Semiconductor optical amplifier array element

Abstract

To provide a semiconductor optical amplifier array element in which semiconductor optical amplifiers having different characteristics are accumulated.SOLUTION: A semiconductor optical amplifier array element 100 comprises: a substrate 100a; and a plurality of semiconductor optical amplifiers which is formed on the substrate, and each of which includes activation regions 110ca1, 110cb1, 120ca1, and 120cb1. Two light input-output ports 111a, 111b, 121a, and 121b included in each of the plurality of semiconductor optical amplifiers are optically connected to each activation region, and are provided on the same end surface of the semiconductor optical amplifier array element. The plurality of semiconductor optical amplifiers includes: a first semiconductor optical amplifier 110 in which the length of each activation region is a first length; and a second semiconductor optical amplifier 120 in which the length of each activation region is a second length different from the first length.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a semiconductor optical amplifier array device.

Background Art

[0002] In an optical communication system, digital coherent communication using a digital coherent method is widely applied. Digital coherent communication has been used for long-distance (long haul). In recent years, its application distance has become shorter, and the digital coherent method has also come to be used between metro systems and data centers. As modulators in a transmitter of a digital coherent communication system, in addition to the existing LN modulators, InP modulators using InP-based semiconductor materials and modulators using Si photonics have come to be used.

[0003] Generally, high output is desired for a transmitter. Therefore, as described in Non-Patent Document 1, an InP modulator often has an integrated semiconductor optical amplifier (SOA). In Non-Patent Document 1, the modulator has four semiconductor optical amplifiers. Two of them are "Pre-semiconductor optical amplifiers" that amplify the input continuous light, and the other two are "Post-semiconductor optical amplifiers" that amplify the modulated light.

[0004] On the other hand, in a modulator using Si photonics, since Si is an indirect transition material, it is difficult to integrate a light-emitting element. One approach to integrating a light-emitting element into a Si photonics element is a method of "hybrid integration" of an InP chip on a Si photonics chip as described in Non-Patent Document 2. By applying this technology to a modulator, a semiconductor optical amplifier can be used together with a Si photonics modulator.

[0005] As a semiconductor optical amplifier for hybrid integration, Patent Document 1 discloses a semiconductor optical amplifier with a U-turn structure. The semiconductor optical amplifier with a U-turn structure has an input port into which the light to be amplified is input and an output port that outputs the amplified light on the same end face, and further has a bent waveguide that folds back the optical path. By using this configuration, the optical coupling positions with Si photonics chips with different waveguides can be concentrated on a single end face, making hybrid mounting easier. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2013 / 035259 [Non-patent literature]

[0007] [Non-Patent Document 1] RA Griffin et al., “InP Coherent Optical Modulator with Integrated Amplification for High Capacity Transmission,” Optical Fiber Communication Conference 2015, Th4E.2. [Non-Patent Document 2] T. Matsumoto et al., “Hybrid-Integration of SOA on Silicon Photonics Platform Based on Flip-Chip Bonding,” JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 37, NO. 2, pp. 307-313. [Overview of the project] [Problems that the invention aims to solve]

[0008] However, existing technologies have not considered the optimal device design when integrating multiple semiconductor optical amplifiers, and when these integrated semiconductor optical amplifiers have different characteristics and are used for different applications.

[0009] The present invention has been made in view of the above, and aims to provide a semiconductor optical amplifier array element in which semiconductor optical amplifiers with different characteristics are integrated. [Means for solving the problem]

[0010] To solve the above-mentioned problems and achieve the objective, one aspect of the present invention is a semiconductor optical amplifier array element comprising a substrate and a plurality of semiconductor optical amplifiers formed on the substrate, each having an active region, wherein the two optical input / output ports of each of the plurality of semiconductor optical amplifiers are optically connected to each of the active regions and are both provided on the same end face of the semiconductor optical amplifier array element, and the plurality of semiconductor optical amplifiers is a semiconductor optical amplifier array element including a first semiconductor optical amplifier whose active region has a first length and a second semiconductor optical amplifier whose active region has a second length different from the first length.

[0011] The plurality of semiconductor optical amplifiers may have a folded section between the two optical input / output ports, which is comprised of a waveguide in which the optical path folds back at a substantially 180-degree angle.

[0012] The first length of the first semiconductor optical amplifier is longer than the second length of the second semiconductor optical amplifier, and continuous light may be input to the optical input / output port of the first semiconductor optical amplifier, while modulated light may be input to the optical input / output port of the second semiconductor optical amplifier. [Effects of the Invention]

[0013] The present invention offers the advantage of realizing a semiconductor optical amplifier array element in which semiconductor optical amplifiers with different characteristics are integrated. [Brief explanation of the drawing]

[0014] [Figure 1] FIG. 1 is a schematic plan view of a semiconductor optical amplifier array element according to Embodiment 1. [Figure 2] FIG. 2 is a schematic partial cross-sectional view of the semiconductor optical amplifier array element shown in FIG. 1. [Figure 3] FIG. 3 is a schematic plan view of a semiconductor optical amplifier array element according to a reference form. [Figure 4] FIG. 4 is a schematic plan view of a semiconductor optical amplifier array element according to Embodiment 2. [Figure 5] FIG. 5 is a schematic configuration diagram of an optical module according to Embodiment 3.

