JP5545847B2 - Optical semiconductor device - Google Patents

Description

  The present invention relates to an optical semiconductor device, and more particularly to an optical semiconductor device such as an electroabsorption optical modulator integrated semiconductor laser having a strained quantum well layer.

  Due to the explosive spread of the current Internet, the opticalization of networks has expanded from backbone networks between large cities to access networks represented by FTTH (Fiber To The Home). It has begun to cover a wide range from applications to data communications. In particular, the opticalization of Ethernet (registered trademark) has been discussed recently, and standardization of various forms and performances of the transceiver is being promoted.

  Among them, a transceiver for 100 Gigabit Ethernet (100 GbE), which is being discussed as one of the next generation networks, has been studied extensively as a future ultra-high speed network. In 100 GbE, various standards are discussed according to the transmission distance, but for transmission over medium distance (10 km) and long distance (40 km) using a single mode fiber (SMF) as a transmission medium, The names are defined as 100GBASE-LR4 (hereinafter referred to as LR4) and 100GBASE-ER4 (hereinafter referred to as ER4), respectively, 1294.53 nm to 1296.59 nm (lane 1), 1299.02 nm to 1301.09 nm (lane 2) ), 1303.54 nm to 1305.63 nm (lane 3), 130.09 nm to 1310.19 nm (lane 4), 4.5 nm intervals, and a total of 15 nm transmitters for four waves are prepared. Each is operated at 25 Gbit / s, and each transmitter Idomodo suppression ratio (Side Mode Suppression Ratio: SMSR) is more than 30 dB, the dynamic extinction ratio and the like are required than 8dB relative to 4dB, ER4 respect LR4, required performance is finely set.

  As a light source in a transmitter for 100 GbE, an electroabsorption modulator integrated laser (Electrobsorption Modulator integrated with DFB laser: EADFB laser) is currently promising. The EADFB laser is known to be very advantageous for high-speed modulation because the semiconductor laser and the modulator can be optimized independently, and the dynamic extinction ratio is 8 dB or more particularly for ER4 of 100 GbE. An EADFB laser that is necessary and easy to obtain a high extinction ratio is almost essential. Further, LR4 and ER4 are premised on a constant temperature operation by a Peltier element, but it is known that the power consumption becomes the smallest when operated at 40 to 50 ° C., which is a little higher than room temperature. In general, the performance of a semiconductor laser deteriorates as the temperature rises. Therefore, it is necessary to have a configuration with little performance deterioration even when the semiconductor laser is operated at these temperatures.

  Currently, a standard package called CFP MSA transceiver has been proposed as a transceiver for 100 GbE, in which four optical transmitters (Transmitter Optical SubAssembly: TOSA) are arranged, separately from this, a multiplexer Is installed. There are four other receivers, duplexers, and electrical signal processing units in the transceiver, and the size thereof is very large at 75 mm × 140 mm. Each TOSA includes, in addition to a light source operating at 25 Gbit / s, a Peltier element for temperature control, a lens for focusing on an optical fiber, an isolator for preventing return light, and an optical fiber. In addition to its large size, a lens, an isolator, a Peltier element, and an optical fiber are required for every four wavelengths, and both the member cost and power consumption increase.

T. Fujisawa, M. Arai, N. Fujiwara, W. Kobayashi, T. Tadokoro, K. Tsuzuki, Y. Akage, R. Iga, T. Yamanaka, and F. Kano, "25 Gbit / s 1.3μm InGaAlAs- based electroabsorption modulator integrated with DFB laser for metro-area (40 km) 100 Gbit / s Ethernet system ", IEE Electronics Letters, vol. 45, no. 17, pp. 900-901, August 13, 2009 W. Kobayashi, M. Arai, T. Yamanaka, N. Fujiwara, T. Fujisawa, M. Ishikawa, K. Tsuzuki, Y. Shibata, Y. Kondo, and F. Kano, "Wide temperature range (-25 ℃- (100 ° C) operation of a 10-Gb / s 1.55-μm electroabsorption modulator integrated DFB laser for 80-km SMF transmission ", IEEE Photonics Technology Letters, vol.21, no. 15, pp.1054-1056, August 2009 1 day T. Saito, T. Yamatoya, Y. Morita, E. Ishimura, C. Watatani, T. Aoyagi, and T. Ishikawa, "Clear eye opening 1.3 μm-25 / 43Gbps EML with novel tensile-strained asymmetric QW absorption layer" , Proc. ECOC 2009, paper 8.1.3, 2009.

  In order to solve these problems, it is effective to integrate four transmitters and a multiplexer. There are two types of integration methods: hybrid integration using different materials and monolithic integration on one substrate. In the hybrid integration, for example, a method of integrating a light source made of another material system into a multiplexer made of a certain material system by some method is used, but between the four transmitters and the multiplexer. Active alignment is almost indispensable to reduce the coupling loss in the process, and the mounting process is inevitably complicated. In addition, since the transmitter and the multiplexer are separately manufactured, there is a limit to downsizing the size even if it is integrated, and the manufacturing and mounting processes are complicated.

  On the other hand, in monolithic integration, since a transmitter and a multiplexer are built on one substrate, alignment is not necessary in the first place, and mounting is easy, and mounting of four elements is completed in one mounting. . Further, since the two elements are directly coupled, the size can be easily reduced. Furthermore, since the number of Peltier elements, lenses, and isolators necessary for manufacturing the TOSA is only one, it is possible to significantly reduce the member cost and power consumption. However, the currently proposed EADFB laser employs a ridge structure in its optical waveguide in order to enable high-speed modulation of 25 Gbit / s. In this structure, the optical confinement is weak, the bending loss of the optical waveguide is large, the bending radius cannot be reduced, the multiplexer is large, and there is a limit to downsizing. Further, since the layer structure of the EA modulator becomes uniform, it is essential to design a layer structure that can ensure an extinction ratio that satisfies the standard over a wide wavelength range of 15 nm required for 100 GbE. Furthermore, in order to simultaneously modulate the four light sources at a high data rate of 25 Gbit / s, suppressing crosstalk between elements remains a major problem. Also, when driving the EA modulator, it is necessary to set the bias voltage and the voltage amplitude. In the prior art, a constant voltage amplitude operation has been reported, but the bias voltage is changed for each wavelength. Complex control was necessary.

  Therefore, the present invention has been made to solve the above-described problems, and is compatible with LR4 and ER4 standards of 100 GbE, easy to control, low cost, low power consumption, An object of the present invention is to provide an optical semiconductor device that can be miniaturized.

