JP6513412B2 - Semiconductor optical integrated device - Google Patents

Description

  The present invention relates to a semiconductor optical integrated device.

  In recent years, the performance required of a semiconductor optical integrated device has been heightened from the viewpoint of advancement of optical communication and cost reduction. Then, in order to integrate a plurality of optical elements in one semiconductor element, it has been made to selectively use a waveguide structure suitable for the function of each element on the same semiconductor element (see, for example, Patent Document 1). For example, the same semiconductor may be used, such as using a buried waveguide structure with high current injection efficiency in the region responsible for the light emission function in the semiconductor optical integrated device, and using a high mesa waveguide structure with low bending loss in the region responsible for bending the waveguide. The waveguide structure is used properly on the optical integrated device.

  As an example of an optical integrated device in which such different waveguide structures are combined, there is an optical integrated device in which a buried type laser device and a high-mesa type AWG (arrayed waveguide grating) are integrated (see, for example, Patent Document 2). In the case of an integrated AWG, it is required to reduce the bending radius of the waveguide in order to miniaturize the AWG. Therefore, a high-mesa waveguide structure is used for the arrayed waveguide of the AWG. Moreover, in AWG, the waveguide is oriented to various plane orientations of the semiconductor by bending the waveguide greatly, so that embedding by crystal growth and processing by wet etching become difficult. It is the reason to use it.

JP 2008-066318 A Japanese Patent Application Laid-Open No. 10-332964

  However, in the case where waveguides having different waveguide structures are connected as in the case of a high mesa waveguide and a buried waveguide, how to connect the two becomes a problem. Between the waveguides of such different waveguide structures, the light confinement is different due to the large difference in the refractive index especially in the lateral direction, which causes a mismatch in the light distribution of the waveguide mode. In addition, when the high mesa waveguide and the buried waveguide are patterned in different steps in the manufacturing process, errors may occur in the connection position. And, the mismatch of the light distribution of the guided mode and the error of the connection position will cause connection loss.

  Various methods have been devised for the design of this connection. For example, one including a mode conversion part, one having fins disposed on the left and right of the connection part, one having a thick waveguide at the connection part, and one sandwiching the MMI are known. Although the connection loss of the connection can be reduced also by such a known connection method, there is a problem that an extra length of waveguide or structure is required for the connection.

  The present invention has been made in view of the above, and it is an object of the present invention to provide a semiconductor optical integrated device capable of reducing connection loss of waveguides different in confinement structure in a direction parallel to a substrate by a simple method. is there.

  In order to solve the problems described above and achieve the object, a semiconductor optical integrated device according to an aspect of the present invention includes a waveguide light input to a slab waveguide on an input side and an slab waveguide on an output side via an arrayed waveguide. A semiconductor optical integrated device including at least an arrayed waveguide grating for focusing light on the input side, the input waveguide having a waveguide structure different from the arrayed waveguide in a confinement structure in a direction parallel to the substrate; It is characterized in that it is directly connected to the facing side of the arrayed waveguide in the waveguide.

  In the semiconductor optical integrated device according to one aspect of the present invention, the arrayed waveguide has a high mesa waveguide structure in which a mesa including at least a waveguide core layer and an upper cladding layer is protruded.

  The semiconductor optical integrated device according to one aspect of the present invention is characterized in that the input waveguide has a buried waveguide structure in which a semiconductor clad material is buried on both sides of a stripe-like waveguide core layer. .

  In the semiconductor optical integrated device according to one aspect of the present invention, the input waveguide includes a low-mesa waveguide in which a semiconductor layer including at least an upper cladding layer above the waveguide core layer continued to the left and right protrudes in a mesa. It is characterized by being a structure.

  In the semiconductor optical integrated device according to one aspect of the present invention, a plurality of semiconductor light emitting devices having the same waveguide structure as the input waveguide and emitting light at different wavelengths are the input via the input waveguide. It is characterized in that it is connected to the side slab waveguide.

  In the semiconductor optical integrated device according to one aspect of the present invention, an output waveguide having the same waveguide structure as the input waveguide is directly connected to the facing side of the arrayed waveguide in the output side slab waveguide. It is characterized by

  Further, the semiconductor optical integrated device according to one aspect of the present invention is characterized in that the guided light is emitted from the output side slab waveguide without passing through the additional waveguide.

  The semiconductor optical integrated device according to the present invention has an effect that connection loss of waveguides different in confinement structure in the direction parallel to the substrate can be reduced by a simple method.

FIG. 1 is a schematic plan view showing a semiconductor optical integrated device according to a first embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of the DFB laser device. FIG. 3 is a schematic cross-sectional view of the input-side slab waveguide. FIG. 4 is a schematic cross-sectional view of the arrayed waveguide. FIG. 5 is a schematic cross-sectional view of the optical amplifier. FIG. 6 is a schematic cross-sectional view of the semiconductor optical integrated device in the waveguide direction. FIG. 7 is a schematic plan view showing a semiconductor optical integrated device according to a second embodiment of the present invention. FIG. 8 is a schematic cross-sectional view of the DFB laser device. FIG. 9 is a schematic cross-sectional view of the input-side slab waveguide. FIG. 10 is a schematic cross-sectional view of the arrayed waveguide. FIG. 11 is a schematic cross-sectional view of the optical amplifier. FIG. 12 is a schematic cross-sectional view of the semiconductor optical integrated device in the waveguide direction. FIG. 13 is a schematic plan view showing a semiconductor optical integrated device according to a third embodiment of the present invention.

  The semiconductor optical integrated device according to the embodiment of the present invention will be described in detail below with reference to the drawings. Note that the present invention is not limited by the embodiments described below. Further, in the description of the drawings, the same parts are denoted by the same reference numerals. In addition, it should be noted that the drawings are schematic, and the relationship between the thickness and width of each layer, the ratio of each layer, and the like are different from reality. Even between the drawings, there are included portions where the dimensional relationships and proportions differ from one another.