MODE FOR CARRYING OUT THE INVENTION

[0015] Embodiments will be described below with reference to the drawings. Note that the present invention is not limited by this embodiment. In the description of the drawings, the same or corresponding elements are appropriately denoted by the same reference numerals, and redundant explanations are appropriately omitted. Also, note that the drawings are schematic, and the dimensional relationships between elements, the ratios of each element, etc. may differ from reality. There may also be parts where the dimensional relationships and ratios differ between the drawings.

[0016] (Embodiment 1) FIG. 1 is a schematic plan view of a semiconductor optical amplifier array element according to Embodiment 1.

[0017] The chip-shaped semiconductor optical amplifier array element 100 includes semiconductor optical amplifiers 110 and 120 as a plurality of semiconductor optical amplifiers. The semiconductor optical amplifiers 110 and 120 are formed on a substrate 100a and integrated on one substrate 100a. The semiconductor optical amplifier 110 is an example of a first semiconductor optical amplifier, and the semiconductor optical amplifier 120 is an example of a second semiconductor optical amplifier. The semiconductor optical amplifier array element 100 is mainly composed of a III-V semiconductor material.

[0018] The semiconductor optical amplifier 110 includes an active section 111 and a passive section 112. The active section 111 has an embedded waveguide structure suitable for a current injection type light emitting element, and as an optical waveguide, it has active layers 110ca and 110cb. The passive section 112 is bent in a U shape and has a high mesa waveguide structure including an optical waveguide as a passive waveguide. The high mesa waveguide structure is also called a deep ridge waveguide structure. The passive section 112 is an example of a folding section composed of a waveguide in which the optical path substantially folds back at an angle of 180 degrees.

[0019] The active layers 110ca and 110cb have a multiple quantum well (MQW) structure made of, for example, a GaInAsP-based semiconductor material or an AlGaInAs-based semiconductor material. The passive section 112 has a clad layer made of n-type InP or i-type InP, and the optical waveguide is made of, for example, an i-type GaInAsP-based semiconductor material with a bandgap wavelength of 1300 nm. The optical waveguides of the active layers 110ca and 110cb and the passive section 112 are optically connected by butt joint connection or the like. The active layer 110ca and the active layer 110cb are substantially parallel to each other and are optically connected through the optical waveguide of the high mesa waveguide structure of the passive section 112. Further, the semiconductor optical amplifier 110 includes a power supply section 110j. Also, the semiconductor optical amplifier 110 has optical input / output ports 111a and 111b provided on an end face 101 which is one end face of the semiconductor optical amplifier array element 100. The optical input / output ports 111a and 111b are connected to the active layers 110ca and 110cb, respectively. The active layers 110ca and 110cb are inclined with respect to the normal of the end face 101 on the end face 101 side.

[0020] The semiconductor optical amplifier 120 comprises an active section 121 and a passive section 122. The active section 121 has an embedded waveguide structure and includes active layers 120ca and 120cb as optical waveguides. The passive section 122 is bent in a U-shape and has a high mesa waveguide structure including an optical waveguide. The passive section 122 is an example of a folded section in which the optical path is composed of a waveguide that folds back at a substantially 180-degree angle. The constituent materials and structure of the active layers 120ca and 120cb are the same as those of the active layers 110ca and 110cb, and the constituent materials of the passive section 122 are the same as those of the passive section 112.

[0021] The active layers 120ca and 120cb and the optical waveguide of the passive section 122 are optically connected by a butt joint connection or the like. The active layers 120ca and 120cb are substantially parallel to each other and are optically connected via the optical waveguide of the high mesa waveguide structure of the passive section 122. The semiconductor optical amplifier 120 also includes a power supply section 120j. The semiconductor optical amplifier 120 also has optical input / output ports 121a and 121b provided on the end face 101 of the semiconductor optical amplifier array element 100. The optical input / output ports 121a and 121b are connected to the active layers 120ca and 120cb, respectively. The active layers 120ca and 120cb are inclined with respect to the normal to the end face 101 on the end face 101 side.

[0022] Furthermore, a conversion region may be provided between the active parts 111, 121 and the passive part 122 for optically connecting waveguides of different structures with low loss.

