JPH04106990A - Optical integrated circuit - Google Patents

Abstract

PURPOSE:To reduce a variation in an emitting angle of a light to be emitted from a condensing grating coupler by providing a reflection type grating coupler for forming part of a resonator for deciding the oscillation wavelength of a semiconductor laser at a part of an optical waveguide between the laser and the coupler. CONSTITUTION:A semiconductor laser 22 is end-coupled to an optical waveguide 23, and a laser light emitted from the active layer of the laser 22 is propagated to a waveguide layer 23b of the waveguide 23. The light is partly reflected at the part of the layer 23b corresponding to the forming region of a reflection type grating coupler 24 in a grating layer 23c of the waveguide 23, and fed back to the laser 22. Since the coupler 24 constitutes the part of an external resonator with respect to the laser 22, the gain of the laser 22 becomes large at a specific value lambdab (lambdab=NLAMBDA1) if a secondary Bragg reflection occurs in the coupler 24) to be decided by the effective refractive index N of the waveguide 23 and the grating period LAMBDA1 of the coupler 24, and the laser 22 stably outputs a laser light having a wavelength lambdab by a single longitudinal mode oscillation.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to optical integrated circuits.

[Conventional technology]

Conventionally, there are three types of optical integrated circuits that are constructed by integrating a light source, an optical waveguide containing various functional elements, a photodetector, etc.: monolithic optical integrated circuits, hybrid optical integrated circuits, and quasi-hybrid optical integrated circuits. Each of these has been proposed. FIG. 7 is a perspective view of an optical integrated circuit configured as an optical head for reading signals from an optical disk. In this figure, 1 is a Si substrate, 2 is a semiconductor laser, 3 is an optical waveguide, 4 is a beam splitter, and 5 is a concentrator. An optical grating coupler, 6 an optical disk, 7 a light receiving element, 8 a signal processing circuit,
The laser light emitted from the semiconductor laser 2 passes through the optical waveguide 3
→ Beam splitter 4 → Condensing grating/cabra 5
→The light is focused on the optical disc 6 along the path of the optical disc 6, and a focused spot is created on the disc surface. The light reflected from the optical disk 6 by the above-mentioned focused spot is given to the light receiving element 7 through the path of the optical disk 6 -> the condensing grating/coupler 5 -> the beam splitter 4 -> the light receiving element 7. At 7, the light incident thereon is photoelectrically converted and supplied to a signal processing circuit 8. The signal processing circuit 8 generates a reproduction signal, a tracking control signal, and a focus control signal, and supplies each of the signals to required circuit parts. By the way, in the optical integrated circuit shown in FIG. 7, the reflected light from the optical disk 6 is fed back to the semiconductor laser 2 as a return light via the optical waveguide 3, and the incidence of the returned light causes the semiconductor laser 2 to have multiple oscillation spectra. mode or mode hopping,
The laser light emitted from the semiconductor laser 2 in the above state may cause multiple focused spots on the optical disc 6 or cause the focused spots to jump in position, making it difficult for the optical head to perform a normal reading operation. was. In the conventional optical head described with reference to FIG. 7, the oscillation spectrum of the semiconductor laser 2 can be made multi-mode due to the incidence of the return light, and an optical integrated circuit without a layer during the occurrence of mode hopping can be realized.For example, as shown in FIG. An optical integrated circuit having a configuration as illustrated in FIG. 9 has been proposed. In FIGS. 8 and 9, 9 is a substrate, 10 is a cladding layer, 11 is an active layer, 12 is a cladding layer, 13 is a cap layer, 14 is a two-dimensional optical waveguide, and LDD is a semiconductor laser section. In FIG. 8, 15 is a diffraction grating, 16 is an optical waveguide section, 17 is a condensing grating coupler, and in FIG. 9, 18 is an output grating coupler. First, the optical integrated circuit shown in FIG.
The laser section LDD, which consists of the optical waveguide section 16, the active layer 11, the cladding layer 12, etc., performs stable single mode oscillation at a specific wavelength determined by the period of the diffraction grating 15, The laser light propagated through the two-dimensional optical waveguide 14 is focused 19 in space by a focusing grating coupler 17. Further, the optical integrated circuit shown in FIG. 9 has an active layer 11.
Active layer 11 of laser section LDD consisting of cladding layer 12 etc.
The laser beam propagated to the two-dimensional optical waveguide 14 is reflected by the output grating coupler 18 formed in the two-dimensional optical waveguide 14 and returns to the active layer 11 of the laser section LDD, thereby generating a laser beam. It constitutes a distributed reflection type semiconductor laser that oscillates, and performs stable single mode oscillation at a specific wavelength determined by the period of the output grating coupler 18, thereby creating a two-dimensional optical waveguide 1.
Parallel light 20 is emitted into space from the four output grating couplers 18.

