It is characterized by being light.

According to the optical integrated device of the fifth aspect, since the reflected light from the optical information recording carrier is a TM mode laser beam, it is liable to receive a propagation loss in the optical waveguide. As a result, the propagation loss is reduced, and the effective use efficiency of the light amount is improved.

According to a sixth aspect of the present invention, there is provided an optical integrated device according to any one of the first to fifth aspects, wherein: A wiring layer or a light shielding layer made of aluminum is formed, and the propagation loss reducing film is provided at a position on the wiring layer or the light shielding layer.

According to the optical integrated device of the sixth aspect, the guided light propagating through the optical waveguide is affected by the absorption of the aluminum wiring layer or the light-shielding layer below the optical waveguide. Since the propagation loss reducing film is provided at a position on these wiring layers or light shielding layers, the above-mentioned effect is suppressed. As a result, the amplitude distribution of the guided light maintains the shape of a Gaussian distribution that is not offset to either the propagation loss reducing film side and the wiring layer or the light shielding layer side, and the propagation loss of the guided light during propagation of the optical waveguide is maintained. Is reduced, and the effective use efficiency of the light amount is improved.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

[First Embodiment] A first embodiment of the present invention will be described with reference to FIGS. First, an outline of the optical pickup device according to the present embodiment will be described.

(Overview of Optical Pickup Device) FIG. 1 is a perspective view showing a schematic configuration of an optical pickup device 1 according to one embodiment of the present invention. In FIG. 1, an optical pickup device 1 includes a semiconductor laser unit 2 provided with a semiconductor laser 12 as a light emitting unit, and an optical integrated device 3 laminated on a semiconductor substrate 20. The semiconductor substrate 20 and the submount 11 are bonded on the mount base 10, and the semiconductor laser 12 is mounted on the optical integrated device 3.
Is set to emit and emit laser light at a predetermined angle with respect to the upper surface of the laser beam.

As shown in FIG. 2 which is a cross-sectional view taken along the line XX 'shown in FIG.
Silicon (Si) on which the first and second light receiving portions 22 are formed
An aluminum light shielding film 23, an SOG (Spin On Glass) layer 24 provided for flattening a step caused by the aluminum light shielding film 23,
An SiO ₂ buffer layer 25 provided on the OG layer 24;
An optical waveguide 27 provided on the SiO ₂ buffer layer 25 for transmitting laser light and propagating it as guided light.
A grating 28 formed on the optical waveguide 27 and serving as a light wave coupling means for separating laser light into transmitted light and guided light, and a propagation loss reducing film 29 provided on the optical waveguide 27; It is configured.

In this embodiment, the grating 28 is
As an example, it was formed of TiO ₂ , the length L was 1.0 mm, and the thickness was 0.05 μm. In this embodiment, the grating 28 and the optical waveguide 27 constitute a grating coupler. The grating coupler reflects the TE-mode laser light emitted from the semiconductor laser 12 to the outside of the optical integrated device 3 and reflects most of the return light, which is reflected on the optical disk and then emitted as the TM-mode laser light, downward. , And a part of the light is propagated by the optical waveguide 27 as guided light. As described above, the grating coupler in the present embodiment has a configuration in which the return light from the optical disc is input-coupled to the optical waveguide 27, and therefore, the grating period is set to be equal to or less than the wavelength of the laser light to be used. Further, the grating 28 in the present embodiment is divided into right and left by a center line O along the propagation direction of the guided light by the optical waveguide 27 as shown in FIG. 1, and the pattern of the grating 28 is divided into right and left. It is set differently. The pattern of the grating 28 is curved on both the left and right, and the period of the grating differs depending on the location.
It is in a so-called chirping state.

The optical waveguide 27 has, for example, a thickness of 0.65
μm Corning 7059 with a refractive index of 1.53
It is. The upper layer side of the optical waveguide 27 is in contact with the air layer except for a region where the above-described grating 28 and a later-described propagation loss reducing film 29 are provided.
8 and the propagation loss reducing film 29 are also in contact with the air layer. The lower layer side of the optical waveguide 27 has a refractive index of 1.4.
3. SOG layer 24 having a thickness of 0.40 μm and a refractive index of 1.4
7. A buffer layer 26 made of a 0.70 μm thick SiO ₂ layer 25 is provided. Thus, the optical waveguide 2
7 is set so that the refractive index is higher than that of the surrounding layers, and is formed to have a predetermined thickness, thereby satisfying a predetermined waveguide condition. The light is propagated in the guided mode. Also,
Around the boundary between the second light receiving portion 22 and the aluminum light shielding film 23, as shown in FIG.
The buffer layer 26 has a slope that descends from the third side to the second light receiving unit 22 side, and the buffer layer 26 above the second light receiving unit 22 is formed thinner than other portions. With such a configuration,
Above the second light receiving unit 22, the optical waveguide 27 is in a radiation mode due to phase matching with the substrate, and emits guided light.

