JP7025629B2 - Optical devices and optical semiconductor devices - Google Patents

Description

The present invention relates to an optical device and an optical semiconductor device.

In recent years, silicon photonics has been widely developed as an integrated optical device technology that realizes a compact and large-capacity optical transceiver. Here, since silicon is an indirect transition type semiconductor material with low luminous efficiency, it is necessary to separately prepare an optical gain medium. As the gain medium, an optical semiconductor element of a III-V compound semiconductor such as an InP-based semiconductor is used, and the optical device is configured by mounting it near the end face of an optical waveguide of a thin silicon wire and directly butt-coupling it. ..

Japanese Unexamined Patent Publication No. 5-297244 Japanese Unexamined Patent Publication No. 2008-241732 Japanese Unexamined Patent Publication No. 2002-328245 Japanese Unexamined Patent Publication No. 8-241732

T. Matsumoto et al., "In-line Optical Amplification for Si Waveguides on 1 × 8 Splitter and Selector by Flip-Chip Bonded InP-SOAs", The Optical Networking and Communication Conference & Exhibition (OFC), Lecture No. Th1C. 1, 2016

In order to obtain highly efficient optical coupling between optical waveguides that are butt-coupled, it is important to perform high-precision alignment between the optical waveguides and suppress excessive loss due to optical axis misalignment. It is necessary to avoid contacting the optical waveguides with each other because it causes damage to the optical waveguides, and therefore it is necessary to provide a gap between the optical waveguides. However, when light propagates in a free space such as the gap, excessive loss due to radiation occurs, so it is important to narrow the gap as much as possible. In particular, in a structure in which an optical waveguide tilted from the vertical to the optical coupling surface is opposed to suppress reflection from the end face, the positional deviation in the gap direction is the positional deviation in the direction perpendicular to the optical axis between the optical waveguides. Therefore, it is necessary to align the gap direction with high accuracy.

In order to improve the quality of the optical device, it is necessary to accurately grasp the above gap in the optical device, but it is difficult to observe and accurately grasp the extremely narrow gap of the completed optical device, and it is ignored. There is a problem that a manufacturing error that cannot be done is included.

An object of the present invention is to accurately grasp the gap even when the gap between the optical waveguides is narrow.

In one embodiment, the optical device comprises a semiconductor substrate, a first optical waveguide formed on the semiconductor substrate, and a second optical waveguide mounted on the semiconductor substrate facing the first optical waveguide. The first plane, which includes an optical semiconductor element including, and the first end surface of the first optical waveguide facing the second optical waveguide is a step recessed from the first plane portion and the first plane portion. It has a second plane portion parallel to the portion and a third plane portion parallel to the first plane portion, which is a step recessed from the first plane portion, and the first plane portion and the second plane portion. In the first gap provided between the portion of the second end surface of the optical waveguide facing the first optical waveguide and the portion facing the first plane portion, the first optical waveguide and the second optical waveguide Is optical connected .

In one embodiment, the optical semiconductor device comprises a semiconductor substrate, a first optical waveguide formed on the semiconductor substrate, a reflection mirror connected to the first optical waveguide, and light passing through the first optical waveguide. The first optical waveguide includes a variable wavelength filter capable of changing the wavelength of the optical waveguide, and an optical semiconductor element including a second optical waveguide mounted on the semiconductor substrate facing the first optical waveguide. The first end surface facing the second optical waveguide is from the first plane portion, the second plane portion parallel to the first plane portion, which is a step recessed from the first plane portion, and the first plane portion. Of the second end surface of the second optical waveguide facing the first optical waveguide, which has a third plane portion parallel to the first plane portion, which is a recessed step. The first optical waveguide and the second optical waveguide are optically connected in a first gap provided between the first plane portion and the opposite portion .

On one side, even if the gap between the optical waveguides is narrow, the gap can be accurately grasped.

It is a schematic diagram which shows the schematic structure of the optical device by 1st Embodiment. It is a schematic diagram for demonstrating the method of calculating a gap in the optical device by 1st Embodiment. It is a schematic diagram for demonstrating the method of calculating the rotation amount of an optical semiconductor element together with a gap in the optical device by 1st Embodiment. It is a schematic diagram which shows the manufacturing method of the optical device by 1st Embodiment in the order of a process. Continuing from FIG. 4, it is a schematic diagram which shows the manufacturing method of the optical device by 1st Embodiment in the order of a process. Continuing from FIG. 5, it is a schematic diagram which shows the manufacturing method of the optical device by 1st Embodiment in the order of a process. It is a schematic diagram which shows the schematic structure of the optical device by the modification 1 of 1st Embodiment. It is a schematic diagram which shows the schematic structure of the optical device by the modification 2 of 1st Embodiment. It is a schematic plan view which shows typically the structure of the tunable laser by 2nd Embodiment. It is the schematic sectional drawing explaining the manufacturing process of the SOA of the tunable laser by 2nd Embodiment. Following FIG. 10, it is a schematic cross-sectional view illustrating the manufacturing process of the SOA of the tunable laser according to the second embodiment. Following FIG. 11, it is a schematic cross-sectional view illustrating the manufacturing process of the SOA of the tunable laser according to the second embodiment. Following FIG. 12, it is a schematic cross-sectional view illustrating the manufacturing process of the SOA of the tunable laser according to the second embodiment. Following FIG. 13, it is a schematic cross-sectional view illustrating the manufacturing process of the SOA of the tunable laser according to the second embodiment. Following FIG. 14, it is a schematic cross-sectional view illustrating the manufacturing process of the SOA of the tunable laser according to the second embodiment. Following FIG. 15, it is a schematic cross-sectional view illustrating the manufacturing process of the SOA of the tunable laser according to the second embodiment. Following FIG. 16, it is a schematic cross-sectional view illustrating the manufacturing process of the SOA of the tunable laser according to the second embodiment. FIG. 3 is a schematic plan view schematically showing an optical transceiver according to a third embodiment.