An optical semiconductor device according to a first invention for solving the above-described problem is
A plurality of semiconductor laser portions provided on a substrate made of a semiconductor mixed crystal and having different oscillation wavelengths, and a plurality of semiconductor laser portions provided for each of the plurality of semiconductor laser portions, for modulating signals emitted from the plurality of semiconductor laser portions. A light source comprising an electroabsorption optical modulator part, a core part and a clad part provided above and below the core part, and a combiner part for combining signals emitted from the light source into one An optical semiconductor device having a formed configuration,
The semiconductor mixed crystal of the substrate is InP,
The semiconductor laser part has an active part of a multiple quantum well structure including a quantum well layer, a barrier layer, and a diffraction grating forming layer, and a cladding part provided above and below the active part,
The electroabsorption optical modulator portion has an active portion of a multiple quantum well structure including a quantum well layer, a barrier layer, and an optical confinement layer, and a cladding portion provided above and below the active portion,
The well layer and the barrier layer in the active part of the electroabsorption optical modulator part are In _1-xy Al _x Ga _y As,
The active portion of the electro-absorption optical modulator has a quantum well number of 7 to 9, a strain amount of the quantum well layer of 0.17% to 0.73% (plus sign is tensile strain), and a barrier Ri 1.05μm der band gap wavelength from 0.9μm of layer,
The upper cladding portions of the plurality of semiconductor laser portions and the plurality of electroabsorption modulator portions are p-InP, and the upper cladding portion of the multiplexer is non-doped InP. And
An optical semiconductor device according to a second invention for solving the above-described problem is
An optical semiconductor device according to a first invention,
A photodiode is provided on the end side of the semiconductor laser portion, and the photodiode has the same layer structure as the semiconductor laser portion.
It is characterized by that.

An optical semiconductor device according to a third invention for solving the above-described problem is
An optical semiconductor device according to the first or second invention,
Provided between the semiconductor laser part and the electroabsorption optical modulator part on the substrate, and having a core part and cladding parts provided above and below the core part, and the semiconductor laser part and the Comprising a passive layer that electrically insulates the electroabsorption optical modulator section;
The core portion of the passive layer has the same multiple quantum well structure as the active portion of the electroabsorption optical modulator portion, or an In _1-x Ga _x As _y P _{1 having a} band gap wavelength of 1.1 μm to 1.2 μm. _-y Bulk feature.

An optical semiconductor device according to a fourth invention for solving the above-described problem is as follows.
An optical semiconductor device according to any one of the first to third inventions ,
The quantum well layer of the active part of the semiconductor laser part has a thickness and strain that achieves the wavelength selected from a material having a wavelength that maximizes the room temperature gain of 1.25 μm to 1.35 μm. It is characterized by that.

An optical semiconductor device according to a fifth invention for solving the above-described problem is
An optical semiconductor device according to any one of the first to fourth inventions,
The diffraction grating forming layer of the active part of the semiconductor laser part is formed with a diffraction grating having a depth and a period with a Bragg wavelength of 1.29 μm to 1.31 μm at 40 to 50 ° C. Features.

An optical semiconductor device according to a sixth invention for solving the above-described problem is
An optical semiconductor device according to a fifth invention,
The quantum well layer of the active part of the electroabsorption optical modulator part has a thickness that achieves a wavelength at which the absorption edge wavelength at room temperature is 40 nm to 80 nm shorter than the black wavelength. .

An optical semiconductor device according to a seventh invention for solving the above-described problem is
An optical semiconductor device according to any one of the third to sixth inventions,
The semiconductor laser section, the electroabsorption optical modulator section, and the passive layer each have an optical waveguide having a ridge structure, and both sides thereof are embedded with an organic material having a dielectric constant smaller than that of a semiconductor. And

An optical semiconductor device according to an eighth invention for solving the above-described problem is
An optical semiconductor device according to any one of the first to seventh inventions,
The core layer of the multiplexer unit may bandgap wavelength of 1.2μm of _{In 1-x Ga x As y} P 1-y bulk from 1.1 .mu.m.

An optical semiconductor device according to a ninth invention for solving the above-described problem is
An optical semiconductor device according to any one of the first to eighth inventions,
The multiplexer unit has an optical waveguide having a high mesa structure, and both sides thereof are embedded with an organic material having a dielectric constant smaller than that of a semiconductor.

An optical semiconductor device according to a tenth invention for solving the above-described problem is
An optical semiconductor device according to any one of the first to ninth inventions,
The multiplexer unit includes an input / output waveguide having a tapered structure.

An optical semiconductor device according to an eleventh invention for solving the above-described problem is
An optical semiconductor device according to any one of the first to tenth inventions,
The light source and the multiplexer unit are connected to each other through a joint portion having a discontinuous taper structure.

An optical semiconductor device control method according to a twelfth aspect of the invention for solving the above-described problem is
An optical semiconductor device control method for controlling an optical semiconductor device according to any one of the first to eleventh inventions,
When driving the plurality of electroabsorption optical modulator sections, each bias voltage and voltage amplitude are fixed.

  According to the optical semiconductor device according to the present invention, a large extinction ratio required by the LR4 and ER4 standards of 100 GbE can be ensured, and the bias voltage and voltage amplitude constant control can be realized. An ultra-small monolithic integrated light source with low cost and low power consumption can be configured.

