JP2014137492A - Semiconductor optical waveguide element and method for manufacturing semiconductor optical waveguide element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor optical waveguide element with a structure capable of correcting a positional displacement in a width direction of two optical waveguides to be aligned.SOLUTION: In a first waveguide structure 15, a twelfth waveguide mesa part 21g and a twenty-second waveguide mesa part 23g are aligned in a second axis Ax2 direction on a second portion 13b of a substrate 13, and thus the twelfth waveguide mesa part 21g is optically coupled to the twenty-second waveguide mesa part 23g via a second semiconductor layer 23a on the second portion 13b of the substrate 13. Optical coupling is formed in the twelfth waveguide mesa part 21g and the twenty-second waveguide mesa part 23g which have wide widths. This coupling structure can compensate for an increase in deterioration of optical coupling due to positional displacement between a first waveguide mesa 21b of the first waveguide structure 15 and a second waveguide mesa 23b of a second waveguide structure 17, by adjusting a coupling length of the twelfth waveguide mesa part 21g and the twenty-second waveguide mesa part 23g which have wide widths.

Description

  The present invention relates to a semiconductor optical waveguide device and a method for manufacturing the semiconductor optical waveguide device.

  Non-Patent Document 1 discloses an optical modulator optically coupled to an SOI waveguide. This optical modulator is formed as follows. A passive waveguide structure is formed on the SOI substrate. After the formation of the waveguide structure, the InP-based epitaxial layer is transferred onto the substrate and the SOI substrate using a bonding method. Then, the optical modulator is formed by processing the waveguide structure and forming electrodes so as to form an optical coupling with the lower SOI waveguide.

Optics express Vol.19, No.7, p5811, 28 March 2011

  A semiconductor epilayer structure constituting a functional element is formed on a semiconductor substrate on which a passive optical waveguide structure is formed, using a bonding method. Thereafter, the optical waveguide device structure constituting the functional device is formed by aligning with the lower optical waveguide structure using a photolithography method.

  As described above, an optical functional element having a stacked structure (for example, a two-story structure) is configured using a bonding method. In order to realize optical coupling between the optical waveguide corresponding to the first floor portion and the optical waveguide structure corresponding to the second floor portion, a vertical optical directional coupler structure is formed.

  In the method of Non-Patent Document 1, a semiconductor epitaxial layer is transferred by bonding to a semiconductor substrate on which an optical waveguide structure is formed. Thereafter, the epitaxial layer is processed.

  There is a manufacturing method different from the manufacturing method described in Non-Patent Document 1. In an alternative method to the method of Non-Patent Document 1, two epitaxial multilayer pieces that have been processed as an optical waveguide in advance are bonded to each other. By this method, an optical functional element having a structure similar to that of Non-Patent Document 1 can be configured. However, according to this method, a semiconductor piece including an epitaxial stack in which an optical waveguide is formed by processing a single epitaxial substrate in advance is prepared, and the semiconductor piece is bonded to a conductor substrate having a plurality of optical waveguide structures. You will be able to adopt the method of doing. According to this method, a process (a process of forming an optical waveguide on an epitaxial substrate) that must be performed for each semiconductor substrate including an optical waveguide structure can be performed in a lump. For this reason, the manufacturing process can be made efficient. However, such a method has not been taken so far. The reason is as follows.

  In a semiconductor optical waveguide in which a semiconductor structure in which a semiconductor layer serving as a core layer with a high refractive index is sandwiched between cladding layers with a low refractive index is processed into a mesa stripe or a ridge stripe, the structure for a vertical optical directional coupler structure As the optical waveguide, an optical waveguide with a narrow stripe width that can stably propagate the fundamental mode is used. For example, an optical waveguide width of 2 μm or less is used for an optical wavelength used in current optical communication.

  A semiconductor optical waveguide having a width of 2 μm is vertically stacked so that the centers in the width direction of the waveguide coincide with each other, thereby forming an optical directional coupler. However, if a positional shift occurs at the center in the width direction of the semiconductor optical waveguide when they are stacked one above the other, the light transmission ratio (transmittance) between the optical waveguides decreases. When the semiconductor optical waveguides having a width of 2 μm are overlapped, this ratio is about 5% when the positional deviation is 0.4 μm, about 20% when the positional deviation is 0.6 μm, and reaches about 75% when the positional deviation is 1 μm. When photolithography using a stepper device is used, a positional deviation of 0.4 μm or less can be achieved. However, in a manufacturing process using an apparatus for joining wafers or wafers and semiconductor pieces, the positional deviation can be suppressed to 1 μm or less. It's not easy. For this reason, alignment that requires a high degree of accuracy such as photolithography by a stepper device reduces the bonding throughput.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a semiconductor optical waveguide device having a structure capable of compensating a positional shift in the width direction of two optical waveguides to be aligned. Another object of the present invention is to provide a method for producing this semiconductor optical waveguide device.

  A semiconductor optical waveguide device according to the present invention includes: (a) a groove including a first portion, a second portion, and a third portion arranged in the direction of the first axis, and the groove extending in the direction of the first axis; (B) a first waveguide structure provided on the main surface of the substrate; and (c) provided on the main surface of the substrate. A second waveguide structure. The first waveguide structure includes a first semiconductor layer supported on the first terrace and the second terrace of the substrate, and a first waveguide mesa provided on the first semiconductor layer, The second waveguide structure includes the first terrace of the first waveguide structure, a second semiconductor layer supported on the second terrace, and a second waveguide mesa provided on the second semiconductor layer. The first waveguide structure includes a first portion, a second portion, and a third portion provided on the first portion, the second portion, and the third portion, respectively, of the substrate; The waveguide structure includes a first portion and a second portion provided on the first portion and the second portion of the first waveguide structure, respectively, and the first waveguide mesa of the first waveguide structure is included. Are twelfth waveguides respectively provided on the second portion and the third portion of the substrate. A width of the twelfth waveguide mesa portion is larger than a width of the thirteenth waveguide mesa portion, and the second waveguide mesa of the second waveguide structure includes: The first waveguide structure includes a twenty-first waveguide mesa portion and a twenty-second waveguide mesa portion provided on the first portion and the second portion, respectively, and the width of the twenty-second waveguide mesa portion is the twenty-first width. A second axis that is larger than a width of the waveguide mesa portion and in the second portion of the substrate, the groove, the twelfth waveguide mesa portion, and the twenty-second waveguide mesa portion intersect the main surface of the substrate; Are arranged in the direction of

  According to this semiconductor optical waveguide device, the first waveguide mesa having the first waveguide structure is aligned with the groove of the substrate, and the second waveguide mesa having the second waveguide structure is the first waveguide structure having the first waveguide structure. Aligned to one waveguide mesa. In the first waveguide structure, the width of the twelfth waveguide mesa portion is larger than the width of the thirteenth waveguide mesa portion, and in the second waveguide structure, the width of the twenty-second waveguide mesa portion is the width of the twenty-first waveguide mesa portion. Greater than. In addition, since the twelfth waveguide mesa portion and the twenty-second waveguide mesa portion are arranged in the second axis direction in the second portion of the substrate, the twelfth waveguide mesa portion in the second portion of the substrate is the second semiconductor layer. Is optically coupled to the 22nd waveguide mesa portion. In this coupling structure, since optical coupling is performed in the wide twelfth waveguide mesa portion and the twenty-second waveguide mesa portion, the first waveguide mesa and the second waveguide structure of the first waveguide structure are formed. An increase in reduction in optical coupling due to a positional shift with the second waveguide mesa can be compensated by adjusting a coupling length of the wide twelfth waveguide mesa portion and the twenty-second waveguide mesa portion.

  Further, in this optical coupling structure, the first waveguide mesa and the second waveguide structure of the first waveguide structure in the structure in which the second waveguide structure is supported on the first terrace and the second terrace of the first waveguide structure. The margin of misalignment with the second waveguide mesa can be increased.

  In the semiconductor optical waveguide device according to the present invention, it is preferable that the first waveguide structure is bonded to the substrate, and the second waveguide structure is bonded to the first waveguide structure. This semiconductor optical waveguide device can be manufactured by bonding the first waveguide structure to the substrate and bonding the second waveguide structure to the first waveguide structure.

  In the semiconductor optical waveguide device according to the present invention, the first waveguide mesa includes a first tapered waveguide portion provided between the twelfth waveguide mesa portion and the thirteenth waveguide mesa portion, The twelfth waveguide mesa portion is preferably terminated. According to this semiconductor optical waveguide device, the first tapered waveguide portion can adiabatically couple the fundamental waveguide mode of the twelfth waveguide mesa portion and the fundamental waveguide mode of the thirteenth waveguide mesa portion.

  In the semiconductor optical waveguide device according to the present invention, the second waveguide mesa includes a second tapered waveguide portion provided between the twenty-first waveguide mesa portion and the twenty-second waveguide mesa portion, The twelfth waveguide mesa portion is preferably terminated. According to this semiconductor optical waveguide device, the second tapered waveguide section can adiabatically couple the fundamental waveguide mode of the twenty-second waveguide mesa section and the fundamental waveguide mode of the twenty-first waveguide mesa section.

  In the semiconductor optical waveguide device according to the present invention, the twelfth waveguide mesa portion extends from one end to the other end of the second portion of the first waveguide structure, and the twenty-second waveguide mesa portion is the second waveguide portion. Preferably, the second portion of the waveguide structure extends from one end to the other end, and the length of the second portion of the substrate is longer than a reference length. The reference length is determined when one of the first waveguide structure and the second waveguide structure is not misaligned with respect to the other in the direction of the third axis intersecting the first axis and the second axis. The length is such that the transmittance of light from one of the first waveguide structure and the second waveguide structure to the other is 1.

  According to this semiconductor optical waveguide device, the length of the second portion of the substrate is made longer than the reference length, thereby adjusting the coupling length between the twelfth waveguide mesa portion and the twenty-second waveguide mesa portion, thereby adjusting the third axis. The change width of the transmittance due to the misalignment in the direction can be reduced by the coupling length in the first axis direction.