[0023] The semiconductor optical amplifier array element 100 further includes trench grooves 131, 132, and 133 extending substantially parallel to each other. Trench groove 132 is formed between semiconductor optical amplifier 110 and semiconductor optical amplifier 120. Trench groove 131 is located opposite trench groove 132, with semiconductor optical amplifier 110 in between. Trench groove 133 is located opposite trench groove 132, with semiconductor optical amplifier 120 in between. The trench grooves 131, 132, and 133 are provided to electrically isolate parts of the semiconductor optical amplifiers 110 and 120 from each other, or between semiconductor optical amplifier 110 and the physical contact area 141, or between semiconductor optical amplifier 120 and the physical contact area 142.

[0024] The semiconductor optical amplifier array element 100 is provided with physical contact regions 141 and 142. The physical contact regions 141 and 142 are located at both ends of the semiconductor optical amplifier array element 100 in a direction perpendicular to the extension direction of the trench grooves 131, 132, and 133. The physical contact regions 141 and 142 are used to make contact with the other component when the semiconductor optical amplifier array element 100 is combined with another component, thereby adjusting the height.

[0025] Figure 2 is a schematic cross-sectional view of the semiconductor optical amplifier array element shown in Figure 1, along line AA. Figure 2 mainly shows the cross-section from the trench groove 132 to the semiconductor optical amplifier 110. Note that the cross-section from the trench groove 132 to the semiconductor optical amplifier 110 is similar, so the explanation will be omitted as appropriate.

[0026] The semiconductor optical amplifier array element 100 comprises a substrate 100a made of n-type InP and a cladding layer 100b made of n-type InP laminated on the substrate 100a. An etching stop layer 100m made of n-type GaInAsP is interposed between the substrate 100a and the cladding layer 100b. The cladding layer 100b in the semiconductor optical amplifier 110 and the physical contact region 141 has three stripe mesa portions 100ba. Active layers 110ca, 110cb, and 100c are laminated on the stripe mesa portions 100ba, respectively.

[0027] A first current-blocking layer 100d made of p-type InP is laminated on one or both sides of the stripe mesa portion 100ba and the active layers 110ca, 110cb, and 100c. A second current-blocking layer 100e made of n-type InP is laminated on top of the first current-blocking layer 100d. The first current-blocking layer 100d and the second current-blocking layer 100e form a current-blocking structure.

[0028] A cladding layer 100f made of p-type InP is laminated on the second current blocking layer 100e and the active layers 110ca and 110cb. A contact layer 100g made of GaInAsP is laminated on top of the cladding layer 100f.

[0029] The trench grooves 131, 132, and 133 extend to a surface depth of 100 m of the etching stop layer. The trench groove 132 electrically isolates the stacked portions of the semiconductor optical amplifiers 110 and 120, which are made of the aforementioned p-type semiconductors.

[0030] The n-side contact electrode 100k is laminated so as to make ohmic contact with the substrate 100a in a portion of the trench groove 132. Similarly, the p-side contact electrode 110h is laminated so as to make ohmic contact with the contact layer 100g in a portion of the surface of the contact layer 100g. The inner surfaces of the trench grooves 131, 132, and 133 and the surface of the contact layer 100g, excluding the areas where the p-side contact electrodes 110h, 120h and the n-side contact electrode 100k are in ohmic contact, are laminated with a passivation film 100i made of, for example, SiNx.

[0031] Power supply sections 110j and 100l, consisting of bonding pads and wiring, are formed on the passivation film 100i. The passivation film 100i has an opening above the p-side contact electrode 110h, and the wiring and the p-side contact electrode 110h are electrically connected at this opening. The passivation film 100i also has an opening above the n-side contact electrode 100k, and the wiring of the power supply section 100l is electrically connected to the n-side contact electrode 100k at this opening. The wiring of the power supply sections 110j and 100l is routed to their respective bonding pads. Each bonding pad is formed above the contact layer 100g. This reduces the height difference between the bonding pads on the p-side and n-side.

[0032] In the physical contact regions 141 and 142, a passivation film 100i is laminated on the active layer 100c.

[0033] In the semiconductor optical amplifier 110, when a voltage is applied between the power supply unit 100l and the power supply unit 110j, and current is injected into the active regions 110ca1 and 110cb1, respectively, which are covered by the p-side contact electrode 110h of the active layers 110ca and 110cb, the active regions 110ca1 and 110cb1 exert an optical amplification effect. The active regions are the areas of the active layer into which current is injected. As a result, the semiconductor optical amplifier 110 optically amplifies the light L1 input from the optical input / output port 111a and outputs it as light L2 from the optical input / output port 111b. Furthermore, since the active layers 110ca and 110cb are inclined with respect to the normal of the end face 101 on the end face 101 side, reflected light generated at the end face 101 is suppressed from being input to the active layers 110ca and 110cb.