1 is a cross-sectional view showing a basic structure of an optical semiconductor device according to the present invention. It is the perspective view which showed the structure of the optical semiconductor device based on the 1st, 2nd Example of this invention. It is a figure which shows the well layer distortion amount dependence of the well layer absorption amount in the electro-absorption type optical modulator which the optical semiconductor device which concerns on a 1st Example comprises. FIGS. 4A and 4B schematically show the structure of an optical waveguide, FIG. 4A shows a buried type, FIG. 4B shows a ridge type, and FIG. 4C shows a high mesa type. Show the case. It is a figure which shows the simulation result of the light source space | interval dependence of the crosstalk between light sources. It is a figure which shows the bending radius dependence of the bending loss of a ridge type | mold optical waveguide and a high mesa type | mold optical waveguide. It is a structural diagram of an MMI coupler. FIGS. 8A and 8B are diagrams showing the electric field distribution in the ridge-type MMI coupler. FIG. 8A shows a longitudinal section of the electric field distribution at the center of the core, and FIG. . FIGS. 9A and 9B are diagrams showing the electric field distribution in the high-mesa MMI coupler, in which FIG. 9A shows a vertical section of the electric field distribution at the center of the core, and FIG. . It is a structural diagram of a MMI coupler with a taper structure. FIGS. 11A and 11B show the MMI length dependence of the coupling efficiency of an MMI coupler with a taper structure. FIG. 11A shows the case where the input waveguide width is 2.0 μm, and FIG. The case of 2.5 μm is shown. FIGS. 12A and 12B show the electric field distribution of the optical waveguide used in the optical semiconductor device according to the first embodiment of the present invention, FIG. 12A shows the case of a ridge type optical waveguide, and FIG. The case of a type optical waveguide is shown. It is a top view of the conventional taper structure junction part which joins a different kind of optical waveguide. It is explanatory drawing of the discontinuous taper structure junction part in the optical waveguide used with the optical semiconductor device which concerns on 1st Example of this invention, Comprising: The plane is shown to Fig.14 (a), and FIG.14 (b) A perspective view is shown. It is a graph which shows the relationship between the coupling efficiency by a discontinuous taper structure junction part, and the magnitude | size of the width direction of a high mesa type | mold optical waveguide. It is a graph which shows the relationship between the coupling efficiency by a discontinuous taper structure junction part, and the taper length of a discontinuous taper structure junction part. It is a photograph of the element which comprises the optical semiconductor device which concerns on 1st Example of this invention. It is a figure which shows the oscillation spectrum of the element which comprises the optical semiconductor device which concerns on 1st Example of this invention. It is a figure which shows the static extinction ratio of the element which comprises the optical semiconductor device which concerns on 1st Example of this invention. It is a figure which shows the small signal frequency response of the element which comprises the optical semiconductor device which concerns on 1st Example of this invention. It is a figure which shows the bias voltage dependence of the dynamic extinction ratio in the electro-absorption type optical modulator part which comprises the optical semiconductor device based on the 1st Example of this invention. FIG. 22A is a cross-sectional view of an optical semiconductor device according to the present invention, and FIG. 22A shows the case of the first embodiment, and FIG. 22B shows the case of the second embodiment. FIG. 23A is a diagram for explaining the flow of photocarriers generated in the electroabsorption optical modulator portion included in the optical semiconductor device according to the present invention, and FIG. 23A shows the case of the first embodiment. FIG. 23B shows the case of the second embodiment.

Examples of the optical semiconductor device according to the present invention will be specifically described below.
First, the basic structure of the optical semiconductor device according to the present invention will be described with reference to FIG.

  As shown in FIG. 1, the optical semiconductor device according to the present invention is a monolithic integrated light source, and on a substrate 1 made of a semiconductor mixed crystal, a semiconductor laser active part (Laser diode: LD part) 21 and a passive layer ( An optical waveguide unit 22, an electroabsorption modulator unit (Electroabsorption modulator unit: EAM unit) 23, and a multiplexer unit 24 are formed.

  The LD portion 21 has an active portion 2 having a multiple quantum well structure including a quantum well layer, a barrier layer, and a diffraction grating formation layer, and cladding portions 3 and 4 provided above and below the active portion 2.

  The EAM portion 23 includes an active portion 5 having a multiple quantum well structure including a quantum well layer, a barrier layer, and an optical confinement layer, and clad portions 6 and 7 provided above and below the active portion 5.

  The passive layer 22 has a core portion 8 and clad portions 9 and 10 provided above and below the core portion 8.

  The multiplexer unit 24 includes a core unit 11 and clad units 12 and 13 provided above and below the core unit 11.

  A lower electrode 14 is provided on the lower surface of the substrate 1. An upper electrode 16 is provided on the upper surface of the upper cladding portion 3 in the LD portion 21 and the upper surface of the upper cladding portion 6 in the EAM portion 23 via a contact layer 15. On the other hand, neither the contact layer nor the upper electrode is provided on the upper surface of the upper cladding portion 9 in the passive layer 22, and the passive layer 22 electrically insulates the LD portion 21 from the EAM portion 23. Neither the contact layer nor the upper electrode is provided on the upper surface of the upper cladding portion 12 in the multiplexer portion 24. A passive layer 22 is also provided between the LD portion 21 and a photodiode portion 25 described later, and the passive layer 22 electrically insulates the LD portion 21 and the photodiode portion 25 from each other.

  An optical semiconductor device according to the first embodiment of the present invention will be described with reference to FIG.

  As shown in FIG. 2, the 100 GbE monolithic integrated light source, which is an optical semiconductor device according to the present embodiment, has a configuration in which four lanes 31 A, 31 B, 31 C, and 31 D are provided on a substrate 1 made of a semiconductor mixed crystal. ing. Each of the lanes 31A to 31D is provided with a photodiode portion (PD portion) 25, an LD portion 21, and an EAM portion 23. The PD portion 25, the LD portion 21, and the EAM portion 23 are disposed on the same substrate 1 via an optical waveguide. Connected on. The four LD units 21 are devices that emit signals having different wavelengths. In the four lanes 31 </ b> A to 31 </ b> D, light guided through the lanes 31 </ b> A to 31 </ b> D is multiplexed into one by a multimode interference coupler (MMI coupler) which is a multiplexer unit 24.

  The LD portion 21 is formed on the n-type InP substrate 1 and includes, in order from the InP substrate 1, the lower n-InP cladding portion 4, an InAlGaAs barrier layer, an InAlGaAs quantum well layer, and an InAlGaAsP diffraction grating formation layer. It has an active portion 2 having a multiple quantum well structure and an upper p-InP clad portion 3. Thus, by using InAlGaAs containing aluminum for the LD portion 21, the temperature characteristics can be improved.

  The EAM part 23 is formed on the n-type InP substrate 1 and is activated in order of the multi-quantum well structure including the lower n-InP clad part 7, the InAlGaAs barrier layer, and the InAlGaAs quantum well layer from the InP substrate 1 side. It has a portion 5, an InAlGaAsP guide layer, and an upper p-InP clad portion 6.

  The core portion 8 and the upper and lower cladding portions 9 and 10 of the passive layer 22 have the same configuration as the EAM portion 23. That is, the passive layer 22 is formed on the n-type InP substrate 1, and in order from the InP substrate 1 side, the lower n-InP cladding portion 10, the multiple quantum well structure including the InAlGaAs barrier layer and the InAlGaAs quantum well layer. A core portion 8 composed of the active portion, an InAlGaAsP guide layer, and an upper p-InP clad portion 9. However, since the PD unit 25, the LD unit 21, and the EAM unit 23 are electrically insulated by the passive layer 22, the passive layer 22 is not provided with an upper electrode.

  The PD unit 25 is provided on one end side of each of the lanes 31A to 31D. The PD unit 25 has substantially the same layer structure as that of the LD unit 21 and is formed on the n-type InP substrate 1, and in order from the InP substrate 1 side, a lower n-InP clad unit, an InAlGaAs barrier layer, and an InAlGaAs It has an active part of a multiple quantum well structure including a quantum well layer, an InAlGaAsP guide layer, and an upper p-InP cladding part.