First Embodiment
FIG. 1 is a schematic plan view showing a semiconductor optical integrated device 100 according to the first embodiment of the present invention. For the sake of simplicity, FIG. 1 shows only the waveguide of the semiconductor optical integrated device 100, and the configuration of the electrodes and the like is omitted. As shown in FIG. 1, the semiconductor optical integrated device 100 includes a buried waveguide structure region 110, a slab waveguide structure region 120, and a high mesa waveguide structure region 130.

  The embedded waveguide structure region 110 is a region in which the constituent waveguide has the embedded waveguide structure. A waveguide having a buried waveguide structure is simply referred to as a buried waveguide. The embedded waveguide structure is a waveguide structure in which a semiconductor clad material is embedded on both sides of a stripe-shaped waveguide core layer, and is suitable, for example, for an element that performs current injection, such as a laser element or an optical amplifier. . This is because the embedded waveguide structure has features such as low surface recombination velocity, low electrical resistance, low thermal resistance, and low light scattering loss.

  In addition, the embedded waveguide structure can easily form the end face window structure adjacent to each other. This is because the embedded waveguide structure performs the optical confinement in the vertical direction and the optical confinement in the horizontal direction in the same structure, so that the facet window structure can be formed only by removing the waveguide core layer. On the other hand, when an end face window structure is to be formed adjacent to the high mesa waveguide structure, removal of the core layer in the end face window structure and formation of the high mesa structure must be performed in separate steps. It is easy to occur.

  Therefore, in the semiconductor optical integrated device 100 of this embodiment, the DFB laser device 111, the optical amplifier 112, the input waveguide 113, and the output waveguide 114 are provided in the embedded waveguide structure region 110.

  Further, an end face window structure 115 is provided between the optical amplifier 112 and the exit surface 116 of the semiconductor optical integrated device 100.

  The high-mesa waveguide structure region 130 is a region in which the constituent waveguide has a high-mesa waveguide structure. A waveguide having a high mesa waveguide structure is simply referred to as a high mesa waveguide. The high-mesa waveguide structure is a waveguide structure in which a semiconductor layer at least including a waveguide core layer protrudes in a mesa shape, and is suitable, for example, for a bent waveguide. The high-mesa waveguide structure has a characteristic that the bending loss is small because the refractive index difference between the core and the cladding is large in the left-right direction. Thus, with the same allowable bending loss, the high mesa waveguide can have a smaller radius of curvature as compared to the buried waveguide. For this reason, a semiconductor optical integrated device employing a high mesa waveguide structure is advantageous for the miniaturization of the device as compared with the one employing a buried waveguide.

  Therefore, in the semiconductor optical integrated device 100 of the present embodiment, the high mesa waveguide structure region 130 is provided with an arrayed waveguide 131 which constitutes a part of the AWG.

  The slab waveguide structure region 120 is a region in which the constituting waveguide has a slab waveguide structure. A waveguide having a slab waveguide structure is simply referred to as a slab waveguide. The slab waveguide structure is a waveguide structure having no light confinement force in the direction parallel to the substrate. Therefore, light propagating in the slab waveguide propagates while spreading in a direction parallel to the substrate. In the AWG, the characteristic that there is no light confinement force in the direction parallel to the substrate in the slab waveguide can be used for the input part and the output part to perform multiplexing or demultiplexing of guided light of different wavelengths.

  Therefore, in the semiconductor optical integrated device 100 of the present embodiment, the slab waveguide structure region 120 is provided with the input side slab waveguide 121 and the output side slab waveguide 122 of the AWG.

  Since the slab waveguide is a waveguide that does not have a light confinement force in the direction parallel to the substrate, it is suitable for being interposed when connecting the embedded waveguide and the high mesa waveguide. The embedded waveguide and the high-mesa waveguide differ greatly in the light confinement power in the direction parallel to the substrate, but are connected by the slab waveguide having no light confinement power in the direction parallel to the substrate. It is possible to eliminate the mismatch of the light distribution of the guided mode between the embedded waveguide and the high-mesa waveguide.

  Therefore, in the semiconductor optical integrated device 100 of the present embodiment, the embedded waveguide and the high mesa waveguide are utilized by utilizing the input-side slab waveguide 121 and the output-side slab waveguide 122 which constitute a part of the AWG. Connected. That is, in the semiconductor optical integrated device 100 of the present embodiment, the input waveguide 113 composed of the embedded waveguide and the input-side slab waveguide 121 are directly connected to each other, and further, the array waveguide composed of the high mesa waveguide The waveguide 131 and the input side slab waveguide 121 are directly connected. Further, the output waveguide 114 formed of the embedded waveguide is directly connected to the output side slab waveguide 122, and the array waveguide 131 formed of the high mesa type waveguide is directly connected to the output side slab waveguide 122. doing.

  As described above, in the semiconductor optical integrated device 100 of the present embodiment, the embedded waveguide and the high mesa type are utilized by utilizing the input-side slab waveguide 121 and the output-side slab waveguide 122 which constitute a part of the AWG. Since the waveguides are connected, it is not necessary to provide a separate special structure at the connection portion between the embedded waveguide and the high mesa waveguide. In other words, by connecting the embedded waveguide and the high-mesa waveguide to the input-side slab waveguide 121 and the output-side slab waveguide 122, waveguides having different confinement structures in the direction parallel to the substrate are guided. The light distribution of the modes can be matched and connected.

  Next, the function of each component in the semiconductor optical integrated device 100 will be described.

  The semiconductor optical integrated device 100 includes a plurality of DFB laser elements 111. The plurality of DFB laser elements 111 are designed to have different oscillation wavelengths by 3.5 nm in the 1.55 μm wavelength band, for example. Further, by changing the temperature of the DFB laser device 111, the oscillation wavelength of the DFB laser device 111 is changed. Therefore, the plurality of DFB laser elements 111 operate as a variable-wavelength light source that performs rough tuning by selecting one of a plurality of filters, performs fine tuning by changing the temperature, and performs oscillation in a continuous wavelength range as a whole. Do. The waveguided light emitted from the plurality of DFB laser elements 111 is guided to the input side slab waveguide 121 via the input waveguide 113.