The aluminum light shielding layer 23 is formed on a thermal oxide film 23a provided on the semiconductor substrate 20, as shown in FIG. 3, and a protective film 23b is formed on the aluminum light shielding layer 23. Have been.

As shown in FIG. 2 and FIG. 3, the upper layer of the optical waveguide 27, which corresponds to the area where the aluminum light shielding layer 23 is provided, has a length W1 of 2.0 mm and a film thickness of 2.0 mm. Is provided with a propagation loss reducing film 29 made of TiO ₂ having a refractive index of 0.05 μm and a refractive index of 2.00. By providing such a propagation loss reducing film 29 on the propagation path of the optical waveguide 27, guided light having a Gaussian distribution and entering the optical waveguide 27 as shown in FIG. This distribution is maintained and the signal is propagated well.

FIG. 5 shows an example of the amplitude distribution of the electromagnetic field in the optical waveguide 27 of the TM mode laser light. FIG.
Propagation loss of the optical waveguide 27 when the length W1 of the propagation loss reducing film 29 is 2.0 mm, the thickness is 0.05 μm, the refractive index is 2.00, and the refractive index of the optical waveguide 27 is 1.53. FIG. 4 is a diagram illustrating an amplitude distribution of an electromagnetic field with respect to a propagation length of a region where a reduction film 29 is provided. Here, the propagation length of the optical waveguide 27 indicates the propagation length from the end a on the grating 28 side where the propagation loss reducing film 29 shown in FIG. 2 is provided to the end b on the opposite side. I have. In FIG. 5, the thickness of the layer on the semiconductor substrate 20 is represented by a positive value with the boundary position c between the aluminum light shielding layer 23 and the semiconductor substrate 20 shown in FIG. The layer thickness is the thickness up to the center of the optical waveguide 27. The position on the semiconductor substrate 20 side is represented by a negative value.

As can be seen from FIG. 5, the position (0.0 mm) of the end a of the propagation loss reducing film 29 is about 1.00.
The amplitude of the electromagnetic field, which has been described above, gradually decreases toward the end b, and decreases to about 0.25 at the position of 2.0 mm, but the distribution of the amplitude maintains the Gaussian Ann distribution. I have. In the present embodiment, the length W1 (b−
Since a) is set to 2.0 mm, it can be seen that the amplitude distribution state of the electromagnetic field is maintained in a Gaussian An distribution state until the guided light has finished propagating through the area of the length W1.

Next, the first light receiving section 21 is a four-divided light receiving section for generating an RF signal and a tracking error signal, and is provided immediately below the grating 28 or at a position slightly shifted from the position immediately below the grating 28. I have.

The second light receiving section 22 is a two-divided light receiving section for generating a focus error signal, is provided at a position distant from the grating 28, and has a sufficient optical path length.

(Comparison with Conventional Optical Integrated Device) Next, the optical integrated device of the present embodiment and a conventional optical integrated device will be described in comparison. FIG. 4 shows a configuration of a conventional optical integrated device. In the conventional optical integrated device, the propagation loss reducing film 29 is not provided on the optical waveguide 27 as shown in FIG. Therefore, the guided light that is incident in the state where the amplitude distribution of the electromagnetic field is Gaussian distribution is affected by the absorption of the aluminum light-shielding film 23 as the propagation proceeds, and the amplitude distribution of the electromagnetic field in the optical waveguide 27 is biased. And a propagation loss occurs.

On the other hand, the optical integrated device of this embodiment is
By providing the propagation loss reducing film 29 having a higher refractive index than the optical waveguide 27 on the optical waveguide 27, the amplitude distribution of the electromagnetic field tends to be shifted to the propagation loss reducing film 29 side. As a result, the amplitude distribution of the electromagnetic field in the optical waveguide 27 can maintain the same Gaussian distribution as that at the time of incidence. Therefore, good transmission can be performed in which the propagation loss of the guided light is prevented and the effective use efficiency of the light is improved.