  In the semiconductor optical waveguide device according to the present invention, it is preferable that the thirteenth waveguide mesa portion is a single mode waveguide and the twelfth waveguide mesa portion is 4 μm or more. According to this semiconductor optical waveguide device, since optical coupling is performed in the wide waveguide section, the alignment between the first waveguide mesa of the first waveguide structure and the second waveguide mesa of the second waveguide structure is performed. The displacement can be relatively relaxed.

  In the semiconductor optical waveguide device according to the present invention, it is preferable that the twenty-third waveguide mesa portion is a single mode waveguide, and the twenty-second waveguide mesa portion is 4 μm or more. According to this semiconductor optical waveguide device, since optical coupling is performed in the wide waveguide section, the alignment between the first waveguide mesa of the first waveguide structure and the second waveguide mesa of the second waveguide structure is performed. The displacement can be relatively relaxed.

  In the semiconductor optical waveguide device according to the present invention, it is preferable that the waveguide width of the twenty-second waveguide mesa portion is substantially equal to the waveguide width of the twelfth waveguide mesa portion. This semiconductor optical waveguide device enables efficient light propagation from one of the twelfth waveguide mesa portion and the twenty-second waveguide mesa portion to the other.

  In the semiconductor optical waveguide device according to the present invention, the first semiconductor layer comprises InP, the first waveguide mesa comprises InGaAsP for the core of the optical waveguide, the second semiconductor layer comprises InP, The two-waveguide mesa can comprise InGaAsP for the core of the optical waveguide. According to this semiconductor optical waveguide device, regarding the refractive index distribution in the direction of the second axis, the InP layer in the second semiconductor layer is composed of the optical waveguide core of the first waveguide mesa and the optical waveguide core of the second waveguide mesa. Are optically separated and optically coupled.

  The invention according to the present invention relates to a method of fabricating a semiconductor optical waveguide device. The manufacturing method includes (a) a first portion, a second portion, and a third portion arranged in the direction of the first axis, a groove extending in the first direction, a first terrace that defines the groove, and Preparing a support substrate having a second terrace; (b) preparing a first epitaxial substrate having a first semiconductor stack for a waveguide structure on the first substrate; and (c) the first Bonding the first semiconductor stack of the first epitaxial substrate to the substrate such that the first terrace and the second terrace of the support substrate support the first semiconductor stack of the epitaxial substrate; ) Removing the first substrate from the first epitaxial substrate after bonding the first semiconductor stack of the first epitaxial substrate to the support substrate; and (e) removing the first substrate from the first epitaxial substrate. The After leaving, the first semiconductor layer is processed to form a first semiconductor layer supported on the first terrace and the second terrace of the support substrate, and a first waveguide provided on the first semiconductor layer Forming a first substrate product including a first waveguide structure including a mesa; and (f) preparing a second epitaxial substrate including a second semiconductor stack for the waveguide structure on the second substrate. And (g) a second semiconductor layer supported on the first terrace and the second terrace of the first waveguide structure, and a second waveguide mesa provided on the second semiconductor layer. Forming a waveguide structure from the second epitaxial substrate. The second waveguide structure is fabricated from the second semiconductor stack, and the first waveguide structure is provided on the first portion, the second portion, and the third portion of the substrate, respectively. The second waveguide structure includes a first part and a second part respectively provided on the first part and the second part of the first waveguide structure. The first waveguide mesa of the first waveguide structure includes a twelfth waveguide mesa portion and a thirteenth waveguide mesa portion provided on the second portion and the third portion of the substrate, respectively. The width of the twelfth waveguide mesa portion is larger than the width of the thirteenth waveguide mesa portion, and the second waveguide mesa of the second waveguide structure includes the first portion of the first waveguide structure and the second portion of the first waveguide structure. A twenty-first waveguide mesa portion and a twenty-second waveguide provided on the second portion, respectively. A width of the twenty-second waveguide mesa portion is larger than a width of the twenty-first waveguide mesa portion, and an extending direction of the twelfth waveguide mesa portion of the first waveguide mesa The second portion is aligned with the extension direction of the groove, and the extension direction of the twenty-second waveguide mesa portion of the second waveguide mesa is the twelfth waveguide mesa of the first waveguide mesa. It is matched with the extending direction of the part.

  In the manufacturing method according to the present invention, the step of forming the second waveguide structure from the second epitaxial substrate includes the step of processing the second epitaxial substrate to include a first semiconductor product including the second waveguide structure. Forming a second semiconductor product by fixing a support on the second waveguide structure of the first semiconductor product, and forming the second substrate from the second semiconductor product. Removing the second semiconductor layer to form a third semiconductor product, and the second semiconductor layer of the third semiconductor product includes the first terrace of the first waveguide structure and Bonding the second waveguide structure to the first waveguide structure to be supported by the second terrace to form a third substrate product; and from the third substrate product to the support Removing. One of the twelfth waveguide mesa portion and the twenty-second waveguide mesa portion may have an end portion.

  The manufacturing method according to the present invention may further include a step of estimating a reference length with respect to the lengths of the twelfth waveguide mesa portion and the twenty-second waveguide mesa portion. The reference length is determined when one of the first waveguide structure and the second waveguide structure is not misaligned with respect to the other in the direction of the third axis intersecting the first axis and the second axis. The length of the twelfth waveguide mesa section and the twenty-second waveguide mesa section is such that the transmittance of light from one of the first waveguide structure and the second waveguide structure to 1 is one. Is longer than the reference length.

  The above and other objects, features, and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments of the present invention, which proceeds with reference to the accompanying drawings.

  As described above, according to the present invention, it is possible to provide a semiconductor optical waveguide device having a structure capable of compensating for a positional deviation in the width direction between two optical waveguides to be aligned. Moreover, according to this invention, the method of producing this semiconductor optical waveguide element can be provided.

FIG. 1 is a diagram schematically showing the structure of a semiconductor optical waveguide device according to the present embodiment. FIG. 2 is a drawing schematically showing the structure of the semiconductor optical waveguide device in the present embodiment. FIG. 3 is a drawing showing an optical directional coupler configured by vertically stacking two waveguide structures having the same layer structure and the same waveguide width. FIG. 4 is a diagram showing the relationship between the normalized coupling length and the transmittance. FIG. 5 is a diagram illustrating optical coupling according to the component κ (vertical) and the component κ (horizontal) of the coupling coefficient. 6 is a drawing showing the relationship between the waveguide offset ratio and the normalized waveguide length at which the transmittance is 1. FIG. FIG. 7 is a drawing showing the relationship between the waveguide offset ratio and the coupling coefficient κ (horizontal). FIG. 8 is a diagram showing the relationship between the waveguide offset ratio and the transmittance. FIG. 9 is a diagram showing the relationship between the normalized waveguide length and the transmittance with respect to several waveguide offset ratios. FIG. 10 is a diagram showing the relationship between the waveguide offset ratio and the transmittance for several coupling lengths. FIG. 11 is a drawing showing major steps in a method for producing a semiconductor optical waveguide device. FIG. 12 is a drawing showing major steps in a method for producing a semiconductor optical waveguide device. FIG. 13 is a drawing showing major steps in a method for producing a semiconductor optical waveguide device. FIG. 14 is a drawing showing major steps in a method for producing a semiconductor optical waveguide device. FIG. 15 is a drawing showing major steps in a method for producing a semiconductor optical waveguide device. FIG. 16 is a drawing showing major steps in a method for producing a semiconductor optical waveguide device. FIG. 17 is a diagram showing the relationship between the coupling coefficient and the transmittance for several wide waveguides. FIG. 18 is a drawing showing the relationship between the waveguide width and the coupling length when the offset ratio is zero. FIG. 19 is a drawing showing main steps in the method of manufacturing the semiconductor optical waveguide device according to the present embodiment.

  The knowledge of the present invention can be easily understood by considering the following detailed description with reference to the accompanying drawings shown as examples. Subsequently, embodiments of the semiconductor optical waveguide device and the method of manufacturing the semiconductor optical waveguide device of the present invention will be described with reference to the accompanying drawings. Where possible, the same parts are denoted by the same reference numerals.

  FIG. 1 is a diagram schematically showing the structure of a semiconductor optical waveguide device according to the present embodiment. FIG. 2 is a drawing schematically showing the structure of the semiconductor optical waveguide device in the present embodiment. The constituent members of the semiconductor optical waveguide element 11 are roughly divided into a member A, a member B, and a member C.

  The semiconductor optical waveguide device 11 includes a substrate 13. The substrate 13 includes a first portion 13a, a second portion 13b, and a third portion 13c, and the first portion 13a to the third portion 13c are arranged in the direction of the first axis Ax1. The substrate 13 includes a groove 19a extending in the direction of the first axis Ax1, and a first terrace 19b and a second terrace 19c that define the groove 19a.

  The semiconductor optical waveguide device 11 includes a first waveguide structure 15, and the first waveguide structure 15 is provided on the main surface 13 d of the substrate 13. The first waveguide structure 15 includes a first portion 15a, a second portion 15b, and a third portion 15c provided on the first portion 13a, the second portion 13b, and the third portion 13c of the substrate 11, respectively. The first waveguide structure 15 includes a first semiconductor layer 21a, a first waveguide mesa 21b, a first terrace 21c, and a second terrace 21d. The first semiconductor layer 21a is supported by the first terrace 19b and the second terrace 19c of the substrate 11. The first waveguide mesa 21b is provided on the first semiconductor layer 21a. The first terrace 21c and the first waveguide mesa 21b define the first groove 21e, and the second terrace 21d and the first waveguide mesa 21b define the second groove 21f. In the present embodiment, in the first portion 15a, the groove 21e and the groove 21f are combined into a single groove. In the second portion 15b and the third portion 15c, the first groove 21e and the second groove 21f define the first waveguide mesa 21b.