  In this embodiment, in the monolithic integrated light source for 100 GbE having the above-described structure, a multi-quantum well structure having a band gap wavelength of 1.3 μm is used as the active layer 2 of the LD unit 21, and the active layer of the EAM unit 23 is used. 5, the band gap wavelength of the well layer is a mixed crystal in which the wavelength between the first quantization levels is 1.23 μm with respect to a given strain so that the detuning with the LD portion 21 is 70 nm at room temperature. Is used. As for the multiplexer unit 24, the core layer 11 is InGaAsP with a band gap wavelength of 1.15 μm, and the lower cladding 13 is n-InP.

  The composition of the barrier material is assumed to lattice match with the substrate, but there is no problem even if strain is introduced into the barrier layer for the purpose of strain compensation. The composition ratio of the semiconductor mixed crystal is specified by the strain amount, the well width, and the wavelength between the first quantization levels, and is not specifically described unless necessary.

As described above, the present invention is for a light source of 1.3 μm band for 100 GbE, and the wavelength range used therein is about 1.25 μm to 1.35 μm in various standards. Therefore, the quantum well layer of the active layer 2 of the LD portion 21 is selected from a material (In _1-xy Al _x Ga _y As) that sets the wavelength of the light wave that maximizes the gain at room temperature to 1.25 μm to 1.35 μm. It is only necessary to have a thickness and strain to achieve the wavelength.

Next, a method for manufacturing a 100 GbE monolithic integrated light source, which is an optical semiconductor device according to this embodiment, will be described.
First, a lower clad portion and an active portion having a multiple quantum well structure are grown on an n-type InP substrate 1 in order from the InP substrate 1 side. Thereby, the lower clad part and active part in LD part 21 and PD part 25 are produced. Further, the lower clad portion in the passive layer 22, the EAM portion 23, and the multiplexer portion 24 is produced.
Next, of the grown active portion of the multiple quantum well structure, portions other than those necessary for the LD portion 21 and the PD portion 25 are scraped off by wet etching, and the active portion of the multiple quantum well structure and the multiple quantum well structure are removed. The butt joint is regrown with the core portion composed of the active portion. Thereby, the active part 5 of the EAM part 23 and the core part 8 of the passive layer 22 are produced.
Of the active layer 5 and the core portion 8 that have been regrown, the portions other than those necessary as the EAM portion 23 and the passive layer 22 are scraped off by wet etching, and the core portion 11 of the multiplexer portion 24 is removed from the butt joint. Grow.

  Subsequently, after forming a diffraction grating in the LD part 21, an upper cladding part is grown by 2 μm on each of the LD part 21, the passive layer 22, the EAM part 23, the multiplexer part 24, and the PD part 25, and By growing the contact layer 15 of p-InGaAs, a wafer in which the PD portion 25, the LD portion 21, the passive layer 22, the EAM portion 23, and the multiplexer portion 24 are formed is completed. Here, if the MMI coupler of the multiplexer unit 24 is made as it is, the upper clad part is p-InP, so that the loss of light is large and the output light power is reduced. Therefore, here, from this state, the upper clad portion of the multiplexer portion 24 is further removed by etching, and non-doped InP is regrown to the butt joint.

  On the completed wafer, the LD portion 21, EAM portion 23, passive layer 22, and PD portion 25 have a ridge waveguide mesa formation process, the multiplexer portion 24 has a high mesa waveguide mesa formation process, and an electrode formation process ( However, the upper electrode is not formed on the passive layer 22 and the multiplexer unit 24), and after cleavage, a non-reflective coating (not shown) is applied to the front and rear end surfaces of the chip.

  The completed optical semiconductor device (device) is used in the following control method. A current is injected into each LD section 21 to generate continuous light. The light incident on the EAM unit 23 is driven with a certain voltage amplitude around a certain bias voltage to modulate the light. The light incident on the PD unit 25 is converted into an absorption current, and the oscillation wavelength of the LD unit 21 is obtained from the value of this current, and this is fed back to the injection current of the LD unit 21 so that the oscillation wavelength does not change. Used as

  Here, the PD unit 25 is disposed on the rear end side of the LD unit 21 in order to monitor the light output before entering the EAM unit 23. Usually, in the LD unit 21, light is output from both sides of the front and rear end faces, but with this arrangement, the output light can be used as signal light and monitor light without waste, improving energy utilization efficiency. effective.

  Below, the characteristic of the individual device in this element is described.

First, the structures of the LD unit 21 and the EAM unit 23 will be described.
Since the oscillation wavelength of the LD portion 21 is strictly determined by the standard, the period and depth of the diffraction grating formed in the LD portion 21 oscillate at a predetermined wavelength (here, 1.29 μm to 1.31 μm). Need to be determined. However, when the light source is driven, in order to reduce power consumption, in order to drive at a temperature higher than room temperature, the oscillation wavelength is set to be achieved at 40 to 50 ° C. In order to stabilize the oscillation wavelength, a phase shift region may be provided in the diffraction grating. In this case, the position where the phase shift is inserted is set so that the output from the front end surface is increased. Move to the side. In addition, since this device is intended for application to 100 GbE LR4 and ER4, a single EAM layer layer structure enables high-speed modulation of 25 Gbit / s over a wide wavelength range of 15 nm, and a desired extinction ratio. Need to get. In order to obtain a large extinction ratio in the EAM section, in addition to the design of the quantum well itself, there is an option of increasing the number of well layers and the modulator length. However, if the number of layers is increased, the insertion loss increases. If the length is increased, the parasitic capacitance increases and it becomes difficult to obtain a band necessary for 25 Gbit / s modulation. Therefore, it is extremely important to increase the amount of extinction per well.

  Here, in order to increase the extinction amount per well, a tensile strain quantum well using an InAlGaAs-based material is used. By using an InAlGaAs-based material, a large conduction band offset can be obtained, and even when a voltage is applied, the overlap of wave functions of electrons and holes is increased, and the extinction ratio can be increased. Further, by adopting a tensile strain quantum well, both heavy hole and light hole bands in the valence band can be used for absorption, and the amount of absorption can be further increased.

  FIG. 3 shows the well layer strain dependency of the well layer absorption when the well width of the EAM portion 23 is 10 nm and the band gap wavelength of the barrier layer is 1 μm. Here, the negative strain amount represents compressive strain, and the positive strain amount represents tensile strain. As can be seen from FIG. 3, when the tensile strain is 0.5%, the extinction amount per well is maximized, and when the strain amount of the quantum well layer is 0.17 to 0.73%, It is possible to ensure 90% of the extinction amount, and it is possible to ensure 95% when 0.25 to 0.65%. The physical reason is that the energy difference between the first band of the valence band heavy hole and the light hole is reduced, and the density of states at the Γ point is increased. Further, regarding the band gap wavelength of the barrier layer, if it is too small, the band gap becomes larger than that of the cladding, and if it is too large, confinement in the well is weakened, so that it is 0.9 μm or more and 1.05 μm or less. desirable. When the number of quantum wells is too large, the insertion loss increases. When the number is too small, the extinction ratio decreases, so 7 to 9 is desirable. Regarding the difference (detuning) between the oscillation wavelength of the LD section and the band edge wavelength of the EAM section, if it is too small, the insertion loss increases. If it is too large, the voltage required for quenching increases and the extinction ratio decreases. Here, it is desirable to set the thickness to 40 nm to 80 nm for the target 100 GbE application.