[0034] Similarly, in the semiconductor optical amplifier 120, when a voltage is applied between the power supply unit 100l and the power supply unit 120j, and current is injected into the active regions 120ca1 and 120cb1 of the active layers 120ca and 120cb, which are covered by the p-side contact electrodes, the active regions 120ca1 and 120cb1 exert an optical amplification effect. As a result, the semiconductor optical amplifier 120 optically amplifies the light L3 input from the optical input / output port 121a and outputs it as light L4 from the optical input / output port 121b. Furthermore, since the active layers 120ca and 120cb are inclined with respect to the normal of the end face 101 on the end face 101 side, reflected light generated at the end face 101 is suppressed from being input to the active layers 120ca and 120cb.

[0035] Since the trench groove 132 electrically isolates the p-type semiconductor layers of the semiconductor optical amplifiers 110 and 120, the semiconductor optical amplifiers 110 and 120 can be driven and controlled independently.

[0036] In the above semiconductor stacked structure, the active layers 110ca, 110cb, 120ca, and 120cb all have equal width, thickness, and effective refractive index.

[0037] In the semiconductor optical amplifier array element 100, the length of the active region in the semiconductor optical amplifier 110 is the sum of the lengths of active regions 110ca1 and 110cb1, and this is referred to as the first length. In the semiconductor optical amplifier 120, the length of the active region is the sum of the lengths of active regions 120ca1 and 120cb1, and this is referred to as the second length. In this embodiment, unlike the first and second lengths, the first length is longer than the second length. This makes it possible to make the amplification characteristics of the semiconductor optical amplifier 110 and the semiconductor optical amplifier 120 different.

[0038] Furthermore, the optical input / output ports 111a, 111b of the semiconductor optical amplifier 110 and the optical input / output ports 121a, 121b of the semiconductor optical amplifier 120 are located on one end face 101 of the semiconductor optical amplifier array element 100, as the optical paths of the passive sections 112, 122 fold back at a substantially 180-degree angle. This has the advantage of consolidating the connection end faces between the semiconductor optical amplifier array element 100 and other waveguide elements onto a single end face. In addition, while consolidating the optical input / output ports 111a, 111b, 121a, 121b onto a single end face, the length of the active layers 110ca, 110cb, and consequently the active regions 110ca1, 110cb1, can be freely adjusted simply by changing the position of the passive section 112 in the extending direction of the active layers 110ca, 110cb. Furthermore, by simply changing the position of the passive portion 122 in the stretching direction of the active layers 120ca and 120cb, the length of the active layers 120ca and 120cb, and consequently the length of the active regions 120ca1 and 120cb1, can be freely adjusted.

[0039] Furthermore, since the optical paths of the passive sections 112 and 122 fold back at a substantially 180-degree angle, the element length of the semiconductor optical amplifier array element 100 can be shortened.

[0040] The following describes an example of the effect of having different lengths for the first active region in semiconductor optical amplifier 110 and the second active region in semiconductor optical amplifier 120.

[0041] For example, continuous light (CW light) is input to semiconductor optical amplifier 110 as light L1. Modulated light is input to semiconductor optical amplifier 120 as light L2. In this case, for example, the first length is 800 μm and the second length is 500 μm.

[0042] High power and high efficiency are required for semiconductor optical amplifiers for CW (continuous wave) light. For high power, a long active region is preferable to prevent thermal rollover of the semiconductor optical amplifier. For high efficiency, it is preferable for the semiconductor optical amplifier to operate in the saturation region so that stimulated emission is dominant. For this reason, it is preferable for the semiconductor optical amplifier to have a long active region or a large optical confinement coefficient in the active layer.

[0043] On the other hand, semiconductor optical amplifiers for modulated light require suppression of pattern effects. To suppress pattern effects, the semiconductor optical amplifier must operate in the linear region such that stimulated emission becomes negligibly small in proportion to its injected current. For this reason, it is preferable that the semiconductor optical amplifier has a short active region or a small optical confinement coefficient in the active layer.

[0044] Thus, the two semiconductor optical amplifiers, each with a different application, require different characteristics, and their optimization strategies are almost diametrically opposed. For this reason, individual optimization is essential for each semiconductor optical amplifier.

[0045] As mentioned above, one method for individual optimization is to use different optical confinement coefficients in the active layer for each component, but this requires the fabrication of two different types of active layers with different structures. However, since the active layer requires more precise compositional control of the multi-component semiconductor material used as its constituent material than passive waveguides, the fabrication method becomes more complex.

[0046] In contrast, the semiconductor optical amplifier array element 100 according to Embodiment 1 enjoys the advantages of folded arrangement and allows for easy individual optimization by adjusting the length of the active region, thus enabling a configuration that includes semiconductor optical amplifiers 110 and 120 individually optimized for CW light and modulated light.

[0047] (Manufacturing method) Next, an example of a method for fabricating a semiconductor optical amplifier array element 100 will be described. First, a buffer layer made of n-type InP is grown on the surface of a wafer-shaped substrate 100a, and then an etching stop layer 100m, a cladding layer 100b, an active layer, and a p-type InP layer are grown in that order.