[Problem to be solved by the invention]

By the way, Figures 8 and 91! ! ! In order for the concentrating grating coupler 17, the output grating coupler 18, etc. used in the optical integrated circuit shown in FIG.
The laser beam has a predetermined wavelength, the refractive index and film thickness of the optical waveguide are set to predetermined values, and the periodic structure of the grating and coupler has a predetermined pattern, etc. However, in the optical integrated circuit illustrated in FIG. 8, the laser section LDD performs stable single mode oscillation at a specific wavelength determined by the period of its diffraction grating 15. too,
A condensing grating formed in the two-dimensional optical waveguide 14
There are problems in that the coupler 17 is not always configured to perform correct focusing operation depending on the wavelength of the laser beam oscillated by the laser section LDD, and the manufacturing conditions are strict and the product becomes expensive. On the other hand, as in the optical integrated circuit illustrated in FIG. 9, an output grating coupler 18 formed in a two-dimensional optical waveguide 14
When configuring a distributed reflection semiconductor laser that oscillates laser light by also serving as a reflector for returning part of the laser light to the active layer 11 of the laser section LDD, the output grating coupler 18 Since the light emitted into space becomes parallel light perpendicular to the substrate, it is necessary to provide a separate condensing lens outside the optical integrated circuit in order to form a spot of light with a minute diameter. Therefore, it is not possible to integrate all optical components, and the optical waveguide is
Another problem is that it is expensive when it is provided on an expensive substrate such as S.

[Means to solve the problem]

The present invention relates to an optical integrated circuit including an optical waveguide formed with a condensing grating coupler and a semiconductor laser coupled to the optical waveguide, the semiconductor laser and the condensing grating coupler being coupled to the optical waveguide. an optical integrated circuit in which a reflective grating coupler forming part of a resonator that determines the oscillation wavelength of the semiconductor laser is provided in the optical waveguide portion between the A semiconductor laser having a substantially non-reflective surface at one end surface coupled to the optical waveguide, a reflecting surface formed on the other end surface of the semiconductor laser, and a condensing grating coupler. An optical integrated circuit is provided in which a distributed Bragg reflection laser is constructed by constructing a resonator that determines the oscillation wavelength by a reflective grating coupler provided in a portion of an optical waveguide between the two.

[Action 1] Consisting of a semiconductor laser coupled to an optical waveguide formed with a condensing grating coupler, and a reflective grating coupler provided in the part of the optical waveguide between the condensing grating coupler. A distributed reflection semiconductor laser equipped with a resonator that determines the oscillation wavelength of the semiconductor laser performs stable single longitudinal mode oscillation at a specific wavelength, and the laser light is fed to a focusing grating and coupler to focus it in the air. let Further, there is provided a semiconductor laser in which one end face portion, which is end face coupled to an optical waveguide formed with a condensing grating coupler, is formed into a substantially non-reflective surface, and a reflective surface formed on the other end face of the semiconductor laser described above. Stable single-longitudinal mode oscillation at a specific wavelength is achieved by a distributed Bragg reflection laser equipped with a resonator that determines the oscillation wavelength by a reflective grating coupler installed in the optical waveguide section between the concentrating grating coupler. The laser beam is then applied to a condensing grating coupler to condense it into the air. A reflective grating coupler and a condensing grating coupler are configured in the same optical waveguide so as to form part of the resonator of a semiconductor laser that performs stable single longitudinal mode oscillation. Therefore, the change in the output angle of the light emitted from the condensing grating/coupler that occurs based on the error in the effective refractive index that occurs during the fabrication of the optical waveguide and the error in expansion and contraction of the pattern that occurs during the fabrication of the grating is due to the above-mentioned change. A semiconductor laser whose oscillation wavelength is determined by a resonator that includes a reflective grating coupler as part of its configuration, which is installed in the same optical waveguide as the condensing grating coupler. The laser beam output from By using the oscillation wavelength that can reduce the change in the emission angle of the light emitted from the condensing grating coupler described above, the error in the effective refractive index that occurs during the fabrication of the guide waveguide can be suppressed. Compared to the change in the output angle of light emitted from the condensing grating coupler that occurs in conventional optical integrated circuits due to errors such as expansion and contraction of patterns that occur during the fabrication of gratings, the optical integrated circuit of the present invention Changes in the angle of light emitted from the optical grating coupler can be greatly reduced. Embodiment The specific contents of the optical integrated circuit of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a perspective view of an embodiment of the optical integrated circuit of the present invention, FIG. 2 is a sectional view of the same from the upper side, and FIGS. 3 to 6 are characteristic diagrams for explanation. In FIG. 1, 21 is a substrate, 22 is a semiconductor laser, and 23 is a semiconductor laser.
is an optical waveguide, 24 is a reflective grating coupler, 2
5 is a condensing grating coupler, 26 is an optical disk,
27 is a grating beam splitter, 28 is a photodiode, and the optical waveguide 23 has a buffer layer 23a and a waveguide layer 23b as shown in FIG.
and a grating layer 23c. The optical integrated circuit of the present invention illustrated in FIG. 1 (and FIG. 2) shows a configuration example in which an optical head is configured by a hybrid optical integrated circuit. Of course, it may also be implemented as a monolithic optical integrated circuit. In the optical integrated circuit shown in FIGS. 1 and 2, the substrate 21
, the optical waveguide 23, etc. may be constructed using any constituent material as long as they can be constructed to exhibit a predetermined function. Examples of constituent materials of the substrate 21 and the optical waveguide 23, etc. described above include Si for the substrate 21, SiO□ for the buffer layer 23a in the optical waveguide 23,
The waveguide layer 23b is #7059 manufactured by Corning, Inc. in the United States.
As the glass and grating layer 23c, SiN can be used. Now, in the optical integrated circuit shown in FIG. 1 and FIG. The laser light that propagates through the waveguide layer 23b of the optical waveguide 23 described above, which propagates to the waveguide layer 23b, passes through the grating layer 23c of the optical waveguide 23.
A portion of the light is reflected back to the semiconductor laser 22 at a portion of the waveguide layer 23b that corresponds to the region where the reflective grating coupler 24 is formed. Since the above-mentioned reflective grating coupler 24 formed in the grating layer 23c of the optical waveguide 23 constitutes a part of the external resonator of the semiconductor laser 22, the gain of the semiconductor laser 22 is equal to that of the optical waveguide. 23 and the grating period of the reflective grating coupler 24 described above.
When the next Bragg reflection is performed, it becomes large at λb=NΔ, ), and the semiconductor laser 22 stably outputs a laser beam of wavelength λb due to single longitudinal mode oscillation. In the optical integrated circuit of the present invention, if the wavelength (design wavelength) of the laser light to be output from the semiconductor laser 22 is λ, and the effective refractive index of the optical waveguide 23 is N, then the grating period of the reflective grating coupler 24 described above A1
is defined as A = λIo/N. Therefore, the above-mentioned reflective grating coupler 24 to be formed in the grating layer 23c of the optical waveguide 23 has a grating formed by concentric circles centered on the light emitting point of the semiconductor laser 22. The pattern is configured such that the period is A1. The semiconductor laser 22 to be end face coupled to the optical waveguide 23 may have a reflective surface on both end faces of its active layer, or may be connected to the optical waveguide 23. Either of these may be used, even if the end face to be end face-bonded is configured as a non-reflective surface. Note that when the reflective grating coupler 24 is configured to perform primary Bragg reflection, laser light can be prevented from being emitted into space from the single reflective grating coupler 24. The optical waveguide 23 described above
Laser light propagates through the waveguide layer 23b of the optical waveguide 23 and passes through a portion of the waveguide layer 23b that corresponds to the formation region of the reflective grating coupler 24 in the grating layer 23c of the optical waveguide 23, that is, a single laser beam in the semiconductor laser 22. A stable laser beam of one wavelength due to one longitudinal mode oscillation is given to the condensing grating coupler 25 via the grating beam splitter 27, and the laser beam is transmitted to the optical disc 25 by the condensing grating coupler 25.
The light is focused on the signal plane. The reflected light from the spot of the laser beam focused on the signal surface of the optical disk 26 as described above is transmitted from the focusing grating coupler 25 to the grating beam splitter 2.
7, return to grating beam splitter 2
After being split into two laser beams by 7, the laser beam propagates within the waveguide layer 23b and is incident on the photodiode 28.28. As described above, in the optical integrated circuit of the present invention, the optical waveguide 23 is connected between the semiconductor laser 22 coupled to the optical waveguide 23 formed with the condensing grating coupler 25 and the condensing grating coupler 25. A distributed reflection semiconductor laser equipped with a resonator that determines the oscillation wavelength of the semiconductor laser, which is configured by a reflection grating coupler 24 provided in the part, performs stable single longitudinal mode oscillation at a specific wavelength. The laser beam is applied to the condensing grating coupler 25 to condense it in the air, and one end face portion that is end-coupled to the optical waveguide 23 formed with the condensing grating coupler 24 is formed into a substantially non-reflective surface. The semiconductor laser 22 described above and the semiconductor laser 2 described above
The reflective surface and condensing grating formed on the other end surface of 2.
A distributed Bragg reflection laser equipped with a resonator that determines the oscillation wavelength by a reflective grating coupler 24 provided in the optical waveguide 23 between the coupler 25 can generate stable single longitudinal mode oscillation at a specific wavelength. By applying the laser light to the condensing grating coupler 25 and concentrating it in the air, the light guide becomes part of the resonator of the semiconductor laser 22 that performs stable single longitudinal mode oscillation. Since the reflective grating coupler 24 and the condensing grating coupler 25 provided in the waveguide 23 are configured in the same leading waveguide 23, the error in the effective refractive index N and the grating that occur during the fabrication of the optical waveguide 23 Changes in the output angle of the light emitted from the condensing grating coupler 25 that occur due to errors such as expansion and contraction of the pattern that occur during the fabrication of the optical waveguide 23 in which the condensing grating coupler 24 is provided as described above. Laser light output from the semiconductor laser 22 whose oscillation wavelength is determined by a resonator including a reflective grating coupler 24 provided in the same guide waveguide 23 as described above In response to errors in the effective refractive index N that occur when producing the waveguide 23 and errors such as pattern expansion and contraction that occur when producing gratings such as the reflective grating coupler 24 and the condensing grating coupler 25, the condensing grating coupler described above 25
By making the oscillation wavelength such that the change in the emission angle of the light emitted from the optical waveguide can be reduced, the error in the effective refractive index that occurs during the fabrication of the optical waveguide and the pattern that occurs during the fabrication of the grating can be suppressed. Compared to the change in the exit angle of the light emitted from the concentrating grating coupler in the optical integrated circuit of the present invention, which occurs in conventional optical integrated circuits due to errors such as expansion and contraction of the light emitted from the condensing grating coupler. Changes in the light emission angle can be greatly reduced. Next, the third point is that the degree of influence of manufacturing errors that occur during the fabrication of optical integrated circuits on the characteristics of optical integrated circuits is significantly different between the optical integrated circuit of the present invention and conventional optical integrated circuits.
The explanation will be given with reference to FIGS. 6 to 6 as well. Now, a minute region in the condensing grating coupler 25 provided in the optical waveguide 23 (since the grating period in the condensing grating coupler 25 is not constant,
Now, the grating period in a very small area is taken out and it is considered as a micro region) is Δ□, the output angle is θ1, and the grating period in the reflective grating coupler 24 provided in the optical waveguide 23 is Δ2. Further, it is assumed that the effective refractive index of the optical waveguide 23 is N, and furthermore, the wavelength of the output light from the semiconductor laser 22 (the oscillation wavelength of the semiconductor laser) is λ. In addition, the optical waveguide 2 described above
The propagation vector diagram in the reflection type grating coupler 24 area provided in FIG. 3 is shown in FIG. shall be shown in the following. First, in the case of second-order Bragg reflection in the region of the reflective grating coupler 24 provided in the optical waveguide 23,
The effective refractive index N of the optical waveguide 23 is. N=□/to=λ/A, (1) However, the grating vector is -2z/person. Wave number vector k = 2 yc /λ When expressed as in equation (1) above, this is a condition in which the grating coupler can operate as a reflective grating, so from this, the oscillation wavelength λ of the semiconductor laser 22 is , the wavelength satisfies the following equation (2). λ=: N A , (2) Next, the condensing grating provided in the optical waveguide 23
In the minute area of the coupler 25, the output angle θ is determined by the condition expressed by the following equation (3). sin θ = N-, / ni = N-λ/ A Lθ = sin
-1(N-λ/AX)-(3) Expression (2) above is transformed into (3)
By substituting into the equation, the following equation (4) is obtained. θ=sin”1N(1-A,/Δt) (4) Now,
There are three types of manufacturing errors that occur during the manufacturing of optical integrated circuits: (a) error in the effective refractive index N of the optical waveguide, (b) error in the size Ly of the grating pattern, and (c) error in the wavelength λ of the semiconductor laser. Set the error and perform the above (a)
,(B). We examined how the output angle θ changes with respect to the three types of individual errors shown in (c) in the case of the optical integrated circuit according to the present invention and in the case of the conventional optical integrated circuit. It looks like this: (a) Study of the influence of the error in the effective refractive index N of the optical waveguide on the characteristics of the optical integrated circuit. ) is assumed to be N' as shown in the equation. N' = αN ... (5) (A) In the case of conventional optical integrated circuits In the above equation (3), only the effective refractive index N of the optical waveguide changes, so the effective refractive index N of the optical waveguide changes due to an error.
The emission angle θ' of light from the condensing grating coupler when N' changes to N' is expressed by the following equation (6). θ' = 5in-1(N'-λ/A,) = sin
−1(aN−λ/A,) ・−(6)(EB) In the case of the optical integrated circuit of the present invention In the above equation (3), the effective refractive index N of the optical waveguide is
Both the oscillation wavelength λ of the semiconductor laser 22 and the oscillation wavelength λ of the semiconductor laser 22 change, and the oscillation wavelength λ of the semiconductor laser 22 becomes the wavelength λ′ shown in equation (7). λ'=αNA,=αλ...(7) Therefore, the emission angle θ'' of light from the condensing grating coupler is expressed by the following equation (8). θ''=sin-'( aN −aλ/A□)=sin-1
a (N-λ/A,) (8) (E-C) Comparison of the conventional optical integrated circuit and the optical integrated circuit of the present invention. Equation (6) represents the emission angle θ' of light from the condensing grating coupler in the conventional optical integrated circuit. In the optical integrated circuit of the present invention, the value of α in the equation (8) indicating the emission angle θ” of light from the condensing grating coupler is varied in the range of 0.94 to 1.06 (±6%). The absolute value of the angular error Δθ obtained when
Figure 4 shows the comparison results with 10'-01 and 1θ''-01. (b) Study of the influence of the error in the size Ly of the grating pattern on the characteristics of the optical integrated circuit, gain fluctuation of the grating drawing system, etc. Assume that an error occurs in the grating period and the grating period Δ1.A2 becomes as shown by the following equations (9) and (10). To = β...(9) Δ2=βA2 (10) (Low A) In the case of conventional optical integrated circuits In the above equation (3), only the grating period A1 of the condensing grating coupler changes, so from the condensing grating coupler in this case, The emission angle θ' of the light is expressed by the following equation (11): θ' = sin -'' (N - λ/AL') = sin -
' (N-λ/βA,)-(11) (low B) In the case of the optical integrated circuit of the present invention In the above equation (3), the grating period A1 of the condensing grating coupler and the oscillation wavelength λ of the semiconductor laser 22 Both change, and the oscillation wavelength λ of the semiconductor laser 22 becomes the wavelength λ' shown in equation (12). λ' = NA□' = NβΔ□ = βλ (12) Therefore, the emission angle θ'' of the light from the condensing grating coupler becomes as shown by the following equation (13). θ''= 5in-1(N-βλ/βA1)=sin-1
(N-λ/Al)=θ-(13) In other words, in the optical integrated circuit of the present invention, even if an error occurs in the grating period due to gain fluctuations in the grating drawing system, the light is emitted from the condensing grating coupler 25. The angle θ” is the same as the design value θ, and no error Δθ occurs. (Rho C) Comparison of the conventional optical integrated circuit and the optical integrated circuit of the present invention, Light from the condensing grating coupler in the conventional optical integrated circuit Equation (11) showing the exit angle θ″ of In the optical integrated circuit of the present invention, the value of α in the equation (13) indicating the emission angle θ” of light from the concentrating grating coupler is varied in the range of 0.94 to 1.06 (±6%). FIG. 5 shows the results of comparison between the absolute value of the angular error obtained when the angle is 10'-01, 1θ''-θI. (c) A study of the effects of three types of errors on the characteristics of optical integrated circuits: errors in the wavelength λ of semiconductor lasers. Assume that the natural oscillation wavelength λ of the semiconductor laser has an error with respect to the designed value and becomes λ' shown by the following equation (14). λ' = γλ ... (14) (Bar A) In the case of a conventional optical integrated circuit In the above equation (3), only the spontaneous oscillation wavelength λ of the semiconductor laser changes, so the output from the condensing grating coupler in this case The light emission angle θ' is expressed by the first-order equation (15). θ' = sin"1(N-λ'/to 80=sin-1(
N-βλ/A□)-(15) (Low B) In the optical integrated circuit of the present invention, the oscillation wavelength λ of the semiconductor laser 22 is the grating period A of the reflective grating coupler 24. The oscillation wavelength λ does not change because it is forcibly determined to the value determined by λ''NA θ”=sin”(N−βλ/βA, )=sin
-" (N-λ/A,) = θ-(13) In the optical integrated circuit of the present invention, the emission angle θ" of light from the condensing grating coupler 25 does not change from the design value θ, and the error Δ
θ does not occur. (Rho C) Comparison of the conventional optical integrated circuit and the optical integrated circuit of the present invention, Equation (15) showing the emission angle θ'' of light from the condensing grating coupler in the conventional optical integrated circuit, and the optical integrated circuit of the present invention. The value of α in the equation (13) indicating the emission angle θ” of light from the condensing grating coupler in the integrated circuit is set to 0.
．． The absolute value of the angular error Δθ obtained when changing it in the range of 94 to 1.06 (±6%), that is, 10'-01
, 1θ''-〇 is shown in Fig. 6. In Figs.
The calculation results are shown for two angles: 0 degrees and 15 degrees.

【Effect of the invention】

As is clear from the above detailed explanation, the optical integrated circuit of the present invention has a structure in which a semiconductor laser coupled to an optical waveguide in which a condensing grating coupler is formed and a condensing grating coupler are connected to each other. Stable single longitudinal mode oscillation at a specific wavelength is achieved by a distributed reflection semiconductor laser equipped with a resonator that determines the oscillation wavelength of the semiconductor laser, which is configured with a reflection grating coupler installed in the optical waveguide. , the laser beam is fed to a focusing grating coupler to focus it into the air, and also. A semiconductor laser whose one end face is formed into a substantially non-reflective surface, which end face is coupled to an optical waveguide having a condensing grating/coupler formed thereon; A distributed Bragg reflection laser with a resonator that determines the oscillation wavelength by a reflective grating coupler installed in the optical waveguide section between the grating coupler performs stable single longitudinal mode oscillation at a specific wavelength. , the laser beam is applied to a condensing grating coupler to condense it in the air.According to the present invention, the laser beam forms part of a resonator of a semiconductor laser that performs stable single longitudinal mode oscillation. Since the reflective grating coupler and the condensing grating coupler provided in the optical waveguide are configured in the same optical waveguide, errors in the effective refractive index that occur during the fabrication of the optical waveguide and errors that occur during the fabrication of the grating are Changes in the output angle of light emitted from the condensing grating coupler that occur due to errors such as expansion and contraction of the pattern can be avoided if the condensing grating coupler is installed in the same optical waveguide as the leading waveguide in which the condensing grating coupler is installed, as described above. Laser light is output from a semiconductor laser whose oscillation wavelength is determined by a resonator that includes a reflective grating coupler. Corresponding to errors in the effective refractive index that occur during the fabrication of the guide waveguide described above and errors in pattern expansion and contraction that occur during the fabrication of gratings such as reflective grating couplers and condensing grating couplers, the above-mentioned condensing grating couplers This can be suppressed by making the oscillation wavelength such that the change in the exit angle of the emitted light can be reduced. Therefore, the error in the effective refractive index that occurs when manufacturing the optical waveguide and the error in the pattern that occurs when manufacturing the grating can be suppressed. Compared to the change in the exit angle of the light emitted from the concentrating grating coupler of the optical integrated circuit of the present invention, which occurs in conventional optical integrated circuits due to errors such as expansion and contraction, the light emitted from the concentrating grating coupler of the optical integrated circuit of the present invention. Of course, it is possible to significantly reduce the change in the emission angle of Moreover, the output angle from the condenser grating and coupler can be freely set, and it is easy to integrate the condenser lens and other components into an integrated circuit. All the problems of the prior art can be satisfactorily solved by the present invention.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of one embodiment of the optical integrated circuit of the present invention, and FIG.
3 to 6 are explanatory characteristic diagrams, FIG. 7 is a perspective view of a conventional optical integrated circuit configured as an optical head for reading signals from an optical disk, and FIG. 9th
The figure is a side sectional view of a conventional optical integrated circuit. DESCRIPTION OF SYMBOLS 1... Si substrate, 2... Semiconductor laser, 3,23.
... Optical waveguide, 4... Beam splitter, 5... Condensing grating coupler, 6... Optical disk, 7.
. . . Light receiving element, 8 is a signal processing circuit, 9 . . . Substrate, 10
．． 12... cladding layer, 11... active layer, 13...
- Cap layer, 14... Two-dimensional optical waveguide, 15...
Diffraction grating, 16... Optical waveguide section, 17.25... Concentrating grating coupler, 18... Output grating coupler, 21... Substrate, 22... Semiconductor laser, 23a... Light guide Buffer layer of wave layer, 23b...
- Waveguide layer, 23c... grating layer, 24...
Reflective grating coupler, LDD... semiconductor laser section, 26... optical disk, 27... grating beam splitter. 28...Photodiode, patent applicant: Victor Company of Japan Co., Ltd.

Claims (1)

[Claims] 1. An optical integrated circuit comprising an optical waveguide formed with a condensing grating coupler and a semiconductor laser coupled to the optical waveguide, the semiconductor laser and An optical integrated circuit 2 comprising a reflective grating coupler that forms part of a resonator that determines the oscillation wavelength of a semiconductor laser is provided in an optical waveguide section between the condensing grating coupler and the condensing grating coupler. an optical waveguide formed thereon, a semiconductor laser whose one end face portion coupled to the optical waveguide is formed into a substantially non-reflective surface, a reflective surface formed on the other end face of the semiconductor laser, and a light condensing surface. An optical integrated circuit in which a distributed Bragg reflection laser is constructed by constructing a resonator that determines the oscillation wavelength by a reflective grating coupler provided in the optical waveguide section between the grating coupler and the grating coupler.