[First Embodiment]
Hereinafter, the optical device according to the first embodiment will be described in detail with reference to the drawings.
1A and 1B are schematic views showing a schematic configuration of an optical device according to the present embodiment, in which FIG. 1A is a plan view and FIG. 1B is a side view.

(Outline configuration of optical device)
This optical device includes a silicon photonics substrate 1 and an optical semiconductor element 2.
The silicon photonics substrate 1 includes a Si substrate 11, a first optical waveguide 12 formed on the Si substrate 11, and an electrode 13 formed on the Si substrate 11. The first optical waveguide 12 is formed on the lower clad layer 21 made of, for example, a silicon oxide, the core layer 22 made of silicon wires formed on the lower clad layer 21, and the lower clad layer 21 so as to cover the core layer 22. It has a formed upper clad layer 23 made of, for example, a silicon oxide.

The optical semiconductor device 2 is, for example, a laser device (InP laser) configured by using a III-V compound semiconductor, for example, InP, and has a second optical waveguide 14 having a core layer 24.
The optical semiconductor element 2 is arranged on the Si substrate 11 via the conductive adhesive material 15 provided on the electrode 13, and is electrically connected to the electrode 13.

In the first optical waveguide 12, a protrusion 12a is formed on the first end surface 12A, and a first portion 12b and a second portion 12c are formed on both sides of the protrusion 12a. The first portion 12b is located on one end side of the protrusion 12a, and the second portion 12c is located on the other end side of the protrusion 12a. (Difference in height). Here, the width of the second site 12c is larger than the width of the first site 12b. The core layer 22 of the first optical waveguide 12 is bent and extends in the middle on the lower clad layer, and the end portion 22b of the bent portion 22a is located in the vicinity of the protrusion 12a. The bent portion 22a extends from the vertical direction (for example, tilted by about 15 ° from the vertical direction) with respect to the first end surface 12A in order to suppress light reflection from the first end surface 12A.

The core layer 24 of the second optical waveguide 14 extends vertically with respect to the second end surface 14A (for example, at an angle of about 7 ° from the vertical) in order to suppress light reflection from the second end surface 14A. , The end portion 24a of the core layer 24 is located on the second end surface 14A. In the first optical waveguide 12 and the second optical waveguide 14, the first end surface 12A and the second end surface 14A are arranged to face each other so that the end portion 22b and the end portion 24a are butted against each other, and are optically coupled. There is. A gap G is formed between the first end surface 12A and the second end surface 14A by a predetermined distance. Due to such an arrangement of the optical semiconductor element 2, a phase larger than the gap G between the first portion 12b and the second portion 12c and the second end surface 14A at the facing portion between the first end surface 12A and the second end surface 14A. Different intervals (here, the latter interval is larger than the former interval) are formed. The region between the first portion 12b and the second end surface 14A is the first observation region 16 (shown in the broken line circle in FIG. 1), and the region between the second portion 12c and the second end surface 14A is the second. The observation area 17 (shown in the broken line circle in FIG. 1). In the present embodiment, for example, the gap G is set to about 1.5 μm, the first observation region 16 is set to about 3 μm, and the second observation region 17 is set to about 5 μm.

Hereinafter, in the optical device according to the present embodiment, a method of calculating and accurately grasping the gap G will be described.
FIG. 2 is a schematic diagram for explaining a method of calculating a gap in the optical device according to the present embodiment.

First, a method of calculating the gap G interval with the first observation region 16 as the measurement site will be described. In the silicon photonics substrate 1, the thickness of the first optical waveguide 12 is d _SiPh , the observation angle is θ, and in the first observation region 16, the observation angle θ is the upper end of the first end surface 12A of the first optical waveguide 12 and the optical semiconductor element. Let d (θ) be the measured value when the distance from the lower end of the second end surface 14A of 2 is measured. The distance between the first portion 12b and the second end surface 14A in the first observation region 16 is d ₁ , the distance between the Si substrate 11 and the optical semiconductor element 2, that is, the thickness of the electrode 13 and the conductive adhesive material 15 is d _metal . .. By observing the first observation region 16 at two observation angles θ ₁ and θ ₂ , the following relational expression can be obtained.

d ₁ = d (θ ₁ ) / cos θ ₁ + (d _SiPh −d _metal ) tan θ ₁
= D (θ ₂ ) / cos θ ₂ + (d _SiPh −d _metal ) tan θ ₂・ ・ ・ (1)
By deleting d _SiPh and d _metal from Eq. (1) and rearranging them, the following relational expression can be obtained.
d ₁ = (d (θ ₁ ) / cos θ ₁ − tan θ ₁ / tan θ ₂ ) × (d (θ ₂ ) / cos θ ₂ )) / (1-tan θ ₁ / tan θ ₂ )) ・ ・ ・ (2)

From the equation (2), the interval d ₁ in the first observation region 16 can be calculated by measuring d (θ ₁ ) and d (θ ₂ ) when the set values θ ₁ and θ ₂ are set.
Since the difference between the gap G and the gap d ₁ in the first observation region 16 is known information determined when the optical device is manufactured, the calculated value of the gap d ₁ in the first observation region 16 can be used. The interval of the gap G can be grasped.

As described above, even if only the first observation region 16 is used as the measurement site, the gap G can be grasped. However, in this case, an error may be included in the set value of the observation angle θ due to an error caused by the observation device, an inclination of the optical device to be measured, or the like. In the present embodiment, in order to eliminate this error, the optical device is provided with a second observation region 17 whose interval is intentionally different from that of the first observation region 16.