  The input-side slab waveguide 121 is a waveguide having no light confinement force in the direction parallel to the substrate, and is guided to the arrayed waveguide 131 while dispersing the waveguided light input from the input waveguide 113 in the direction parallel to the substrate. Wave light is guided.

  The arrayed waveguide 131 is composed of a large number of waveguides formed by bending the path, and a wavelength-dependent optical path length difference is provided. Therefore, when the incident position in the input side slab waveguide 121 is changed according to the optical path length difference depending on the wavelength, the condensing position at the output end of the output side slab waveguide 122 does not change. Using such a principle, the AWG functions as a coupler that combines guided light of different oscillation wavelengths emitted from a plurality of DFB laser elements 111.

  If the coupler provided between the plurality of DFB laser elements 111 and the optical amplifier 112 has no wavelength selectivity, the coupling efficiency between the DFB laser element 111 and the optical amplifier 112 is equal to that of the DFB laser element. It will be less than a fraction of the number. For example, assuming that the number of DFB laser elements 111 is eight, the coupling efficiency between each DFB laser element 111 and the optical amplifier 112 is 1/8 or less (12.5% or less).

  In other words, in the semiconductor optical integrated device 100, since the AWG is used as a coupler interposed between the plurality of DFB laser devices 111 and the optical amplifier 112, the coupling efficiency from the DFB laser device 111 to the optical amplifier 112 becomes high. ing.

  In the example used in this embodiment, the focal length of the AWG is 630 μm, and 80 array waveguides 131 are provided at an interval of 3.5 μm, and the input waveguide 113 connected to the input-side slab waveguide 121 Is 5 μm.

  The output waveguide 114 guides the guided light multiplexed in the output side slab waveguide 122 to the optical amplifier 112. Then, the optical amplifier 112 amplifies the guided light input from the output waveguide 114 and emits the light to the outside of the semiconductor optical integrated device 100 through the end face window structure 115.

  The end face window structure 115 is formed by removing the waveguide core layer near the end face. A low reflection coating is applied to the end face of the semiconductor optical integrated device 100 in order to reduce the reflectance, but by providing the end face window structure 115, the reflectance can be further reduced.

  In the semiconductor optical integrated device 100 of the present embodiment, the DFB laser device 111 and the optical amplifier 112 have the advantage that the surface recombination speed at the side of the waveguide is small by adopting the embedded type waveguide structure. it can. In addition, by adopting a high-mesa waveguide structure, the AWG arrayed waveguides 131 can have a small radius of curvature and closely spaced waveguides, thereby enabling significant downsizing.

  Here, it is assumed that the pattern position deviates from the design value between the embedded waveguide structure region 110 and the high mesa waveguide structure region 130. For example, the embedded waveguide structure region 110 and the high mesa waveguide structure region 130 may be patterned in different steps in the manufacturing process, and the input waveguide 113 to the input-side slab waveguide 121 of the AWG may be patterned. Errors may occur in the connection position. However, the lateral shift from the incident direction in the AWG affects only the shift of the transmission wavelength of the AWG, and does not affect the transmission efficiency at the transmission wavelength. This is a point where the connection between the high mesa waveguide according to the prior art and the embedded waveguide according to the prior art greatly differs, which directly leads to a decrease in efficiency.

  Furthermore, the transmission wavelength shift in this embodiment will be examined. In the semiconductor optical integrated device 100 of the present embodiment, the input waveguide 113 and the output waveguide 114 are opposed to each other, and the input waveguide 113 and the output waveguide 114 are simultaneously displaced. It will be added. The transmission wavelength interval of the AWG of the above configuration is 3.5 nm, and the interval between the input waveguides 113 is 5 μm. Therefore, when a pattern deviation of 1 μm occurs, 1 nm transmission with 1 μm × 2 ÷ 5 μm × 3.5 nm A wavelength shift will occur. Therefore, if the tolerance of the transmission wavelength is larger than 1 nm, even a pattern deviation of 1 μm is acceptable.

  Next, the cross-sectional structure of each component of the semiconductor optical integrated device 100 will be described with reference to FIGS. 2 to 6 correspond to the cross sections A-A, B-B, C-C, D-D, and E-E in FIG. 1, respectively.

(Cross-sectional structure: DFB laser device)
FIG. 2 is a schematic cross-sectional view of the DFB laser device 111. As shown in FIG. As shown in FIG. 2, the DFB laser device 111 has a structure in which a lower cladding layer 102, a waveguide core layer 103a, and an upper cladding layer 104 are sequentially stacked on a substrate 101.

  The material of the substrate 101 is InP, and the material of the lower cladding layer 102 is n-type InP. The material of the substrate 101 may be n-type InP. When importance is attached to high frequency characteristics, the n-side electrode may be provided in the lower cladding layer 102, and the material of the substrate 101 may be semi-insulating InP.

  The waveguide core layer 103 a is configured as an active layer of a multiple quantum well structure made of GaInAsP that emits light by current injection. A diffraction grating layer 103aa is provided in the vicinity of the upper side of the waveguide core layer 103a. The thickness of the waveguide core layer 103a is 150 nm including the SCH layer, and the width is 2 μm.

  The material of the upper cladding layer 104 is p-type InP, and an etching stopper layer 105 having an etching resistance different from that of the upper cladding layer 104 is inserted in the upper cladding layer 104. Note that this etching stop layer 105 can be omitted depending on the manufacturing method. The thickness of the upper cladding layer 104, including the etching stopper layer 105, is 4.5 μm. The thickness of the etching stopper layer 105 when the etching stopper layer 105 is inserted is, for example, 10 nm.

  The waveguide core layer 103a of the DFB laser device 111 has a structure in which the lower buried cladding layer 106 and the upper buried cladding layer 107 are buried in the vicinity of both sides of the waveguide core layer 103a. The materials of the lower buried cladding layer 106 and the upper buried cladding layer 107 are p-type InP and n-type InP, respectively. The lower buried cladding layer 106 and the upper buried cladding layer 107 function as a current blocking layer to enhance the injection efficiency of the current injected into the waveguide core layer 103a.