(Method for Manufacturing Optical Integrated Device) Next, a method for manufacturing the optical integrated device 3 according to the present embodiment as described above will be described. In this embodiment, first, as shown in FIG. 2, a semiconductor substrate 20 and an aluminum light shielding film 23 are formed, and light receiving surfaces of a first light receiving portion 21 and a second light receiving portion 22 are formed on the same plane of the semiconductor substrate 20. The manufactured photodetector 4 is manufactured. Or OEI instead of photodetector 4
C (Opto-Electronic-Integrated Circuit (photodetector with amplifier)) may be used. Such a photodetector 4 or OEIC is generally a CD (Compac
t Disc), LVD (Laser Vision Disc), DVD, etc., it has the same configuration as that used in playback devices, so it can be manufactured only by changing the pattern, and no process change is required It is. Therefore, it can be manufactured using existing equipment.

Next, the above-described photodetector 4 or OEIC is provided with an aluminum wiring or an aluminum light-shielding film 23, and these are the first light-receiving section 21 and the second light-receiving section 2 respectively.
Since a step is formed on the light receiving surface of No. 2, a buffer layer (insulating film) 26 is applied (formed) as shown in FIG. This buffer layer 26
As an example, SOG layer 24 and sputtered SiO ₂ layer 2
5 multilayer structure. The step is reduced by the SOG layer 24, and the distance between the first light receiving section 21 and the optical waveguide 27 is adjusted by the SiO ₂ layer 25. This adjustment is performed by optimizing the distance between the first light receiving unit 21 and the optical waveguide 27. This is because the input coupling efficiency of the grating coupler changes depending on the buffer layer thickness.

Next, the buffer layer 26 above the second light receiving section 22 is removed and processed into a shape having a very gentle slope. As a processing method, wet etching or the like may be used. By forming such a slope, the second
The distance between the light receiving unit 22 and the optical waveguide 27 is
And the optical waveguide 27 can be shorter than the distance, and the mode of the guided light propagating through the optical waveguide 27 can be changed from the guided mode to the radiation mode so that the propagating light can be leaked to the second light receiving unit 22 satisfactorily. Can be done. In order to reduce the propagation loss due to the inclination, it is desirable that the angle of the inclination fluctuate as much as possible.

Next, an optical waveguide 27 is formed on the buffer layer 26 as described above, and a grating 28 having the function of an optical element is provided on the optical waveguide 27. Form a grating coupler.
At the same time, the propagation loss reducing film 29 is formed. The position of the grating 28 is directly above the first light receiving portion 21 or a position shifted in the direction opposite to the propagation direction, and the position of the propagation loss reducing film 29 is a region corresponding to the region where the aluminum light shielding layer 23 is formed. . Grating couplers are easier to manufacture with configurations that increase the amount of transmitted light compared to guided light,
This embodiment also has such a configuration. Therefore, by arranging the light receiving portion at a position where a sufficient amount of transmitted light can be efficiently received as compared with the guided light, an RF signal important for signal reproduction can be satisfactorily generated. Similarly, a tracking error signal can be satisfactorily generated. The grating 28 is formed by forming TiO ₂ on the optical waveguide 27 and then etching as shown in FIG. This is because in the present embodiment, the grating 28 and the propagation loss reducing film 29 are formed in the same step as the same layer. For this reason, the height of the grating 28 is considered in consideration of both the height at which the input coupling efficiency is saturated and the thickness of the propagation loss reducing film 29 capable of reliably preventing transmission loss by the propagation loss reducing film 29. Height. 9 and 10 show the relationship between the height (depth) of the grating 28 and the input coupling efficiency.

9 and 10, the horizontal axis represents the height (depth) (μm) of the grating 28 and the vertical axis represents the radiation loss coefficient (1 / m) corresponding to the input coupling efficiency. FIG. 9 is a diagram when the grating layer is formed of SiO ₂ , and FIG. 10 is a diagram when the grating layer is formed of TiO ₂ .

Generally, the relationship between the radiation loss coefficient α and the input coupling efficiency η is as follows: η = 1−exp (−2 · α · L), where L is the length of the grating (coupling length). In the design according to the present embodiment, the length L of the grating is unified to 1.0 mm. Therefore, as can be seen from FIG. 9, in the case of the grating formed of SiO ₂ ,
At a depth of 0.1 μm or more, and as can be seen from FIG.
For a grating formed of O ₂ , a depth of 0.05
At μm or more, it is considered that the input coupling efficiency is sufficiently saturated.

Therefore, the factor for determining the height of the grating 28 to a specific value that is considered to be sufficiently saturated with the input coupling depends on the thickness of the propagation loss reducing film 29 described later. Accordingly, a configuration with high efficiency and small propagation loss can be realized. The thickness of the propagation loss reducing film 29 will be described in detail together with examples described later.

