JP2007094336A - Optical semiconductor device and method of manufacturing optical semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical semiconductor device capable of suppressing propagation of generated stray light, and to provide a method of manufacturing the optical semiconductor device. <P>SOLUTION: An optical semiconductor device 1 has a semiconductor laser 2 and a MZ interference optical modulator 4 connected by a branching coupler 3, a multiplexing coupler 5, and optical waveguides 11 to 16 and is monolithically integrated, and absorption layers 6 having a longer band gap wavelength than that corresponding to operation light emitted from the semiconductor laser 2 are provided adjacently to at least an output end of the multiplexing coupler 5 and the optical waveguide 16. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical semiconductor element in which a plurality of optical semiconductor devices such as a semiconductor laser and a Mach-Zehnder (MZ) type interferometer are connected by an optical coupler and an optical waveguide and monolithically integrated.

  In recent years, an optical semiconductor device in which an optical control device such as an optical modulator, an optical switch, and a wavelength conversion device and a semiconductor laser device are monolithically integrated on the same semiconductor substrate has been proposed, and partly due to progress in semiconductor processing technology and integration technology. It has been put into practical use. Here, there are an electroabsorption type and an MZ type as an optical modulator. As the optical transmission speed increases, an MZ interference type optical modulator that can control wavelength fluctuation (chirp) during modulation is used. Attention has been paid.

  The MZ interference type optical modulator has a 1-input 2-output optical coupler, a curved optical waveguide, two optical waveguides having a control electrode section (arm), and a 2-input 1-output optical coupler. The light is turned on and off by inverting the phase of the light propagating through the arm. Further, the optical coupler used here is a multimode interference (MMI) optical coupler, and this MMI optical coupler uses interference between a plurality of modes excited in an optical waveguide and has one input and two outputs (1 Optical multiplexing / demultiplexing such as × 2) or 1 input 4 output (1 × 4) is realized.

JP-A-5-2195

  By the way, an optical semiconductor element in which a semiconductor laser and an MZ interferometric optical modulator are monolithically integrated has at least four bent optical waveguide portions and two MMI couplers. There is a light component that leaks out. This optical component causes optical loss in the bent optical waveguide part, and depending on the propagation direction, there is a problem in that it is coupled to another optical waveguide to deteriorate the extinction ratio. Even in the MMI coupler, there is an optical component that leaks from a position different from the output port. For example, as shown in FIG. 23, in the 2 × 1 MMI coupler 100 connected to the preceding stage MZ interference type optical modulator, the phases of the light guided from the respective optical waveguides 101 and 102 are opposite in phase. In the off state, all input light leaks out on the output side.

  These leaking light components propagate as so-called stray light in the optical semiconductor element, and if this stray light is coupled to the optical fiber coupled to the output light from the optical semiconductor element, the extinction ratio and the like are deteriorated. There was a problem. Note that these problems become more prominent when the bent optical waveguide width, the element length of the MMI coupler, and the element width deviate from the design values due to errors in manufacturing the optical semiconductor element.

  On the other hand, in the MMI coupler, the effect of stray light increases as the number of ports to be multiplexed / demultiplexed increases. For example, when a plurality of n semiconductor lasers and MZ interferometric optical modulators are monolithically integrated, an n × 2 MMI coupler is required, but the amount of stray light increases as the number of ports n increases. Generally, in the case of a P port × Q port MMI coupler, the amount of stray light that leaks increases as (P−Q / P) when P ≧ Q. That is, the greater the number of ports that are integrated, the greater the amount of stray light. In particular, the light leaking from the center of the branch side of the MMI coupler is directly coupled to the opposite MMI coupler on the multiplexing side, so that the extinction operation is greatly deteriorated.

  Note that the problem of stray light also occurs when a larger number of semiconductor devices, such as wavelength conversion elements, are integrated.

  The present invention has been made in view of the above, and relates to an optical semiconductor element and a method for manufacturing the optical semiconductor element that can suppress the propagation of stray light generated.

  In order to solve the above-described problems and achieve the object, an optical semiconductor device according to claim 1 is an optical semiconductor device in which a plurality of optical semiconductor devices are connected by an optical coupler and an optical waveguide, and are monolithically integrated. An absorption region having a band gap wavelength longer than the band gap wavelength corresponding to the operating light propagating through the optical coupler and the optical waveguide is provided adjacent to the optical coupler or the optical waveguide.

  The optical semiconductor element according to claim 2 is characterized in that, in the above invention, the absorption region extends in the width direction from the optical coupler or the optical waveguide and is provided over the entire output direction in the subsequent stage. .