Next, the waveguide structure of the EAM portion 23 will be described with reference to FIG.
There are mainly three types of optical waveguide structures used in semiconductor optical devices: buried optical waveguides, ridge optical waveguides, and high-mesa optical waveguides. The schematic diagrams of these are shown in FIGS. 4 (a) and 4 (b). As shown in FIG.

  In the buried optical waveguide 100, as shown in FIG. 4A, a lower clad portion 102, an active layer 103 having a multiple quantum well (MQW) structure, and an upper clad portion 104 are sequentially formed on a substrate 101. In this structure, both sides of the active layer 103 with the MQW structure are etched until reaching the substrate 101, and both sides of the active layer 103 with the MQW structure are embedded and embedded with the semiconductor 105. Is possible. Further, since the beam shape can be made close to a circle, it can be easily coupled with an optical fiber and has been widely used in semiconductor lasers. However, when considering application to the EAM portion, since the electrode is formed on the top of the semiconductor having a large dielectric constant, there is a problem that parasitic capacitance increases and high-speed modulation necessary for the 100 giga standard is difficult. In addition, since the InAlGaAs-based material is oxidized when exposed to air, the active layer is exposed at the time of etching on both sides of the active layer, so that the quality of the crystal may be deteriorated.

  As shown in FIG. 4B, the ridge-type optical waveguide 110 is formed by sequentially forming a lower clad part 112, an MQW structure active layer 113, and an upper clad part 114 on a substrate 111, thereby forming an MQW structure active. A mesa is formed by etching only the upper clad portion 114 without cutting the layer 113 to form a waveguide. By embedding both sides of the mesa with an organic substance 115 having a small dielectric constant such as benzocyclobutane (BCB), it is possible to greatly reduce the parasitic capacitance in the EAM portion, which is considered advantageous for high-speed modulation. In addition, when an etching stop layer is sandwiched between the upper clad portion 114 and the active layer 113 having the MQW structure, the MQW structure active layer 113 can be manufactured without being exposed to the air, and an InAlGaAs-based material is used. It is possible to protect the crystal quality of the active layer. As a disadvantage, the beam shape is elliptical, so that the coupling with the fiber is difficult compared to the buried type.

  As shown in FIG. 4C, the high-mesa optical waveguide 120 is formed by sequentially forming a lower clad portion 122, an MQW structure active layer 123, and an upper clad portion 124 on a substrate 121 so as to activate the MQW structure. Etching is performed on both sides of the layer 123 until it reaches the substrate 121, and is usually embedded with an organic material 125 having a low dielectric constant such as BCB. This optical waveguide has the advantage that the difference between the refractive index in the lateral direction and the active layer 123 of the MQW structure becomes very large, so that the light is confined strongly, so that it is difficult to emit light even if the optical waveguide is bent. However, since both sides of the MQW structure active layer 123 are etched, deterioration of crystal quality is inevitable. Therefore, here, both the LD portion 21 and the EAM portion 23 employ an organic-embedded ridge structure that protects the crystal quality of InAlGaAs and can secure a large modulation band.

  In the present device, when the light sources are integrated on one chip, each light source is modulated at a high rate of 25 Gbit / s, so that electrical crosstalk between the light sources becomes a problem. Therefore, it is necessary to pay sufficient attention to the in-chip layout of the light source. FIG. 5 is a diagram illustrating a simulation result of the dependency of the crosstalk between light sources on the light source interval. From FIG. 5, it can be seen that the distance between the light sources needs to be 400 μm or more in order to achieve the normally required crosstalk amount of approximately −40 dB or less. However, if the distance between the light sources is too large, the length of the optical waveguide for reaching the multiplexer becomes long and the loss of light becomes large. In this embodiment, the interval between the light sources is 500 μm. In this embodiment, the EAM unit 23 is used as a modulator of a multichannel optical element having a high-speed modulator. Conventionally, as a modulator for a multi-channel integrated device, a Mach-Zehnder interferometer type optical modulator is generally used. In this case, two high-frequency traveling-wave electrodes are required for each modulator. Thus, there are problems that the number of terminals of the package on which the element is mounted increases and the element length becomes very large (˜1 mm). By adopting the EAM section 23 as a modulator to constitute an integrated device, only one high-frequency electrode is required for each modulator, which is very effective for crosstalk suppression, package, and chip size reduction. .

Next, the structure of the multiplexer unit 24 will be described.
Of course, the multiplexer unit 24 also requires an optical waveguide structure, but the required performance is different from that of the LD unit 21 which is an optical transmission unit and the EAM unit 23 which is a signal conversion unit. In order to integrate a large number of elements on one chip, it is usually inevitable to bend the optical waveguide when wiring a signal output from one element to the output section. It is known that when an optical waveguide is bent, light is emitted to a region outside the bending, which is called bending loss. This loss is smaller as it is gently bent (larger bend radius) and larger as it is bent more rapidly (lower bend loss). The magnitude of this loss is determined by the difference between the refractive index of the core portion of the optical waveguide and the refractive index of the cladding portion surrounding it. The greater the difference in the refractive index, the better the light is confined in the core part. Therefore, if the bending loss is small, the waveguide can be bent at a steeper angle, which is advantageous for downsizing of the chip. Also in the MMI coupler, the radiation loss of light can be suppressed as the refractive index difference between the core and the clad of the waveguide increases. Considering the waveguide structure used in the integrated portion from these viewpoints, it is considered that the ridge type and buried type optical waveguides have a large bending loss and are not suitable for the optical waveguide for integration. The high-mesa optical waveguide has a very large difference in refractive index between the core portion of the waveguide and the cladding portion in the lateral direction, can reduce bending loss, and can also suppress radiation loss in the MMI coupler. However, it is considered that InGaAsP is more suitable for the core portion of the optical waveguide than InAlGaAs, which has oxidation problems.