  The first waveguide mesa 21b of the first waveguide structure 15 includes a twelfth waveguide mesa portion 21g and a thirteenth waveguide mesa portion 21h, and the twelfth waveguide mesa portion 21g and the thirteenth waveguide mesa portion 21h are the substrate 13. Are provided on the second part 13b (15b) and the third part 13c (15c), respectively. The waveguide width of the twelfth waveguide mesa portion 21g is larger than the waveguide width of the thirteenth waveguide mesa portion 21h. The twelfth waveguide mesa portion 21g is optically coupled to the thirteenth waveguide mesa portion 21h. The width WG1 (W) of the twelfth waveguide mesa portion 21g is larger than the width WG1 (N) of the thirteenth waveguide mesa portion 21h. The twelfth waveguide mesa portion 21g may extend linearly in the direction of the first axis Ax1, and the thirteenth waveguide mesa portion 21h may include a portion extending in the direction of the first axis Ax1.

  The semiconductor optical waveguide device 11 includes a second waveguide structure 17, and the second waveguide structure 17 is provided on the main surface 13 d of the substrate 13. The second waveguide structure 17 includes a first portion 17a and a second portion provided on the first portion 15a (first portion 13a) and the second portion 15b (second portion 13b) of the first waveguide structure 15, respectively. 17b, and may include a third portion 17c provided on the third portion 15c (third portion 13c) of the first waveguide structure 15 if necessary. The second waveguide structure 17 includes a second semiconductor layer 23a supported on the first terrace 21c and the second terrace 21d of the first waveguide structure 15, and a second waveguide member provided on the second semiconductor layer 23a. 23b, and a first terrace 23c and a second terrace 23d. The first terrace 23c and the second waveguide mesa 23b define the first groove 23e, and the second terrace 23d and the first waveguide mesa 23b define the second groove 23f. The first groove 23e and the second groove 23f define the first waveguide mesa 23b. The second waveguide mesa 23b of the second waveguide structure 17 includes a twenty-first waveguide mesa portion 23h and a twenty-second waveguide mesa portion 23g. The twenty-first waveguide mesa portion 23h and the twenty-second waveguide mesa portion 23g are respectively The first waveguide structure 15 is provided on the first portion 15a (17a) and the second portion 15b (17b). The twenty-second waveguide mesa portion 23g is optically coupled to the twenty-first waveguide mesa portion 23h. The width WG2 (W) of the 22nd waveguide mesa portion 23g is larger than the width WG2 (N) of the 21st waveguide mesa portion 23h. The twenty-second waveguide mesa portion 23g may extend linearly in the direction of the first axis Ax1, and the thirteenth waveguide mesa portion 23h may include a portion extending in the direction of the first axis Ax1.

  In the second portion 13b of the substrate 13, the grooves 19a, the twelfth waveguide mesa portion 21g, and the twenty-second waveguide mesa portion 23g are arranged in the direction of the second axis Ax2 intersecting the main surface 13d of the substrate 13.

  According to this semiconductor optical waveguide device 11, the first waveguide mesa 21b of the first waveguide structure 15 is aligned with the groove 19a of the substrate 13, and the second waveguide mesa 23b of the second waveguide structure 17 is The first waveguide structure 15 is aligned with the first waveguide mesa 21b. In the first waveguide structure 15, the width of the twelfth waveguide mesa portion 21g is larger than the width of the thirteenth waveguide mesa portion 21h, and the width of the twenty-second waveguide mesa portion 23g in the second waveguide structure 17 is the first. It is larger than the width of the 21 waveguide mesa portion 23h. Further, since the twelfth waveguide mesa portion 21g and the twenty-second waveguide mesa portion 23g are arranged in the direction of the second axis Ax2 in the second portion 13b of the substrate 13, the twelfth waveguide mesa portion 21g and the twenty-second waveguide mesa portion 23g are arranged on the second portion 13b of the substrate 13. The waveguide mesa unit 21g is optically coupled to the twenty-second waveguide mesa unit 23g via the second semiconductor layer 23a. In this coupling structure, since the optical coupling is performed in the wide twelfth waveguide mesa portion 21g and the wide twenty-second waveguide mesa portion 23g, the second waveguide structure 17 is connected to the first waveguide structure 15. In the structure supported by the first terrace 21c and the second terrace 21d, the margin of positional deviation between the first waveguide mesa 21b of the first waveguide structure 15 and the second waveguide mesa 23b of the second waveguide structure 23 can be enlarged. .

  Further, in this optical coupling structure, the change width of the optical coupling due to the positional deviation between the first waveguide mesa 21b of the first waveguide structure 15 and the second waveguide mesa 23b of the second waveguide structure 17. Can be adjusted by increasing the coupling length of the wide twelfth waveguide mesa portion 21g and the twenty-second waveguide mesa portion 23g.

  In the semiconductor optical waveguide device 11, the first waveguide structure 15 forms a junction J1 with the main surface 13 d of the substrate 13, and the second waveguide structure 17 has a junction J2 with the main surface 15 d of the first waveguide structure 15. It is made. It can be manufactured by bonding the first waveguide structure 15 to the substrate 13 according to the arrow AR1 and bonding the second waveguide structure 17 to the first waveguide structure 15 according to the arrow AR2.

  When the semiconductor optical waveguide device 11 is a directional coupler, one of the twelfth waveguide mesa portion 21g and the twenty-second waveguide mesa portion 23g has an end portion. In the present embodiment, both the twelfth waveguide mesa portion 21g and the twenty-second waveguide mesa portion 23g have end portions 21j and 23j. When the twelfth waveguide mesa portion 21g and the twenty-second waveguide mesa portion 23g are not terminated, the second axis is used to avoid optical coupling between the twelfth waveguide mesa portion 21g and the twenty-second waveguide mesa portion 23g. One or both of the twelfth waveguide mesa portion 21g and the twenty-second waveguide mesa portion 23g can form a bent waveguide so as not to form an overlap related to Ax2.

  The first waveguide mesa 21b can include a first tapered waveguide portion 21i provided between the twelfth waveguide mesa portion 21g and the thirteenth waveguide mesa portion 21h. According to this semiconductor optical waveguide device 11, the first tapered waveguide portion 21i adiabatically couples the fundamental waveguide mode of the twelfth waveguide mesa portion 21g and the fundamental waveguide mode of the thirteenth waveguide mesa portion 21h. be able to. The twelfth waveguide mesa portion is preferably terminated. The width of the first tapered waveguide portion 21i monotonously changes in the direction from the thirteenth waveguide mesa portion 21h to the twelfth waveguide mesa portion 21g. More specifically, the first tapered waveguide portion 21i has one end connected to the thirteenth waveguide mesa portion 21h and the other end connected to the twelfth waveguide mesa portion 21g. One end of the first taper waveguide portion 21i has a waveguide width substantially equal to the waveguide width of the thirteenth waveguide mesa portion 21h, and the other end of the first taper waveguide portion 21i is the twelfth waveguide mesa portion. It has a waveguide width substantially equal to the waveguide width of 21 g. In the preferred embodiment, the first tapered waveguide portion 21i increases monotonously in the direction from one end to the other end.

  The second waveguide mesa 23b includes a second tapered waveguide portion 23i provided between the twenty-first waveguide mesa portion 23h and the twenty-second waveguide mesa portion 23g. The second tapered waveguide portion 23i can adiabatically couple the fundamental waveguide mode of the twenty-second waveguide mesa 23g and the fundamental waveguide mode of the twenty-first waveguide mesa 23h. The twelfth waveguide mesa portion is preferably terminated.

  The width of the second tapered waveguide portion 23i monotonously changes in the direction from the 21st waveguide mesa portion 23h to the 22nd waveguide mesa portion 23g. More specifically, the second tapered waveguide portion 23i has one end connected to the 21st waveguide mesa portion 23h and the other end connected to the 22nd waveguide mesa portion 23g. One end of the second tapered waveguide portion 23i has a waveguide width substantially equal to the waveguide width of the twenty-first waveguide mesa portion 23h, and the other end of the second tapered waveguide portion 23i is the twenty-second waveguide mesa. The waveguide width is substantially equal to the waveguide width of the portion 23g. In a preferred embodiment, the second tapered waveguide portion 23i increases monotonously in the direction from one end to the other end.

  In a preferred embodiment according to the semiconductor optical waveguide device 11, the twelfth waveguide mesa portion 21g extends over the whole from one end to the other end of the second portion 15b of the first waveguide structure 15, and the twenty-second waveguide mesa. The portion 23g extends over the entire length from one end to the other end of the second portion 17b (13b, 15b) of the second waveguide structure 17. The length of the second portion 13b of the substrate 13 is longer than the reference length, and this reference length is related to the first waveguide structure 15 and the second waveguide with respect to the direction of the third axis Ax3 intersecting the first axis Ax1 and the second axis Ax2. When one of the waveguide structures 17 is not off-axis with respect to the other, the first waveguide structure 15 and the second waveguide structure 17 have such a length that the transmittance of light from one to the other becomes 1. Preferably there is. According to this semiconductor optical waveguide device, the length of the second portion 13b (15b, 17b) of the substrate 13 is made longer than the reference length, so that the twelfth waveguide mesa portion 21g and the twenty-second waveguide mesa portion 23g are formed. By adjusting the coupling length, it is possible to compensate for a decrease in transmittance due to misalignment in the direction of the third axis Ax3 by increasing the coupling length in the direction of the first axis Ax1.

  The thirteenth waveguide mesa portion 21h is a single mode waveguide, and the width of the twelfth waveguide mesa portion 21g is preferably 4 μm or more. At this time, optical coupling is performed in the wide waveguide portion. The misalignment between the first waveguide mesa 21b of the waveguide structure 15 and the second waveguide mesa 23b of the second waveguide structure 17 can be relatively relaxed. However, if the width of the twelfth waveguide mesa portion 21 is too wide, it becomes difficult to keep the optical mode propagating through the twelfth waveguide mesa portion 21 unimodal when there is structural perturbation. The waveguide mesa portion 21g is preferably 10 μm or less.

  The 23rd waveguide mesa portion 23h is a single mode waveguide, and the 22nd waveguide mesa portion 23g is preferably 4 μm or more. At this time, optical coupling is performed in the wide waveguide portion. The misalignment between the first waveguide mesa 21b of the waveguide structure 15 and the second waveguide mesa 23b of the second waveguide structure 17 can be relatively relaxed. However, if the width of the twelfth waveguide mesa portion 21 is too wide, it becomes difficult to keep the optical mode propagating through the twelfth waveguide mesa portion 21 unimodal when there is structural perturbation. The waveguide mesa portion 21g is preferably 10 μm or less.

