Semiconductor Optical Amplifier Integrated Laser

Abstract

To improve the characteristics and reliability of a semiconductor optical amplifier integrated laser.SOLUTION: A semiconductor optical amplifier integrated laser comprises a semiconductor laser oscillator section which oscillates a laser light having a wavelength included in a gain band, and a semiconductor optical amplifier section which amplifies the laser light output from the semiconductor oscillator section. In the semiconductor optical amplifier integrated laser, the semiconductor laser oscillator section and the semiconductor optical amplifier section have one common p-i-n structure, which has an active layer, a cladding layer disposed separately from the active layer, and one common function layer formed in the cladding layer, wherein the one common function layer has a first portion, reflecting light having a wavelength in the gain band, in the semiconductor laser oscillator section, and also has a second portion, transmitting the light having the wavelength within the gain band, in the semiconductor optical amplifier section.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a semiconductor optical amplifier integrated laser. [Background technology]

[0002] A semiconductor optical amplifier integrated laser is a semiconductor device that integrates a semiconductor laser and a semiconductor optical amplifier. Semiconductor optical amplifier integrated lasers have attracted attention in recent years because they are small, low power, can operate in both the 1.3 μm and 1.55 μm wavelength bands, and are capable of nonlinear operations such as wavelength conversion.

[0003] Patent Document 1 discloses an optical transmission module with reduced noise, which includes a first semiconductor layer provided with a first electrode, an active layer formed in a stripe pattern on the first semiconductor layer, and a second semiconductor layer formed in a stripe pattern on the active layer, provided with a second electrode, and including a diffraction grating provided along an extension direction of the active layer, wherein the active layer includes a first portion extending from one end face with a first stripe width, a second portion extending from the opposite side of the one end face with a second stripe width smaller than the first stripe width, and a connection portion whose stripe width changes and connects the first portion and the second portion, and wherein the diffraction grating overlaps with the first portion but does not overlap with the second portion in a planar view. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-157583 A Summary of the Invention [Problem to be solved by the invention]

[0005] As semiconductor optical amplifiers integrated into semiconductor lasers or modulator-integrated semiconductor lasers have been attracting attention, there has been a demand for improving the characteristics of semiconductor optical amplifiers. Specifically, there is a demand for increasing the optical output increase relative to the current injected into the semiconductor optical amplifier (the difference between the input and output of the optical amplifier).

[0006] In order to efficiently amplify the laser light of a semiconductor laser, it is preferable that the gain band (wavelength range of the gain spectrum) of the semiconductor optical amplifier and the gain band of the semiconductor laser are close to each other. In addition, considering the simplicity and cost of the wafer process, it is desirable that the semiconductor optical amplifier and the semiconductor laser have the same active layer.

[0007] When integrating a semiconductor optical amplifier into a distributed feedback laser diode (DFB-LD) that can obtain a single wavelength output, a diffraction grating is created only in the DFB-LD section, and no diffraction grating is created in the semiconductor optical amplifier section. If a diffraction grating is formed in the semiconductor optical amplifier section, light will be returned from the semiconductor optical amplifier section to the DFB-LD section, making the oscillation of the DFB-LD unstable.

[0008] The floating type structure is known as a diffraction grating structure with good structural controllability during fabrication. A floating type diffraction grating structure is, for example, a structure in which a diffraction grating is formed in a p-type cladding layer using a material different from the cladding layer. Since the thickness of the layers that make up the diffraction grating can be controlled during multilayer growth, the thickness of the diffraction grating layer is highly controllable, and this structure is widely used in the diffraction grating structure of DFB-LD parts.

[0009] For example, there is a method of simultaneously growing the active layer of the DFB-LD section and the semiconductor optical amplifier section in one multi-layer growth step. From the viewpoint of the reliability of the multi-layer grown semiconductor layers, it is preferable to grow the diffraction grating layer that will later form the diffraction grating in one multi-layer growth step. The diffraction grating layer is etched only in the DFB-LB section to a period corresponding to the desired oscillation wavelength, forming a diffraction grating structure. On the other hand, in the semiconductor optical amplifier section, the diffraction grating layer is entirely removed by etching.