The distance between the second portion 12c and the second end surface 14A in the second observation region 17 is d ₂ (= d ₁ + Δd, Δd is the difference value of d ₂ from d ₁ ), and the first and the first are at the same observation angle θ1. When the second observation areas 16 and 17 are measured, the following relational expression is obtained. In the second observation region 17, the measured value when the distance between the upper end portion of the first end surface 12A of the first optical waveguide 12 and the lower end portion of the second end surface 14A of the optical semiconductor element 2 is measured at the observation angle θ is d'. Let it be (θ).

d ₁ = d (θ ₁ ) / cos θ ₁ + (d _SiPh −d _metal ) tan θ ₁ ··· (3)
d ₂ = d ₁ + Δd
= D'(θ ₁ ) / cosθ ₁ + (d _SiPh −d _metal ) tan θ ₁ ... (4)

By deleting d ₁ , d _SiPh , and d _metal from the equations (3) and (4) and rearranging them, the following relational equations can be obtained.
cos θ ₁ = (d'(θ ₁ ) −d (θ ₁ )) / Δd ・ ・ ・ (5)

From the equation (5), the observation angle θ ₁ can be grasped from the known information Δd and the measured values d (θ ₁ ) and d'(θ ₁ ). Similarly, the observation angle θ ₂ can be grasped by measuring the first and _second observation regions 16 and 17. By substituting the obtained measured values (θ ₁ , θ ₂ , d (θ ₁ ), d (θ ₂ )) into Eq. (2), the interval d ₁ (and the second observation region) in the first observation region 16 The interval d ₂ ) in 17 is obtained, and the interval of the gap G can be grasped.

In the optical device according to the present embodiment, the error of the observation angle is removed from the calculated value, and the gap G can be accurately grasped. Further, even when the gap G is narrow, it is possible to measure the intervals in the first and second observation areas 16 and 17 by providing the first and second observation areas 16 and 17 having a wider interval than the gap G. There is, and the gap G can be accurately grasped from the measured value.

In the optical device according to the present embodiment, the optical semiconductor element 2 may be slightly rotated and arranged in the surface of the Si substrate 1 at the time of its manufacture. If the amount of rotation of the optical semiconductor element 2 is within a predetermined allowable range, there is no problem as a product. In order to judge the approval or disapproval of the product, it is necessary to accurately grasp the rotation amount of the optical semiconductor element 2 as well as the interval of the gap G.

FIG. 3 is a schematic diagram for explaining a method of calculating the rotation amount of the optical semiconductor element together with the gap in the optical device according to the present embodiment.
As shown in FIG. 3A, consider a case where the optical semiconductor device 2 has no rotational deviation (the first end surface 12A and the second end surface 12A are parallel to each other). In this case, since the design value of the interval of the first observation region 16 is 3 μm and the design value of the interval of the second observation region 17 is 5 μm, the difference value between the two (the difference value that should be in the design) is 2 μm. Is. The difference value obtained from the value obtained by the above method according to the present embodiment is also 2 μm.

On the other hand, as shown in FIG. 3B, consider a case where the optical semiconductor element 2 has a rotational deviation (the first end surface 12A and the second end surface 12A are not parallel). In this case, the intervals between the first and second observation regions 16 and 17 deviate from the design difference value. Therefore, in the present embodiment, the intervals between the first and second observation regions 16 and 17 are accurately grasped by the above method according to the present embodiment, and the difference value between these and the desired difference in design (5 μm-in the present embodiment). 3 μm = 2 μm) are compared. As a result, the amount of rotation of the optical semiconductor element 2 can be accurately grasped.

(Manufacturing method of optical device)
Hereinafter, a method for manufacturing an optical device according to the present embodiment will be described. 4 to 6 are schematic views showing the manufacturing method of the optical device according to the present embodiment in the order of processes, where FIG. 4A is a plan view and FIG. 6B is a side view.

First, as shown in FIG. 4, the first optical waveguide 12 is formed.
Specifically, first, an SOI (Silicon On Insulator) substrate having an SOI layer formed on the Si substrate 1 via a BOX layer is prepared. The thickness of the BOX layer is about 3 μm, and the thickness of the SOI layer is about 0.22 μm. The SOI layer is processed into a fine line shape by using EB exposure, stepper exposure, or the like. As a result, the core layer 22 extending on the BOX layer and having the bent portion 22a is formed.

Next, a silicon insulating layer, here a TEOS layer, is formed on the BOX layer to a thickness of about 1.5 μm so as to cover the core layer 22. At this time, various parts such as a spot size converter, an impurity doping region, an electrode, and a heater are formed as needed.
Next, the BOX layer and the TEOS layer are processed by photolithography and etching. As a result, on the Si substrate 1, the lower clad layer 21 made of a BOX layer, the core layer 22 on the lower clad layer 21, and the upper part made of a TEOS layer formed on the lower clad layer 21 so as to cover the core layer 22. The first optical waveguide 12 having the clad layer 23 is formed. In the first optical waveguide 12, a protrusion 12a is formed on the first end surface 12A, and the first part 12b and the second part 12c are present on both sides of the protrusion 12a, and the first part 12b and the second part 12c are present. It is said that the width is different. Here, the width of the first portion 12b is about 1.5 μm, and the width of the second portion 12c is about 3.5 μm. In the core layer 22, the end portion 22b of the bent portion 22a is located in the vicinity of the protrusion portion 12a. The bent portion 22a extends at an angle from the vertical to the first end surface 12A.
As described above, the uneven portion can be accurately formed on the first end surface 12A by photolithography and etching.

Subsequently, as shown in FIG. 5, the electrode 13 is formed.
Specifically, a resist mask is formed on the Si substrate 1 from which the BOX layer and the TEOS layer are removed and exposed to open a portion where an electrode is to be formed. By sputtering, an electrode material such as Ti / Pt / Au is formed into a film having a thickness of about 0.1 μm, about 0.2 μm, and about 0.5 μm, respectively. Lift-off removes the resist mask and the electrode material on it. As a result, the electrode 13 is formed on the exposed portion of the Si substrate 1.

Subsequently, as shown in FIG. 6, the conductive adhesive material 15 is formed on the electrode 13.
Specifically, a resist mask is formed on the electrode 13 to open a portion where the conductive material is to be formed. By sputtering, a conductive material such as AuSn is formed into a film having a thickness of about 4.0 μm. Lift-off removes the resist mask and the conductive material on it. As a result, the conductive adhesive material 15 is formed on the electrode 13.
As a result, the silicon photonics substrate 1 is formed.