  More preferably, when the waveguide width of the 22nd waveguide mesa portion 21g is substantially equal to the waveguide width of the 12th waveguide mesa portion 23g, the 12th waveguide mesa portion 21g and the 22nd waveguide mesa portion 23g Enables efficient light propagation from one to the other. This is because the propagation constant of light propagating through each waveguide is the same.

  In the semiconductor optical waveguide device 11, the first semiconductor layer 21a can include, for example, InP. The first waveguide mesa 21b can include, for example, an InGaAsP core layer for an optical waveguide and an InP cladding layer sandwiching the InGaAsP core layer. The second semiconductor layer 23a can comprise InP, for example. The second waveguide mesa 23b can include, for example, an InGaAsP core layer for an optical waveguide and an InP cladding layer sandwiching the InGaAsP core layer. According to this stacked structure, regarding the refractive index distribution in the direction of the second axis Ax2, the InP layer in the second semiconductor layer 23a is formed by the optical waveguide core of the first waveguide mesa 21b and the optical waveguide of the second waveguide mesa 23b. The waveguide core can be optically separated and optically coupled.

  A semiconductor optical waveguide device according to a preferred example of the present embodiment has an optical waveguide having a narrow optical waveguide width that allows a mode having a single-modal mode to stably propagate, and a waveguide width wider than this. A composite optical waveguide structure including an optical waveguide is employed. In this composite optical waveguide structure, it is preferable to connect these optical waveguides having different widths with an optical waveguide whose optical waveguide width changes continuously (or stepwise).

  The composite optical waveguide structure is applied to both the first optical waveguide structure 15 provided on the substrate and the second optical waveguide structure 17 bonded thereon. In the composite optical waveguide structure, optical waveguide portions constituting a directional coupler having a wide waveguide width are optically coupled to each other, and light is transmitted from one optical waveguide to the other optical waveguide.

  Referring to FIG. 2 again, the constituent members of the semiconductor optical waveguide device are roughly divided into a member A, a member B, and a member C.

  The member A is a support substrate in which, for example, a Si substrate is processed to form a groove.

  The member B is, for example, a waveguide obtained by processing a ridge-like or mesa-like structure in an epitaxial stack of InP-based semiconductor (a laminate including two clad layers and a core layer provided between the clad layers). It is a structure. The lower waveguide structure 15 includes a semiconductor mesa for a single mode optical waveguide, a semiconductor mesa for a tapered waveguide whose width is changed to a tapered shape, and a pair of grooves that define these mesa shapes. A third portion 15c, a second portion 15b including a semiconductor mesa for an optical waveguide having a width wider than that of the single mode optical waveguide, and a pair of grooves defining the mesa shape, and a pair of grooves without including the semiconductor mesa. A first portion 15a including a single groove constituted by a combination is included. The semiconductor mesa in the third portion 15c and the semiconductor mesa in the second portion 15b extend in the direction of the first axis Ax1, and a pair of grooves in the third portion 15c and the second portion 15b and a single groove in the first portion 15a. Also extends in the direction of the first axis Ax1. Due to the single groove in the first portion 15a, the semiconductor mesa 21g in the second portion 15b includes one end connected to the semiconductor mesas 21h and 21i in the third portion 15c and the other end terminated.

  The member C is, for example, a waveguide obtained by processing a ridge-like or mesa-like structure in an epitaxial layer of an InP-based semiconductor (a layered body including two clad layers and a core layer provided between the clad layers). It is a structure. The upper waveguide structure 17 includes a semiconductor mesa for a single mode optical waveguide, a semiconductor mesa for a tapered waveguide whose width is changed to a tapered shape, and a pair of grooves defining these mesa shapes. 1 part 17a, 2nd part 17b including the semiconductor mesa for the optical waveguide wider than the single mode optical waveguide, and a pair of grooves defining the mesa shape, and a combination of the pair of grooves without including the semiconductor mesa A third portion 17c including a single groove constituted by The semiconductor mesa in the first portion 17a and the semiconductor mesa in the second portion 17b extend in the direction of the first axis Ax1, and a pair of grooves in the second portion 17b and the first portion 17a and a single groove in the third portion 17c. Also extends in the direction of the first axis Ax1. Due to the single groove in the third portion 17c, the semiconductor mesa 23g in the second portion 17b includes one end connected to the semiconductor mesas 23h and 23i in the first portion 17a and the other end terminated.

  The first portion 17a, the second portion 17b, and the third portion 17c of the upper waveguide structure 17 are on the first portion 15a, the second portion 15b, and the third portion 15c of the lower waveguide structure 15, respectively. Is provided. The first portion 15a, the second portion 15b, and the third portion 15c of the lower waveguide structure 15 are provided on the first portion 13a, the second portion 13b, and the third portion 13c of the support substrate 13, respectively. Yes. Because of this overlapping structure, the wide optical waveguide 21g in the second portion 15b of the lower waveguide structure 15 is optically coupled to the wide optical waveguide 23g in the second portion 17b of the upper waveguide structure 17. Is done. A groove 19 a of the support substrate 13 extends below the wide optical waveguide 21 g in the second portion 15 b of the lower waveguide structure 15. Therefore, the member A has a hollow structure located below the first portion 15a to the third portion 15c of the lower waveguide structure 15 and includes the hollow portion. The refractive index distribution of the waveguide layer is defined. The member B has a hollow structure (single groove) located on the lower side of the first portion 17a of the upper waveguide structure 17 and includes the hollow portion. A refractive index distribution is defined. In order to define a desired profile of the refractive index distribution in the vertical direction in the waveguide structure of the upper waveguide structure 17 and the lower waveguide structure 15, the hollow structure as described above is provided.

  When the optical directional coupler is configured by the superposition structure, the wide optical waveguide portions 21g and 23g are formed in the second portions 17b and 15b in the upper waveguide structure 17 and the lower waveguide structure 15. Arranged so as to overlap vertically. With this arrangement, even if a positional deviation in the width direction between the semiconductor optical waveguides occurs in the overlapping junction portion, the longitudinal waveguides related to the upper waveguide structure 17 and the lower waveguide structure 15 are arranged. A decrease in light transmittance can be suppressed.

  The operation principle of the semiconductor optical waveguide device in this embodiment will be described. The inventor examined the cause of the decrease in light transmittance in an element in which the alignment misalignment occurred in the waveguide width direction (direction orthogonal to the waveguide extending direction) in the vertical optical directional coupler. To do.

  As shown in FIG. 3, two waveguide structures having the same layer structure and the same waveguide width are stacked one above the other to constitute an optical directional coupler. In this optical directional coupler, for example, when light is transmitted from the lower optical waveguide to the upper optical waveguide, a lateral misalignment (offset) is generated in the two waveguide structures superimposed one above the other. Sometimes, the light transmittance of the optical directional coupler changes. The length Lc of the overlapping portion between the lower optical waveguide and the upper optical waveguide is the coupled waveguide length of the portion constituting the directional coupler. Referring to FIG. 4, the change in the light transmittance of the optical directional coupler with respect to the normalized coupling length is shown. The offset ratio indicates the ratio of deviation (offset) with respect to the waveguide width. The horizontal axis indicates the normalized coupling length. When this normalized coupling length is zero offset (no deviation), 100% light transition (transmission) occurs from one waveguide to the other. It is the length of the waveguide normalized by the coupling length. Light incident from one end of the lower optical waveguide in this optical directional coupler propagates through the lower optical waveguide. The guided light is transmitted through the upper optical waveguide while propagating through the lower optical waveguide in the optical directional coupler. The light is completely transmitted at the normalized waveguide length of 1. Furthermore, when the coupled waveguide is long beyond this, a transition from the upper waveguide to the lower waveguide occurs. Therefore, the transmittance becomes 0 at the normalized waveguide length of 2.

  Next, when a deviation (offset) occurs in the waveguide width direction, there is a normalized coupling length at which the transmittance peak reaches 100%, but the normalized coupling length (the length at which the light transition becomes 100%). Is greater than the unit value of 1. That is, the waveguide length (coupling length) required for complete transition becomes longer. This ratio of increasing becomes larger as the offset amount increases.

  In a directional coupler in which the coupling waveguide length is set to a length that gives the maximum transmittance when the offset is zero (standardized waveguide length 1), the waveguide length that gives the maximum transmission with an offset larger than zero is Since the length becomes longer, the optical waveguide to be coupled constituting the directional coupler is terminated before the light is completely transmitted to the upper waveguide. Therefore, the remaining untransmitted light becomes a transmission loss.

  Here, the inventor uses an offset amount, an optical waveguide width (2 μm or more), and several layer structures with respect to the optical waveguide, so that when the unimodal mode propagates through the waveguide, the optical directional coupler When the optical waveguide length (coupling length) that gives a transmittance of 1 was investigated, knowledge on the structure dependence of the coupling coefficient κ indicating the degree of optical coupling between the two waveguides was obtained.

  The coupling coefficient κ is substantially a component κ (vertical) determined by the vertical light overlap of the upper and lower optical waveguides, and a component κ (horizontal) determined by the horizontal light overlap of the upper and lower optical waveguides. Given by the product.

  FIG. 5 is a diagram showing optical coupling relating to two components of the coupling coefficient, that is, a vertical component κ (vertical) and a horizontal component κ (horizontal). As shown in FIGS. 5A and 5B, the upper and lower coupling coefficients κ (vertical) are determined by the overlap integral of the oozing of the guided light in the vertical direction of the upper and lower optical waveguides. When there is no offset in the upper and lower waveguides, the overlap of guided light in the horizontal direction is the same, so κ (horizontal) determined by the overlap integral is 1.

  Next, when an offset occurs, the vertical coupling coefficient κ (vertical) does not change, but the lateral overlap integral is small, so κ (parallel) is smaller than 1, and the coupling coefficient κ is proportional to it. As a result, the length of the optical waveguide giving the transmittance of 1 is increased.