  An optical semiconductor element according to a third aspect of the present invention is characterized in that, in the above invention, the absorption region is provided on an output end side of the optical coupler.

  According to a fourth aspect of the present invention, in the above invention, when there are a plurality of the optical couplers, an input terminal of a rear-stage optical coupler connected to the front-stage optical coupler from an output terminal of the front-stage optical coupler. The absorption region is provided between the two.

  The optical semiconductor element according to claim 5 is characterized in that, in the above invention, the absorption region is provided between an optical coupler that performs optical branching and an optical coupler that performs optical multiplexing.

  According to a sixth aspect of the present invention, in the above invention, when two optical couplers are connected by a plurality of optical waveguides, the region surrounded by the two optical couplers and the plurality of optical waveguides is absorbed. It is a region.

  According to a seventh aspect of the present invention, there is provided an optical semiconductor device according to the above invention, wherein, when the optical coupler is a multimode interference optical coupler having a plurality of output ends, an optical waveguide for absorption at a light concentration end between the output ends. And the absorption region is provided between the optical waveguides connected to the output end.

  An optical semiconductor element according to an eighth aspect of the present invention is characterized in that, in the above invention, the absorption region is provided over the entire region excluding the optical semiconductor device, the optical coupler, and the optical waveguide.

  According to a ninth aspect of the present invention, in the above invention, the optical semiconductor device is a semiconductor laser device and a light control function device.

  The optical semiconductor element according to claim 10 is the above invention, wherein the semiconductor laser device is one or more distributed feedback semiconductor lasers, and the optical control function device is a Mach-Zehnder optical interferometer. Features.

  An optical semiconductor element according to an eleventh aspect of the present invention is the optical semiconductor device according to the above invention, wherein the optical waveguide has a ridge-type optical waveguide structure formed in a plane parallel to the semiconductor substrate, and is optically compared with a ridge width. The waveguide layer is wide.

  An optical semiconductor device according to a twelfth aspect of the present invention is the optical semiconductor device according to the above invention, wherein each arm of the Mach-Zehnder optical interferometer has a ridge-type optical waveguide structure formed in a plane parallel to the semiconductor substrate. The optical waveguide layer is wider than the width.

  According to a thirteenth aspect of the present invention, in the optical semiconductor device according to the above invention, the optical coupler adjacent to the absorption region or the optical waveguide adjacent to the absorption region has a ridge-type optical waveguide structure and has a ridge width. In comparison, the optical waveguide layer is wide.

  According to a fourteenth aspect of the present invention, there is provided a method for manufacturing an optical semiconductor device, which is a method for manufacturing an optical semiconductor device in which a plurality of optical semiconductor devices are connected by an optical coupler and an optical waveguide, and is monolithically integrated. In addition, an absorption region having a band gap wavelength longer than the band gap wavelength corresponding to the operating light propagating through the optical coupler and the optical waveguide is formed adjacent to the optical coupler or the optical waveguide by a selective growth method. It is characterized by doing.

  An optical semiconductor device manufacturing method according to claim 15 is a method for manufacturing an optical semiconductor device in which a plurality of optical semiconductor devices are connected by an optical coupler and an optical waveguide and integrated monolithically, and in a plane parallel to the semiconductor substrate. Further, an absorption region having a band gap wavelength longer than the band gap wavelength corresponding to the operating light propagating through the optical coupler and the optical waveguide is adjacent to the optical coupler or the optical waveguide by the B / J regrowth method. It is characterized by forming.

  According to a sixteenth aspect of the present invention, there is provided the method for manufacturing an optical semiconductor device according to the above invention, wherein the absorption region extends in the width direction from the optical coupler or the optical waveguide and is provided over the entire output direction in the subsequent stage. Features.

  The optical semiconductor device manufacturing method according to claim 17 is characterized in that, in the above invention, the absorption region is provided on an output end side of the optical coupler.

  An optical semiconductor element manufacturing method according to claim 18 is characterized in that, in the above invention, the optical semiconductor device is a semiconductor laser device and a light control function device.

  According to a nineteenth aspect of the present invention, there is provided an optical semiconductor device manufacturing method according to the above invention, wherein the semiconductor laser device is one or more distributed feedback semiconductor lasers, and the optical control function device is a Mach-Zehnder optical interferometer. It is characterized by being.

  According to a twenty-second aspect of the present invention, there is provided an optical semiconductor device manufacturing method according to the above invention, wherein the optical waveguide has a ridge-type optical waveguide structure formed in a plane parallel to the semiconductor substrate, and has a width that is larger than the ridge width. Thus, the width of the optical waveguide layer is wide.