Subsequently, the optical semiconductor element 2 is arranged and fixed in the same manner as in FIG.
Specifically, in the optical semiconductor device 2, the first end surface 12A and the second end surface 14A face each other, and the end portion 24a of the second optical waveguide 14 and the end portion 22a of the first optical waveguide 12 are butted against each other. It is arranged and fixed on the conductive adhesive material 15 at a junction down. The optical axes of the first optical waveguide 12 and the second optical waveguide 14 are aligned and photocoupled, and a gap G is formed between the first end surface 12A and the second end surface 14A. A first observation region 16 is formed between the first portion 12b and the second end surface 14A, and a second observation region 17 is formed between the second portion 12c and the second end surface 14A.
As described above, the optical device according to the present embodiment is manufactured.
Since the second end surface 14A of the optical semiconductor element 2 is formed by cleavage, it does not have an uneven shape like the first end surface 12A of the first optical waveguide 12.

An example of calculating the intervals d ₁ and d ₂ in the first and second observation regions 16 and 17 for the optical device manufactured as described above is shown below.
In this calculation example, d _SiPh is 4.5 μm and d _metal is 3 μm. When d (θ ₁ ) and d'(θ ₁ ) were measured at the observation angles θ ₁ for the first and second observation regions 16 and 17 of the optical device, d (θ ₁ ) was 2.3 μm and d'(. θ ₁ ) was 4.2 μm. By substituting the obtained value into the above equation (5), it can be seen that the observation angle θ ₁ is 20 °. When the observation angles θ ₂ different from θ ₁ are measured in the same manner for the first and second observation regions 16 and 17, d (θ ₂ ) is 1.9 μm and d'(θ ₂ ) is 3.6 μm. It can be seen from Eq. (5) that the observation angle θ ₂ is 30 °. Then, by substituting the obtained measured values (θ ₁ , θ ₂ , d (θ ₁ ), d (θ ₂ )) into the above equation (2), the interval d ₁ in the first observation region 16 is 3 μm. It can be seen that the interval d ₂ in the second observation region 17 is 5 μm.

As described above, according to the present embodiment, even when the gap G between the first and second optical waveguides 12 and 14 is narrow without being affected by the manufacturing error, the gap G and the optical semiconductor can be accurately measured. A highly reliable optical device capable of grasping the amount of rotation of the element 2 is realized.
Since the height of the optical semiconductor element 2 is about 150 μm and the height of d _SiPh is 4.5 μm, which are extremely different, it is not possible to observe both at the same time with high accuracy. It is measured at.

[Modification example]
Hereinafter, various modifications of the optical device according to the first embodiment will be described. In these modifications, the optical device is disclosed as in the present embodiment, but it differs from the first embodiment in that the configuration of the first optical waveguide is slightly different.

(Modification 1)
7A and 7B are schematic views showing a schematic configuration of an optical device according to a modification 1 of the first embodiment, in which FIG. 7A is a plan view and FIG. 7B is a side view. The same components as those of the optical device according to the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

This optical device includes a silicon photonics substrate 1 and an optical semiconductor element 2.
In the first optical waveguide 12 of the silicon photonics substrate 1, a protrusion 12d is formed on the first end surface 12A, and the first is on one side of the protrusion 12d (lower side of the protrusion 12d in FIG. 7A). The site 12e and the second site 12f are formed side by side. The widths of the first portion 12e and the second portion 12f are different (the difference in height from the protrusion 12d). Here, the width of the second portion 12f is larger than the width of the first portion 12e. The core layer 22 of the first optical waveguide 12 is bent and extends in the middle on the lower clad layer, and the end portion 22b of the bent portion 22a is located in the vicinity of the protrusion 12d. The bent portion 22a extends from the vertical direction (for example, tilted by about 15 ° from the vertical direction) with respect to the first end surface 12A in order to suppress light reflection from the first end surface 12A.

The core layer 24 of the second optical waveguide 14 extends vertically with respect to the second end surface 14A (for example, at an angle of about 7 ° from the vertical) in order to suppress light reflection from the second end surface 14A. , The end portion 24a of the core layer 24 is located on the second end surface 14A. In the first optical waveguide 12 and the second optical waveguide 14, the first end surface 12A and the second end surface 14A are arranged to face each other so that the end portion 22b and the end portion 24a are butted against each other, and are optically coupled. There is. A gap G is formed between the first end surface 12A and the second end surface 14A by a predetermined distance. Due to such an arrangement of the optical semiconductor element 2, a phase larger than the gap G between the first portion 12e and the second portion 12f and the second end surface 14A at the facing portion between the first end surface 12A and the second end surface 14A. Different intervals (here, the latter interval is larger than the former interval) are formed. The region between the first portion 12e and the second end surface 14A is the first observation region 18 (shown in the broken line circle in FIG. 7), and the region between the second portion 12f and the second end surface 14A is the second. The observation area 18 (shown in the broken line circle in FIG. 7). In the present embodiment, for example, the distance between the gaps G is about 1.5 μm, the distance between the first observation regions 18 is about 3 μm, and the distance between the second observation regions 19 is about 5 μm.

Also in the first modification, as in the first embodiment, the observation angle θ ₁ is obtained from the known information Δd and the measured values d (θ ₁ ) and d'(θ ₁ ) from the above equation (5). Can be grasped. Similarly, the observation angle θ ₂ can be grasped by measuring the first and _second observation regions 18 and 19. By substituting the obtained measured values (θ ₁ , θ ₂ , d (θ ₁ ), d (θ ₂ )) into Eq. (2), the interval d ₁ (and the second observation region) in the first observation region 18 The interval d ₂ ) at 19 is obtained, and the interval of the gap G can be grasped.