6 shows that the band gap wavelength of InGaAsP in the core layer 11 of the multiplexer unit 24 is 1.15 μm, the thickness of the core layer 11 is 0.3 μm, and the wavelength of light entering the multiplexer unit 24 is 1. It is a figure which shows the bending radius dependence of the bending loss of a ridge type | mold optical waveguide and a high mesa type | mold optical waveguide when it is 3 micrometers and a waveguide width is 1.5 micrometers. The allowable bending radius depends on the length of the optical wiring, but if the allowable bending loss is 10 ⁻⁴ dB / μm, the allowable bending radius is about 130 μm for the high-mesa optical waveguide and about 400 μm for the ridge-type optical waveguide. Thus, it can be reduced to about one third. If the band gap wavelength of the core layer 11 of the multiplexer unit 24 is too close to the oscillation wavelength of the laser, the loss due to absorption increases. Therefore, the band gap wavelength needs to be sufficiently shorter than that, and is about 100 nm shorter than the oscillation wavelength. If so, this absorption loss is not a problem. In this embodiment, since the oscillation wavelength is around 1.3 μm, the band gap wavelength of the core layer 11 needs to be shorter than about 1.2 μm. However, if the wavelength is too short, a difference in refractive index from the substrate cannot be obtained, making it difficult to produce a small optical waveguide structure. The band gap wavelength of the core layer 11 capable of producing an optical waveguide of the same size as that of the InP substrate 1 is usually 1.1 μm or more, which is compared with the laser having an oscillation wavelength of 1.3 μm in this embodiment. Thus, the optimum band gap wavelength of the core layer 11 is about 1.1 μm to 1.2 μm. In this embodiment, the band gap wavelength of the core layer 11 is 1.15 μm, but the same effect can be obtained if it is 1.1 μm or more.

FIG. 7 shows a structural diagram of the MMI coupler of the multiplexer unit 24. As shown in FIG. As shown in FIG. 7, the MMI coupler 150 includes four input ports 151, 152, and 153 including four input ports and one output port for condensing four wavelengths of light into one waveguide. , 154 and one output waveguide 155. The waveguide width of the MMI coupler 150 is W, and the width of the output waveguide 155 is W _hm . FIG. 8A shows a vertical cross-sectional electric field distribution at the core center of the ridge type MMI when the output waveguide width W _hm = 1.5 μm and the MMI width W = 20 μm. FIG. 8B shows a transverse cross-sectional electric field distribution at a propagation distance of 225 μm. FIG. 9A shows the vertical cross-sectional electric field distribution at the core center of the high mesa type MMI when the MMI width W = 20 μm. FIG. 9B shows the transverse cross-sectional electric field distribution at a propagation distance of 250 μm. As can be seen from these figures, the ridge type MMI coupler emits light in a large cross section, whereas the high mesa type MMI coupler has little light emission and can suppress radiation loss. .

In order to further reduce the wavelength dependence, an MMI coupler 160 composed of an MMI coupler body provided with a tapered structure in the input waveguides 161 to 164 and the output waveguide 165 as shown in FIG. 10 is used. The widths of the input waveguides 161 to 164 and the output waveguide 165 are formed so as to gradually increase toward the MMI coupler main body. Here, the waveguide width at the input / output end of the MMI is W _taper . 11A and 11B show the MMI of the coupling efficiency from the input port to the output port at four wavelengths (1295 nm, 1300 nm, 1305 nm, and 1310 nm) when W _taper = 2.0 μm and 2.5 μm. Each shows the length dependence. From these figures, it can be seen that the wavelength dependency is reduced by increasing W _taper . However, if W _taper is too large, the distance between adjacent waveguides becomes narrow, making it difficult to manufacture. In an ordinary photolithography process for producing an input / output waveguide of an MMI coupler, an accurate pattern cannot be transferred unless there is a size of at least 1 μm between the waveguides. In this case, since the four waveguides must be accommodated in a width of 5 μm, W _taper is optimally about 2.5 μm to 3 μm. In this embodiment, the length of the tapered portion is 100 μm.

Finally, the structure of the connecting portion between the ridge waveguide and the high mesa structure will be described.
12A and 12B show electric field distributions of the ridge waveguide and the high mesa waveguide, respectively. As is clear from the figure, the electric field distributions of the two waveguides are very different, so that simply by butt joint coupling, the coupling loss increases and becomes a reflection point. In such a case, a method of adiabatically converting the electric field distribution using a tapered optical waveguide 130 as shown in FIG. The optical waveguide 130 is connected to the ridge type optical waveguide 141 and to the high mesa type optical waveguide 142. The width of one end 131 of the optical waveguide 130 is formed to be the same as the width W _ridge of the ridge type optical waveguide 141. The width of the other end 132 of the optical waveguide 130 is formed to be the same as the width W _hm of the high mesa optical waveguide 142. The width of the optical waveguide 130 is formed so as to gradually narrow from one end 131 toward the other end 132. However, as shown in FIG. 12A, the electric field distribution of the ridge-type waveguide is distributed in a wider range under the ridge mesa than the ridge mesa, and therefore, in the tapered structure optical waveguide 130 as shown in FIG. The light distributed outside the mesa is lost.

Therefore, in this embodiment, a discontinuous tapered structure joint as shown in FIG. 14 is used. As shown in FIG. 14, the discontinuous taper structure joint portion is an optical waveguide in contact with the ridge-type optical waveguide 41 and the high mesa optical waveguide 42, and has a predetermined length L _taper and a discontinuous taper structure joint body 50. Consists of. One end 51 of the discontinuous tapered structure joint body 50 is in contact with one waveguide 41, and the other end 52 of the discontinuous taper structure joint body 50 is in contact with the other waveguide 42. One waveguide 41 has a structure in which the lateral spread of light guided through the one waveguide 41 is wider than the lateral spread of light guided through the other waveguide 42. have. The mesa height of one optical waveguide 41 is formed lower than the mesa height of the other optical waveguide. The width of the discontinuous taper structure joint body 50 is formed so as to gradually narrow from one end 51 toward the other end 52. The width W _taper of one end 51 in the discontinuous tapered structure joint body 50 is formed wider than the width W _ridge of one waveguide 41. With such a discontinuous tapered structure joint body 50, the width of the high mesa optical waveguide is widened at the joint of one waveguide 41, which is a ridge optical waveguide, and the other waveguide 42, which is a high mesa optical waveguide. By doing so, the light distributed outside the mesa in the ridge structure can also be taken into the high mesa waveguide. The discontinuous taper structure junction is manufactured by a mesa formation process for a high mesa waveguide, and the mesa height of the discontinuous taper structure main body 50 is the same as the mesa height of the other waveguide 42. is there. In FIG. 14, mesas involved in light guiding in the waveguides 41 and 42 and the optical waveguide body 50 with the discontinuous taper structure are illustrated, and the other portions are not shown.