  According to a twenty-first aspect of the present invention, there is provided an optical semiconductor device manufacturing method according to the above invention, wherein each arm of the Mach-Zehnder optical interferometer has a ridge type optical waveguide structure formed in a plane parallel to the semiconductor substrate. In addition, the width of the optical waveguide layer is wider than the ridge width.

  According to a twenty-second aspect of the present invention, there is provided an optical semiconductor device manufacturing method according to the above invention, wherein the optical coupler adjacent to the absorption region or the optical waveguide adjacent to the absorption region has a ridge-type optical waveguide structure, and The optical waveguide layer is wider than the ridge width.

  In the optical semiconductor device and the method for manufacturing the optical semiconductor device according to the present invention, an absorption region having a band gap wavelength longer than the band gap wavelength corresponding to the operating light propagating through the optical coupler and the optical waveguide is formed in the optical coupler or the optical coupler. Since it is provided adjacent to the optical waveguide, the stray light leaking from the output end of the optical coupler and the optical waveguide is absorbed, and deterioration of the extinction ratio and the like due to the coupling of the stray light with the operating light can be prevented. Play.

  Hereinafter, an optical semiconductor device and a method for manufacturing the optical semiconductor device, which are the best mode for carrying out the invention, will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a diagram showing a schematic configuration of an optical semiconductor element according to Embodiment 1 of the present invention. 1, the optical semiconductor element 1 includes a semiconductor laser 2 on a semiconductor substrate such as InP, and a branch coupler 3 and a branch coupler realized by an MMI coupler that branches the output light from the semiconductor laser 2 into two. MZ interference type optical modulator 4 that performs light modulation by propagating the light branched by 3 to arms 4-1 and 4-2 and changing the phase of one or both of arms 4-1 and 4-2, A multiplexing coupler 5 realized by an MMI coupler that combines the lights output from the arms 4-1 and 4-2 of the MZ interference optical modulator 4 is formed and monolithically integrated.

  The semiconductor laser 2 and the branch coupler 3 are connected by the optical waveguide 11, and the branch coupler 3 and the arms 4-1 and 4-2 are connected by the optical waveguides 12 and 13, respectively, and the arm 4-1. 4-2, and the multiplexing coupler 5 are connected by optical waveguides 14 and 15, respectively, and the output side of the multiplexing coupler 5 is connected to the optical waveguide 16 and is multiplexed by the multiplexing coupler 5. Is output through the optical waveguide 16.

  The semiconductor laser 2 is a DFB laser having an active layer having a quantum well structure with a band gap wavelength of 1550 nm, and its oscillation wavelength is in the vicinity of 1550 nm. Each of the arms 4-1 and 4-2 has an optical waveguide formed by an active layer having a quantum well structure with a band gap wavelength of 1460 nm, and the light guided through the refractive index change caused by voltage application to the electrodes 18 and 19 is generated. Change the phase. Each of the optical waveguides 11 to 16 is formed by an active layer having a quantum well structure with a band gap wavelength of 1300 nm.

  Here, the semiconductor laser 2, the MZ interference type optical modulator 4 and the like on the semiconductor substrate are monolithically formed, and the absorption layer 6 is formed on the entire output end side of the multiplexing coupler 5. . That is, the absorption layer 6 extends from the line that passes through the input end of the multiplexing coupler 5 to which the optical waveguides 14 and 15 are connected and is orthogonal to the light output direction in the longitudinal direction of the optical semiconductor element 1 to the entire surface in the light output direction. Is provided. Of course, the region of the multiplexing coupler 5 and the optical waveguide 16 is excluded. The absorption layer 6 is formed of an active layer having a quantum well structure with a band gap wavelength of 1550 nm, and absorbs light from near 1550 nm to less than 1550 nm. In particular, stray light leaking from the output end where the multiplexing coupler 5 and the optical waveguide 16 are connected is absorbed, and stray light is prevented from being mixed with the light guided through the optical waveguide 16 to deteriorate the extinction ratio.

  Here, with reference to FIGS. 2-12, the manufacturing method of the optical semiconductor element 1 shown in FIG. 1 is demonstrated. 2 to 5 are plan views accompanying the manufacturing process of the optical semiconductor device 1, and FIGS. 6 to 12 are cross-sectional views accompanying the manufacturing process of the optical semiconductor device 1. First, as shown in FIG. 6, a semiconductor laser active layer 22 having a quantum well structure (InGaAsP / InGaAsP) with a band gap wavelength of 1550 nm is grown on the entire surface of the n-InP substrate 21 using an MOCVD crystal growth apparatus or the like. Let Further, an InP layer is formed on the semiconductor laser active layer 22. At this time, the diffraction grating 22b is formed in the region E1 where the semiconductor laser 2 is formed in order to realize wavelength selection of the DFB laser.