  A contact layer 108 made of p-type GaInAs is provided on the upper cladding layer 104, and is in ohmic contact with the p-side electrode 109a. In addition, a passivation film 141 made of SiNx is formed on the upper surface and the side surface of the DFB laser device 111, and each of the adjacent DFB laser devices 111 is electrically separated. Further, the p-side electrode 109a is in contact with a multilayer electrode of titanium, platinum and gold and the on-chip wiring 143a by gold plating.

(Cross-sectional structure: slab waveguide)
FIG. 3 is a schematic cross-sectional view of the input-side slab waveguide 121. As shown in FIG. As shown in FIG. 3, the input-side slab waveguide 121 has a structure in which a lower cladding layer 102, a waveguide core layer 103b, and an upper cladding layer 104 are sequentially stacked on a substrate 101. The material of the substrate 101, the lower cladding layer 102, and the upper cladding layer 104 is the same as that of the DFB laser device 111.

  The waveguide core layer 103 b has a bulk structure using GaInAsP as a material. The thickness of the waveguide core layer 103b is 200 nm. The width of the waveguide core layer 103 b is wide enough to prevent the influence of the guided light while spreading in the direction parallel to the substrate 101.

  Although the contact layer 108 is provided on the upper cladding layer 104, the contact layer 108 may be removed. In addition, on the upper surface of the input-side slab waveguide 121, a passivation film 141 made of SiNx is appropriately formed.

(Cross-sectional structure: arrayed waveguide)
FIG. 4 is a schematic cross-sectional view of the arrayed waveguide 131. As shown in FIG. 4, the arrayed waveguide 131 has a structure in which a lower cladding layer 102, a waveguide core layer 103c, and an upper cladding layer 104 are sequentially stacked on a substrate 101. The material of the substrate 101, the lower cladding layer 102, and the upper cladding layer 104 is the same as that of the DFB laser device 111.

  The waveguide core layer 103 c has a bulk structure using GaInAsP as a material. The thickness of the waveguide core layer 103c is 200 nm and the width is 2 μm.

  The thickness of the upper cladding layer 104 is 2.3 μm thinner than the upper cladding layer in the DFB laser device 111.

  The arrayed waveguide 131 has a high-mesa waveguide structure in which the upper cladding layer 104, the waveguide core layer 103c, and part of the lower cladding layer 102 protrude in a mesa shape. Here, the etching depth for the lower cladding layer 102 is 300 nm.

  The etching stopper layer 105 is provided on the upper cladding layer 104, but the etching stopper layer 105 may be removed. In addition, a passivation film 141 made of SiNx is appropriately formed on the top surface of the arrayed waveguide 131.

(Cross-sectional structure: optical amplifier)
FIG. 5 is a schematic cross-sectional view of the optical amplifier 112. As shown in FIG. As shown in FIG. 5, the optical amplifier 112 has a structure in which a lower cladding layer 102, a waveguide core layer 103d, and an upper cladding layer 104 are sequentially stacked on a substrate 101. Also, it has a waveguide structure in which the lower buried cladding layer 106 and the upper buried cladding layer 107 are buried in the vicinity of both sides of the waveguide core layer 103d. A p-side electrode 109d is connected to the upper cladding layer 104 via a contact layer 108, and the p-side electrode 109d is in contact with a multilayer electrode of titanium, platinum and gold and a chip on-chip wiring 143d by gold plating.

  The optical amplifier 112 has substantially the same configuration as the DFB laser device 111, and the material and layer thickness of each layer are the same as the DFB laser device 111. The difference between the optical amplifier 112 and the DFB laser element 111 is the presence of a grating layer and the presence of a trench. There is no diffraction grating layer above the waveguide core layer 103 d of the optical amplifier 112. In addition, the optical amplifier 112 does not have a trench for electrical isolation.

(Cross-sectional structure: guiding direction)
FIG. 6 is a schematic cross-sectional view of the semiconductor optical integrated device 100 in the waveguiding direction. The cross-sectional schematic view of FIG. 6 shows the DFB laser device 111, the input waveguide 113, the input-side slab waveguide 121, the arrayed waveguide 131, the output-side slab waveguide 122, the output waveguide 114, and the light in the semiconductor optical integrated device 100. The cross section which connected the amplifier 112 and the end surface window structure 115 one by one is shown.

  As shown in FIG. 6, in the arrayed waveguide 131, the thickness of the upper cladding layer 104 is thin as compared to other waveguide portions. The position of the etching stopper layer 105 corresponds to the thickness of the upper cladding layer 104 of the arrayed waveguide 131, and the thickness of the upper cladding layer 104 can be realized by etching up to the etching stopper layer 105. .

  In the end face window structure 115, no waveguide core layer is present. Instead, the lower buried cladding layer 106 and the upper buried cladding layer 107 in the buried waveguide extend into the core portion.

(Production method)
Next, a method of manufacturing the semiconductor optical integrated device 100 will be described.

  First, on the substrate 101 made of n-type InP, the n-type InP as the lower cladding layer 102 using the metal organic chemical vapor deposition (MOCVD) method, the waveguide core layer 103 a of the DFB laser element 111 and the optical amplifier 112. , 103d, a p-type InP as a part of the upper cladding layer 104, and a GaInAsP as a diffraction grating layer 103aa in this order.

  Next, a SiNx film is deposited on the entire surface of the device, and then a periodic diffraction grating pattern is formed in the region where the DFB laser device 111 is to be formed, and SiNx near the region where the optical amplifier 112 is to be formed is removed. Then, etching is performed using the SiNx film as a mask to remove the diffraction grating layer. After removing all the SiNx film, p-type InP is stacked as the upper cladding layer 104 by diffraction grating embedded growth by the MOCVD method. Thereby, the diffraction grating layer 103 aa embedded in the upper cladding layer 104 is formed in the vicinity of the upper side of the waveguide core layer 103 a of the DFB laser device 111.

  Again, after depositing a SiNx film on the entire surface of the device, the region where the DFB laser device 111 and the optical amplifier 112 are to be formed is patterned to have a slightly wider pattern. Then, etching is performed using the SiNx film as a mask to remove the GaInAsP multiple quantum well active layer and expose the n-type InP layer as the lower cladding layer 102. Subsequently, the mask of the SiNx film is used as it is as a mask for selective growth, and on the n-type InP layer as the lower cladding layer 102, GaInAsP as the waveguide core layers 103b and 103c and the upper cladding layer 104 by MOCVD. Stack p-type InP.