FIG. 15 shows the taper width W _taper dependence of the coupling efficiency of the ridge type optical waveguide and the high mesa type optical waveguide at the joint portion of the discontinuous taper structure. As shown in FIG. 15, when the taper width W _taper , that is, the width of one end 51 of the discontinuous tapered structure joint body 50 is increased, the coupling efficiency increases, and the coupling efficiency decreases above a certain width. . From FIG. 15, it is understood that the taper width W _taper may be set to 2.0 μm or more and 2.8 μm or less in order to obtain a coupling efficiency of 95% or more.

FIG. 16 shows the taper length dependence of the coupling efficiency when the _taper width W _taper = 2.5 μm in the discontinuous taper structure joint. When the taper length L _taper is 40 μm or more, the coupling efficiency is saturated, and when the taper length L _taper is 20 μm, a coupling efficiency of 95% or more is obtained, and when the taper length L _taper is 40 μm or more, it becomes 98% or more. I understand that. However, since there is a loss of the optical waveguide itself, if it is too long, the waveguide loss will increase. Therefore, it is preferable that the optical waveguide be at most about 100 μm. Similarly, the taper length L _taper of the MMI coupler 160 having the tapered input / output waveguides 161 to 164 and 165 shown in FIG. 10 may be set to 40 μm or more.

FIG. 17 shows an appearance of an element manufactured based on the optical semiconductor device having the above-described configuration. The chip size could be suppressed to a very small size of 2 × 2.6 mm ² by using a high mesa waveguide in the multiplexer section. If a ridge-type waveguide is used for the multiplexer unit, it is necessary to have at least three times the size from the estimation of bending loss. FIG. 18 shows an oscillation spectrum of each semiconductor laser portion of an element manufactured based on the optical semiconductor device having the above-described configuration. As shown in FIG. 18, it can be seen that the laser can be operated within the wavelength range required by the 100 GbE standard by adjusting the period and depth of the diffraction grating in the semiconductor laser portion included in the optical semiconductor device.

  FIG. 19 shows a static extinction ratio of an element manufactured based on the optical semiconductor device having the above-described configuration. All measurements were performed at 40 ° C., slightly above room temperature, to reduce module power consumption. A static extinction ratio of 16 dB or more was obtained at all four lane wavelengths, and as shown later, it was found that the value was sufficient to obtain a dynamic extinction ratio of 8 dB. FIG. 20 shows a small signal response of an element including the above-described optical semiconductor device. As shown in FIG. 20, by using a ridge structure waveguide in which both sides are embedded with BCB, a 3 dB band of about 20 GHz can be obtained in all four lanes, which is sufficient for 25 Gbit / s modulation. I understand that. FIG. 21 shows the bias voltage dependence of the dynamic extinction ratio of the electroabsorption optical modulator section when the modulation speed is 25 Gbit / s and the modulation amplitude is 2V. As shown in FIG. 21, the dynamic extinction ratio 4 dB required for the LR 4 is obtained in all the displayed ranges, and it can be seen that any place can be used. Further, the dynamic extinction ratio 8 dB required for ER4 is satisfied in all lanes with a bias voltage of −2V. If the bias voltage is set to −2V, the operation of the bias voltage and the modulation amplitude is constant with the modulation amplitude of 2V. It turns out that it is possible. In the conventional EAM unit, when the operating wavelength is different, it is common knowledge that the driving is performed by changing the bias voltage. However, by appropriately designing, the bias voltage can be applied over a wide wavelength range of 15 nm with one structure. It can be seen that constant modulation amplitude control is possible. This means that control of the manufactured device is simplified. As described above, the performance required for the LR4 and ER4 standards of 100 GbE is obtained by using an InAlGaAs-based tensile strain quantum well based on an appropriate design according to the present embodiment and an organic waveguide embedded ridge structure optical waveguide in the EAM portion. In addition, it has been proved that the bias voltage and voltage amplitude constant operation can be performed without changing the bias voltage according to the operating wavelength, which is common sense in the conventional EAM.

  Therefore, according to the optical semiconductor device of the present embodiment, the light source and the multiplexer unit 24 are monolithically integrated on one chip, and the bias voltage and voltage amplitude of the EAM unit 23 can be controlled at a constant level. It becomes possible to realize light sources for LR4 and ER4, and members and power consumption necessary for the configuration of the transmitter are reduced to about a quarter, and a large industrial effect can be obtained.

  Note that polyimide can be used as the organic materials 115 and 125 having a low dielectric constant in addition to BCB.

  An optical semiconductor device according to the second embodiment of the present invention will be described with reference to FIG. 2, FIG. 22, and FIG.

  The monolithic integrated light source for 100 GbE, which is an optical semiconductor device according to the present embodiment, has a configuration in which four lanes 31A, 31B, 31C, and 31D are provided on a substrate 1 made of a semiconductor mixed crystal, as shown in FIG. ing. Each of the lanes 31A to 31D is provided with a photodiode portion (PD portion) 25, an LD portion 21, and an EAM portion 23. The PD portion 25, the LD portion 21, and the EAM portion 23 are disposed on the same substrate 1 via an optical waveguide. Connected on. The four LD units 21 are devices that emit signals having different wavelengths. In the four lanes 31 </ b> A to 31 </ b> D, light guided through the lanes 31 </ b> A to 31 </ b> D is multiplexed into one by a multimode interference coupler (MMI coupler) which is a multiplexer unit 24.

In the optical semiconductor device according to this example, the core portion of the passive layer included in the optical semiconductor device according to the first example described above is not a layer structure similar to that of the EAM portion, but In _1-x Ga _x As _y. The P _1-y bulk configuration is the same as that of the optical semiconductor device according to the first embodiment described above. Here, the optimum band gap wavelength of the In _1-x Ga _x As _y P _1-y bulk is 1.1 μm to 1.2 μm based on the discussion of the multiplexer unit 24 in the first embodiment described above. It becomes.

Next, a method for manufacturing a 100 GbE monolithic integrated light source, which is an optical semiconductor device according to this embodiment, will be described.
In the case of the optical semiconductor device according to the present embodiment, when the core part 11 of the multiplexer unit 24 is regrown after the active part 5 of the EAM part 23 is regrown with the butt joint, the LD part 21 and the EAM The portion 23 is again etched by wet etching, and then an InGaAsP bulk having the same composition as that of the multiplexer portion 24 is regrown. Other manufacturing processes are the same as those in the first embodiment.