  Thereafter, as shown in FIGS. 2 and 7, the region E1 where the semiconductor laser 2 is formed and the region E2 where the absorption layer 6 is formed are masked with SiNx20a, and the other region E11 is removed by etching and selected. The MZ active layer 23 having a band gap wavelength of 1460 nm is grown by the growth method. Instead of the selective growth method, the MZ active layer 23 may be formed by a B / J (butt joint) regrowth method.

  Further, as shown in FIGS. 3 and 8, the region E3 where the arms 4-1 and 4-2 are formed in addition to the regions E1 and E2 is masked with SiNx20a, and the other region E12 is etched and removed. Then, the optical waveguide layer 24 having a band gap wavelength of 1300 nm is grown by a selective growth method. Instead of the selective growth method, the MZ active layer 23 may be formed by a B / J (butt joint) regrowth method.

  Thereafter, as shown in FIG. 9, an InP layer 25 is formed on the entire upper surface of the formed semiconductor laser active layer 22, MZ active layer 23, and optical waveguide layer 24, and a contact layer 26 is stacked on the entire upper layer of the InP layer 25. To do. Thereafter, as shown in FIG. 10, a photomask is formed with SiNx20c, the optical waveguide pattern is transferred, and the portion other than the optical waveguide pattern is dry-etched to the front of the uppermost layer of the optical waveguide layer 24 to obtain a low mesa optical waveguide. Form. The optical waveguide pattern refers to regions of the optical waveguides 11 to 16, the semiconductor laser 2, the branch coupler 3, the arms 4-1 and 4-2, the multiplexing coupler 5, and the absorption layer 6.

  Further, as shown in FIG. 11, for example, the insulating layer 31 is formed except for the portions corresponding to the arms 4-1 and 4-2 that require electrical contact, and the upper surfaces of the arms 4-1 and 4-2 are formed. Then, the contact layer 32 and the contact layer 33 for forming the electrode surface are formed, the electrode 19 is formed on the upper surface of the contact layer 33, and the electrode 30 is formed on the entire lower surface of the n-InP layer 21. An electrode similar to the electrodes 19 and 18 is formed in the semiconductor laser 2, and the electrode 17 of the semiconductor laser 2 is formed (see FIG. 5).

  Although the above-described optical waveguide has a low mesa structure, it may have a high mesa structure as shown in FIG. This high-mesa optical waveguide is formed by dry etching until the portion other than the optical waveguide pattern reaches the lower layer of the MZ active layer 23 and the optical waveguide layer 24, here the n-InP layer 21. The optical waveguide may have a buried mesa structure embedded with a semiconductor, polymer, or the like.

  In the optical semiconductor device 1 formed in this way, light leaks in a direction other than the optical waveguide from the optical waveguides 12 to 15 that are bent optical waveguides, the branch coupler 3 that is an MMI coupler, the multiplexing coupler 5, and the like. Since the stray light as a component is absorbed by the absorption layer 6 provided on the output end side of the optical semiconductor element 1, the stray light component coupled to the optical fiber via the optical waveguide 16 is eliminated. In this optical semiconductor element 1, an extinction ratio of 32 dB was obtained at an operating voltage of 3V. When the absorption layer 6 was not provided, the extinction ratio was 27 dB.

  In the first embodiment, the absorption layer 6 adjacent to the multiplexing coupler 5 and the optical waveguide 16 on the output end side of the optical semiconductor element 1 is provided so as to absorb stray light, so that deterioration of the extinction ratio is prevented. be able to.

(Embodiment 2)
Next, a second embodiment of the present invention will be described. In the first embodiment described above, an optical semiconductor element in which one semiconductor laser and one MZ interference optical modulator are monolithically integrated is used. However, in the second embodiment, a plurality of semiconductor lasers and one MZ interference are used. It is intended for monolithically integrated type optical modulators.

  FIG. 13 is a diagram showing a schematic configuration of an optical semiconductor element 41 according to the second embodiment of the present invention. As shown in FIG. 13, this optical semiconductor element 41 has the same configuration as that of the optical semiconductor element 1 shown in FIG. This optical semiconductor element 41 has three semiconductor lasers 42-1 to 42-3 in the preceding stage of the branching coupler 3, and 3 × of the laser light selectively output from each of the semiconductor lasers 42-1 to 42-3. One MMI coupler 43 outputs the signal to one optical waveguide 11.