  5 (c) and 5 (d), the layer structure of the upper and lower optical waveguides does not change, but the waveguide having a wider waveguide width than the waveguides (a) and (b) in FIG. The bond structure is shown. When there is no offset in the upper and lower waveguides, there is no change in the coupling constant κ (vertical) in the vertical direction as shown in FIG. 5C, and the horizontal coupling coefficient κ (horizontal) is also 1. Therefore, the total coupling coefficient κ considering both couplings is the same as the coupling structure shown in the part (a) of FIG. 5, and the optical waveguide length giving the transmittance 1 is the same. Next, when the offset occurs, the vertical coupling coefficient κ (vertical) does not change, but the horizontal overlap integral becomes small as shown in FIG. 5D.

  Here, in the structure in which only the fundamental mode is stably excited and propagated in the semiconductor waveguide, the width of the optical waveguide exceeds the upper limit of, for example, 2 μm, and the optical waveguide width is widened. Is almost completely confined in the optical waveguide (its shape has a nearly raised cosine type). Even if the optical waveguide width changes, the light intensity distribution in the waveguide width direction is similar. For this reason, when the offset ratio normalized by the waveguide width is the same, the knowledge that the value of κ (horizontal) is the same regardless of the absolute value of the waveguide width is obtained.

  6 and 7 show the optical waveguide length that gives the transmittance 1 when the offset ratio is changed, and the dependency on κ (horizontal).

  As shown in part (e) of FIG. 5, when the layer structure of the upper and lower waveguides is changed and the offset between the upper and lower waveguides is zero, the overlap integral of the light in the vertical direction changes. The coupling coefficient κ (vertical) in the direction changes, and as a result, the coupling constant κ changes and the absolute value of the optical waveguide length giving the transmittance 1 also changes. As shown in FIG. 5 (f), when a non-zero offset is further applied, the horizontal coupling coefficient κ (horizontal) determined by the overlap integral of the horizontal optical mode is the vertical coupling coefficient. It changes independently of the change in κ (vertical).

  In other words, according to the inventor's study, even if the layer structure of the upper and lower waveguides changes, the waveguide length is normalized using a coupling length that gives a transmittance of 1 when the offset at that time is zero When this is done, the dependence of the normalized waveguide length or coupling constant κ (horizontal) that provides transmittance 1 on the waveguide offset ratio is all the same as in FIGS. 6 and 7.

  As described with reference to FIG. 4, the waveguide length of the portion constituting the directional coupler (the portion where the lower optical waveguide and the upper optical waveguide overlap) is the normalized waveguide length 1 (offset). If the offset is generated when the directional coupler is formed by the junction, the length of the waveguide that gives the transmittance of 1 becomes long. For this reason, before the light is completely transmitted from one waveguide to the other waveguide, a portion of the waveguide constituting the directional coupler is terminated, and light that is not transmitted becomes a transmission loss.

  FIG. 8 shows the relationship between the waveguide offset ratio and the transmittance. Referring to FIG. 8, in order to obtain within 5% (95% or more transmission) for the decrease in transmittance, the allowable value of the waveguide offset ratio is 18%.

  Since the transmittance depends only on the waveguide offset ratio, the absolute value of the allowable offset can be increased in proportion to the waveguide width in a structure using a wide waveguide width in the portion constituting the directional coupler. For this reason, when a monomodal single mode propagates in an optical waveguide having a wide waveguide width, the absolute value of the waveguide offset allowed in the bonding process is increased in proportion to the waveguide width of the wide portion. It becomes possible.

  Such a directional coupler is composed of, for example, the following composite optical waveguide structure. In the composite optical waveguide structure, an optical waveguide having a narrow optical waveguide width capable of stably propagating a unimodal mode is changed to an optical waveguide having a wider waveguide width. Waveguide structures that are optically coupled via a waveguide are stacked in multiple layers (for example, in two layers), and optically coupled vertically through optical waveguide portions having a wide waveguide width. With this configuration, a directional coupler can be configured. In this directional coupler, the absolute value of the waveguide offset allowed at the time of joining can be increased in proportion to the waveguide width in a wide portion.

  In this composite optical waveguide structure, when the offset is not zero, the coupling length giving the transmittance of 1 becomes long. In the directional coupler in which the length of the optical coupling portion of the directional coupler portion is made larger than the length of the coupling waveguide that gives a transmittance of 1 at zero offset, the allowable offset ratio is increased. At the same time, the maximum optical coupling within the permissible offset amount can be kept the same (that is, 1) while achieving a transmittance exceeding the permissible level.

  FIG. 9 shows a composite optical waveguide structure in which the length of the optical coupling portion of the directional coupler portion is set to 1.14 times (1.14 times the coupling length value that gives the maximum coupling when there is no offset). The relationship between the normalized waveguide length and the transmittance is shown. By setting the length of the optical coupling portion of the directional coupler portion to 1.14 times, the transmittance is 0.95 for the waveguide offset ratio 0, while the transmittance is increased when the offset ratio increases. As the offset ratio increases to 1 and the offset ratio further increases, the transmittance gradually decreases.

  FIG. 10 shows that the length of the optical coupling part of the directional coupler part is set to 1, 1, 14, 1.21, and 1.26 times the coupling length that gives the maximum coupling when there is no offset. In the composite optical waveguide structure, the relationship between the waveguide offset ratio and the transmittance is shown. When the ratio is 1.14 times, the waveguide offset ratio giving the optical coupling of 0.95 or more in the directional coupler portion can be improved from 0.18 to 0.25 while keeping the maximum coupling ratio at 1. . Also in this case, the actual allowable waveguide offset can be increased as the waveguide width of the directional coupler is increased.

  From the above description, the following can be understood. In other words, by making the length of the optical coupling portion of the directional coupler portion longer than the coupling length that gives the maximum coupling when there is no offset, the light of the directional coupler portion is maintained while keeping the maximum coupling rate at 1. The amount of offset by which the coupling can be made larger than the desired value can be increased.

(Example)
First, a method for manufacturing an optical waveguide device using a bonding method will be described. A directional coupler is manufactured as an optical waveguide element. The following description will be made with reference to a cross section taken in a direction crossing the extending direction of the two optical waveguides of the directional coupler. As shown in FIG. 11A, a substrate is prepared. As this substrate, for example, a silicon substrate, an InP substrate, or the like can be used. As shown in part (b) of FIG. 11, a mask for defining a groove is formed on a silicon (Si) substrate. The mask is manufactured by forming a mask film, processing using photolithography and etching. The mask material can be SiN, SiO ₂ or the like. For example, a vapor deposition method can be applied to form the mask film.

  After a SiN layer mask is formed on the Si substrate, the Si substrate is etched to form grooves as shown in FIG. 11 (c). The depth of the groove is, for example, 0.5 μm. For example, chlorine gas or the like is used as the etching gas. After forming the groove in the Si substrate, as shown in FIG. 11D, the SiN mask is removed using buffered hydrofluoric acid to prepare a Si processed substrate. The Si processed substrate has a groove extending in the direction of the first axis, and a first terrace and a second terrace that define the groove, and the first axis is an extending direction of the groove. The Si processed substrate includes a first portion, a second portion, and a third portion, and the first portion, the second portion, and the third portion are arranged in the direction of the first axis.

  Next, an epitaxial substrate (substrate product) including an epitaxial stack for a waveguide structure grown on a III-V semiconductor substrate is prepared. For example, the epitaxial substrate is manufactured as follows. On an InP substrate, an InGaAs layer having a thickness of 0.2 μm, an InP layer having a thickness of 0.6 μm, an InGaAsP layer having a thickness of 0.5 μm (a semiconductor having a PL wavelength λp of 1.35 μm at room temperature), a thickness of 0 An epitaxial substrate is fabricated by sequentially epitaxially growing a 6 μm InP layer.

  As shown in part (a) of FIG. 12, the epitaxial substrate is bonded onto the Si processed substrate. At the time of this bonding, plasma processing is performed on the Si processed substrate and the epitaxial substrate using an ICP plasma generator. The plasma processing of the Si processed substrate is performed using, for example, excited N2 plasma. For this plasma treatment, conditions of gas pressure 0.3 Pa and ICP excitation power 300 W are used. The plasma processing time for the Si processed substrate is, for example, 2 minutes. The plasma processing time for the epitaxial substrate is, for example, 6 minutes. By this plasma treatment, the semiconductor surface can be hydrophilized. The hydrophilic substrate products are lightly pressed together in air at room temperature (for example, 25 ° C.) to bond both substrates (this is referred to as temporary bonding). After this temporary bonding, the temporarily bonded substrate product is heat-treated and firmly fixed to form a combined substrate product. The temperature of this heat treatment is, for example, about 350 degrees Celsius, a hot plate can be used for this heat treatment, and the heat treatment time is, for example, about 2 hours.

  Thereafter, as shown in part (b) of FIG. 12, the III-V semiconductor substrate of the epitaxial substrate is removed from the bonded substrate product. In this removal, for example, etching with concentrated hydrochloric acid can be used to remove the InP substrate. By this process, the Si processed substrate can be left and the InP substrate can be selectively etched. Specifically, since the InGaAs layer in the epitaxial stack is insoluble in concentrated hydrochloric acid, the etching stops on the surface of the InGaAs layer. After removing the III-V semiconductor substrate, the remaining InGaAs layer is selected using another etchant (mixed solution of sulfuric acid: hydrogen peroxide: pure water) as shown in FIG. 12 (c). Etch. Since the InP layer located under the remaining InGaAs layer is insoluble in the above etchant (mixed solution of sulfuric acid: hydrogen peroxide: pure water), the etching stops on the surface of the InP layer. After these steps, an InP layer is exposed on the surface of the bonded substrate product.

  As shown in part (d) of FIG. 12, a mask for forming the first waveguide structure is formed in the epitaxial stack of the bonded substrate products. This mask can be made of SiN, for example. The SiN mask is manufactured in the same manner as described above, but is not limited to this.