  22A and 22B are cross-sectional views of the optical semiconductor device according to the present invention. FIG. 22A shows the case of the first embodiment, and FIG. 22B shows the case of the second embodiment. In FIG. 22, only the LD portion 21, the passive layers 22 and 26, and the EAM portion 23 are illustrated. As shown in FIG. 22A, in the case of the optical semiconductor device according to the first embodiment, the same layer as the EAM portion 23 is regrowth as the optical waveguide layer structure of the passive layer 22, that is, a plurality of Therefore, in the vicinity of the end face of the butt joint, it is difficult to control the composition, the crystal quality is deteriorated, and the shape is also deteriorated. This degrades the coupling efficiency between the LD unit 21 and the EAM unit 23 and also reduces long-term reliability. However, in the optical semiconductor device according to the present embodiment, as shown in FIG. 22B, the upper layer of the lower cladding portion 10 in the passive layer 26 between the LD portion 21 and the EAM portion 23 is etched away to remove the bulk. The core portion 18 is produced by re-growing the crystal. As described above, the core portion 18 made of a bulk material having a single composition and a single layer structure of the optical waveguide layer is easier to control the composition and the film thickness. The composition variation at the growth interface is also reduced.

  FIG. 23 is a diagram for explaining the flow of photocarriers generated in the electro-absorption optical modulator unit included in the optical semiconductor device. FIG. 23A shows the case of the first embodiment. FIG. 23B shows the case of the second embodiment. In the optical semiconductor device according to the first embodiment, as shown in FIG. 23A, the passive layer 22 has the same layer structure as the EAM portion 23, and the photocarriers 60 generated in the EAM portion 23 are formed in the passive layer 22. Enters and adversely affects modulation characteristics. On the other hand, in the optical semiconductor device according to this example, as shown in FIG. 23B, the passive layer 26 of the photocarrier 60 is replaced by replacing the core portion 18 of the passive layer 26 with a bulk material having a large band gap. This is advantageous for high-speed modulation because it is possible to reduce the entry of the core 18 into the core portion 18.

  The present invention relates to an optical semiconductor device, and can realize a light source for LR4 and ER4 of 100 GbE, and can be downsized, reduced in cost, and reduced in power consumption. It can be used beneficially.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Active part 3 of multiple quantum well structure 3, 4 Clad part 5 Active part 6 of multiple quantum well structure 6, 7 Clad part 8 Core part 9, 10 Clad part 11 Core part 12, 13 Clad part 14 Lower electrode 15 Contact layer 16 Upper electrode 18 Core part 21 Semiconductor laser active part (LD part)
22 Passive layer (optical waveguide)
23 Electroabsorption optical modulator (EAM)
24 Multiplexer 25 Photodiode (PD)
26 Passive layer (optical waveguide)
31A to 31D Lane 50 Discontinuous tapered structure joint body 51 One end 52 The other end 60 Photocarrier 160 Tapered MMI couplers 161 to 164 Input waveguide 165 Output waveguide

Claims (12)

A plurality of semiconductor laser portions provided on a substrate made of a semiconductor mixed crystal and having different oscillation wavelengths, and a plurality of semiconductor laser portions provided for each of the plurality of semiconductor laser portions, for modulating signals emitted from the plurality of semiconductor laser portions. A light source comprising an electroabsorption optical modulator part, a core part and a clad part provided above and below the core part, and a combiner part for combining signals emitted from the light source into one An optical semiconductor device having a formed configuration,
The semiconductor mixed crystal of the substrate is InP,
The semiconductor laser part has an active part of a multiple quantum well structure including a quantum well layer, a barrier layer, and a diffraction grating forming layer, and a cladding part provided above and below the active part,
The electroabsorption optical modulator portion has an active portion of a multiple quantum well structure including a quantum well layer, a barrier layer, and an optical confinement layer, and a cladding portion provided above and below the active portion,
The well layer and the barrier layer in the active part of the electroabsorption optical modulator part are In _1-xy Al _x Ga _y As,
The active portion of the electro-absorption optical modulator has a quantum well number of 7 to 9, a strain amount of the quantum well layer of 0.17% to 0.73% (plus sign is tensile strain), and a barrier Ri 1.05μm der band gap wavelength from 0.9μm of layer,
The upper cladding portions of the plurality of semiconductor laser portions and the plurality of electroabsorption modulator portions are p-InP, and the upper cladding portion of the multiplexer is non-doped InP. An optical semiconductor device. A photodiode is provided on the end side of the semiconductor laser portion, and the photodiode has the same layer structure as the semiconductor laser portion.
The optical semiconductor device according to claim 1. Provided between the semiconductor laser part and the electroabsorption optical modulator part on the substrate, and having a core part and cladding parts provided above and below the core part, and the semiconductor laser part and the Comprising a passive layer that electrically insulates the electroabsorption optical modulator section;
The core portion of the passive layer has the same multiple quantum well structure as the active portion of the electroabsorption optical modulator portion, or an In _1-x Ga _x As _y P _{1 having a} band gap wavelength of 1.1 μm to 1.2 μm. 3. The optical semiconductor device according to claim 1, wherein the optical semiconductor device is a _-y bulk. The quantum well layer of the active part of the semiconductor laser part has a thickness and strain that achieves the wavelength selected from a material having a wavelength that maximizes the room temperature gain of 1.25 μm to 1.35 μm. the optical semiconductor device according to any one of claims 1 to 3, characterized in that. The diffraction grating forming layer of the active part of the semiconductor laser part is formed with a diffraction grating having a depth and a period with a Bragg wavelength of 1.29 μm to 1.31 μm at 40 to 50 ° C. The optical semiconductor device according to any one of claims 1 to 4 , wherein the optical semiconductor device is characterized in that: The quantum well layer of the active part of the electroabsorption optical modulator part has a thickness that achieves a wavelength at which the absorption edge wavelength at room temperature is 40 nm to 80 nm shorter than the black wavelength. The optical semiconductor device according to claim 5 . The semiconductor laser section, the electroabsorption optical modulator section, and the passive layer each have an optical waveguide having a ridge structure, and both sides thereof are embedded with an organic material having a dielectric constant smaller than that of a semiconductor. the optical semiconductor device according to any one of claims 3 to 6,. The core layer of the multiplexer unit of claim 1 to claim 7 bandgap wavelength is characterized in that the 1.2μm of _{In 1-x Ga x As y} P 1-y bulk from 1.1μm The optical semiconductor device according to any one of the above. The multiplexer unit has an optical waveguide of high mesa structure, any one of claims 1 to 8, characterized in that embedded the both sides in small organic material dielectric constant than the semiconductor An optical semiconductor device according to item. The optical semiconductor device according to any one of claims 1 to 9, wherein the multiplexer unit includes an input / output waveguide having a tapered structure. 11. The optical semiconductor device according to claim 1, wherein the light source and the multiplexer unit are connected via a joint portion having a discontinuous taper structure. An optical semiconductor device control method for controlling an optical semiconductor device according to any one of claims 1 to 11 ,
A method for controlling an optical semiconductor device, characterized in that, when driving the plurality of electroabsorption optical modulator sections, the bias voltage and the voltage amplitude are made constant.