  Here, as described above, in the case of a P port × Q port MMI coupler, the amount of stray light leaking increases by (P−Q / P) when P ≧ Q, and the number of integrated ports is large. The amount of stray light increases. Therefore, an absorption layer 46 that is adjacent to at least the output end face of the MMI coupler 43 and adjacent to the input end faces of the optical waveguide 11 and the branch coupler 3 and extends to the side face in the width direction of the optical semiconductor element 1 is further provided. The absorption layer 46 is realized by the same semiconductor laser active layer as the absorption layer 6. This prevents stray light from the MMI coupler 43 from affecting other optical waveguides. In this optical semiconductor element 41, an extinction ratio of 32 dB was obtained at an operating voltage of 3V. When the absorption layer 6 and the absorption layer 46 were not provided, the extinction ratio was 20 dB.

  In the second embodiment, the absorption layer 46 is further provided in addition to the absorption layer 6 so that stray light is absorbed as soon as possible after generation of stray light. Therefore, deterioration of the extinction ratio due to stray light can be further prevented.

(Embodiment 3)
Next, a third embodiment of the present invention will be described. In the third embodiment, the MMI coupler 43 and the branch coupler 3 described in the second embodiment are realized by one 3 × 2 MMI coupler 53.

  FIG. 14 is a diagram showing a schematic configuration of an optical semiconductor element 51 according to the third embodiment of the present invention. As shown in FIG. 14, in this optical semiconductor device 51, the MMI coupler 43, the optical waveguide 11 and the branch coupler 3 shown in FIG. 13 are replaced with one 3 × 2 MMI coupler 53. Further, an absorption layer 56 is formed in a region surrounded by the output end face of the MMI coupler 53 and the arms 4-1, 4-2. The absorption layer 56 is realized by the same semiconductor laser active layer as the absorption layer 6. By providing this absorption layer 56, stray light leaking from the output end face of the MMI coupler 53 is immediately absorbed so that other optical waveguides and the like are not affected. In this optical semiconductor element 51, an extinction ratio of 32 dB was obtained at an operating voltage of 3V. When the absorption layer 6 and the absorption layer 56 were not provided, the extinction ratio was 18 dB.

  In the third embodiment, the absorption layer 56 is provided at the output end of the MMI coupler 53 so that stray light is absorbed as soon as possible after generation of stray light. Therefore, the deterioration of the extinction ratio due to stray light can be further prevented.

(Embodiment 4)
Next, a fourth embodiment of the present invention will be described. In the fourth embodiment, an absorption optical waveguide 65 is provided in the region of the absorption layer 56 shown in the third embodiment.

  FIG. 15 is a diagram showing a schematic configuration of an optical semiconductor element 61 according to the fourth embodiment of the present invention. As shown in FIG. 15, the optical semiconductor element 61 has arms 4-1 and 4-2 in the central region parallel to the arms 4-1 and 4-2 in the region of the absorption layer 56 shown in FIG. The absorption optical waveguide 65 realized by the same MZ active layer is formed. Also, an absorption layer 66 realized by a semiconductor laser active layer is formed in a region corresponding to the absorption layer 56 excluding the absorption optical waveguide 65. Thus, stray light is guided to the absorption optical waveguide 65, and the stray light is efficiently absorbed by the absorption layer 66 adjacent to the absorption optical waveguide 65. The 3 × 2 MMI coupler 53 is designed to efficiently absorb stray light leaking from this portion in the wide area using the absorption optical waveguide 65 because the leak output concentrates in the center portion of the two output ports. It is. In this optical semiconductor element 61, an extinction ratio of 32 dB was obtained at an operating voltage of 3V. In the case where the absorption layer 6, the absorption layer 66, and the absorption optical waveguide 65 were not provided, the extinction ratio was 18 dB.

  In the fourth embodiment, the absorption optical waveguide 65 and the absorption layer 66 are provided at the output end of the MMI coupler 53 so that stray light is absorbed as much as possible immediately after the generation of stray light. Deterioration can be prevented.

(Embodiment 5)
Next, a fifth embodiment of the present invention will be described. In the fifth embodiment, in order to further reduce the loss of light to be guided, a ridge type optical waveguide structure in which the width of the optical waveguide layer is made wider than the ridge width is adopted.