[0010] However, the structure in which a semiconductor optical amplifier is integrated into the DFB-LD section having the above-mentioned floating type diffraction grating has the following problems.

[0011] The first problem is that the presence or absence of a diffraction grating layer results in a different doping profile. Since a floating type diffraction grating layer in the upper cladding layer generally suppresses the diffusion of dopants, the dopant diffusion profile is affected by the presence or absence of a floating type diffraction grating layer. The doping profile is one of the most important parameters for laser characteristics and gain characteristics (e.g., optical output intensity, threshold current, etc.), and the difference in doping profile means that it is impossible to simultaneously optimize the doping profile for both the DFB-LD section and the semiconductor optical amplifier section. This problem becomes more pronounced when the upper cladding layer is p-type.

[0012] The second problem is that the presence or absence of a diffraction grating layer causes the current density in the active layer to differ for the same voltage. In a semiconductor optical amplifier integrated laser, current injection into the DFB-LD section and the semiconductor optical amplifier section is sometimes performed via a single electrode. When the DFB-LD section and the semiconductor optical amplifier section are driven by a single electrode, the floating type diffraction grating layer acts as a current injection barrier, so the current density in the active layer for the same voltage differs depending on whether or not a diffraction grating layer is present. Current density is a very important parameter that determines the reliability of a semiconductor optical amplifier integrated laser, and non-uniformity in current density has an adverse effect on reliability. [Means for solving the problem]

[0013] (1) A semiconductor optical amplifier integrated laser according to a first aspect of the present application includes a semiconductor laser oscillator section that oscillates laser light having a wavelength included in a gain band, and a semiconductor optical amplifier section that amplifies the laser light output from the semiconductor laser oscillator section. In the semiconductor optical amplifier integrated laser, the semiconductor laser oscillator section and the semiconductor optical amplifier section have a common pin structure, the common pin structure having an active layer, a cladding layer provided at a distance from the active layer, and a common functional layer formed in the cladding layer, the common functional layer having a first portion in the semiconductor laser oscillator section that reflects light having a wavelength within the gain band, and a second portion in the semiconductor optical amplifier section that transmits light having a wavelength within the gain band.

[0014] (2) In the semiconductor optical amplifier integrated laser described in (1), the one common functional layer includes an area where a layer is formed and an area where a layer is not formed, and in a planar view of the one common functional layer, the difference between the ratio of the area of ​​the area where a layer is formed to the area of ​​the area where a layer is not formed in the first part and the ratio of the area of ​​the area where a layer is formed to the area of ​​the area where a layer is not formed in the second part is within 10%.

[0015] (3) In the semiconductor optical amplifier integrated laser described in (1) or (2), the first portion has a first diffraction grating structure that reflects light having a wavelength within the gain band, and the second portion has a second diffraction grating structure that transmits light having a wavelength within the gain band.

[0016] (4) In the semiconductor optical amplifier integrated laser described in (3), the period of the second diffraction grating structure is 1.1 times or more or 0.9 times or less the period of the first diffraction grating structure.

[0017] (5) In the semiconductor optical amplifier integrated laser described in any one of (1) to (4), the common pin structure is formed as a mesa structure, and further includes an embedded semiconductor layer that embeds both sides of the mesa structure.

[0018] (6) In the semiconductor optical amplifier integrated laser according to any one of (1) to (5), the cladding layer has a composition different from that of the functional layer.

[0019] (7) The semiconductor optical amplifier integrated laser according to any one of (1) to (6) above, further comprising an electrode for injecting a current into the semiconductor laser oscillator section and the semiconductor optical amplifier section.

[0020] (8) In the semiconductor optical amplifier integrated laser described in any one of (1) to (7), the semiconductor optical amplifier section has a near end in contact with the semiconductor laser oscillator section and a far end farthest from the semiconductor laser oscillator section, and in a planar view of the semiconductor optical amplifier integrated laser, the width of the far end is 1.2 times or more or 0.8 times or less than the width of the near end.