[0048] Next, the p-type InP layer and active layer in the areas other than the active layers 110ca, 110cb, 120ca, 120cb, and the areas that should remain as active layers (such as active layer 100c) in the physical contact regions 141 and 142 are removed by etching, and i-type GaInAsP layers and i-type InP layers are grown in the removed areas using butt joints. The i-type GaInAsP layers become optical waveguides in the passive parts 112 and 122, and the i-type InP layers become cladding layers in the passive parts 112 and 122.

[0049] Next, mesa etching is performed to form the embedded (BH) structure of the cladding layer 100b and the active layer, creating the stripe mesa portion 100ba, and the active layers 110ca, 110cb, 100c, etc. Furthermore, crystal growth is carried out with the first current blocking layer 100d and the second current blocking layer 100e to form the BH structure. At this time, as described above, the regions that will become physical contact regions 141 and 142 are protected, leaving the active layer 100c, etc. Also, the region that will later become a high mesa waveguide is protected to a slightly wider extent.

[0050] Next, the cladding layer 100f and the contact layer 100g are sequentially grown on the entire surface of the substrate 100a on which the above crystal growth was performed.

[0051] Next, the contact layer 100g, excluding the necessary parts, is removed by etching. At this time, the cladding layer 100f may be partially thinned.

[0052] Next, the p-side contact electrode 110h is formed by vapor deposition.

[0053] Next, the high mesa waveguide structure of the passive sections 112 and 122 is formed by etching.

[0054] Next, physical contact regions 141 and 142 and trench grooves 131, 132, and 133 are formed by wet etching. At this time, by selectively etching InP with hydrochloric acid-based etching, the etching stops at the surface of the etching stop layer 100m and the active layer 100c made of GaInAsP, thereby allowing the physical contact regions 141 and 142 and the trench grooves 131, 132, and 133 to be formed to the desired depth with good reproducibility, and the surface to be exposed.

[0055] In particular, since the active layer 100c is used as an etching stop layer, the relative height accuracy between the physical contact regions 141 and 142 and the active layers 110ca, 110cb, 120ca, and 120cb is improved. For example, when forming physical contact regions on the same surface as the bonding pad, the height difference between the physical contact regions and the active layers 110ca, 110cb, 120ca, and 120cb is approximately 4.5 μm as the design center value. On the other hand, with the semiconductor optical amplifier array element 100, the height difference between the physical contact regions 141 and 142 and the active layers 110ca, 110cb, 120ca, and 120cb is approximately 0.4 μm as the design center value. Therefore, even if the manufacturing thickness deviation in the deposition of the passivation film 100i is 10%, the configuration of the semiconductor optical amplifier array element 100 can reduce the amount of variation to less than 1 / 10.

[0056] Next, the n-side contact electrode 100k is formed by vapor deposition. Furthermore, a passivation film 100i is formed. After that, in order to make electrical contact, the passivation film 100i at a predetermined position is removed by etching. Subsequently, the power supply sections 110j, 120j, and 100l are formed by vapor deposition.

[0057] Next, the wafer is polished to a predetermined thickness. This completes the wafer process. Furthermore, the finished wafer is cleaved to form the end faces of each semiconductor optical amplifier array element 100. Subsequently, a low-reflection coating is applied to the end face 101 where the input / output ports are located. After that, the semiconductor optical amplifier array elements 100 are cut out chip by chip from the wafer and subjected to predetermined inspections to complete the semiconductor optical amplifier array elements 100.

[0058] (Reference form) Here, as a reference example, we consider a semiconductor optical amplifier array element 1000 with the configuration shown in Figure 3.

[0059] The semiconductor optical amplifier array element 1000 mainly consists of III-V semiconductor materials and includes semiconductor optical amplifiers 1100 and 1200.

[0060] The semiconductor optical amplifier 1100 has an embedded waveguide structure and includes an active layer 1100c with an MQW structure made of, for example, a GaInAsP-based semiconductor material or an AlGaInAs-based semiconductor material as an optical waveguide. The semiconductor optical amplifier 1100 also includes a power supply unit 1100j. The semiconductor optical amplifier 1100 also has optical input / output ports 1110a and 1110b. The optical input / output ports 1110a and 1110b are provided on the end faces 1010 and 1020, which are opposing end faces of the semiconductor optical amplifier array element 1000, respectively.

[0061] The semiconductor optical amplifier 1200 has an active layer 1200c as an optical waveguide. The constituent materials and structure of the active layer 1200c are the same as those of the active layer 1100c.

[0062] The semiconductor optical amplifier 1200 includes a power supply unit 1200j. The semiconductor optical amplifier 1200 also has optical input / output ports 1120a and 1120b. The optical input / output ports 1120a and 1120b are provided on end faces 1010 and 1020, respectively.