  FIG. 16 is a cross-sectional view of the arm 4-1, 4-2 corresponding to FIG. As shown in the lower part of FIG. 16, it is a figure which shows schematic structure of the optical semiconductor element 61 which is Embodiment 4 of this invention. As shown in FIG. 15, when the light to be guided is approximately the same as the mesa width 2 b and the width 2 w of the MZ active layer and has a Gaussian distribution, as shown in the lower part of FIG. 15, the light passing through the optical waveguide is The optical waveguide layer 24 exudes beyond the mesa width 2b, and the exuded light is absorbed or scattered by the optical waveguide layer 24, resulting in a loss of light guided through the optical waveguide in the loss regions C1 and C2. In FIG. 16, the width 2w of the MZ active layer is substantially the same as twice the width of the light spot size. Here, the spot size refers to the width from the center point of light to the point where the electric field amplitude of light becomes 1 / e of the center value.

Here, if the ratio of the width w from the center of the MZ active layer 23 to the mesa width b is a, the ratio h (a) ² of light confined inside the MZ active layer is as shown in FIG. The larger a is, the closer it is to 1. In the case of the optical waveguide structure shown in FIG. 16, the width ratio a = 1, and the ratio h (a) ² of light confined inside the MZ active layer at this time is 0.71, and 29% of the light is The semiconductor laser active layer oozes and suffers loss. Further, by setting the width ratio a = 2, the proportion of light that receives loss is 1%. Conversely, the width ratio a = 1.38 or more may be set in order to reduce the ratio of light that receives loss to 10% or less.

  Therefore, as shown in FIG. 18, by forming the extended portion 23a in the MZ active layer 23 and setting the width a · w = 1.38 of the MZ active layer 23, the loss in the loss regions C21 and C22 is 10%. It can be: Of course, by setting the width a · w = 2 of the MZ active layer 23, the loss can be reduced to 1% or less.

  FIG. 19 is a diagram showing a structure when the optical waveguide structure of the fifth embodiment is applied to the optical semiconductor element shown in FIG. As shown in FIG. 19, the extended portion 23 a is formed in the low-mesa ridge structure MZ active layer 23 of the low-mesa ridge structure arms 4-1 and 4-2, and the MZ active layer 23 is widened. Can be reduced. Further, in FIG. 19, an optical waveguide layer 24 a wider than the mesa widths of the synthetic coupler 5 and the optical waveguide 16 is formed in the width direction of the synthetic coupler 5 and the optical waveguide 16 so that the absorption layer 6 is not directly connected. The absorption layer 6 is arranged adjacent to the optical waveguide layer 24a. As a result, it is possible to reduce the loss of light passing through the composite coupler 5 and the optical waveguide 16 and to prevent the influence of stray light.

  FIG. 20 is a diagram showing a structure when the optical waveguide structure of the fifth embodiment is applied to the optical semiconductor element shown in FIG. As shown in FIG. 20, this optical semiconductor element has an extension portion 23a and an optical waveguide layer 24a formed on the arms 4-1 and 4-2, similarly to the optical semiconductor element shown in FIG. The loss of guided light is reduced. Further, with respect to the low mesa ridge structure of the optical waveguide 11 connecting the MMI coupler 43 and the branch coupler 3, an optical waveguide layer 24b wider than the mesa width is formed, and an absorption layer 46 is formed on the optical waveguide layer 24b. Adjacent to each other. As a result, the loss of light passing through the optical waveguide 11 can be reduced and the influence of stray light can be prevented.

  FIG. 21 is a diagram showing a structure when the optical waveguide structure of the fifth embodiment is applied to the optical semiconductor element shown in FIG. As shown in FIG. 21, this optical semiconductor element has an extended portion 23a and an optical waveguide layer 24a formed on the arms 4-1 and 4-2, similarly to the optical semiconductor element shown in FIG. The loss of guided light is reduced. Further, the optical waveguide layer 24c is formed between the extended portion 23a and the absorption layer 56, and the absorption layer 56 is disposed adjacent to the optical waveguide layer 24c. As a result, the loss of light passing through the arms 4-1 and 4-2 can be reduced, and the influence of stray light can be prevented.

  FIG. 22 is a diagram showing a structure when the optical waveguide structure of the fifth embodiment is applied to the optical semiconductor element having the absorption optical waveguide 65 shown in FIG. As shown in FIG. 22, this optical semiconductor element has an extension portion 23a and an optical waveguide layer 24a formed on the arms 4-1 and 4-2, similarly to the optical semiconductor element shown in FIG. The loss of guided light is reduced. Further, the optical waveguide layer 24d is formed between the extended portion 23a and the absorption layer 56, and the absorption layer 56 is disposed adjacent to the optical waveguide layer 24d. As a result, the loss of light passing through the arms 4-1 and 4-2 can be reduced, and the influence of stray light can be prevented.

  In the first to fifth embodiments described above, the absorption layer is provided in part on the monolithically integrated semiconductor substrate. However, the present invention is not limited to this, and the semiconductor element 2, the branch coupler 3, and the arm 4-1. 4-2, the coupling coupler 5, and the optical waveguides 11 to 16 may be provided with an absorption layer realized by a semiconductor laser active layer over the entire region other than the functional portions. Further, the absorption layer is not limited to the semiconductor laser active layer, and may be any active layer having a band gap wavelength exceeding the band gap wavelength of the operating light as long as it can absorb the operating light to be guided.

  In the first to fifth embodiments described above, the optical semiconductor element using the MMI coupler has been described. However, the present invention is not limited to this, and the present invention can also be applied to the case where a directional coupler is used.

  Furthermore, in the above-described embodiment, the optical semiconductor element on which the semiconductor laser and the MZ interference type optical modulator are mounted has been described. However, the present invention is not limited to this, and many other semiconductor devices such as a wavelength conversion element are integrated. Similarly, the effect of stray light can be prevented by forming an absorption layer.

It is a figure which shows schematic structure of the optical semiconductor element concerning Embodiment 1 of this invention. FIG. 7 is a plan view showing a manufacturing process of the optical semiconductor element shown in FIG. 1. FIG. 7 is a plan view showing a manufacturing process of the optical semiconductor element shown in FIG. 1. FIG. 7 is a plan view showing a manufacturing process of the optical semiconductor element shown in FIG. 1. FIG. 7 is a plan view showing a manufacturing process of the optical semiconductor element shown in FIG. 1. FIG. 7 is a cross-sectional view showing a manufacturing process of the optical semiconductor element shown in FIG. 1. FIG. 7 is a cross-sectional view showing a manufacturing process of the optical semiconductor element shown in FIG. 1. FIG. 7 is a cross-sectional view showing a manufacturing process of the optical semiconductor element shown in FIG. 1. FIG. 7 is a cross-sectional view showing a manufacturing process of the optical semiconductor element shown in FIG. 1. FIG. 7 is a cross-sectional view showing a manufacturing process of the optical semiconductor element shown in FIG. 1. FIG. 7 is a cross-sectional view showing a manufacturing process of the optical semiconductor element shown in FIG. 1. FIG. 7 is a cross-sectional view showing a manufacturing process of the optical semiconductor element shown in FIG. 1. It is a figure which shows schematic structure of the optical semiconductor element concerning Embodiment 2 of this invention. It is a figure which shows schematic structure of the optical semiconductor element concerning Embodiment 3 of this invention. It is a figure which shows schematic structure of the optical semiconductor element concerning Embodiment 4 of this invention. It is sectional drawing of the arm part corresponding to FIG. It is a figure which shows the change of the permeation | transmission ratio with respect to width ratio. It is sectional drawing of the arm part in which the MZ active layer wider than a mesa width | variety was formed. It is a figure which shows the structure at the time of applying the optical waveguide structure of Embodiment 5 of this invention to the optical semiconductor element shown in FIG. It is a figure which shows the structure at the time of applying the optical waveguide structure of Embodiment 5 of this invention to the optical semiconductor element shown in FIG. It is a figure which shows the structure at the time of applying the optical waveguide structure of Embodiment 5 of this invention to the optical semiconductor element shown in FIG. FIG. 16 is a diagram showing a structure when the optical waveguide structure according to the fifth embodiment of the present invention is applied to the optical semiconductor element having the absorbing optical waveguide 65 shown in FIG. It is a figure which shows the state of the stray light which leaks from an MMI coupler.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,41,51,61 Optical semiconductor element 2,42-1 to 42-3 Semiconductor laser 3 Branch coupler 4 MZ interference type optical modulator 4-1, 4-2 Arm 5 Combined coupler 6, 46, 56, 66 Absorption layer 11-16 Optical waveguide 17-19, 30, 44-1 to 44-3 Electrode 20a to 20c SiNx
21 n-InP substrate 22 Semiconductor laser active layer 22a, 25 InP layer 22b Diffraction grating 23 MZ active layer 23a Extended portion 24, 24a-24d Optical waveguide layer 26, 32, 33 Contact layer 31 Insulating layer 43, 53 MMI coupler 65 Absorption Optical waveguide

Claims (22)