[0021] (9) The semiconductor optical amplifier integrated laser according to any one of (1) to (8), further comprising a modulator section for modulating the laser light oscillated by the semiconductor laser oscillator section.

[0022] (10) The semiconductor optical amplifier integrated laser according to any one of (1) to (9), characterized in that the cladding layer is p-type.

[0023] (11) A semiconductor optical amplifier integrated laser according to a second aspect of the present application includes a substrate having a first conductivity type, an active layer formed on a first surface of the substrate, a cladding layer of a second conductivity type formed on the active layer, a common functional layer formed in the cladding layer and spaced apart from the active layer, an electrode of the first conductivity type provided on a second surface opposite to the first surface of the substrate, and an electrode of the second conductivity type provided on the cladding layer. The semiconductor optical amplifier integrated laser has a first region and a second region optically connected to the first region, and the functional layer has a first portion in the first region that reflects light having a specific wavelength within a gain band of the active layer, and a second portion in the second region that transmits light having a specific wavelength within the gain band of the active layer.

[0024] (12) In the semiconductor optical amplifier integrated laser described in (11), the one common functional layer includes an area where a layer is formed and an area where a layer is not formed, and in a planar view of the one common functional layer, the difference between the ratio of the area of ​​the area where a layer is formed to the area of ​​the area where a layer is not formed in the first part and the ratio of the area of ​​the area where a layer is formed to the area of ​​the area where a layer is not formed in the second part is within 10%.

[0025] (13) In the semiconductor optical amplifier integrated laser described in (11) or (12), the first portion has a first diffraction grating structure that reflects light having a specific wavelength within the gain band of the active layer, and the second portion has a second diffraction grating structure that transmits light having a specific wavelength within the gain band of the active layer. Effect of the Invention

[0026] According to the present invention, it is possible to realize a semiconductor optical amplifier integrated laser in which a semiconductor optical amplifier and a semiconductor laser are integrated, which has excellent optical characteristics and reliability. [Brief description of the drawings]

[0027] [Figure 1]1 is an example of a plan view of a semiconductor optical amplifier integrated laser according to a first embodiment. [Diagram 2] 2 is a schematic cross-sectional view of the semiconductor optical amplifier integrated laser taken along line AA' in FIG. 1. [Diagram 3] 2 is a schematic cross-sectional view of the semiconductor optical amplifier integrated laser taken along line BB' in FIG. [Figure 4] 2 is a schematic cross-sectional view of the semiconductor optical amplifier integrated laser taken along line CC' in FIG. [Diagram 5] 13 is an example of a plan view of a semiconductor optical amplifier integrated laser according to a modified example. [Figure 6] 13 is an example of a plan view of a semiconductor optical amplifier integrated laser according to a second embodiment. [Figure 7] 7 is an enlarged plan view of a semiconductor optical amplifier portion of the semiconductor optical amplifier integrated laser of FIG. 6. [Figure 8] 1 is a plan view of an example of a semiconductor optical amplifier integrated laser with an integrated modulator; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Fig. 1 shows a plan view of a semiconductor optical amplifier integrated laser. Fig. 2 shows a schematic cross-sectional view taken along line A-A' in Fig. 1. Fig. 3 shows a schematic cross-sectional view taken along line B-B' in Fig. 1, and Fig. 4 shows a schematic cross-sectional view taken along line C-C' in Fig. 1.

[0029] 1, the semiconductor optical amplifier integrated laser 100 comprises a semiconductor laser oscillator section 20 that oscillates light of a predetermined wavelength, and a semiconductor optical amplifier section 10 that amplifies the oscillated light. In this embodiment, the semiconductor laser oscillator section 20 is a DFB laser (DFB-LD).