  Thereafter, using this insulating film mask, the epitaxial layer transferred on the Si processed substrate is processed to form a first waveguide structure as shown in FIG. 13 (a). The insulating film mask has a pattern that defines an optical waveguide configured by epitaxial lamination. As shown in FIGS. 1 and 2, the insulating mask pattern defines the planar shapes of the twelfth and thirteenth waveguide portions on the second and third portions of the Si processed substrate, respectively. . The insulating film mask is removed to produce a substrate product including the first waveguide structure. As shown in part (b) of FIG. 13, the semiconductor mesa structure is located on the groove of the Si processed substrate. The first waveguide structure includes a first semiconductor layer (InP layer) supported on the first terrace and the second terrace of the Si processed substrate, a first waveguide mesa provided on the first semiconductor layer, A first groove defining a first waveguide mesa; and a second groove. The first waveguide structure includes a first portion, a second portion, and a third portion provided on the first portion, the second portion, and the third portion of the Si processed substrate, respectively. The first waveguide mesa having the first waveguide structure includes a twelfth waveguide mesa portion and a thirteenth waveguide mesa portion provided on the second portion and the third portion of the Si processed substrate, respectively. The width of the mesa portion is larger than the width of the thirteenth waveguide mesa portion.

  The SiN mask defines a narrow optical waveguide and a wide optical waveguide. The narrow optical waveguide has a width of 1.5 μm and the wide optical waveguide has a width of 8 μm. If necessary, the optical coupling between the narrow optical waveguide and the wide optical waveguide is configured via an intermediate waveguide. Can. A tapered waveguide having a continuously varying waveguide width can be employed as the intermediate waveguide. The width of the tapered waveguide varies linearly between a waveguide width of 1.5 μm and 8 μm and a length of 450 μm. At this time, the SiN mask defines a narrow-width optical waveguide, a tapered optical waveguide, and a wide-width optical waveguide.

  In this embodiment, the first waveguide mesa etches an epitaxial layer of InP / InGaAsP / InP at a depth of 1.5 μm. The remaining InP layer (first semiconductor layer) is 0.2 μm. For processing the first waveguide mesa, for example, HI gas can be used. After forming the first waveguide structure by etching, the SiN mask is removed using buffered hydrofluoric acid. By these steps, the first substrate product or the first waveguide product including the Si processed substrate and the first waveguide structure provided on the Si processed substrate is manufactured.

  Next, a second waveguide product to be bonded onto the substrate on which the waveguide is formed is produced. The second waveguide product can comprise, for example, a semiconductor element piece. The semiconductor element piece may include a functional element and an optical waveguide connected to the functional element.

  Next, another epitaxial substrate (substrate product) including an epitaxial stack for the waveguide structure grown on the III-V semiconductor substrate is prepared. For example, the epitaxial substrate is manufactured as follows. On an InP substrate, an InGaAs layer having a thickness of 0.2 μm, an InP layer having a thickness of 0.6 μm, an InGaAsP layer having a thickness of 0.5 μm (a semiconductor having a PL wavelength λp of 1.35 μm at room temperature), a thickness of 0 A 6 μm InP layer is epitaxially grown in order to produce an epitaxial substrate as shown in FIG.

  A second optical waveguide structure is produced using the epitaxial substrate. The second optical waveguide structure includes a wide optical waveguide optically coupled to the first optical waveguide structure and a narrow optical waveguide coupled to the optical waveguide. Further, the optical waveguide has a monolithic light receiving structure. Functional elements such as elements and light emitting elements can be combined. The epitaxial layer structure for these functional elements can be grown separately from the above epitaxial layer structure. Epi structures for these waveguide structures and functional elements are grown on InGaAs layers.

  FIG. 14 shows a cross section taken to intersect a wide optical waveguide. As shown in part (a) of FIG. 14, a mask for defining the second optical waveguide structure is formed on the epitaxial stack for the second optical waveguide structure. The mask can be made of SiN, and the SiN mask can be manufactured in the same manner as described above, but is not limited thereto.

  This SiN mask defines the waveguide width of at least the wide optical waveguide and the optical waveguide portion where the waveguide width continuously changes. The wide optical waveguide can be 8 μm, for example, and the narrow optical waveguide can be 1.5 μm, for example.

  The second waveguide structure includes a second semiconductor layer supported on the III-V compound semiconductor substrate, a second waveguide mesa provided on the second semiconductor layer, and a second waveguide mesa that defines the second waveguide mesa. Includes 1 terrace and 2nd terrace. The second waveguide structure may include a first part, a second part, and a third part arranged to align with the first part, the second part, and the third part of the Si processed substrate.

  The second waveguide mesa having the second waveguide structure includes a twenty-first waveguide mesa portion and a twenty-second waveguide mesa portion provided to match the first portion and the second portion of the Si processed substrate, respectively. The width of the 22nd waveguide mesa portion is larger than the width of the 21st waveguide mesa portion.

  The SiN mask defines a narrow optical waveguide and a wide optical waveguide. The narrow optical waveguide has a width of 1.5 μm and the wide optical waveguide has a width of 8 μm. If necessary, the optical coupling between the narrow optical waveguide and the wide optical waveguide is configured via an intermediate waveguide. Can. A tapered waveguide having a continuously varying waveguide width can be employed as the intermediate waveguide. The width of the tapered waveguide varies linearly between a waveguide width of 1.5 μm and 8 μm and a length of 450 μm. At this time, the SiN mask defines a narrow-width optical waveguide, a tapered optical waveguide, and a wide-width optical waveguide.

  As shown in part (b) of FIG. 14, the second waveguide mesa is produced by etching an epitaxial layer of InP / InGaAsP / InP at a depth of 1.5 μm in this embodiment. The remaining InP layer (first semiconductor layer) is 0.2 μm. For processing the second waveguide mesa, for example, HI gas can be used. After the second waveguide structure is formed by etching, the SiN mask is removed using buffered hydrofluoric acid as shown in FIG. 14 (c). By these steps, a second substrate product including a III-V compound semiconductor substrate and a second waveguide structure provided on the substrate is produced.

  In this embodiment, a second waveguide product (for example, a semiconductor element piece) to be bonded to the first substrate product is produced from the second substrate product. The second waveguide product may be a second substrate product, but in a preferred embodiment, it may be a semiconductor device piece that includes a functional device and an optical waveguide connected thereto. For example, a semiconductor element piece can be produced by cutting the second substrate product.

  As shown in FIG. 14D, the semiconductor element piece is bonded to the support substrate using a bonding material. In this embodiment, a sapphire substrate is used as the support substrate. The semiconductor element piece is temporarily fixed to the sapphire support substrate using a temporary bonding material (for example, a wax material containing terpene phenol resin as a main component). Temporary fixing is performed with the second waveguide structure facing the sapphire support substrate, and the back surface of the III-V compound semiconductor substrate is exposed.

  After temporarily fixing the second waveguide structure to the support substrate, the III-V compound semiconductor substrate (for example, InP substrate) is removed as shown in FIG. Concentrated hydrochloric acid can be used to remove the InP substrate. Etching of the InP substrate stops at the InGaAs layer. Thereafter, as shown in FIG. 15B, the InGaAs layer is removed using another etchant (for example, a mixed solution of sulfuric acid: hydrogen peroxide: pure water). After these selective etchings, the second waveguide structure is temporarily fixed to the support substrate upside down, so that the second waveguide structure is embedded in the temporary fixing material and the back surface of the second semiconductor layer of the second waveguide structure is Exposed. More specifically, the second waveguide mesa provided on the second semiconductor layer and the first groove and the second groove defining the second waveguide mesa are embedded in the temporary fixing material. By these steps, an intermediate product including a support substrate and a second waveguide product fixed to the support substrate, for example, a semiconductor element piece, is produced.

  As shown in part (a) of FIG. 16, this second waveguide product is joined to the first waveguide product. At the time of joining, plasma processing is performed on the first waveguide product and the second waveguide product using an ICP plasma generator. This plasma treatment is performed using, for example, excited N2 plasma. For this plasma treatment, conditions of gas pressure 0.3 Pa and ICP excitation power 300 W are used. The plasma treatment time for both products is for example 6 minutes. The semiconductor surface can be hydrophilized by plasma treatment. By bringing these hydrophilized semiconductor products into contact with each other in air at room temperature (for example, lightly press-contacting), both substrates are bonded (this is referred to as temporary bonding). After this temporary bonding, the temporarily bonded product is immersed in heated acetone, and the temporary bonding material is dissolved in acetone, thereby temporarily fixing as shown in part (a) of FIG. Remove the support board.

  The temporarily bonded product is heat treated and firmly fixed to form a combined substrate product. The temperature of this heat treatment is, for example, about 350 degrees Celsius, a hot plate can be used for this heat treatment, and the heat treatment time is, for example, about 2 hours. By this heat treatment, the bonded epi layer (including the functional element) can be firmly fixed. In this way, a semiconductor optical waveguide device is manufactured.

  In the semiconductor optical waveguide device manufactured in this example, the narrow waveguide width WG1 (N) in the first substrate product and the narrow waveguide width W2 (N) in the second waveguide product are both 2 μm or less. Yes, the width of the single mode waveguide. The length Lt of the tapered waveguide is 450 μm. When light having a wavelength of 1.55 μm is propagated through the coupling portion of these optical waveguides, the coupling length Lc of the optical directional coupler that provides the transmittance 1 in the layer structure shown in the present embodiment is 335 μm. Therefore, the tolerance of the waveguide offset that compensates the transmittance of 0.95 or more is 1 in the case where light is transmitted between the waveguides while the narrow waveguide is used in an element having a wide optical waveguide portion having a length of 335 μm. It is improved from 5 μm × 0.18 = 0.27 μm to 8 μm × 0.18 = 1.44 μm. Further, in an element in which the length Lc of the wide optical waveguide portion is 335 μm × 1.14 = 381.9 μm, the tolerance of the waveguide offset for compensating the transmittance of 0.95 or more is 1.5 μm × 0.18 = 0. Increased from 27 μm to 8 μm × 0.25 = 2 μm.

  Next, consider the case where light that has shifted from the lower optical waveguide to the upper optical waveguide propagates through the tapered portion when there is a waveguide offset.