On the other hand, since the conventional optical integrated device does not have the propagation loss reducing film 29, the grating 28 is formed by performing lift-off using a mask sputtering method as shown in FIG. ing. At this time, the height of the grating 28 is set to the minimum height that can saturate the input coupling efficiency because of the ease of manufacturing.

As described above, the optical integrated device according to the present embodiment can use a general photodetector or OEIC, so that it can be easily manufactured, and a conventional manufacturing device can be used. In addition, the manufacturing cost can be reduced. (Operation of Optical Pickup Device 1) Next, the operation of the optical pickup device 1 of the present embodiment as described above will be described with reference to FIGS.
This will be described with reference to FIGS. FIG. 8 is an overall configuration diagram of an optical system including a disk using the optical pickup device of the present embodiment.

First, the laser light emitted from the semiconductor laser 12 is emitted toward the grating 28 of the optical integrated device 3 at a predetermined angle. Laser light is grating 2
8 reflects only the TE mode laser light and irradiates it toward the reflection mirror 5. The TE mode laser light is reflected by the reflection mirror 5, collimated by the collimator lens 6, incident on the objective lens 7, and condensed on the information recording surface of the optical disk 8 by the objective lens 7.

Next, the return light reflected on the information recording surface of the optical disk 8 follows the reverse path and enters the grating 28 again. The return light is in the TM mode, and the grating coupler composed of the grating 28 and the optical waveguide 27 transmits the return light in the TM mode to the transmitted light on the first light receiving unit 21 side and the second light receiving unit 22 side. To the guided light. Most of the light becomes transmitted light, and is received by the first light receiving unit 21 provided immediately below the grating 28 or in the vicinity of the position immediately below the grating 28. In the present embodiment, the first light receiving unit 21 is a four-divided light receiving unit, and an RF signal is generated based on the output of the first light receiving unit 21. Further, a tracking error signal is generated from the output of the first light receiving unit 21 by a phase difference method or a push-pull method.

On the other hand, the guided light is propagated to the second light receiving portion 22 side by the optical waveguide 27, but propagates to the region on the optical waveguide 27 corresponding to the region where the aluminum light shielding layer 23 is provided. Since the loss reducing film 29 is provided, the waveguide light tends to be affected by the absorption of the aluminum light shielding layer 23,
The amplitude distribution of the electromagnetic field is balanced with the tendency to shift to the side of the propagation loss reducing film 29 having a high refractive index, and as a result, the guided light is transmitted while maintaining the initial Gaussian distribution state.

Next, the buffer layer 2 on the second light receiving section 22
6 is thinner than the other parts due to the inclination as described above, the guided light propagated in the waveguide mode by the optical waveguide 27 becomes the radiation mode on the second light receiving unit 22 and becomes the second mode. The light is radiated to the light receiving unit 22. At this time, this emitted light is condensed by the grating coupler,
The light is condensed toward the left and right light receiving portions of the second light receiving portion 22 which are divided into two. In the present embodiment, the focusing effect of the grating coupler is configured to be focused on the left and right light receiving units at different focal lengths. Therefore, the focal position of the laser light on the optical disc 8 varies due to the eccentricity of the optical disc 8 or the like. However, when the focal position with respect to the light receiving unit shifts, the area of the beam spot changes between the left and right light receiving units. The output change of the light receiving section due to the change of the area is calculated using an amplifier (not shown),
Generate a focus error signal. As described above, in the present embodiment, it is possible to generate a focus error signal by using a reliable beam size method (Fuco method). Further, in the present embodiment, since the propagation mode of the guided light in the optical waveguide 27 is changed to the radiation mode and detected by the second light receiving unit 22, the amount of light received by the second light receiving unit 22 is equal to the second light receiving unit. It can be adjusted by the size of 22 (coupling length) or the thickness of the buffer layer 26.

Although not shown, the optical pickup device of this embodiment is provided with a light receiving portion for monitoring a semiconductor laser, and the semiconductor laser is provided on the basis of a signal obtained at the light receiving portion for monitoring. Power can be monitored and the power is adjusted at any time. For example, light can be incident on the monitor light receiving unit by reflecting light from behind the chip with a reflecting mirror or the like.