[0030] The semiconductor laser oscillator section 20 and the semiconductor optical amplifier section 10 have one common pin structure. In this application, "one common pin structure" means a pin structure made of the same material and formed by the same process. Since the semiconductor laser oscillator section 20 and the semiconductor optical amplifier section 10 have one common structure, the gain band of the semiconductor laser oscillator section 20 and the gain band of the semiconductor optical amplifier section 10 are approximately the same. Here, the gain band indicates the wavelength range of the gain spectrum. The semiconductor optical amplifier integrated laser 100 also has a low-reflection end face coating film 11 provided on the laser emission surface and a high-reflection end face coating film 12 on the surface opposite to the laser emission surface. In this embodiment, the oscillation wavelength of the semiconductor laser oscillator section 20 is in the 1.3 μm band, but it may be in the 1.55 μm band.

[0031] 3 and 4, the semiconductor optical amplifier integrated laser 100 has a mesa portion 1 and a burying layer 27 that buries the mesa portion 1 from both sides. The semiconductor optical amplifier integrated laser 100 further has an insulating film 26 that covers a part of the burying layer 27, and an electrode 13 that covers a part of the mesa portion 1 and the insulating film 26. The solid line that defines the mesa portion 1 represents the outline of the mesa portion 1.

[0032] Referring to FIG. 2, the semiconductor optical amplifier integrated laser 100 has a first conductive type substrate 21 and a pin structure provided on the first conductive type substrate 21. In this embodiment, the pin structure has a first conductive type SCH layer 22, an active layer 23, a second conductive type SCH layer 24, and a second conductive type cladding layer 25, but is not limited thereto. In this embodiment, the first conductive type is n-type, the second conductive type is p-type, and the first conductive type substrate 21 is n-InP. The first conductive type SCH layer 22 is n-InGaAsP, the active layer 23 is a multiple quantum well made of InGaAsP or InGaAlAs, the second conductive type SCH layer 24 is p-InGaAsP, and the second conductive type cladding layer 25 is p-InP. In this embodiment, the second conductive type dopant is Zn. In this embodiment, the composition of InGaAsP or InGaAlAs in the active layer 23 is adjusted so as to emit light at 1.3 μm, but when light is to be emitted at another wavelength, it is adjusted so as to emit light at that wavelength.

[0033] The semiconductor optical amplifier integrated laser 100 further has a first conductivity type electrode 14 provided on the lower surface of the first conductivity type substrate 21, and a second conductivity type electrode 13 provided on the pin structure. The electrodes 13, 14 are used to inject a current from an external power source (not shown) into the semiconductor optical amplifier integrated laser 100 (the semiconductor laser oscillator section 20 and the semiconductor optical amplifier section 10). The electrodes 13, 14 are each made of a single member. That is, the semiconductor optical amplifier section 10 and the semiconductor laser oscillator section 20 are energized by a common electrode. In this embodiment, the substrate 21 and the SCH layer 22 are n-type, and the SCH layer 24 and the cladding layer 25 are p-type, but the p-type and n-type may be reversed.

[0034] The semiconductor optical amplifier integrated laser 100 further includes one common functional layer 2 in the p-type cladding layer 25 of the pin structure. The functional layer 2 is separated from the active layer 23 of the pin structure. The functional layer 2 is composed of a first portion 4 and a second portion 3. The functional layer 2 is composed of a different composition from the p-type cladding layer 25. Here, the functional layer 2 is composed of InGaAsP. As will be described later, the functional layer 2 is composed of a deposition region and a non-deposition region, the deposition region is InGaAsP, and the non-deposition region is the same p-InP as the p-type cladding layer 25.

[0035] As shown in FIGS. 1 and 2, the first portion 4 and the second portion 3 have openings. In other words, the first portion 4 and the second portion 3 include, in plan view, a region where a layer is formed (hereinafter, referred to as a "film-formed region") and a region where a layer is not formed (hereinafter, referred to as a "non-film-formed region"). In the first portion 4, film-formed regions and non-film-formed regions are periodically provided so as to reflect light of a specific wavelength within the gain band of the pin structure (first diffraction grating structure). By having this diffraction grating structure, the semiconductor laser oscillator section 20 oscillates laser light of a single oscillation wavelength (DFB wavelength). Generally, a diffraction grating structure is provided so as to oscillate at a wavelength near the peak of the gain band. In this embodiment, the first portion 4 is a floating type diffraction grating, has a diffraction grating period of 200 nm so as to oscillate at 1.3 μm, and has a duty ratio of 50%. That is, in plan view of the first portion 4, the area ratio of the film-formed region to the non-film-formed region is 1:1.