  Next, after removing the mask of the SiNx film, a SiNx film is newly deposited, and the DFB laser device 111, the optical amplifier 112, the input waveguide 113, the output waveguide 114, the input side slab waveguide 121, the output side slab guide Patterning is performed to form a pattern corresponding to the waveguides 122 and the waveguides of the arrayed waveguides 131. At this time, in the region of the arrayed waveguide 131 of the AWG forming the high mesa waveguide later, since the waveguide spacing is narrow, no gap is provided, and patterning is performed wide to cover the entire area of the arrayed waveguide 131 deep. Further, since the core layer is not provided in the portion to be the end face window structure 115, the SiNx film is patterned so as to be removed.

  Next, etching is performed using this SiN film as a mask to form a mesa structure corresponding to the waveguides of the DFB laser device 111, the optical amplifier 112, the input waveguide 113, and the output waveguide 114, and as the lower cladding layer 102. The n-type InP layer is exposed. Then, using the mask of this SiNx film as a mask for selective growth, using MOCVD on the n-type InP layer as the lower cladding layer 102, p-type InP as the lower buried cladding layer 106, and the upper embedding. An n-type InP as the cladding layer 107 is stacked.

  Next, after removing the SiNx film mask, p-type InP as the upper cladding layer 104, p-type GaInAsP as the etching stopper layer 105, and a 10-nm-thick p-type GaInAsP over the entire surface of the device using MOCVD. A p-type InP as the layer 104 and a p-type GaInAs as the contact layer 108 are stacked.

  Next, patterning is performed to cover regions other than the region forming the high-mesa waveguide later, and the pattern is used as a mask to remove p-type GaInAs as the contact layer 108 by an etchant containing sulfuric acid and hydrogen peroxide. The p-type InP up to the etching stopper layer 105 is removed by wet etching with a hydrochloric acid based etchant.

  Next, a SiNx film is deposited on the entire surface of the device, and patterning is performed so that an opening can be made in portions corresponding to the left and right of the arrayed waveguide 131 which is a high mesa waveguide. At this time, the peripheral region of the optical amplifier 112 portion and the DFB laser device 111 portion is covered with SiNx, and patterning is performed so as to make an opening in the left and right trenches of the DFB laser device 111. . Then, a portion of the lower cladding layer 102 is etched by dry etching using this SiNx as a mask to form a high mesa waveguide.

  In this process, etching is performed so that the etching depth of the lower cladding layer 102 on both sides of the high mesa structure matches the design value. Also, the left and right trenches of the DFB laser element 111 are etched to reach at least GaInAsP which is the etching stop layer 105, and then the other part is covered with a mask, and the etching depth of this trench is Form by enlarging.

  Thereafter, a passivation film, its opening, electrodes for current injection, etc. are formed on each portion by a known method. After the processing of the surface of the element is completed, the substrate 101 is polished to a desired thickness, and an electrode is formed on the back surface of the element.

  Further, the end face is formed by cleavage of the substrate, end face coating and element separation are performed, and the semiconductor optical integrated device 100 is completed.

Second Embodiment
FIG. 7 is a schematic plan view showing a semiconductor optical integrated device 200 according to the second embodiment of the present invention. FIG. 7 shows only the waveguide of the semiconductor optical integrated device 200 for the sake of simplicity, and the configuration of the electrodes and the like is omitted. As shown in FIG. 7, the semiconductor optical integrated device 200 according to the second embodiment has substantially the same configuration as the semiconductor optical integrated device 100 according to the first embodiment.

  The semiconductor optical integrated device 200 according to the second embodiment differs from the semiconductor optical integrated device 100 according to the first embodiment in that the embedded waveguide structure is replaced by a low mesa waveguide structure. That is, the semiconductor optical integrated device 200 according to the second embodiment includes the low mesa waveguide region 210, the slab waveguide region 220, and the high mesa waveguide region 230.

  The low mesa waveguide structure region 210 is a region in which the constituent waveguide has a low mesa waveguide structure. A waveguide having a low mesa waveguide structure is simply referred to as a low mesa waveguide. The low-mesa waveguide structure is a waveguide structure in which a semiconductor layer including at least an upper cladding layer above the waveguide core layer continuous to the left and right protrudes in a mesa shape, and, for example, a current such as a laser element or an optical amplifier Suitable for injection devices. In the high mesa waveguide structure, carriers do not recombine through the surface state due to the absence of the semiconductor on the side surface of the active layer, and the efficiency of the light emitting element decreases. Since it is contained in a semiconductor, there is no surface level and efficiency is good.

  In addition, when the low mesa type waveguide structure is compared with the embedded type waveguide structure, there is an advantage that processing into the active layer is not necessary, and when an easily oxidizable material containing Al such as AlGaInAs is used for the active layer. Is preferably a low mesa waveguide structure.

  Therefore, in the semiconductor optical integrated device 200 of the present embodiment, the low mesa waveguide structure region 210 is provided with the DFB laser element 211, the optical amplifier 212, the input waveguide 213, and the output waveguide 214.

  On the other hand, as in the first embodiment, in the semiconductor optical integrated device 200, the high mesa waveguide structure region 230 is provided with the arrayed waveguide 231 which constitutes a part of the AWG.

  Further, as in the first embodiment, in the semiconductor optical integrated device 200, the slab waveguide structure region 220 is provided with the input side slab waveguide 221 and the output side slab waveguide 222 of the AWG.

  Since the slab waveguide is a waveguide that does not have a light confinement force in the direction parallel to the substrate, it is suitable for being interposed when connecting the low mesa waveguide and the high mesa waveguide. The low-mesa waveguide and the high-mesa waveguide have a large difference in light confinement power in the direction parallel to the substrate, but are connected by a slab waveguide having no light confinement power in the direction parallel to the substrate. Misalignment of the light distribution of the guided mode between the low mesa waveguide and the high mesa waveguide can be avoided.