(Embodiment 1) Next, a description will be given of an embodiment 1 in which the optimum film thickness of the propagation loss reducing film 29 is examined. In this embodiment, the refractive index of the propagation loss reducing film 29 is set to 2.00,
Was set higher than the refractive index of 1.53. The transmission length W1 in the optical waveguide 27 in the region where the propagation loss reducing film 29 was provided was 2.0 mm. Also in this embodiment, the transmission length in the optical waveguide 27 refers to the length from the position of the end a shown in FIG. 2 to the end b on the opposite side. Further, the optical waveguide 27 and the grating 28
In addition, nothing is provided on the propagation loss reducing film 29, and only the air layer exists. In the first embodiment,
The thickness of the propagation loss reducing film 29 is set to 0 μm, 0.05 μm,
With various changes of 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, and 0.5 μm, the amplitude distribution of the electromagnetic field at the end b position shown in FIG. 2 was calculated. The results of Example 1 are shown in FIGS. In FIGS. 11 and 12, the thickness of the layer on the horizontal axis is measured on the optical waveguide 27 side with the boundary position c between the aluminum light shielding layer 23 and the semiconductor substrate 20 as the origin, as in the case of FIG. Refers to the thickness of the layer. Also, in FIGS. 11B to 11D and FIG. 12, for easy understanding, the distribution when the propagation loss reducing film 29 is not provided is indicated by a dotted line, and the propagation loss reducing film 2
9 is shown by a solid line.

FIG. 11A shows the case where the film thickness of the propagation loss reducing film 29 is 0 μm, that is, the propagation loss reducing film 29.
Is not provided. In this case, FIG.
As shown in (A), the peak of the amplitude distribution in the optical waveguide 27 is not at the center of the optical waveguide 27, but is in the buffer layer 26.
You can see that it is leaning to the side. This is because the guided light is
It is considered that this was due to the influence of the absorption of the aluminum light shielding layer 23. As described above, it was confirmed that the propagation loss could not be prevented when the propagation loss reducing film 29 was not provided.

FIG. 11B shows a case where the thickness of the propagation loss reducing film 29 is 0.05 μm. As can be seen from FIG. 11B, in this case, the peak of the amplitude distribution is at the center of the optical waveguide 27, and the Gaussian An distribution is maintained. Therefore, in this case, it was confirmed that propagation loss can be favorably prevented.

FIG. 11C shows the case where the thickness of the propagation loss reducing film 29 is 0.1 μm. As can be seen from FIG. 11C, in this case, the peak of the amplitude distribution is not offset toward the buffer layer 26, and it can be confirmed that the influence of the absorption of the aluminum light shielding film 23 is prevented. However, the peak of the amplitude distribution is closer to the propagation loss reducing film 29 side than the center of the optical waveguide 27, and the state of the Gaussian distribution is slightly distorted. However, the peak value itself is shown in FIG.
1 (B), and in this case, the propagation loss can be suppressed to a practically acceptable level.

FIG. 11D shows the case where the thickness of the propagation loss reducing film 29 is 0.2 μm. As can be seen from FIG. 11D, also in this case, the peak of the amplitude distribution is not offset toward the buffer layer 26, and it can be confirmed that the influence of the absorption of the aluminum light shielding film 23 is prevented. However, the peak of the amplitude distribution is outside the optical waveguide 27,
It can be confirmed that it is largely offset to the propagation loss reducing film 29 side. Therefore, in this case, a propagation loss occurs.

FIG. 12A shows the case where the thickness of the propagation loss reducing film 29 is 0.3 μm. As can be seen from FIG. 12A, in this case, two peaks of the amplitude distribution appear, one on the side of the propagation loss reducing film 29 outside the optical waveguide 27 and the other on the center of the optical waveguide 27. It is located in. However, the peak located at the center of the optical waveguide 27 has a smaller peak value than that in the case of FIG. 11B, which causes a slight propagation loss.

FIG. 12B shows the case where the thickness of the propagation loss reducing film 29 is 0.4 μm. As can be seen from FIG. 12B, in this case, a very large peak appears at the boundary between the optical waveguide 27 and the propagation loss reducing film 29. Since the deviation of the amplitude distribution is very large on the side of the propagation loss reducing film 29, the propagation loss is also large.

FIG. 12C shows the case where the thickness of the propagation loss reducing film 29 is 0.5 μm. As can be seen from FIG. 12C, in this case, two peaks of the amplitude distribution appear, one on the side of the propagation loss reducing film 29 outside the optical waveguide 27, and the other on the center of the optical waveguide 27. It is located in. However, the peak of the amplitude inside the optical waveguide 27 is shown in FIG.
Compared with the case of 2 (A), the transmission loss is reduced to the same extent as that of the conventional device not having the propagation loss reduction film 29, and it can be seen that the transmission loss occurs.

From the above results, under the conditions of this embodiment, the thickness of the propagation loss reducing film 29 is set to 0.05 μm
It turns out that it is optimal to set Further, this layer thickness is a thickness sufficiently in the saturation region of the input coupling efficiency.