[0036] On the other hand, the second portion 3 is provided with an opening so as not to reflect (transmit) light of a wavelength within the gain band of the pin structure. That is, the second portion 3 is provided with a film-formed region and a non-film-formed region so as not to reflect (transmit) light of a wavelength within the gain band of the pin structure (second diffraction grating structure). In the first portion 4 and the second portion 3, it is preferable that the ratio of the area of ​​the film-formed region to the area of ​​the non-film-formed region (opening ratio) is approximately the same. That is, in a plan view of the functional layer 2, it is preferable that the ratio of the total area of ​​the film-formed region to the total area of ​​the non-film-formed region in the first portion 4 and the ratio of the total area of ​​the film-formed region to the total area of ​​the non-film-formed region in the second portion 3 are approximately the same. In this embodiment, in a plan view of the functional layer 2, the difference between the ratio of the total area of ​​the film-formed region to the total area of ​​the non-film-formed region in the first portion 4 and the ratio of the total area of ​​the film-formed region to the total area of ​​the non-film-formed region in the second portion 3 is within 10%. For convenience, the structure of the second portion 3 is referred to as a diffraction grating, but as described above, it does not reflect light with wavelengths within the gain band.

[0037] In this embodiment, the second portion 3 also has periodic film regions and non-film regions, but is configured not to reflect light of wavelengths within the gain band of the pin structure of the semiconductor optical amplifier integrated laser 100. In this embodiment, the second portion 3 has a structure (diffraction grating structure) in which the film regions and non-film regions are alternately arranged at the same period, but the film regions and non-film regions of the second portion 3 do not have to be arranged periodically (see FIG. 5). When the second portion 3 has a structure in which the film regions and non-film regions are alternately arranged at the same period, the duty ratio of the first portion 4 may be 1.1 times or more or 0.9 times or less than the duty ratio of the second portion 3, taking into account the wavelength range of the gain spectrum of InGaAsP or InGaAlAs that constitutes the active layer 23.

[0038] The semiconductor laser oscillator section 20 having the first portion 4 functioning as a diffraction grating may be, for example, a uniform diffraction grating type DFB-LD in which a diffraction grating with the same period is formed over the entire DFB-LD, a λ / 4 shift DFB-LD in which a phase shift of a diffraction grating phase π is introduced midway through the diffraction grating, a CPM (Corrugation Pitch Modulated)-DFB-LD in which a phase shift equivalent to λ / 4 is realized by slightly changing the diffraction grating period, a multi-phase shift DFB-LD in which a λ / 4 shift is realized by multiple phase shifts, or the like.

[0039] If the second portion 3 has periodicity, the period must be such that it does not reflect light of the DFB wavelength. In addition, in order to suppress DFB mode oscillation at unintended wavelengths, it is desirable that the second portion 3 has a period and a diffractive structure that does not reflect light over the entire wavelength band in which the active layer 23 has gain.

[0040] 3, the mesa portion 1 has a substrate 21 of a first conductivity type and a pin structure provided on the substrate 21 of the first conductivity type. In this embodiment, the pin structure has, but is not limited to, an SCH layer 22 of a first conductivity type, an active layer 23, an SCH layer 24 of a second conductivity type, and a cladding layer 25 of a second conductivity type. The mesa portion 1 further includes a first portion 4 formed in the semiconductor layer of the second conductivity type of the pin structure. The first portion 4 functions as a diffraction grating that reflects light of the oscillation wavelength of the active layer 23.