[0063] The semiconductor optical amplifier array element 1000 further includes trench grooves 1310, 1320, and 1330 that extend substantially parallel to each other. Trench groove 1320 is formed between semiconductor optical amplifier 1100 and semiconductor optical amplifier 1200. Trench groove 1310 is positioned opposite trench groove 1320, with semiconductor optical amplifier 1100 in between.

[0064] Furthermore, the semiconductor optical amplifier array element 100 is provided with physical contact regions 1410 and 1420. The physical contact regions 1410 and 1420 are located at both ends of the semiconductor optical amplifier array element 1000 in a direction perpendicular to the extension direction of the trench grooves 1310, 1320, and 1330.

[0065] In the semiconductor optical amplifier 1100, with current injected into the active layer 1100c to exert its optical amplification effect, the light L10 input from the optical input / output port 1110a on the end face 1010 side is optically amplified and output as light L20 from the optical input / output port 1110b on the end face 1020 side. Similarly, in the semiconductor optical amplifier 1200, with current injected into the active layer 1200c to exert its optical amplification effect, the light L30 input from the optical input / output port 1120a on the end face 1010 side is optically amplified and output as light L40 from the optical input / output port 1120b on the end face 1020 side.

[0066] In such a semiconductor optical amplifier 1100, the connection end faces with other waveguide elements are two opposing end faces. This increases the number of connection points, and if the distances between the connection points of the other elements and the end faces 1010 and 1020 are not precisely matched, connection losses may increase. Furthermore, it is difficult to make the lengths of the active layers 1100c and 1200c different in the semiconductor optical amplifier 1100, making it unsuitable for individual optimization.

[0067] (Embodiment 2) Figure 4 is a schematic plan view of a semiconductor optical amplifier array element according to Embodiment 4.

[0068] The chip-shaped semiconductor optical amplifier array element 200 comprises multiple semiconductor optical amplifiers 110A, 110B, 120A, and 120B integrated on a single substrate. Semiconductor optical amplifiers 110A and 110B are examples of first semiconductor optical amplifiers, and semiconductor optical amplifiers 120A and 120B are examples of second semiconductor optical amplifiers. The semiconductor optical amplifier array element 200 is mainly composed of III-V group semiconductor materials.

[0069] The semiconductor optical amplifiers 110A and 110B have the same configuration as the semiconductor optical amplifier 110 of Embodiment 1. That is, the semiconductor optical amplifier 110A comprises an active part 111A and a passive part 112A. The semiconductor optical amplifier 110B comprises an active part 111B and a passive part 112B. The active parts 111A and 111B each have active layers 110Aca, 110Acb, and 110Bca, 110Bcb, respectively. The semiconductor optical amplifiers 110A and 110B also each have power supply parts 110Aj and 110Bj, respectively. Furthermore, the semiconductor optical amplifiers 110A and 110B each have optical input / output ports 111Aa, 111Ab, and optical input / output ports 111Ba, 111Bb, respectively, provided on the end face 201, which is one end face of the semiconductor optical amplifier array element 200.

[0070] The semiconductor optical amplifiers 120A and 120B have the same configuration as the semiconductor optical amplifier 120 of Embodiment 1. That is, the semiconductor optical amplifier 120A comprises an active part 121A and a passive part 122A. The semiconductor optical amplifier 120B comprises an active part 121B and a passive part 122B. The active parts 121A and 121B each have active layers 120Aca, 120Acb, 120Bca, and 120Bcb, respectively. The semiconductor optical amplifiers 120A and 120B also each have power supply parts 120Aj and 120Bj, respectively. Furthermore, the semiconductor optical amplifiers 120A and 120B each have optical input / output ports 121Aa, 121Ab, 121Ba, and 121Bb, respectively, provided on the end face 201 of the semiconductor optical amplifier array element 200.

[0071] The semiconductor optical amplifier array element 200 further includes trench grooves 231, 232, 233, 234, and 235 extending substantially parallel to each other. Trench groove 232 is formed between semiconductor optical amplifiers 110A and 110B. Trench groove 233 is formed between semiconductor optical amplifiers 110B and 120A. Trench groove 234 is formed between semiconductor optical amplifiers 120A and 120B. Trench groove 231 is located opposite trench groove 232, with semiconductor optical amplifier 110A in between. Trench groove 235 is located opposite trench groove 234, with semiconductor optical amplifier 120B in between. The trench grooves 231, 232, 233, 234, and 235 are provided to electrically isolate parts of each of the semiconductor optical amplifiers 110A, 110B, 120A, and 120B, or between the semiconductor optical amplifier 110A and the physical contact area 141, or between the semiconductor optical amplifier 120B and the physical contact area 142.