[Second Embodiment] Next, a second embodiment of the present invention will be described with reference to FIGS. In addition, the overlapping description about the common part with 1st Embodiment is abbreviate | omitted.

In the first embodiment, the case where the refractive index of the propagation loss reducing film 29 is higher than the refractive index of the optical waveguide 27 has been described. However, the present invention is not limited to such a configuration. Absent. In the present embodiment, the refractive index of the propagation loss reducing film 29 is set lower than the refractive index of the optical waveguide 27, and is set to be equal to the refractive index of the buffer layer 26. The conditions of the other components are the same as in the first embodiment.

Second Embodiment Next, a description will be given of a second embodiment in which the optimum thickness of the propagation loss reducing film 29 is examined. In this embodiment, the refractive index of the propagation loss reducing film 29 is set to 1.47 which is equal to the refractive index of the buffer layer 26, and the refractive index of the optical waveguide 27 is set to 1.5.
It was set lower than 3. The transmission length W1 in the optical waveguide 27 in the region where the propagation loss reducing film 29 was provided was 2.0 mm. Also in this embodiment, the transmission length in the optical waveguide 27 refers to the length from the position of the end a shown in FIG. 2 to the end b on the opposite side. Further, nothing was provided on the optical waveguide 27, the grating 28, and the propagation loss reducing film 29, and only the air layer was present. In the second embodiment, the propagation loss reducing film 29
Of 0.1 μm, 0.2 μm, 0.3 μm, 0.
With various changes of 4 μm and 0.5 μm, the amplitude distribution of the electromagnetic field at the position of the end b shown in FIG. 2 was calculated. The results of Example 2 are shown in FIGS. In FIGS. 13 and 14, the thickness of the layer on the horizontal axis is the same as in the first embodiment.
The thickness of the layer measured on the side of the optical waveguide 27 with the boundary position c with respect to the origin as the origin. Further, FIGS. 13B to 13D
14 and FIG. 14, for easy understanding, the distribution when the propagation loss reducing film 29 is not provided is shown by a dotted line, and the distribution when the propagation loss reducing film 29 is provided is shown by a solid line.

As can be seen from FIGS. 13A to 14, the peak of the amplitude distribution in the optical waveguide 27 is obtained in any case where the thickness of the propagation loss reducing film 29 is 0.1 μm to 0.5 μm. Is located at the center of the optical waveguide 27, and the peak value itself is higher than before.

As described above, even if the propagation loss reducing film 29 has a predetermined layer thickness even if the refractive index is lower than that of the optical waveguide 27, the effect of stabilizing the amplitude distribution of the electromagnetic field is as follows.
It can be seen that it can be obtained in any case.

Unlike the prior art, there is no propagation loss reducing film 29,
When the guided light is confined in the optical waveguide 27 by the configuration of the air-optical waveguide-buffer layer, the amplitude distribution of the electromagnetic field of the guided light is reduced by the thickness distribution of the optical waveguide because the refractive index relationship is asymmetric with respect to the optical waveguide. It is easy to vibrate in the vertical direction. As a result, the guided light propagated by the optical waveguide is easily affected by the aluminum light shielding layer located below the optical waveguide.

On the other hand, in the case of the present embodiment, since the propagation loss reducing film 29 having the same refractive index as the buffer layer 26 is provided, the relationship between the refractive indices is symmetric with respect to the optical waveguide.
Vibration of the amplitude distribution of the guided light can be suppressed in the thickness direction of the optical waveguide. As a result, it is hardly affected by the aluminum light shielding layer 23 located below the optical waveguide 27,
It is considered that the amplitude distribution of the electromagnetic field was stabilized as described above.

The result of the above calculation shows that the propagation loss reducing film 2
When the film thickness of No. 9 was 0.3 μm or more, it was found that the shape and peak value of the amplitude distribution in the optical waveguide 27 did not change, and the propagation loss reducing ability was saturated.

Further, as in this embodiment, the refractive index of the propagation loss reducing film 29 is equal to the refractive index of the buffer layer 26.
If it is set to 47, the refractive index of the grating 28 also becomes as low as 1.47, so that the input coupling efficiency tends to decrease. Therefore, in this embodiment, it is desirable to set the height of the grating 28 higher than in the first embodiment in order to improve the input coupling efficiency.

However, since the lower the grating 28 is, the easier it is to manufacture, considering the above items, in the case of the present embodiment, the thickness of the propagation loss reducing film 29 is set to 0.3 μm
It turns out that it is optimal to set

In the first and second embodiments, since the grating 28 is provided in a region corresponding to the region where the first light receiving section 21 is provided, the propagation loss is located at this position. It goes without saying that the reduction film 29 cannot be provided, but also in a region corresponding to the region where the second light receiving section 22 is provided, the radiation mode is affected, so that the propagation loss reduction film 29 cannot be provided.