[0041] 4, the mesa portion 1 has a substrate 21 of a first conductivity type and a pin structure provided on the substrate 21 of the first conductivity type. In this embodiment, the pin structure has, but is not limited to, an SCH layer 22 of a first conductivity type, an active layer 23, an SCH layer 24 of a second conductivity type, and a cladding layer 25 of a second conductivity type. The mesa portion 1 further includes a second portion 3 formed in the p-type semiconductor layer of the pin structure. The second portion 3 does not reflect (transmits) light of a wavelength within the gain band of the active layer 23.

[0042] FIG. 5 shows an example of a plan view of a semiconductor optical amplifier integrated laser according to a modification. The modification shown in FIG. 5 is the same as the embodiment shown in FIGS. 1 to 4 except for the second portion 3. More specifically, in FIG. 5, the second portion 3 does not have a structure in which the deposition regions and the non-deposition regions are alternately arranged at the same period. That is, the deposition regions and the non-deposition regions in the second portion 3 are not arranged periodically. In this modification, the areas of the deposition regions and the non-deposition regions may be non-uniform. However, the difference between the aperture ratio of the second portion 3 and the aperture ratio of the first portion 4 is within 10% in a plan view.

[0043] As described above, the semiconductor optical amplifier section 10 and the semiconductor laser oscillator section 20 have a common structure except for the functional layer 2. Therefore, the gain bands of the semiconductor optical amplifier section 10 and the semiconductor laser oscillator section 20 are approximately the same. Furthermore, since the electrodes 13, 14 are each made of the same material, the same voltage is applied to the semiconductor optical amplifier section 10 and the semiconductor laser oscillator section 20. When a voltage is applied to the semiconductor optical amplifier section 10 and the semiconductor laser oscillator section 20, carriers are injected into the semiconductor optical amplifier section 10 and the semiconductor laser oscillator section 20. After the carrier injection, the semiconductor optical amplifier section 10 and the semiconductor laser oscillator section 20 cause luminescent recombination.

[0044] The semiconductor optical amplifier integrated laser of the present application comprises a first portion 4 functioning as a diffraction grating layer in a semiconductor laser oscillator portion 20, and a second portion 3 in a semiconductor optical amplifier portion 10. Since the first portion 4 has a high reflectance for a specific wavelength within the gain band, the semiconductor laser oscillator portion 20 oscillates light of a single wavelength. On the other hand, the second portion 3 does not reflect light of a wavelength within the gain band (does not cause Bragg reflection), and therefore does not feed back light of a wavelength within the gain band, including the DFB light. Therefore, the semiconductor optical amplifier portion 10 amplifies the laser light (DFB light) output from the semiconductor laser oscillator portion 20.

[0045] Since the aperture ratios of the first portion 4 and the second portion 3 are substantially the same, the diffusion profiles of the second conductivity type dopant in the semiconductor laser oscillator portion and the semiconductor optical amplifier portion are substantially the same within the range of manufacturing variations. Therefore, it is possible to simultaneously optimize the diffusion profiles of the second conductivity type dopant for both the semiconductor laser oscillator portion 20 and the semiconductor optical amplifier portion 10. As a result, the characteristics of the semiconductor optical amplifier integrated laser of the present application are improved.

[0046] Furthermore, since the aperture ratios of the first portion 4 and the second portion 3 are approximately the same, the density of the current injected into each active layer 23 of the semiconductor laser oscillator portion 20 and the semiconductor optical amplifier portion 10 becomes substantially the same within the range of manufacturing variations. Therefore, the difference in current density between the semiconductor laser oscillator portion 20 and the semiconductor optical amplifier portion 10 can be made smaller compared to a semiconductor optical amplifier integrated laser in which the semiconductor optical amplifier portion 10 does not include the second portion. As a result, the operational reliability of the semiconductor optical amplifier integrated laser of the present application is improved compared to a conventional semiconductor optical amplifier integrated laser in which the semiconductor optical amplifier portion 10 does not include the second portion.