[0072] The semiconductor optical amplifier array element 200, like the semiconductor optical amplifier array element 100, is equipped with physical contact regions 141 and 142. The physical contact regions 141 and 142 are located at both ends of the semiconductor optical amplifier array element 200 in a direction perpendicular to the extension direction of the trench grooves 231, 232, 233, 234, and 235.

[0073] The cross-sectional structure and constituent materials of each element of the semiconductor optical amplifier array element 200 are the same as those of the corresponding cross-sectional structure and constituent materials of each element of the semiconductor optical amplifier array element 100, so their explanation is omitted.

[0074] In the semiconductor optical amplifier 110A, when current is injected into the active regions 110Aca1 and 110Acb1, respectively, which are covered by the p-side contact electrodes of the active layers 110Aca and 110Acb, the active regions 110Aca1 and 110Acb1 exert an optical amplification effect. As a result, the semiconductor optical amplifier 110A optically amplifies the optical light L1A input from the optical input / output port 111Aa and outputs it as optical light L2A from the optical input / output port 111Ab.

[0075] Similarly, in the semiconductor optical amplifier 110B, when current is injected into the active regions 110Bca1 and 110Bcb1, respectively, which are covered by the p-side contact electrodes in the active layers 110Bca and 110Bcb, the active regions 110Bca1 and 110Bcb1 exert an optical amplification effect. As a result, the semiconductor optical amplifier 110B optically amplifies the optical signal L1B input from the optical input / output port 111Ba and outputs it as optical signal L2B from the optical input / output port 111Bb.

[0076] Similarly, in the semiconductor optical amplifier 120A, when current is injected into the active regions 120Aca1 and 120Acb1, respectively, which are covered by the p-side contact electrodes in the active layers 120Aca and 120Acb, the active regions 120Aca1 and 120Acb1 exert an optical amplification effect. As a result, the semiconductor optical amplifier 120A optically amplifies the optical signal L3A input from the optical input / output port 121Aa and outputs it as optical signal L3B from the optical input / output port 111Ab.

[0077] Similarly, in the semiconductor optical amplifier 120B, when current is injected into the active regions 120Bca1 and 120Bcb1, respectively, which are covered by the p-side contact electrodes of the active layers 120Bca and 120Bcb, the active regions 120Bca1 and 120Bcb1 exert an optical amplification effect. As a result, the semiconductor optical amplifier 120B optically amplifies the optical signal L4A input from the optical input / output port 121Ba and outputs it as optical signal L4B from the optical input / output port 111Bb.

[0078] Furthermore, the presence of trench grooves 232, 233, and 234 allows the semiconductor optical amplifiers 110A, 110B, 120A, and 120B to be driven and controlled independently.

[0079] In the above semiconductor stacked structure, the active layers 110Aca, 110Acb, 110Bca, 110Bcb, 120Aca, 120Acb, 120Bca, and 120Bcb all have equal width, thickness, and effective refractive index.

[0080] In the semiconductor optical amplifier array element 200, the first lengths of the active regions in semiconductor optical amplifiers 110A and 110B are equal, and the second lengths of the active regions in semiconductor optical amplifiers 120A and 120B are equal. Furthermore, unlike the first and second lengths, in this embodiment the first length is longer than the second length. As a result, the amplification characteristics of semiconductor optical amplifiers 110A and 110B can be made equal, the amplification characteristics of semiconductor optical amplifiers 120A and 120B can be made equal, and the amplification characteristics of semiconductor optical amplifiers 110A and 110B can be made different from those of semiconductor optical amplifiers 120A and 120B.

[0081] Furthermore, since the optical input / output ports of the semiconductor optical amplifiers 110A, 110B, 120A, and 120B are provided on one end face 201 of the semiconductor optical amplifier array element 200, there is an advantage in that the connection end faces between the semiconductor optical amplifier array element 200 and other waveguide elements can be concentrated on one end face. In addition, the length of each active layer and each active region can be freely adjusted simply by changing the position of the passive parts 112A, 112B, 122A, and 122B.

[0082] Furthermore, since the optical paths of the passive sections 112A, 112B, 122A, and 122B fold back at a substantially 180-degree angle, the element length of the semiconductor optical amplifier array element 200 can be shortened.

[0083] Based on the above, the semiconductor optical amplifier array element 200 enjoys the advantages of folded arrangement, and individual optimization can be easily achieved by adjusting the length of the active region. For example, a configuration can be realized that includes semiconductor optical amplifiers 110A, 110B, 120A, and 120B that are individually optimized for CW light and modulated light.

[0084] The semiconductor optical amplifier array element 200 is preferably used in combination with a DP (Dual Polarization)-IQ modulator, for example. For example, CW light having mutually orthogonal linear polarization is input to the semiconductor optical amplifier array element 200 as light L1A and L1B, and is optically amplified by semiconductor optical amplifiers 110A and 110B, respectively, to output as light L2A and L2B. Then, light L2A and L2B are input to an IQ modulator to generate light L3A and L3B as modulated light. Furthermore, light L3A and L3B are input to the semiconductor optical amplifier array element 200, and is optically amplified by semiconductor optical amplifiers 120A and 120B, respectively, to output as light L2A and L2B. Since the semiconductor optical amplifier array element 200 integrates four semiconductor optical amplifiers on a single chip, the man-hours for manufacturing and assembly can be reduced.