An optical semiconductor element in which a plurality of optical semiconductor devices are connected by an optical coupler and an optical waveguide and monolithically integrated,
Light having an absorption region having a band gap wavelength longer than a band gap wavelength corresponding to operating light propagating through the optical coupler and the optical waveguide, adjacent to the optical coupler or the optical waveguide Semiconductor element.   2. The optical semiconductor device according to claim 1, wherein the absorption region extends in the width direction from the optical coupler or the optical waveguide and is provided over the entire output direction in the subsequent stage.   The optical semiconductor element according to claim 1, wherein the absorption region is provided on an output end side of the optical coupler.   2. The absorption region is provided between an output end of a preceding optical coupler and an input end of a subsequent optical coupler connected to the preceding optical coupler when there are a plurality of the optical couplers. The optical semiconductor element as described in any one of -3.   5. The optical semiconductor element according to claim 1, wherein the absorption region is provided between an optical coupler that performs optical branching and an optical coupler that performs optical multiplexing.   When two optical couplers are connected by a plurality of optical waveguides, a region surrounded by the two optical couplers and the plurality of optical waveguides is defined as the absorption region. The optical semiconductor element described in 1.   When the optical coupler is a multimode interference optical coupler having a plurality of output ends, an absorption optical waveguide is provided at the light concentration end between the output ends, and the absorption is provided between the optical waveguides connected to the output end. An optical semiconductor element according to claim 1, wherein a region is provided.   The optical semiconductor element according to claim 1, wherein the absorption region is provided over the entire region excluding the optical semiconductor device, the optical coupler, and the optical waveguide.   The optical semiconductor device according to claim 1, wherein the optical semiconductor device is a semiconductor laser device or a light control function device. The semiconductor laser device is one or more distributed feedback semiconductor lasers;
The optical semiconductor device according to claim 9, wherein the light control functional device is a Mach-Zehnder optical interferometer.   11. The optical waveguide according to claim 1, wherein the optical waveguide has a ridge type optical waveguide structure formed in a plane parallel to the semiconductor substrate, and the width of the optical waveguide layer is wider than the ridge width. The optical semiconductor element as described in any one.   Each arm of the Mach-Zehnder type optical interferometer has a ridge type optical waveguide structure formed in a plane parallel to the semiconductor substrate, and the width of the optical waveguide layer is wider than the ridge width. The optical semiconductor device according to claim 10 or 11.   The optical coupler adjacent to the absorption region or the optical waveguide adjacent to the absorption region has a ridge-type optical waveguide structure and has an optical waveguide layer wider than the ridge width. 12. The optical semiconductor device according to any one of 12 above. A method of manufacturing an optical semiconductor element in which a plurality of optical semiconductor devices are connected by an optical coupler and an optical waveguide and integrated monolithically,
In a plane parallel to the semiconductor substrate, an absorption region having a band gap wavelength longer than the band gap wavelength corresponding to the operating light propagating through the optical coupler and the optical waveguide is selected by the selective growth method. A method for manufacturing an optical semiconductor element, characterized by being formed adjacent to an optical waveguide. A method of manufacturing an optical semiconductor element in which a plurality of optical semiconductor devices are connected by an optical coupler and an optical waveguide and integrated monolithically,
An absorption region having a band gap wavelength longer than the band gap wavelength corresponding to the operating light propagating through the optical coupler and the optical waveguide is formed in the plane parallel to the semiconductor substrate by the B / J regrowth method. A method for manufacturing an optical semiconductor device, comprising: forming a coupler or adjacent to the optical waveguide.   16. The method of manufacturing an optical semiconductor element according to claim 14, wherein the absorption region extends in the width direction from the optical coupler or the optical waveguide and is provided over the entire output direction in the subsequent stage.   The method for manufacturing an optical semiconductor element according to claim 14, wherein the absorption region is provided on an output end side of the optical coupler.   The method of manufacturing an optical semiconductor element according to claim 14, wherein the optical semiconductor device is a semiconductor laser device or an optical control function device. The semiconductor laser device is one or more distributed feedback semiconductor lasers;
The method of manufacturing an optical semiconductor element according to claim 18, wherein the light control functional device is a Mach-Zehnder optical interferometer.   The optical waveguide has a ridge-type optical waveguide structure formed in a plane parallel to the semiconductor substrate, and the width of the optical waveguide layer is wider than the ridge width. The manufacturing method of the optical-semiconductor element as described in any one.   Each arm of the Mach-Zehnder type optical interferometer has a ridge type optical waveguide structure formed in a plane parallel to the semiconductor substrate, and the width of the optical waveguide layer is wider than the ridge width. 21. A method of manufacturing an optical semiconductor element according to claim 19 or 20.   15. The optical coupler adjacent to the absorption region or the optical waveguide adjacent to the absorption region has a ridge-type optical waveguide structure, and has an optical waveguide layer wider than the ridge width. 21. The method for producing an optical semiconductor element according to any one of 21.

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