[0047] Fig. 6 shows a plan view of a semiconductor optical amplifier integrated laser according to the second embodiment. Fig. 7 shows an enlarged plan view of the semiconductor optical amplifier portion of the semiconductor optical amplifier integrated laser of Fig. 6. The semiconductor optical amplifier integrated laser shown in Fig. 6 is the same as the semiconductor optical amplifier integrated laser of Fig. 1 except that the width of the mesa portion 1' varies. As in the embodiment shown in Figs. 1 to 5, the solid line defining the mesa portion 1' represents the outline of the mesa portion 1', and one common pin structure is formed under the mesa portion 1'.

[0048] Within region 10, mesa portion 1' has a near end in contact with region 20 and a far end in contact with low-reflection endface coating film 11. As shown in FIG. 7, the mesa stripe width W1 at the far end is narrower than the mesa stripe width W2 at the near end. As shown in the figure, the mesa stripe width of mesa portion 1' gradually narrows from the near end to the far end within region 10. Therefore, mesa portion 1' functions as a spot size converter (SSC).

[0049] By making the width of the far end of the mesa portion 1' narrower than the width of the near end, the photon distribution centered on the active layer relatively widens, and the FFP (Far Field Pattern) can be narrowed. In this embodiment, in a plan view of the semiconductor optical amplifier integrated laser, the width of the far end is 0.8 times or less the width of the near end. Conversely, the width of the far end may be wider than the width of the near end. For example, in a plan view of the semiconductor optical amplifier integrated laser, the width of the far end is 1.2 times or more the width of the near end.

[0050] FIG. 8 shows a plan view of an example of a semiconductor optical amplifier integrated laser integrated with a modulator. The semiconductor optical amplifier integrated laser shown in FIG. 8 is the same as the semiconductor optical amplifier integrated laser shown in FIG. 1 except that it includes a semiconductor modulator section 30. The semiconductor optical amplifier integrated laser includes a semiconductor laser oscillator section 20 that oscillates light of a predetermined wavelength, a semiconductor optical amplifier section 10 that amplifies the oscillated light, and a semiconductor modulator section 30 that modulates the amplified laser light. The semiconductor modulator section 30 includes an electrode 40. The semiconductor modulator section 30 applies a voltage (modulation signal) to the electrode 40 to modulate the light output from the semiconductor optical amplifier section 10, and outputs the modulated light from an output surface on which a low-reflection end face coating film 11 is formed. The semiconductor modulator section 30 may be an electroabsorption modulator or an MZ type modulator. [Explanation of symbols]

[0051] 1,1' mesa portion, 2 functional layer, 11 low-reflection end face coating film, 12 high-reflection end face coating film, 13 second conductivity type electrode, 14 first conductivity type electrode, 20 semiconductor laser oscillator portion, 21 first conductivity type substrate, 22 first conductivity type SCH layer, 23 active layer, 24 second conductivity type SCH layer, 25 second conductivity type cladding layer, 26 insulating film, 27 buried layer, 30 semiconductor modulator portion, 40 electrode.

Claims

1. A substrate; a cladding layer disposed above the substrate; an active layer formed between the substrate and the cladding layer; a common functional layer formed in the cladding layer and spaced apart from the active layer; Including, a first domain for oscillating light having a wavelength included in a gain band and a second domain for amplifying the light from the first domain; the common functional layer includes a first portion that reflects light having a specific wavelength within a gain band of the active layer in the first domain, and a second portion that transmits light having a wavelength within the gain band of the active layer in the second domain; the first portion has a first grating structure having a grating period; the second portion has a second grating structure that is non-periodic; Semiconductor optical amplifier integrated laser.

2. 2. The semiconductor optical amplifier integrated laser according to claim 1, the first portion and the second portion include a first region where a layer is formed and a second region where a layer is not formed, In a plan view of the common functional layer, a difference between the first ratio and the second ratio is within 10%; the first ratio is defined by an area of ​​the first region within the first portion relative to an area of ​​the second region within the first portion; the second ratio being defined by an area of ​​the first region within the second portion relative to an area of ​​the second region within the second portion; Semiconductor optical amplifier integrated laser.

3. 3. The semiconductor optical amplifier integrated laser according to claim 2, The first region and the second region are not provided periodically within the second portion. Semiconductor optical amplifier integrated laser.