[0085] (Embodiment 3) Figure 5 is a schematic diagram of the optical module according to Embodiment 3. The optical module 500 comprises a semiconductor optical amplifier array element 100 according to Embodiment 1, a CW light source 300 such as a laser light source, and a modulator 400 such as an InP modulator.

[0086] In the optical module 500, the CW light source 300 outputs CW light, specifically light L1, to the semiconductor optical amplifier array element 100. The semiconductor optical amplifier array element 100 optically amplifies light L1 using the semiconductor optical amplifier 110 and outputs it as light L2 to the modulator 400. The modulator 400 modulates the input light L2 and outputs it as light L3 to the semiconductor optical amplifier array element 100. The semiconductor optical amplifier array element 100 optically amplifies light L3 using the semiconductor optical amplifier 120 and outputs it as light L4 from the optical module 500.

[0087] In the above embodiment, the passive section is bent in a U-shape, forming a folded section where the optical path folds back at a substantially 180-degree angle. However, the bending is not continuous and may be divided into several sections with a straight section in between, or there may be slight angle differences of a few degrees. Furthermore, the sum of the bending angles of the parts of the active layer that are bent from the optical input / output port may be 180 degrees. Moreover, by making the inclination angle of the optical input / output port side where light is input and the inclination angle of the optical input / output port side where light is output in opposite directions, the folding angle in the passive section can be set to an angle other than 180 degrees. However, since the waveguide formation process of the active layer depends on the crystal orientation of the semiconductor material, it is preferable to set the folding and bending angles so that the angle of each active layer with respect to the crystal plane orientation is approximately the same.

[0088] It should be noted that the present invention is not limited to the embodiments described above. Configurations that appropriately combine the above-described components are also included in the present invention. Furthermore, further effects and modifications can be easily derived by those skilled in the art. Therefore, broader aspects of the present invention are not limited to the embodiments described above, and various modifications are possible. [Explanation of symbols]

[0089] 100, 200 semiconductor optical amplifier array elements 100a substrate 100b, 100f cladding layer 100ba Stripe Mesa Section 100c, 110ca, 110cb, 120ca, 120cb, 110Aca, 110Acb, 110Bca, 110Bcb, 120Aca, 120Acb, 120Bca, 120Bcb Active layer 100d First current blocking layer 100e Second current block layer 100g Contact layer 100i Passivation Film 100L, 110J, 120J, 110AJ, 110BJ, 120AJ, 120BJ Power supply unit 100kJ N-side contact electrode 100m etching stop layer 101, 201 end face 110, 120, 110A, 110B, 120A, 120B Semiconductor Optical Amplifiers 110ca1, 110cb1, 120ca1, 120cb1, 110Aca1, 110Acb1, 110Bca1, 110Bcb1, 120Aca1, 120Acb1, 120Bca1, 120Bcb1 active region 110h p-side contact electrode 111, 121, 111A, 111B, 121A, 121B active part 111a, 111b, 121a, 121b, 111Aa, 111Ab, 111Ba, 111Bb, 121Aa, 121Ab, 121Ba, 121Bb Optical Input / Output Ports 112, 112A, 112B, 122, 122A, 122B Passive parts 131, 132, 133, 231, 232, 233, 234, 235 Trench grooves 141, 142 Physical contact area 300 CW light source 400 modulator 500 optical modules L1, L2, L3, L4, L1A, L1B, L2A, L2B, L3A, L3B, L4A, L4B light

Claims

1. circuit board and A plurality of semiconductor optical amplifiers are formed on the substrate, each having two active regions and a passive region, A semiconductor optical amplifier array element comprising, Each of the aforementioned plurality of semiconductor optical amplifiers has two optical input / output ports, each of which is optically connected to the respective active region, and both are provided on the same end face of the semiconductor optical amplifier array element. The plurality of semiconductor optical amplifiers include a first semiconductor optical amplifier whose active region has a first length, and a second semiconductor optical amplifier whose active region has a second length different from the first length. The two active regions are substantially parallel to each other and are optically connected via the passive portion. The passive section is a folding section, which is composed of a waveguide in which the optical path folds back at a substantially 180-degree angle. Semiconductor optical amplifier array element.

2. The first length of the first semiconductor optical amplifier is longer than the second length of the second semiconductor optical amplifier. The optical input / output port of the first semiconductor optical amplifier receives continuous light, and the optical input / output port of the second semiconductor optical amplifier receives modulated light. The semiconductor optical amplifier array element according to claim 1.

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