  Therefore, in the semiconductor optical integrated device 200 according to the present embodiment, the low-mesa waveguide and the high-mesa waveguide are utilized by utilizing the input-side slab waveguide 221 and the output-side slab waveguide 222 which constitute a part of the AWG. Connected. That is, in the semiconductor optical integrated device 200 of this embodiment, the input waveguide 213 formed of a low-mesa waveguide is directly connected to the input-side slab waveguide 221, and an array waveguide formed of a high-mesa waveguide is further provided. The waveguide 231 and the input side slab waveguide 221 are directly connected. In addition, the output waveguide 214 composed of the low mesa waveguide is directly connected to the output side slab waveguide 222, and the array waveguide 231 composed of the high mesa waveguide is directly connected to the output side slab waveguide 222 doing.

  As described above, in the semiconductor optical integrated device 200 of the present embodiment, the low-mesa waveguide and the high-mesa waveguide are utilized by utilizing the input-side slab waveguide 221 and the output-side slab waveguide 222 which constitute a part of the AWG. Since the waveguides are connected, it is not necessary to provide a separate special structure at the connection portion between the low-mesa waveguide and the high-mesa waveguide. In other words, by connecting the low-mesa waveguide and the high-mesa waveguide to the input-side slab waveguide 221 and the output-side slab waveguide 222, waveguides having different confinement structures in the direction parallel to the substrate are guided. The light distribution of the modes can be matched and connected.

  Next, the cross-sectional structure of each component of the semiconductor optical integrated device 200 will be described with reference to FIGS. 8 to 12. 8 to 12 correspond to the F-F cross section, the G-G cross section, the H-H cross section, the I-I cross section, and the J-J cross section in FIG. 7, respectively.

(Cross-sectional structure: DFB laser device)
FIG. 8 is a schematic cross-sectional view of the DFB laser device 211. As shown in FIG. 8, the DFB laser device 211 has a structure in which a lower cladding layer 202, a waveguide core layer 203a, and an upper cladding layer 204 are sequentially stacked on a substrate 201.

  The material of the substrate 201 is InP, and the material of the lower cladding layer 202 is n-type InP. The material of the substrate 201 may be n-type InP. When importance is attached to high frequency characteristics, the n-side electrode may be provided in the lower cladding layer 202, and the material of the substrate 201 may be semi-insulating InP.

  The waveguide core layer 203a is configured as an active layer of a multiple quantum well structure made of GaInAsP that emits light by current injection. Further, a diffraction grating layer 203aa is provided in the vicinity of the upper side of the waveguide core layer 203a. The thickness of the waveguide core layer 203a is 150 nm including the SCH layer, and the width is 2 μm.

  The material of the upper cladding layer 204 is p-type InP. A contact layer 208 made of p-type GaInAs is provided on the upper cladding layer 104, and is in ohmic contact with the p-side electrode 209a.

  The DFB laser element 211 has a low mesa waveguide structure. That is, the DFB laser device 211 has a shape in which the contact layer 208 and a part of the upper cladding layer 204 protrude in a mesa shape. The remaining etching thickness in the upper cladding layer 204 is 100 nm, and the diffraction grating layer 203aa is not included in the mesa structure.

  Further, a passivation film 241 made of SiNx is formed on the upper surface of the DFB laser element 211 except for the portion to which the electrode is attached. Furthermore, the p-side electrode 209a is in contact with the on-chip wiring 243a by gold plating.

(Cross-sectional structure: slab waveguide)
FIG. 9 is a schematic cross-sectional view of the input side slab waveguide 221. As shown in FIG. 9, the input-side slab waveguide 221 has a structure in which a lower cladding layer 202, a waveguide core layer 203b, and an upper cladding layer 204 are sequentially stacked on a substrate 201. The material of the substrate 201, the lower cladding layer 202, and the upper cladding layer 204 is the same as that of the DFB laser device 211.

  The waveguide core layer 203b is configured in a bulk structure using GaInAsP as a material. The thickness of the waveguide core layer 203b is 200 nm. The width of the waveguide core layer 203 b is wide enough to prevent the influence of the guided light while spreading in the direction parallel to the substrate 201.

  Although the contact layer 208 is provided on the upper cladding layer 204, the contact layer 208 may be removed. In addition, a passivation film 241 made of SiNx is appropriately formed on the entire upper surface of the input-side slab waveguide 221.

(Cross-sectional structure: arrayed waveguide)
FIG. 10 is a schematic cross-sectional view of the arrayed waveguide 231. As shown in FIG. 10, the arrayed waveguide 231 has a structure in which a lower cladding layer 202, a waveguide core layer 203c, and an upper cladding layer 204 are sequentially stacked on a substrate 201. The material of the substrate 201, the lower cladding layer 202, and the upper cladding layer 204 is the same as that of the DFB laser device 211.

  The waveguide core layer 203c has a bulk structure using GaInAsP as a material. The thickness of the waveguide core layer 203c is 200 nm and the width is 2 μm.

  The arrayed waveguide 231 has a high-mesa waveguide structure in which the upper cladding layer 204, the waveguide core layer 203c, and part of the lower cladding layer 202 protrude in a mesa shape. Here, the etching depth corresponding to the lower cladding layer 202 is 300 nm.

  Although the contact layer 208 is provided on the upper cladding layer 204, the contact layer 208 may be removed. In addition, a passivation film 241 made of SiNx is appropriately formed on the entire upper surface of the arrayed waveguide 231.

(Cross-sectional structure: optical amplifier)
FIG. 11 is a schematic cross-sectional view of the optical amplifier 212. As shown in FIG. 11, the optical amplifier 212 has a structure in which a lower cladding layer 202, a waveguide core layer 203d, and an upper cladding layer 204 are sequentially stacked on a substrate 201. Also, the optical amplifier 212 has a low mesa waveguide structure. That is, the contact layer 208 and a part of the upper cladding layer 204 have a shape projecting in a mesa shape. The p-side electrode 209 d is connected to the upper cladding layer 204 via the contact layer 208, and the p-side electrode 209 d is in contact with the on-chip wiring 243 d formed by gold plating.