In the optical device according to the first modification, the error of the observation angle is removed from the calculated value, and the gap G can be accurately grasped. Further, even when the gap G is narrow, it is possible to measure the intervals in the first and second observation regions 18 and 19 by providing the first and second observation regions 18 and 19 having a wider interval than the gap G. Yes, the gap G and the amount of rotation of the optical semiconductor element 2 can be accurately grasped from the measured values.

(Modification 2)
8A and 8B are schematic views showing a schematic configuration of an optical device according to a modification 2 of the first embodiment, in which FIG. 8A is a plan view and FIG. 8B is a side view. The same components as those of the optical device according to the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

This optical device includes a silicon photonics substrate 1 and an optical semiconductor element 2.
In the first optical waveguide 12 of the silicon photonics substrate 1, a protrusion 12a and a first portion 12b and a second portion 12c on both sides thereof are formed on the first end surface 12A.
In the optical semiconductor device 2, a gap G is formed between the second end surface 14A facing the first end surface 12A and the first end surface 12A.

In the second modification, the first optical waveguide 12 has a first pattern 25 formed alongside the core layer 22 (below the core layer 22 in FIG. 8A). The first pattern 25 is a structure for confirming the mounting accuracy of the first and second optical waveguides 12, 14, and one end thereof is located on the first end surface 12A. The first pattern 25 is formed as a dummy optical waveguide in the same manner as the first optical waveguide 12 (in the same process).

In the second modification, the second optical waveguide 14 of the optical semiconductor device 2 has a second pattern 26 formed alongside the core layer 24 (below the core layer 24 in FIG. 8A). The second pattern 26 is a structure for confirming the mounting accuracy of the first and second optical waveguides 12, 14, and one end thereof is located on the second end surface 14A. The second pattern 26 is configured as a dummy optical waveguide in the same manner as the second optical waveguide 14.

In the manufactured optical device, the first pattern 25 and the second pattern 26 face each other and align with each other on the first and second end faces 12A and 14A. By aligning the positions of the first and second patterns 25 and 26, the end portion 22b of the core layer 22 and the end portion 24a of the core layer 24 are butted without any positional deviation.

Also in the second modification, as in the first embodiment, the observation angle θ ₁ is obtained from the known information Δd and the measured values d (θ ₁ ) and d'(θ ₁ ) from the above equation (5). Can be grasped. Similarly, the observation angle θ ₂ can be grasped by measuring the first and _second observation regions 16 and 17. By substituting the obtained measured values (θ ₁ , θ ₂ , d (θ ₁ ), d (θ ₂ )) into Eq. (2), the interval d ₁ (and the second observation region) in the first observation region 16 The interval d ₂ ) in 17 is obtained, and the interval of the gap G can be grasped.

In the optical device according to the second modification, the error of the observation angle is removed from the calculated value, and the gap G can be accurately grasped. Further, even when the gap G is narrow, it is possible to measure the intervals in the first and second observation areas 16 and 17 by providing the first and second observation areas 16 and 17 having a wider interval than the gap G. Yes, the gap G and the amount of rotation of the optical semiconductor element 2 can be accurately grasped from the measured values.

In the second modification, the first and second optical waveguides 12 are further observed by observing the first and second patterns 25 and 26 and confirming whether or not the first and second patterns 25 and 26 are position-aligned. It is possible to grasp the positional deviation between, and 14.

In the first embodiment and various modifications, the case where the first and second portions having different widths are provided and the first and second observation regions are formed in the first optical waveguide 12 is exemplified. However, the configuration is not limited to this. For example, three or more parts having different widths may be provided to form three or more observation areas.

[Second Embodiment]
The present embodiment discloses a tunable laser, which is an optical semiconductor device to which one type of optical device selected from the first embodiment and various modifications is applied. In the following description, a tunable laser to which the optical device of the first embodiment is applied will be exemplified.
FIG. 9 is a schematic plan view schematically showing the configuration of the tunable laser according to the present embodiment. The same components as those of the optical device according to the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

(Rough configuration of tunable laser)
This tunable laser includes a silicon photonics substrate 31, a first SOA (Semiconductor Optical Amplifier) 32, and a second SOA 33.
The silicon photonics substrate 31 includes a Si substrate 11, a first optical waveguide 12, a partial reflection mirror 41, a phase adjuster 42, and a wavelength variable filter 43 formed on the Si substrate 11, and an electrode formed on the Si substrate 11. (The same electrode as the electrode 13 in FIG. 1) is provided. The first optical waveguide 12 is formed on the lower clad layer 21 made of, for example, a silicon oxide, the core layer 22 made of silicon wires formed on the lower clad layer 21, and the lower clad layer 21 so as to cover the core layer 22. It has a formed upper clad layer 23 made of, for example, a silicon oxide.

The partial reflection mirror 41, the phase adjuster 42, and the tunable filter 43 have a thin silicon wire connected to the core layer 22 of the first optical waveguide 12. The partial reflection mirror 41 is configured as a loop mirror by thin silicon wires. The phase adjuster 42 is configured to have a heater 42a that covers the thin silicon wire. The tunable filter 43 is a so-called vernier type, and includes ring resonators 43a and 43b which are made of silicon fine wires and have slightly different circumferences and heaters 43c and 43d which cover them.

The first and second SOAs 32 and 33 are optical semiconductor devices configured by using a III-V compound semiconductor, for example, InP, and the first SOA32 functions as a light source and the second SOA33 functions as an optical amplifier. In the first SOA 32, an AR (Anti-Reflection) coating film 32a is formed on the right end surface, and an HR (High-Reflection) coating film 32b is formed on the left end surface, and a second optical waveguide 14 having a core layer 24 between them is formed. Is provided. In the second SOA 33, AR coating films 33a and 33b are formed on both end faces, and a second optical waveguide 34 having a core layer 35 is provided between them. The first and second SOAs 32 and 33 are arranged on the Si substrate 11 via a conductive adhesive material (the same material as the conductive adhesive material 15 in FIG. 1) provided on the electrodes, and are electrically arranged with the electrodes. It is connected.