4. 4. The semiconductor optical amplifier integrated laser according to claim 3, the first region and the second region are periodically provided within the first portion; Semiconductor optical amplifier integrated laser.

5. 2. The semiconductor optical amplifier integrated laser according to claim 1, the first portion has a first diffraction grating structure that reflects light having the particular wavelength within the gain band of the active layer; the second portion has a second grating structure that transmits light having a wavelength within the gain band of the active layer. Semiconductor optical amplifier integrated laser.

6. 6. The semiconductor optical amplifier integrated laser according to claim 5, The period of the second diffraction grating structure is 1.1 times or more or 0.9 times or less than the period of the first diffraction grating structure. Semiconductor optical amplifier integrated laser.

7. 2. The semiconductor optical amplifier integrated laser according to claim 1, the active layer and the cladding layer are formed in a mesa structure; Semiconductor optical amplifier integrated laser.

8. 8. The semiconductor optical amplifier integrated laser according to claim 7, Further comprising a buried semiconductor layer burying both sides of the mesa structure. Semiconductor optical amplifier integrated laser.

9. 2. The semiconductor optical amplifier integrated laser according to claim 1, The cladding layer has a composition different from the composition of the common functional layer. Semiconductor optical amplifier integrated laser.

10. 2. The semiconductor optical amplifier integrated laser according to claim 1, further comprising electrodes for injecting a current into the first domain and the second domain. Semiconductor optical amplifier integrated laser.

11. 2. The semiconductor optical amplifier integrated laser according to claim 1, the second domain has a first end in contact with the first domain and a second end furthest from the first domain; In a plan view of the semiconductor optical amplifier integrated laser, a width of the second end is 1.2 times or more or 0.8 times or less than a width of the first end. Semiconductor optical amplifier integrated laser.

12. 2. The semiconductor optical amplifier integrated laser according to claim 1, Further comprising a modulator section for modulating the light amplified by the second domain. Semiconductor optical amplifier integrated laser.

13. 2. The semiconductor optical amplifier integrated laser according to claim 1, The specific wavelength is in the 1.3 μm band or the 1.55 μm band. Semiconductor optical amplifier integrated laser.

14. a first domain that oscillates light having a wavelength included in a gain band, and a second domain that amplifies the light output from the first domain; the first domain and the second domain have a common layer structure; the common layer structure includes an active layer, a clad layer spaced apart from the active layer, and a common functional layer formed in the clad layer; The common functional layer is a first portion in the first domain that reflects light having the wavelength within the gain band; a second portion in the second domain that transmits light having the wavelength within the gain band; the first portion has a first grating structure having a grating period; the second portion has a second grating structure that is non-periodic; Semiconductor optical amplifier integrated laser.

15. 15. The semiconductor optical amplifier integrated laser according to claim 14, The common functional layer further includes a first region in which a layer is formed and a second region in which a layer is not formed. Semiconductor optical amplifier integrated laser.

16. 15. The semiconductor optical amplifier integrated laser according to claim 14, the first portion is periodically provided with filmed and unfilmed regions that reflect light having the wavelength within the gain band; the second portion is periodically provided with filmed regions and non-filmed regions that transmit light having the wavelength within the gain band; Semiconductor optical amplifier integrated laser.

17. 15. The semiconductor optical amplifier integrated laser according to claim 14, the first portion has a first grating structure that reflects light having the wavelength within the gain band; the second portion having a second grating structure that transmits light having the wavelength within the gain band; Semiconductor optical amplifier integrated laser.

18. 15. The semiconductor optical amplifier integrated laser according to claim 14, The common layer structure is formed as a mesa structure. Semiconductor optical amplifier integrated laser.

19. 20. The semiconductor optical amplifier integrated laser of claim 18, Further comprising a buried semiconductor layer burying both sides of the mesa structure. Semiconductor optical amplifier integrated laser.

20. 15. The semiconductor optical amplifier integrated laser according to claim 14, The cladding layer has a composition different from the composition of the common functional layer. Semiconductor optical amplifier integrated laser.

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