  The light transmitted to the upper waveguide is asymmetric with respect to the electric field distribution in the waveguide width direction due to the fact that the alignment offset during fabrication of the directional coupler portion is not zero. The optical waveguide includes an InP cladding layer having a thickness of 0.6 μm and an InGaAsP (λp = 1.35 μm) core layer having a thickness of 0.4 μm, and has a wide waveguide width WG1 (W), WG2 ( When W) is 8 μm, the upper narrow optical waveguide width WG2 (N) is 2 μm, the taper waveguide length Lt is 450 μm, and the waveguide offset ratio is 0.3, the upper waveguide is transmitted. Waveguide light has a peak of light intensity that deviates from the center of the waveguide due to the waveguide offset. The light intensity peak propagates in a tapered portion while being shifted to the left or right from the center of the waveguide depending on the direction of the derived waveguide offset, and swings to the left and right. This is because the refractive index distribution of the optical waveguide in the upper waveguide structure is perturbed due to the presence of the offset, so that in addition to the unimodal mode bilaterally symmetric in the waveguide width direction, the waveguide width direction A mode having an even number of peaks is excited by a directional coupler. Since the propagation constant differs between the unimodal mode and the mode having an even number of peaks, the distribution of the optical field of the propagating light determined by the superposition of these modes fluctuates left and right in the waveguide width direction. Since a mode having an even number of peaks in the waveguide width direction is a higher-order mode, as the waveguide width becomes narrower in a wide tapered waveguide, a part of the higher-order mode is cut off, and the cutoff The mode is radiated out of the waveguide and becomes a waveguide loss.

  FIG. 17 shows a case where the waveguide offset ratio is changed for each layer structure in which the core layer thickness and the cladding layer thickness in the waveguide layer are changed to change the vertical coupling coefficient κ (vertical). It is drawing which shows the change of the fall of the transmittance | permeability for every optical waveguide width | variety. The horizontal axis indicates the value of κ (vertical) when the waveguide offset ratio is 0, and the vertical axis indicates the transmittance. In this structure, the transmittance is reduced when a part of the light is emitted outside the waveguide.

  In the upper optical waveguide structure, the narrow waveguide width WG2 (N) is 2 μm. When the transmittance is 1, it indicates that the light is propagated without an optical loss, and as the transmittance is smaller, the optical loss in the tapered waveguide is larger.

As the coupling coefficient κ increases for each waveguide width, the perturbation of the refractive index distribution that the upper waveguide receives from the lower waveguide increases. At this time, the low transmittance indicates that the higher-order mode is easily excited. As shown in FIG. 17, the coupling coefficient κ required to reliably provide the transmittance of 0.95 decreases as the waveguide width increases, and the waveguide width W (transmittance of 0.95) is 4 μm. , 6 μm, 8 μm, and 10 μm are 105 cm ⁻¹ , 67.5 cm ⁻¹ , 45 cm ⁻¹ , and 30 cm ⁻¹ , respectively. As the width of the optical waveguide is narrower, higher-order modes are less likely to be excited, and therefore, it is possible to propagate up to a high κ value without optical loss in the tapered portion.

From this explanation, the value of the coupling coefficient κ (vertical) can be directly converted into the optical waveguide length (coupling length z) that gives the transmittance 1 at the optical directional coupler portion (the transmittance 1 when κz = π / 2). The bond length is π / 2κ. In this embodiment, as shown in FIG. 18, the coupling coefficient ^{κ = 105cm -1, 67.5cm -1,} 45cm -1, relative to 30 cm ^-1, coupling length of the optical directional coupler moiety, 149 .6 μm, 232.7 μm, 349.1 μm, and 523 μm. In this specific example, this relationship relates to the waveguide width x (μm), and the coupling length y μm is expressed by the following relational expression.
y = 5.7139x < ² > -18.077x + 131.73.
By appropriately selecting the core layer thickness and the clad layer thickness in the waveguide layer so that the coupling length of the optical directional coupler portion is greater than that given by the above equation with respect to the waveguide width x, the taper It is possible to propagate without optical loss in the part. According to the semiconductor optical waveguide device according to the present embodiment, it is possible to provide a structure capable of reducing the dissipation loss at the tapered portion while increasing the waveguide offset margin at the optical directional coupler portion.

  As described above, according to this embodiment, even if the positional deviation in the width direction between the semiconductor optical waveguides constituting the vertical optical directional coupler is large, the decrease in the transmittance between the optical waveguides is small. An optical directional coupler can be realized. Further, according to the present embodiment, it is possible to adopt an optical waveguide configuration with little light dissipation at the tapered optical waveguide portion.

  FIG. 19 is a drawing showing main steps in the method of manufacturing the semiconductor optical waveguide device according to the present embodiment. For ease of understanding, reference is made to the schematic cross sections of the steps shown in FIGS. 11 to 16 and reference numerals attached to FIGS. 1 and 2 when possible.

  In step S101, the support substrate 13 is prepared (part (a) to (d) in FIG. 11). The support substrate 13 includes a first portion 13a, a second portion 13b, and a third portion 13c arranged in the direction of the first axis Ax1, and includes a groove 19a extending in the direction of the first axis Ax1 and the groove 19a. The first terrace 19b and the second terrace 19c are defined.

  In step S102, a first epitaxial substrate E1 including a first semiconductor multilayer SS1 for a waveguide structure on a first substrate (InP substrate shown in FIG. 12A) is prepared.

  In step S103, the first semiconductor stack SS1 of the first epitaxial substrate E1 is bonded to the support substrate so that the first terrace 19b and the second terrace 19b of the support substrate support the first semiconductor stack SS1 of the first epitaxial substrate E1. (Part (a) in FIG. 12).

  In step S104, after bonding the first semiconductor stack SS1 of the first epitaxial substrate E1 to the support substrate, the first substrate (InP substrate shown in FIG. 12A) is removed from the first epitaxial substrate E1. (Part (b) and (c) of FIG. 12).

  In step S105, after removing the first substrate from the first epitaxial substrate E1, the first semiconductor stacked layer SS1 is processed, and the first semiconductor layer 21a supported on the first terrace 19b and the second terrace 19c of the support substrate A first substrate product including a first waveguide structure 15 including a first waveguide mesa 21b provided on the first semiconductor layer 21a is formed (portions (b) and (c) in FIG. 12 and (A) part and (b) part of Drawing 13). The first waveguide structure 15 includes a first portion 15a, a second portion 15b, and a third portion 15c provided on the first portion 13a, the second portion 13b, and the third portion 13c of the substrate 13, respectively. The first waveguide mesa 21b of the first waveguide structure 15 includes a twelfth waveguide mesa portion 21g and a thirteenth waveguide mesa portion 21h provided on the second portion 13b and the third portion 13c of the substrate 13, respectively. The width of the twelfth waveguide mesa 21g is larger than the width of the thirteenth waveguide mesa 21h. Regarding the alignment between the substrate 13 and the first waveguide structure 15, the extending direction of the twelfth waveguide mesa portion 21g of the first waveguide mesa 21b is the extension of the groove 19a in the second portion 13b of the substrate 13. It is aligned with the direction.

  In step S106, a second epitaxial substrate E2 including the second semiconductor multilayer SS2 for the waveguide structure on the second substrate is prepared (part (a) of FIG. 14).

  Step S107 includes a second semiconductor layer 23a supported by the first terrace 21c and the second terrace 21d of the first waveguide structure 15, and a second waveguide mesa 23b provided on the second semiconductor layer 23a. The second waveguide structure 17 is formed from the second epitaxial substrate E2, and the support substrate 13, the first waveguide structure 15 and the second waveguide structure 17 are arranged in the direction of the second axis (FIG. 16 ( b) part). Since the second waveguide structure 17 is formed from the second semiconductor multilayer SS2 by processing the second epitaxial substrate E2, the second waveguide structure 17 is fabricated from the second semiconductor multilayer SS2. The second waveguide structure 17 includes a first portion 17a and a second portion 17b provided on the first portion 15a and the second portion 15b of the first waveguide structure 15, respectively. The second waveguide mesa 21b of the second waveguide structure 17 includes a twenty-first waveguide mesa portion 23h and a twenty-second waveguide mesa provided on the first portion 15a and the second portion 15b of the first waveguide structure 15, respectively. Part 23g. The width of the 22nd waveguide mesa portion 23g is larger than the width of the 21st waveguide mesa portion 23h. Regarding the alignment between the first waveguide structure 15 and the second waveguide structure 17, the extending direction of the 22nd waveguide mesa portion 23g of the second waveguide mesa 23b is the twelfth of the first waveguide mesa 21b. It is matched with the extending direction of the waveguide mesa portion 21g.

  In a preferred example according to the present embodiment, prior to the production of the first waveguide structure 15 and the second waveguide structure 17, in step S108, the twelfth waveguide mesa part 21g and the twenty-second waveguide to be produced. A reference length is estimated for the length of the waveguide mesa portion 23g. This reference length is determined when one of the first waveguide structure 15 and the second waveguide structure 17 is not shifted from the other axis with respect to the direction of the third axis Ax3 intersecting the first axis Ax1 and the second axis Ax2. Is defined as a length at which the transmittance of light from one of the first waveguide structure 15 and the second waveguide structure 17 to 1 is 1. The lengths of the twelfth waveguide mesa portion 21g and the twenty-second waveguide mesa portion 23g are longer than the reference length. According to this estimation, when the above-described axial deviation is larger than zero, a decrease in the transmittance due to the axial deviation in a certain axial deviation range is caused by the twelfth guide including the portion extended with respect to the above-mentioned reference length. Compensation can be achieved by using the waveguide mesa portion 21g and the 22nd waveguide mesa portion 23g.

  Step S107 (a step of forming the second waveguide structure 17 from the second epitaxial substrate E2) can include the following steps. In step S109, the second epitaxial substrate E2 is processed to form a first semiconductor product including the second waveguide structure 17 (parts (a) to (c) in FIG. 14). In step S110, the first semiconductor product is fixed to a support (support substrate) to form a second semiconductor product (part (d) of FIG. 14). In step S111, the second substrate (InP substrate shown in FIG. 14D) is removed from the second semiconductor product to expose the second semiconductor layer 23a, thereby forming a third semiconductor product. (Parts (a) and (b) in FIG. 15). In step S112, the second waveguide structure 17 is first guided so that the second semiconductor layer 23a of the third semiconductor product is supported by the first terrace 21c and the second terrace 21d of the first waveguide structure 15. A third substrate product is formed by bonding to the waveguide structure 15 (part (a) of FIG. 16). In step S113, the support (support substrate and temporary fixing material) is removed from the third substrate product (part (b) of FIG. 16). When a directional coupler is manufactured using this manufacturing method, the first waveguide structure is formed such that at least one of the twelfth waveguide mesa portion 21g and the twenty-second waveguide mesa portion 23g has an end portion. 15 and / or the second waveguide structure 17 can be made.

  The present invention is not limited to the specific configuration disclosed in the present embodiment.

  As described above, according to the present embodiment, it is possible to provide a semiconductor optical waveguide device having a structure capable of compensating for a positional deviation in the width direction between two optical waveguides to be aligned. Moreover, according to this Embodiment, the method of producing this semiconductor optical waveguide element can be provided.

DESCRIPTION OF SYMBOLS 11 ... Semiconductor optical waveguide element, 13 ... Board | substrate, 13a ... 1st part, 13b ... 2nd part, 13c ... 3rd part, 13d ... Substrate main surface, 15 ... 1st waveguide structure, 15a ... 1st part, 15b 2nd part, 15c ... 3rd part, 17 ... 2nd waveguide structure, 17a ... 1st part, 17b ... 2nd part, 17c ... 3rd part, 19a ... Groove, 19b, 19c ... Terrace, 21a ... 1st DESCRIPTION OF SYMBOLS 1 Semiconductor layer, 21b ... 1st waveguide mesa, 21c ... 1st terrace, 21d ... 2nd terrace, 21e ... 1st groove | channel, 21f ... 2nd groove | channel, 21g ... 12th waveguide mesa part, 21h ... 13th conductor Waveguide mesa, 23a ... second semiconductor layer, 23b ... second waveguide mesa, 23c ... first terrace, 23d ... second terrace, 23e ... first groove, 23f ... second groove, 23g ... 22nd waveguide mesa Part, 23h... 21st waveguide mesa part.

Claims (12)

A semiconductor optical waveguide element,
A first portion, a second portion, and a third portion arranged in the direction of the first axis, the groove extending in the direction of the first axis, and the first terrace and the second terrace that define the groove. A substrate,
A first waveguide structure provided on a main surface of the substrate;
A second waveguide structure provided on the main surface of the substrate;
With
The first waveguide structure includes a first semiconductor layer supported on the first terrace and the second terrace of the substrate, and a first waveguide mesa provided on the first semiconductor layer,
The second waveguide structure includes a first terrace of the first waveguide structure, a second semiconductor layer supported on the second terrace, and a second waveguide mesa provided on the second semiconductor layer. ,
The first waveguide structure includes a first portion, a second portion, and a third portion provided on the first portion, the second portion, and the third portion of the substrate, respectively.
The second waveguide structure includes a first part and a second part respectively provided on the first part and the second part of the first waveguide structure;
The first waveguide mesa of the first waveguide structure includes a twelfth waveguide mesa portion and a thirteenth waveguide mesa portion provided on the second portion and the third portion of the substrate, respectively. The width of the twelfth waveguide mesa portion is larger than the width of the thirteenth waveguide mesa portion,
The second waveguide mesa of the second waveguide structure includes a twenty-first waveguide mesa portion and a twenty-second waveguide mesa portion provided on the first portion and the second portion of the first waveguide structure, respectively. And the width of the 22nd waveguide mesa portion is larger than the width of the 21st waveguide mesa portion,
In the second portion of the substrate, the groove, the twelfth waveguide mesa portion, and the twenty-second waveguide mesa portion are arranged in a direction of a second axis that intersects the main surface of the substrate. Optical waveguide element. The first waveguide structure is bonded to the substrate;
The second waveguide structure is joined to the first waveguide structure;
2. The semiconductor optical waveguide device according to claim 1, wherein one of the twelfth waveguide mesa portion and the twenty-second waveguide mesa portion has an end portion. The first waveguide mesa includes a first taper waveguide portion provided between the twelfth waveguide mesa portion and the thirteenth waveguide mesa portion;
The semiconductor optical waveguide device according to claim 1, wherein the twelfth waveguide mesa portion is terminated. The second waveguide mesa includes a second tapered waveguide portion provided between the twenty-first waveguide mesa portion and the twenty-second waveguide mesa portion,
The semiconductor optical waveguide device according to any one of claims 1 to 3, wherein the 22nd waveguide mesa portion is terminated.   5. The semiconductor optical waveguide device according to claim 1, wherein a width of the twelfth waveguide mesa portion is substantially equal to a width of the twenty-second waveguide mesa portion. 6. The twelfth waveguide mesa portion extends from one end to the other end of the second portion of the first waveguide structure;
The 22nd waveguide mesa portion extends from one end to the other end of the second portion of the second waveguide structure;
A length of the second portion of the first waveguide structure is longer than a reference length;
A length of the second portion of the second waveguide structure is longer than a reference length;
The reference length is determined when one of the first waveguide structure and the second waveguide structure is not misaligned with respect to the other in the direction of the third axis intersecting the first axis and the second axis. 6. The semiconductor optical device according to claim 1, wherein the semiconductor optical waveguide has a length that allows a light transmittance from one of the first waveguide structure and the second waveguide structure to be one. Waveguide element. The thirteenth waveguide mesa portion is a single mode waveguide,
The semiconductor optical waveguide device according to claim 1, wherein the twelfth waveguide mesa portion is 4 μm or more. The twenty-first waveguide mesa portion is a single mode waveguide;
The semiconductor optical waveguide device according to claim 1, wherein the 22nd waveguide mesa portion is 4 μm or more. The first semiconductor layer comprises InP;
The first waveguide mesa comprises InGaAsP for the core of the optical waveguide;
The second semiconductor layer comprises InP;
The semiconductor optical waveguide device according to claim 1, wherein the second waveguide mesa includes InGaAsP for a core of the optical waveguide. A method for producing a semiconductor optical waveguide device, comprising:
A first portion, a second portion, and a third portion that are disposed in the direction of the first axis, and each includes a groove that extends in the direction of the first axis, and a first terrace and a second terrace that define the groove. Preparing a support substrate;
Providing a first epitaxial substrate comprising a first semiconductor stack for a waveguide structure on a first substrate;
Bonding the first semiconductor stack of the first epitaxial substrate to the support substrate such that the first terrace and the second terrace of the support substrate support the first semiconductor stack of the first epitaxial substrate. When,
Removing the first substrate from the first epitaxial substrate after bonding the first semiconductor stack of the first epitaxial substrate to the support substrate;
After removing the first substrate from the first epitaxial substrate, the first semiconductor stack is processed to form a first semiconductor layer supported on the first terrace and the second terrace of the support substrate and the first semiconductor layer. Forming a first substrate product including a first waveguide structure including a first waveguide mesa provided on the semiconductor layer;
Providing a second epitaxial substrate comprising a second semiconductor stack for a waveguide structure on a second substrate;
A second waveguide structure including a second semiconductor layer supported on the first terrace and the second terrace of the first waveguide structure, and a second waveguide mesa provided on the second semiconductor layer is provided in the second waveguide structure. Forming an array with respect to the direction of the second axis of the support substrate, the second waveguide structure and the second waveguide structure, formed from an epitaxial substrate;
With
The second waveguide structure is fabricated from the second semiconductor stack;
The first waveguide structure includes a first portion, a second portion, and a third portion provided on the first portion, the second portion, and the third portion of the substrate, respectively.
The second waveguide structure includes a first part and a second part respectively provided on the first part and the second part of the first waveguide structure;
The first waveguide mesa of the first waveguide structure includes a twelfth waveguide mesa portion and a thirteenth waveguide mesa portion provided on the second portion and the third portion of the substrate, respectively. The width of the twelfth waveguide mesa portion is larger than the width of the thirteenth waveguide mesa portion,
The second waveguide mesa of the second waveguide structure includes a twenty-first waveguide mesa portion and a twenty-second waveguide mesa portion provided on the first portion and the second portion of the first waveguide structure, respectively. And the width of the 22nd waveguide mesa portion is larger than the width of the 21st waveguide mesa portion,
The extending direction of the twelfth waveguide mesa portion of the first waveguide mesa is aligned with the extending direction of the groove in the second portion of the support substrate, and the second waveguide mesa has the first extending direction. 22. A method of manufacturing a semiconductor optical waveguide device, wherein an extending direction of a 22 waveguide mesa portion is matched with an extending direction of the twelfth waveguide mesa portion of the first waveguide mesa. In the step of forming the array,
Processing the second epitaxial substrate to form a first semiconductor product including the second waveguide structure;
Fixing the first semiconductor product to a support to form a second semiconductor product;
Removing the second substrate from the second semiconductor product to expose the second semiconductor layer to form a third semiconductor product;
The second waveguide structure is changed to the first waveguide structure so that the second semiconductor layer of the third semiconductor product is supported by the first terrace and the second terrace of the first waveguide structure. Bonding and forming a third substrate product;
Removing the support from the third substrate product;
Including
The method of manufacturing a semiconductor optical waveguide device according to claim 10, wherein one of the twelfth waveguide mesa portion and the twenty-second waveguide mesa portion has an end portion. A step of estimating a reference length for the lengths of the twelfth waveguide mesa portion and the twenty-second waveguide mesa portion;
The reference length is determined when one of the first waveguide structure and the second waveguide structure is not misaligned with respect to the other in the direction of the third axis intersecting the first axis and the second axis. A length at which the transmittance of light from one of the first waveguide structure and the second waveguide structure to one is 1,
12. The method of manufacturing a semiconductor optical waveguide device according to claim 10, wherein lengths of the twelfth waveguide mesa portion and the twenty-second waveguide mesa portion are longer than a reference length.

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