In each of the embodiments described above, the case where the TM mode laser light is used as the guided light has been described. However, the TE mode laser light can be used. However, since the TE mode laser light has such a property that a propagation loss does not occur much, if the present invention is applied to the case where the TM mode laser light is used as the guided light, the light use efficiency can be improved. it can.

As described above, the present invention has been described based on the embodiments. However, the present invention is not limited to the above embodiments, and various improvements and modifications can be made without departing from the spirit of the present invention. Can easily be inferred.

[0069]

According to the optical integrated device of the first aspect,
An optical waveguide that propagates the guided light, and a coupler that is stacked on the optical waveguide and that is coupled to the guided light that propagates the reflected light to the optical waveguide and the transmitted light that is transmitted through the optical waveguide; Light wave coupling means to be formed, and a propagation loss reducing film laminated on the optical waveguide outside the region where the coupler is formed and having a different refractive index from the optical waveguide. Gaussian distribution that does not shift in the wave path can be maintained,
It is possible to reduce the propagation loss of the guided light during the propagation of the optical waveguide and improve the effective use amount of light.

According to the optical integrated device of the second aspect, since the propagation loss reducing film has a refractive index higher than the refractive index of the optical waveguide, the light shielding film or the wiring made of aluminum is formed on the lower layer side of the optical waveguide. Even when a layer is present, it is possible to prevent the amplitude distribution of the guided light propagating through the optical waveguide from being biased toward the aluminum light-shielding film or the wiring layer side, thereby reducing the propagation loss of the guided light during the propagation of the optical waveguide. Thus, the effective use efficiency of the light amount can be improved.

According to the optical integrated device of the third aspect, since the propagation loss reducing film has a refractive index lower than the refractive index of the optical waveguide and equal to the buffer layer, the lower layer of the optical waveguide is made of aluminum. Even when a light-shielding layer or a wiring layer is present, it prevents the amplitude distribution of the guided light propagating through the optical waveguide from being shifted, reduces the propagation loss of the guided light during the propagation of the optical waveguide, and improves the effective use amount of light. Can be done.

According to the optical integrated device of the fourth aspect, the height of the light wave coupling means is a height that saturates the input coupling efficiency, and the height of the propagation loss reducing film that obtains a predetermined loss reducing ability. Since the height is set to be equal to the film thickness, the light wave coupling means and the propagation loss reducing film can be manufactured in the same step, and the manufacturing cost of the optical integrated device can be reduced. Further, by manufacturing the above-described light wave coupling means and the propagation loss reducing film in the same process, the input coupling efficiency is saturated, the propagation loss by the propagation loss reducing film is reduced, and the effective use amount of light is improved. be able to.

According to the optical integrated device of the fifth aspect, since the reflected light is a TM mode laser light, it is liable to receive a propagation loss in the optical waveguide, but the propagation loss is reduced by the propagation loss reducing film as described above. In addition, the effective use efficiency of the light amount can be improved.

According to the optical integrated device of the sixth aspect, a wiring layer or a light shielding layer made of aluminum is formed below the optical waveguide, and a propagation loss reducing film is formed at a position on the wiring layer or the light shielding layer. With this arrangement, the amplitude distribution of the guided light can be maintained in the form of a Gaussian distribution that is not offset to either the propagation loss reducing film side and the wiring layer or the light shielding layer side. It is possible to reduce the propagation loss of the wave light and improve the effective use efficiency of the light amount.

[Brief description of the drawings]

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

FIG. 2 is a sectional view showing a section of the optical integrated device taken along line XX ′ of FIG. 1;

FIG. 3 is an enlarged sectional view of a portion provided with a propagation loss preventing film in the optical integrated device of FIG. 2;

FIG. 4 is a cross-sectional view of a portion corresponding to FIG. 2 in a conventional example compared with the present invention.

5 is a diagram showing an example of a change in intensity of an electromagnetic field distribution with respect to a propagation length of a TM mode laser beam in an optical waveguide in a region provided with a propagation loss prevention film having a length W1 shown in FIG.

FIG. 6 is a diagram for explaining a method of manufacturing a grating in the optical integrated device of FIG. 2;

FIG. 7 is a diagram for explaining a method of manufacturing a grating in a conventional example compared with the present invention.

FIG. 8 is an overall configuration diagram of an optical system including a disk using the optical pickup device of the first embodiment.