  The optical amplifier 212 has substantially the same configuration as the DFB laser element 211, and the material and layer thickness of each layer are the same as the DFB laser element 211. The difference between the optical amplifier 212 and the DFB laser element 211 is the presence of a grating layer. There is no diffraction grating layer above the waveguide core layer 203d of the optical amplifier 212.

(Cross-sectional structure: guiding direction)
FIG. 12 is a schematic cross-sectional view of the semiconductor optical integrated device 200 in the waveguide direction. The cross-sectional schematic view of FIG. 12 shows the DFB laser element 211, the input waveguide 213, the input side slab waveguide 221, the arrayed waveguide 231, the output side slab waveguide 222, the output waveguide 214, and the light in the semiconductor optical integrated device 200. The cross section which connected the amplifier 212 one by one is shown.

  As shown in FIG. 12, unlike the first embodiment, in the semiconductor optical integrated device 200 according to the second embodiment, the upper cladding layer 204 is configured to have substantially the same thickness throughout.

(Production method)
Next, a method of manufacturing the semiconductor optical integrated device 200 will be described.

  First, n-type InP as the lower cladding layer 202, the DFB laser element 211 as the lower cladding layer 202, and GaInAsP multiple quantum as the waveguide core layers 203a and 203d of the optical amplifier 212 on the substrate 201 made of n-type InP. The well active layer, p-type InP as a part of the upper cladding layer 204, and GaInAsP as the diffraction grating layer 203aa are stacked in this order.

  Next, a SiNx film is deposited on the entire surface of the device, and then a periodic diffraction grating pattern is formed in the region where the DFB laser device 211 is to be formed, and SiNx near the region where the optical amplifier 212 is to be formed is removed. Then, etching is performed using the SiNx film as a mask to remove the diffraction grating layer. After the SiNx film is completely removed, p-type InP as the upper cladding layer 204 is stacked by diffraction grating embedded growth by the MOCVD method. Thereby, the diffraction grating layer 203 aa embedded in the upper cladding layer 204 is formed in the vicinity of the upper side of the waveguide core layer 203 a of the DFB laser element 211.

  Again, after depositing a SiNx film on the entire surface of the device, the region where the DFB laser device 211 and the optical amplifier 212 are to be formed is patterned to have a slightly wider pattern. Then, etching is performed using the SiNx film as a mask to remove the GaInAsP multiple quantum well active layer and expose the n-type InP layer as the lower cladding layer 202. Subsequently, using the mask of the SiNx film as it is as a mask for selective growth, GaInAsP as the waveguide core layers 203b and 203c, and as the upper cladding layer 204 on the n-type InP layer as the lower cladding layer 202 by MOCVD. Stack p-type InP.

  Next, after removing the SiNx film mask, p-type InP as the upper cladding layer 204 and p-type GaInAs as the contact layer 208 are stacked.

  Next, a SiNx film is deposited on the entire surface of the device, and patterning is performed so as to make openings in portions corresponding to the left and right of the arrayed waveguide 231 which is a high mesa waveguide. At this time, the peripheral region of the optical amplifier 212 and the DFB laser element 211 is covered with SiNx. Then, a part of the lower cladding layer 202 is etched by dry etching using the SiNx as a mask to form a high mesa structure. In this process, etching is performed such that the etching depth of the lower cladding layer 202 on both sides of the high mesa structure matches the design value.

  Next, after removing the mask of the SiNx film, a SiNx film is deposited again on the entire surface, and patterning is performed so as to make openings in portions corresponding to the left and right of the low mesa waveguide. At this time, the peripheral region of the arrayed waveguide portion is covered with SiNx. Using the SiNx as a mask, a portion of the upper cladding layer 204 is etched by dry etching to form a low mesa structure. In this process, etching is performed such that the remaining etching thickness of the upper cladding layer 204 on both sides of the low mesa structure matches the design value.

  Thereafter, a passivation film, its opening, electrodes for current injection, etc. are formed on each portion by a known method. After the processing of the surface of the device is completed, the substrate 201 is polished to a desired thickness, and an electrode is formed on the back surface of the device.

  Further, the end face is formed by cleavage of the substrate, and the end face coating and the element separation are performed to complete the semiconductor optical integrated device 200.

Third Embodiment
FIG. 13 is a schematic plan view showing a semiconductor optical integrated device 300 according to the third embodiment of the present invention. For the sake of simplicity, FIG. 13 shows only the waveguide of the semiconductor optical integrated device 300, and the configuration of the electrodes and the like is omitted. The semiconductor optical integrated device 300 according to the third embodiment has a substantially the same cross section and the like in the respective components in the semiconductor optical integrated device 100 according to the first embodiment, and therefore will be appropriately omitted in the following description.

  As shown in FIG. 13, the semiconductor optical integrated device 300 has a buried waveguide structure region 310, slab waveguide structure regions 320a and 320b, and a high mesa waveguide structure region 330. The embedded waveguide region 310 includes a plurality of DFB laser elements 311 and an input waveguide 313. The slab waveguide structure region 320 a includes an AWG input-side slab waveguide 321, and the slab waveguide structure region 320 b includes an AWG output-side slab waveguide 322. The high mesa waveguide structure region 330 includes an arrayed waveguide 331 of AWG.

  The plurality of DFB laser elements 311 are designed to have different oscillation wavelengths by 3.5 nm in a 1.55 μm wavelength band, for example. In addition, by changing the temperature of the DFB laser element 311, the oscillation wavelength of the DFB laser element 311 is changed. Therefore, the plurality of DFB laser elements 311 operate as a variable-wavelength light source that performs rough tuning by selecting one of a plurality of filters, performs fine tuning by changing the temperature, and performs oscillation in a continuous wavelength range as a whole. Do. The waveguided light emitted from the plurality of DFB laser elements 311 is guided to the input side slab waveguide 321 via the input waveguide 313.

  The input-side slab waveguide 321 is a waveguide having no light confinement force in the direction parallel to the substrate, and is guided to the arrayed waveguide 331 while dispersing the waveguided light input from the input waveguide 313 in the direction parallel to the substrate. Wave light is guided.

  The arrayed waveguide 331 is composed of a large number of waveguides configured by bending the path, and a wavelength-dependent optical path length difference is provided. Therefore, when the input position of the input side slab waveguide 321 is shifted corresponding to the optical path length difference depending on the wavelength, the output side slab waveguide 322 is coupled to the same position. As described above, the AWG functions as a coupler that combines the waveguided lights of different oscillation wavelengths emitted from the plurality of DFB laser elements 311. When the oscillation wavelength of the DFB laser element 311 is changed by changing the temperature of the entire element, the transmission wavelength of the AWG changes substantially the same as the change of the DFB laser element 311. It will bind to the same position.

  In the example used in this embodiment, the focal length of the AWG is 480 μm, and 40 array waveguides 331 are provided at an interval of 3.5 μm, and the input waveguide 313 connected to the input-side slab waveguide 321 Is 2 μm.

  In the semiconductor optical integrated device 300 of this embodiment, the output waveguide is not connected to the output side slab waveguide 322, and the waveguided light is emitted from the output side slab waveguide 322 via the end face window structure 323. The end face window structure 323 has the same configuration and function as the end face window structure 115 in the first embodiment.

  Even in the above configuration, in the semiconductor optical integrated device 300 according to the present embodiment, the embedded waveguide and the high mesa waveguide are connected by using the input-side slab waveguide 321 which constitutes a part of the AWG. Therefore, it is not necessary to provide a separate special structure at the connection portion between the buried waveguide and the high mesa waveguide. That is, by connecting the embedded waveguide and the high-mesa waveguide to the input-side slab waveguide 321, it is possible to easily connect two waveguides having a large difference in light confinement power in the direction parallel to the substrate. be able to.

  Here, a case is considered in which the pattern position between the high-mesa waveguide and the buried waveguide deviates from the design value for the reason of fabrication. In the configuration of the present embodiment, the input side slab waveguide 321 and the output side slab waveguide 322 have the same direction. Therefore, even if the pattern positions of the high mesa waveguide and the buried waveguide deviate from the design values due to manufacturing reasons, the condensing position in the output side slab waveguide 322 does not change.

  Furthermore, in the semiconductor optical integrated device 300 of the present embodiment, the output side slab waveguide 322 is configured to emit light without providing the output waveguide. It is not a factor of efficiency reduction because For this reason, in the semiconductor optical integrated device 300 of this embodiment, the pattern deviation between the high-mesa waveguide and the embedded waveguide is allowed to a considerable degree, and even if a pattern deviation of several μm occurs, for example. The characteristics do not deteriorate.

  That is, the semiconductor optical integrated device 300 of this embodiment can be obtained even if the conventional connection method between the high-mesa waveguide and the embedded waveguide is used in which a pattern deviation may occur such that an increase in loss can not be tolerated. It can be produced while sufficiently suppressing the loss.

  As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, Various deformation | transformation based on the technical idea of this invention are possible. For example, the numerical values listed in the above-described embodiment are merely examples, and different numerical values may be used as needed. Further, the present invention is not limited by the above-described embodiment. The present invention also includes those configured by appropriately combining the above-described components. Further, further effects and modifications can be easily derived by those skilled in the art.

100, 200, 300 Semiconductor Optical Integrated Device 101, 201 Substrate 102, 202 Lower clad layer 103a, 103b, 103c, 103d, 203a, 203b, 203c, 203d Waveguide core layer 103aa, 203aa Diffraction grating layer 104, 204 Upper clad layer 105 etching stop layer 106 lower buried cladding layer 107 upper buried cladding layer 108, 208 contact layer 109a, 109d, 209a, 209d p-side electrode 110, 310 embedded waveguide structure region 111, 211, 311 DFB laser element 112, 212 light Amplifier 113, 213, 313 Input waveguide 114, 214 Output waveguide 115, 323 End window structure 116, 216 Emitting surface 120, 220, 320a, 320b Slab waveguide structure region 121, 21 and 321 Input side slab waveguide 122, 222 and 322 Output side slab waveguide 130, 230 and 330 High mesa type waveguide structure region 131, 231 and 331 Array waveguide 141 and 241 Passivation film 143a, 143d, 243a and 243d Chip Upper wiring 210 Low mesa waveguide area

Claims (7)

A semiconductor optical integrated device comprising at least an arrayed waveguide diffraction grating for condensing guided light input to an input side slab waveguide onto an output side slab waveguide via an arrayed waveguide,
An input waveguide having a waveguide structure whose confinement structure in a direction parallel to the substrate is different from the arrayed waveguide is directly connected to the facing side of the arrayed waveguide in the input side slab waveguide ,
The input-side slab waveguide and the output-side slab waveguide have a slab-waveguide structure having no light confinement force in a direction parallel to the substrate.
Semiconductor optical integrated device characterized in that.   The semiconductor optical integrated device according to claim 1, wherein the arrayed waveguide has a high-mesa waveguide structure in which a mesa including at least a waveguide core layer and an upper cladding layer is protruded.   The semiconductor optical integrated device according to claim 1 or 2, wherein the input waveguide has a buried waveguide structure in which a semiconductor clad material is buried on both sides of a stripe-like waveguide core layer.   The input waveguide according to claim 1 or 2, wherein the input waveguide has a low-mesa waveguide structure in which a semiconductor layer including at least an upper cladding layer above the waveguide core layer continuous to the left and right protrudes in a mesa shape. Semiconductor optical integrated devices. A plurality of semiconductor light emitting devices having the same waveguide structure as the input waveguide and emitting light at different wavelengths are connected to the input-side slab waveguide via the input waveguide.
The semiconductor optical integrated device according to any one of claims 1 to 4, characterized in that: An output waveguide having the same waveguide structure as the input waveguide is directly connected to the facing side of the arrayed waveguide in the output side slab waveguide,
The semiconductor optical integrated device according to any one of claims 1 to 5, characterized in that: The guided light is emitted from the output side slab waveguide without passing through the additional waveguide.
The semiconductor optical integrated device according to any one of claims 1 to 5, characterized in that:

Images