In this tunable laser, a laser cavity is formed by the path of the first SOA 32, the tunable filter 43, the phase adjuster 42, and the partial reflection mirror 41. Here, if the light intensity in the second optical waveguide 14 is high, the operation of the silicon photonics substrate 31 becomes unstable due to the non-linear effect of light, so the driving conditions of the first SOA 32 are set so that the light intensity becomes sufficiently small. do. Finally, high optical output can be obtained by optical amplification with the second SOA33.

In the first optical waveguide 12, a protrusion 12a is formed on the first end surface 12A, and a first portion 12b and a second portion 12c are formed on both sides of the protrusion 12a. The first portion 12b is located on one end side of the protrusion 12a, and the second portion 12c is located on the other end side of the protrusion 12a. (Difference in height). Here, the width of the second site 12c is larger than the width of the first site 12b. The core layer 22 of the first optical waveguide 12 is bent and extends in the middle on the lower clad layer, and the end portion 22b of the bent portion 22a is located in the vicinity of the protrusion 12a. The bent portion 22a extends at an angle from the vertical to the first end surface 12A in order to suppress light reflection from the first end surface 12A.

The core layer 35 of the second optical waveguide 34 extends at an angle perpendicular to the second end surface 34A in order to suppress light reflection from the second end surface 34A, and the core layer 35 extends to the second end surface 34A. The end 35a is located. In the first optical waveguide 12 and the second optical waveguide 34, the first end surface 12A and the second end surface 34A are arranged so as to face each other so that the end portion 22b and the end portion 35a are butted, and the first optical waveguide 12A and the second end surface 34A are optically coupled. There is. A gap G is formed between the first end surface 12A and the second end surface 34A so as to be separated by a predetermined distance. Due to such arrangement of the first and second SOAs 32 and 33, at the position where the first end surface 12A and the second end surface 34A face each other, the gap G between the first part 12b and the second part 12c and the second end face 34A Large different intervals (here, the latter interval is larger than the former interval) are formed. The region between the first portion 12b and the second end surface 34A is referred to as the first observation region 36, and the region between the second portion 12c and the second end surface 34A is referred to as the second observation region 37.

Also in this embodiment, as in the first embodiment, the observation angle θ ₁ is obtained from the known information Δd and the measured values d (θ ₁ ) and d'(θ ₁ ) from the above equation (5). Can be grasped. Similarly, the observation angle θ ₂ can be grasped by measuring the first and _second observation regions 36 and 37. By substituting the obtained measured values (θ ₁ , θ ₂ , d (θ ₁ ), d (θ ₂ )) into Eq. (2), the interval d ₁ (and the second observation region) in the first observation region 36 The interval d ₂ ) at 37 is obtained, and the interval of the gap G can be grasped.

In the optical device according to the present embodiment, the error of the observation angle is removed from the calculated value, and the gap G can be accurately grasped. Further, even when the gap G is narrow, it is possible to measure the intervals in the first and second observation areas 36 and 37 by providing the first and second observation areas 36 and 37 having a wider interval than the gap G. Yes, the gap G and the rotation amounts of the first and second SOAs 32 and 33 can be accurately grasped from the measured values.

(Manufacturing method of tunable laser)
A method for manufacturing a tunable laser according to the present embodiment will be described.
Among the tunable lasers, for the silicon photonics substrate 31, the SOI layer is processed into a fine line in FIGS. 4 to 6 in the first embodiment, and heaters 42a, 43c, and 43d are formed. A partial reflection mirror 41, a phase adjuster 42, and a tunable wavelength filter 43 are formed together with the first optical waveguide 12.

Hereinafter, among the tunable lasers, the manufacturing processes of the first and second SOAs 32 and 33 will be described.
10 to 17 are schematic cross-sectional views illustrating the manufacturing process of the SOA of the tunable laser according to the present embodiment. 10 to 17 correspond to the cross section along the broken line I-I'of FIG. 9, and show the manufacturing process of only the first SOA32 of the first and second SOA32, 33.

First, as shown in FIG. 10, for example, by using the organic metal vapor phase growth method (MOCVD method), the n-InP clad layer 52, the quantum well active layer 53, and the p-InP clad layer 54 are placed on the n-InP substrate 51. , And the p-InGaAsP contact layer 55 are sequentially grown. The n-InP clad layer 52 is formed to have a thickness of, for example, about 2.0 μm. The quantum well active layer 53 is formed to have a thickness of, for example, about 0.2 μm. The p-InP clad layer 54 is formed to have a thickness of, for example, about 1.5 μm. The p-InGaAsP contact layer 55 is formed to have a thickness of, for example, about 0.3 μm.

Subsequently, as shown in FIG. 11, SiO ₂ is deposited on the p-InGaAsP contact layer 55 by, for example, a CVD method. This SiO ₂ is processed by photolithography and etching to form the SiO ₂ mask 56.
Next, the p-InGaAsP contact layer 55, the p-InP clad layer 54, the quantum well active layer 53, and the n-InP are subjected to inductively coupled plasma reactive ion etching (ICP-RIE) using the SiO ₂ mask 56. Etching is performed halfway through the clad layer 52. As a result, a mesa structure as shown in the figure is formed. The etched quantum well active layer 53 becomes the core layer 35 in FIG.

Subsequently, as shown in FIG. 12, the semi-insulating InP (SI-InP) layer 57 is grown so as to embed the mesa structure, for example, by using the MOCVD method. The SiO ₂ mask 56 is removed by predetermined wet etching or the like.

Subsequently, as shown in FIG. 13, a resist mask (not shown) is formed, and the SI-InP layer 57 and the n-InP clad layer 52 are etched with, for example, a mixed solution of hydrochloric acid and phosphoric acid. At this time, the region to be etched is, for example, a region other than the mesa structure. The resist mask is removed by a predetermined wet etching or the like. The second optical waveguide 34 in FIG. 9 has a p-InP clad layer 54, a quantum well active layer 53, an n-InP clad layer 52, and an SI-InP layer 57.

Next, for example, plasma CVD is used to form the SiN passivation film 58 to a thickness of, for example, about 0.5 μm. After that, a resist mask (not shown) is formed, and the SiN passivation film 58 is etched to form the electrode window opening 58a. The resist mask is removed by a predetermined wet etching or the like.

Subsequently, as shown in FIG. 14, for example, using a sputtering method, TiW / Au59 is formed on the entire surface to a thickness of, for example, about 0.1 μm.

Subsequently, as shown in FIG. 15, a resist mask (not shown) is formed, and the Au plating film 61 is formed to a thickness of, for example, about 2.0 μm by using, for example, electrolytic plating with TiW / Au59 as an electrode. The resist mask is removed by a predetermined wet etching or the like.

Subsequently, as shown in FIG. 16, the entire surface is etched using the Au plating film 61 as a mask to remove TiW / Au59 in the non-formed region of the Au plating film 61.

Subsequently, as shown in FIG. 17, the back surface side of the n-InP substrate 51 is polished so that the element thickness is, for example, about 150 μm.
Next, AuGe / Au62 is formed on the back surface of the n-InP substrate 51 by using, for example, a vacuum vapor deposition method. Then, after appropriately patterning AuGe / Au62, the Au plating film 63 is formed on AuGe / Au62.
As a result, the first SOA 32 (second SOA 33) is formed.

As described above, according to the present embodiment, even when the gap G between the first and second optical waveguides 12 and 34 is narrow without being affected by the manufacturing error, the gap G and the first are accurately measured. And a highly reliable tunable laser capable of grasping the rotation amount of the second SOA 32 and 33 is realized.

[Third Embodiment]
The present embodiment discloses an optical transceiver to which a tunable laser according to the second embodiment is applied.
FIG. 18 is a schematic plan view schematically showing an optical transceiver according to the present embodiment. The same components as those of the tunable laser according to the second embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

The optical transceiver comprises a tunable laser 70, a DP-QPSK optical modulator 71, and a coherent receiver 72 according to a second embodiment.
The DP-QPSK optical modulator 71 is a polarization-multiplexed four-value phase modulation (DP-QPSK) optical transmitter for modulating the output light from the variable wavelength laser 70 and generating transmission signal light. The coherent receiver 72 is an optical receiver for receiving signal light from the outside. With this optical transceiver, it is possible to realize a module capable of transmitting and receiving light at any wavelength.

According to the present embodiment, even when the gap G between the first and second optical waveguides 12 and 34 is narrow without being affected by the manufacturing error, the gap G and the first and second SOA 32 and 33 can be accurately measured. A highly reliable optical transceiver equipped with a tunable laser 70 capable of grasping the amount of rotation is realized.

Hereinafter, various aspects of the optical device, the optical semiconductor device, and the optical transceiver will be described together as an appendix.

(Appendix 1) Semiconductor substrate and
The first optical waveguide formed on the semiconductor substrate and
The first of the portions facing the first optical waveguide and the second optical waveguide, including an optical semiconductor element including a second optical waveguide mounted on the semiconductor substrate facing the first optical waveguide. The portion where the 1 optical waveguide and the second optical waveguide are optically connected has a first gap, and the portion where the first optical waveguide and the second optical waveguide are not optically connected is larger than the first gap. An optical device characterized by having a gap of two.

(Supplementary Note 2) The optical device according to Supplementary Note 1, wherein the second gap is provided on both sides of the first gap.

(Supplementary Note 3) The optical device according to Supplementary Note 1, wherein the second gap is provided on one side of the first gap.

(Supplementary Note 4) The optical device according to any one of Supplementary note 1 to 3, wherein the second gap is a plurality of gaps having different sizes.

(Appendix 5) The first pattern is on the first end surface of the first optical waveguide facing the second optical waveguide, and the second pattern is on the second end surface of the second optical waveguide facing the first optical waveguide. It is provided,
The optical device according to any one of Supplementary note 1 to 4, wherein the first pattern and the second pattern are position-aligned.

(Appendix 6) The first optical waveguide extends vertically inclined with respect to the first end surface, and the second optical waveguide extends vertically inclined with respect to the second end surface. The optical device according to any one of Supplementary note 1 to 5, wherein the optical device is characterized by the above-mentioned item 1.

(Appendix 7) Semiconductor substrate and
The first optical waveguide formed on the semiconductor substrate and
A reflection mirror connected to the first optical waveguide,
A tunable wavelength filter capable of changing the wavelength of light passing through the first optical waveguide,
The first of the portions facing the first optical waveguide and the second optical waveguide, including an optical semiconductor element including a second optical waveguide mounted on the semiconductor substrate facing the first optical waveguide. The portion where the 1 optical waveguide and the second optical waveguide are optically connected has a first gap, and the portion where the first optical waveguide and the second optical waveguide are not optically connected is larger than the first gap. An optical semiconductor device having a gap of 2.

(Appendix 8) The optical semiconductor device according to Appendix 7, wherein the second gap is provided on both sides of the first gap.

(Supplementary Note 9) The optical semiconductor device according to Supplementary Note 7, wherein the second gap is provided on one side of the first gap.

(Supplementary Note 10) The optical semiconductor device according to any one of Supplementary note 7 to 9, wherein the second gap is a plurality of gaps having different sizes.

(Appendix 11) The first pattern is on the first end surface of the first optical waveguide facing the second optical waveguide, and the second pattern is on the second end surface of the second optical waveguide facing the first optical waveguide. It is provided,
The optical semiconductor device according to any one of Supplementary note 7 to 10, wherein the first pattern and the second pattern are position-matched.

(Appendix 12) The first optical waveguide extends vertically with respect to the first end surface, and the second optical waveguide extends vertically with respect to the second end surface. The optical semiconductor device according to any one of Supplementary Provisions 7 to 10, wherein the optical semiconductor device is characterized.

(Appendix 13) The two second optical waveguides are arranged side by side.
The optical semiconductor device according to any one of Supplementary note 7 to 12, wherein one of the second optical waveguides is a light source and the other second optical waveguide is an optical amplifier.

(Appendix 14) Optical semiconductor devices and
An optical transmitter that modulates the light output from the optical semiconductor device to generate signal light and transmits it to the outside.
Including an optical receiver that receives signal light from the outside,
The optical semiconductor device is
With a semiconductor substrate,
The first optical waveguide formed on the semiconductor substrate and
The first of the portions facing the first optical waveguide and the second optical waveguide, including an optical semiconductor element including a second optical waveguide mounted on the semiconductor substrate facing the first optical waveguide. The portion where the 1 optical waveguide and the second optical waveguide are optically connected has a first gap, and the portion where the first optical waveguide and the second optical waveguide are not optically connected is larger than the first gap. An optical waveguide characterized by having a gap of two.

1,31 Silicon Photonics Substrate 2 Optical Semiconductor Device 11 Si Substrate 12 First Optical Waveguide 12A First End Face 12a, 12d Projection 12b, 12e First Part 12c, 12f Second Part 13 Electrode 14,34 Second Optical Waveguide 14A, 34A 2nd end face 15 Conductive adhesive material 16,18,36 1st observation area 17,19,37 2nd observation area 21 Lower clad layer 22,24,35 Core layer 22a Bending part 22b, 24a, 35a End part 23 Upper part Clad layer 25 1st pattern 26 2nd pattern 32 1st SOA
33 Second SOA
41 Partial reflection mirror 42 Phase adjuster 42a, 43c, 43d Heater 43 Variable wavelength filter 43a, 43b Ring resonator 51 n-InP substrate 52 n-InP clad layer 53 Quantum well active layer 54 p-InP clad layer 55 p-InGaAsP Contact layer 56 SiO ₂ Mask 57 Semi-insulating InP (SI-InP) layer 58 SiN Passionation film 58a Electrochemical window opening 59 TiW / Au
61, 63 Au plating film 62 AuGe / Au
70 Tunable Laser 71 DP-QPSK Optical Modulator 72 Coherent Receiver

Claims (13)

With a semiconductor substrate,
The first optical waveguide formed on the semiconductor substrate and
An optical semiconductor device including a second optical waveguide mounted on the semiconductor substrate facing the first optical waveguide, and the like.
The first end surface of the first optical waveguide facing the second optical waveguide has a first plane portion and a second plane portion parallel to the first plane portion, which is a step recessed from the first plane portion. , A third flat surface portion parallel to the first flat surface portion, which is a step recessed from the first flat surface portion.
In the first gap provided between the first plane portion and the portion of the second optical waveguide facing the first optical waveguide and facing the first plane portion, the first An optical device characterized in that the 1 optical waveguide and the second optical waveguide are optically connected. A second gap provided between the second plane portion and a portion of the second end surface facing the second plane portion, the third plane portion, and the second end surface of the second end surface. 3. The optical device according to claim 1, wherein the third gap provided between the two plane portions and the facing portion is provided on both sides of the first gap. A second gap provided between the second plane portion and a portion of the second end surface facing the second plane portion, the third plane portion, and the second end surface of the second end surface. 3. The optical device according to claim 1, wherein the third gap provided between the flat surface portion and the facing portion is provided on one side of the first gap. The optical device according to claim 2 or 3, wherein the second gap and the third gap are gaps of different sizes. The first pattern is provided on the second plane portion or the third plane portion of the first optical waveguide, and the second pattern is provided on the second end surface of the second optical waveguide.
The optical device according to any one of claims 1 to 4, wherein the first pattern and the second pattern are position-aligned. The first optical waveguide extends vertically inclined with respect to the first end surface, and the second optical waveguide extends vertically inclined with respect to the second end surface. The optical device according to any one of claims 1 to 5. With a semiconductor substrate,
The first optical waveguide formed on the semiconductor substrate and
A reflection mirror connected to the first optical waveguide,
A tunable wavelength filter capable of changing the wavelength of light passing through the first optical waveguide,
An optical semiconductor device including a second optical waveguide mounted on the semiconductor substrate facing the first optical waveguide, and the like.
The first end surface of the first optical waveguide facing the second optical waveguide has a first plane portion and a second plane portion parallel to the first plane portion, which is a step recessed from the first plane portion. , A third flat surface portion parallel to the first flat surface portion, which is a step recessed from the first flat surface portion.
In the first gap provided between the first plane portion and the portion of the second optical waveguide facing the first optical waveguide and facing the first plane portion, the first An optical semiconductor device characterized in that the 1 optical waveguide and the second optical waveguide are optically connected. A second gap provided between the second plane portion and a portion of the second end surface facing the second plane portion, the third plane portion, and the second end surface of the second end surface. 3. The optical semiconductor device according to claim 7, wherein the third gap provided between the flat surface portion and the facing portion is provided on both sides of the first gap. A second gap provided between the second plane portion and a portion of the second end surface facing the second plane portion, the third plane portion, and the second end surface of the second end surface. 3. The optical semiconductor device according to claim 7, wherein the third gap provided between the flat surface portion and the facing portion is provided on one side of the first gap. The optical semiconductor device according to claim 8 or 9 , wherein the second gap and the third gap are gaps of different sizes. The first pattern is provided on the second plane portion or the third plane portion of the first optical waveguide, and the second pattern is provided on the second end surface of the second optical waveguide.
The optical semiconductor device according to any one of claims 7 to 10, wherein the first pattern and the second pattern are position-matched. The first optical waveguide extends vertically inclined with respect to the first end surface, and the second optical waveguide extends vertically inclined with respect to the second end surface. The optical semiconductor device according to any one of claims 7 to 10. The two said second optical waveguides are arranged side by side,
The optical semiconductor device according to any one of claims 7 to 12, wherein one of the second optical waveguides is a light source and the other second optical waveguide is an optical amplifier.

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