FIG. 9 is a diagram showing the relationship between the grating depth and the input coupling efficiency when the grating is formed of SiO 2 in the optical integrated device of the first embodiment.

FIG. 10 is a diagram showing the relationship between the grating depth and the input coupling efficiency when the grating is formed of TiO2 in the optical integrated device of the first embodiment.

FIG. 11 is a diagram illustrating the electromagnetic wave at the position of the end b shown in FIG. 2 when the cladding layer is an air layer and the thickness of the propagation loss reducing film of the optical integrated device is changed in Example 1 of the first embodiment. It is a figure which shows the measurement result of the amplitude distribution of a field, (A) is 0 micrometer in film thickness, (B) is 0.05 micrometer in film thickness, (C) is 0.1 micrometer in film thickness, (D) is film thickness. FIG. 9 is a diagram showing respective results when is set to 0.2 μm.

FIG. 12 is a diagram illustrating the electromagnetic wave at the position of the end b shown in FIG. 2 when the cladding layer is an air layer and the thickness of the propagation loss reducing film of the optical integrated device is changed in Example 1 of the first embodiment. It is a figure which shows the measurement result of the amplitude distribution of a field, (A) when the film thickness is 0.3 micrometer, (B) when the film thickness is 0.4 micrometer, (C) when the film thickness is 0.5 micrometer, respectively. It is a figure which shows the result of.

FIG. 13 is a graph showing a case where the thickness of the propagation loss reducing film of the optical integrated device is changed in Example 2 of the second embodiment.
5A and 5B are diagrams showing measurement results of the amplitude distribution of the electromagnetic field at the end b position shown in FIG. 5A, wherein FIG. 5A shows a film thickness of 0.1 μm, FIG. 5B shows a film thickness of 0.2 μm, and FIG. 0.3 μm, (D)
FIG. 4 is a diagram showing respective results when the film thickness is 0.4 μm.

FIG. 14 is a graph showing a case where the thickness of the propagation loss reducing film of the optical integrated device is changed in Example 2 of the second embodiment.
FIG. 9 is a diagram showing a measurement result of the amplitude distribution of the electromagnetic field at the position of the end b shown in FIG.

[Explanation of symbols]

 Reference Signs List 1 optical pickup device 2 semiconductor laser unit 3 optical integrated device 4 photodetector 8 optical disk 12 semiconductor laser 20 semiconductor substrate 21 first light receiving unit 22 second light receiving unit 23 aluminum light shielding layer 26 buffer layer 27 optical waveguide 28 grating 29 reduction of propagation loss film

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 2H037 AA04 BA02 BA11 BA25 CA33 CA34 2H047 KA04 KB06 KB08 LA03 LA11 MA01 MA07 PA02 PA04 PA24 PA30 QA02 RA04 TA05 TA22 TA31 TA43 TA44 5D119 AA40 AA43 CA10 FA05 FA17 JA36 JB03

Claims (6)

[Claims] 1. An optical pickup device which irradiates light emitted and emitted from a light emitting means onto an optical information recording carrier on which recording information is recorded and receives light reflected by the optical information recording carrier. An optical integrated device laminated and formed on a semiconductor substrate, comprising: an optical waveguide that propagates guided light; a waveguide light that is laminated on the optical waveguide and propagates the reflected light to the optical waveguide; and the optical waveguide. Light wave coupling means for forming a coupler for input coupling with the transmitted light transmitting the optical waveguide together with the optical waveguide; and a propagation layer having a different refractive index from the optical waveguide laminated on the optical waveguide outside a region where the coupler is formed. An optical integrated device comprising: a loss reduction film. 2. The optical integrated device according to claim 1, wherein the propagation loss reducing film has a higher refractive index than a refractive index of the optical waveguide. 3. The optical waveguide according to claim 1, wherein the optical waveguide is laminated on a buffer layer, and the propagation loss reducing film has a refractive index lower than that of the waveguide and equal to the refractive index of the buffer layer. The optical integrated device according to claim 1. 4. The height of the light wave coupling means is set to a height that saturates the input coupling efficiency, and is set to a height corresponding to the thickness of the propagation loss reducing film that obtains a predetermined loss reducing ability. The optical integrated device according to any one of claims 1 to 3, wherein: 5. The optical integrated device according to claim 1, wherein the reflected light is a TM mode laser light. 6. A wiring layer or a light-shielding layer made of aluminum is formed below the optical waveguide, and the propagation loss reducing film is provided at a position on the wiring layer or the light-shielding layer. The optical integrated device according to any one of claims 1 to 5, wherein: