Papers - ARAI Masakazu
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InGaAs metamorphic laser for low-power-consumption operation
Arai M., Kobayashi W., Kohtoku M.
NTT Technical Review 10 ( 12 ) 2012.12
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：NTT Technical Review
In this article, we review our efforts to reduce the power consumption of optical transmitter modules for Ethernet and telecommunications use. To reduce the power consumption, we aim to eliminate the light source's temperature controller and improve the stability of the output power and modulation characteristics under ambient temperature conditions. We describe a 1.3-μm-range metamorphic laser on a GaAs substrate that exhibits improved temperature characteristics. It has a characteristic temperature of 220 K and is capable of lasing up to 200°C. In addition, the bias current for 10-Gbit/s modulation at high temperature has been reduced. This laser is promising for uncooled light sources operating with low power consumption.
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Fujisawa T., Yamanaka T., Tadokoro T., Fujiwara N., Arai M., Kobayashi W., Kawaguchi Y., Tsuzuki K., Kano F.
IEEE Journal of Quantum Electronics 47 ( 1 ) 60 - 65 2011
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：IEEE Journal of Quantum Electronics
We have found that the extinction ratio (ER) of an electroabsorption modulator integrated with a distributed feedback laser strongly depends on the incident power to the modulator. Our theoretical consideration based on full device simulation reveals that the temperature change in the modulator dominates the phenomenon. To obtain the intrinsic extinction characteristics of the modulator, we use microscopic theory, which takes into account quantum mechanical many-body interactions in semiconductors and makes it possible to exclude unknown experimental fitting parameters. A heat-flux analysis is performed for the calculation of the temperature distribution in the entire device. As the incident power to the modulator increases, the photocurrent also increases, leading to an increase in the temperature of the modulator by some tens of degrees Celsius by Joule heating. The increase red-shifts the absorption spectrum of the modulator, and the detuning, which is the difference between the lasing wavelength and the band-edge wavelength of the modulator, becomes small, leading to a larger ER. The calculated results are in good agreement with the experiment, showing the validity of our discussion, and indicate that the ER of electroabsorption modulators is strongly affected by the internal heating of the device. © 2010 IEEE.
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Kobayashi W., Arai M., Fujiwara N., Fujisawa T., Tadokoro T., Tsuzuki K., Yamanaka T., Kano F.
Technical Digest - 15th OptoElectronics and Communications Conference, OECC2010 840 - 841 2010.11
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Technical Digest - 15th OptoElectronics and Communications Conference, OECC2010
10-Gb/s 80-km and 40-Gb/s 2-km SMF transmissions with low power penalty over wide temperature range are demonstrated with a 1.55-μm InGaAlAs EAM-integrated DFB laser. These devices are suitable for use as 10-/40-Gb/s uncooled light sources.
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Full C-band 10-Gb/s 40-km SMF transmission of InGaAlAs electroabsorption modulator
Kobayashi W., Fujiwara N., Yamanaka T., Tadokoro T., Fujisawa T., Shibata Y., Ishikawa M., Arai M., Tsuzuki K., Kano F.
Journal of Lightwave Technology 28 ( 20 ) 3012 - 3018 2010.10
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of Lightwave Technology
This paper describes the 10-Gb/s, full C-band (1530 to 1565 nm) operation of 1.55-μm electroabsorption modulators (EAMs) designed to eliminate the cost of a back up light source for a 10-Gb/s dense wavelength division multiplexing (DWDM) system. We employ InGaAlAs as the material for the EAM multiple-quantum well (MQW), and design it to achieve a sufficient extinction ratio and a low chirp (α) parameter over a wide wavelength range. A ridge waveguide buried in benzocyclobutene (BCB) is also introduced for the EAM waveguide. We design the width of the ridge waveguide and the thickness of a core layer that includes an MQW and separate confinement hetero-structure (SCH) layers by calculating the EAM capacitance. 6-well and 12-well based EAMs are fabricated to allow us to compare the wavelength dependence of their static/dynamic extinction ratios (SER/DER), and their small-signal electrical to optical (E/O) responses. We confirm that the 12-well based EAM provides a sufficient DER over the C band. We also determine that the wavelength detuning (Δλ) between an input light wavelength and an EA absorption peak is 100 nm at an input wavelength of 1530 nm, and evaluate the wavelength dependence of the chirp parameter, and the 40-km SMF transmission characteristics such as eye diagrams and the power penalty (PP). These experiments were conducted using a wavelength tunable laser while maintaining the input power of the EAM at about 13 dBm and changing the input wavelength over the C band. The EAM was also driven with a constant modulation voltage swing (VPP)of 2.0 V while changing only the EAM bias voltage (Vb). We also measured the input power dependence of the chirp parameter. These results show that the 12-well based InGaAlAs EAM is a promising candidate for an optical modulator that can be used over the C band in a low cost 10-Gb/s optical network system. © 2010 IEEE.
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Fujisawa T., Yamanaka T., Tadokoro T., Fujiwara N., Arai M., Kobayashi W., Kawaguchi Y., Tsuzuki K., Kano F.
Lasers and Electro-Optics/Quantum Electronics and Laser Science Conference: 2010 Laser Science to Photonic Applications, CLEO/QELS 2010 2010.10
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Lasers and Electro-Optics/Quantum Electronics and Laser Science Conference: 2010 Laser Science to Photonic Applications, CLEO/QELS 2010
Incident-power-dependent extinction ratio of electroabsorption modulators is shown and theoretically investigated by using microscopic theory combined with heat-flux calculation. The phenomenon stems from voltage-dependent temperature rise and the calculated results agree well with the experiment. © 2010 Optical Society of America.
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Growth of large platy InGaAs crystals and fabrication of semiconductor laser diodes
Kinoshita K., Yoda S., Arai M., Kawaguchi Y., Kondo Y., Kano F., Aoki H., Hosokawa T., Yamamoto S., Matsushima M.
Conference Proceedings - International Conference on Indium Phosphide and Related Materials 74 - 76 2010.8
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Conference Proceedings - International Conference on Indium Phosphide and Related Materials
We have succeeded in increasing size of InxGa 1-x As (x: 0.1 - 0.13) platy single crystals to 30 x30 mm 2 in surface area for mass production of laser diodes. Key points are to suppress convection in a melt and to keep constant temperature gradient for obtaining homogeneous crystals. Grown crystals have enough quality as substrates for 1.3 μm laser diodes. Fabricated laser diodes on these substrates were evaluated by measuring lasing characteristics at various temperatures and by measuring bit error rate for transmission through a single mode fiber up to 20 km. Lasers showed high temperature stability and error free transmission and showed the merit of ternary substrates.
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Fujisawa T., Arai M., Kano F.
Journal of Applied Physics 107 ( 9 ) 2010.5
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of Applied Physics
Electroabsorption in highly strained GaInAs and GaInNAs quantum wells (QWs) grown on GaInAs or quasi-GaInAs substrates is investigated by using microscopic many-body theory. The effects of various parameters, such as strain, barrier height, substrate composition, and temperature are thoroughly examined. It is shown that the value of the absorption coefficient strongly depends on the depth of the QWs under large bias electric field due to the small overlap integral of wave functions between the conduction and valence bands. The use of GaInNAs QWs makes the strain in the well layer very small. Further, the effective quantum-well depth is increased in GaInNAs QWs due to the anticrossing interaction between the conduction and N-resonant bands, making it possible to obtain larger absorption coefficient under large bias electric fields without using wide-band gap materials for barriers. © 2010 American Institute of Physics.
DOI： 10.1063/1.3360937
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Kobayashi W., Arai M., Yamanaka T., Fujiwara N., Fujisawa T., Tadokoro T., Tsuzuki K., Kondo Y., Kano F.
Journal of Lightwave Technology 28 ( 1 ) 164 - 171 2010.1
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of Lightwave Technology
This paper describes the wide temperature range operation of an electroabsorption modulator (EAM) integrated with DFB laser diodes (LDs) (EML) designed to reduce the power consumption and size of optical transmitters.We optimized the multiquantum wells (MQWs) for LD and EAM separately to realize uncooled operation. We employed a conduction band offset (ΔE c ) of around 250 meV for the LD and 150 meV for the EAM. The number of well layers was set at 6 for the LD and 12 for the EAM, respectively.We fabricated theEMLusing a butt-joint (BJ) process to allow us to design the LD and the EAM independently. We introduced a ridge waveguide structure for the LD and EAM waveguides, and designed the width of the LD and EAM mesa to achieve a high optical coupling efficiency between the LD and the EAM. We then used the 200- m-long EAM for 10-Gb/s operation and the 150-μm-long EAM for 40-Gb/s operation, and thus obtained a dynamic extinction ratio of over 9 dB at 10 Gb/s from -25 °C to 100 C and of 8.2 dB at 40 Gb/s from -15 to 80°C. We achieved a power penalty of less than 2 dB after an 80-km single-mode fiber (SMF) transmission at 10 Gb/s and a 2-km SMF transmission at 40 Gb/s over a wide temperature range. These results confirm the suitability of this EML with a BJ structure for use as a 10-Gb/s or 40-Gb/s uncooled light source. © 2009 IEEE.
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Fujisawa T., Arai M., Fujiwara N., Kobayashi W., Tadokoro T., Tsuzuki K., Akage Y., Iga R., Yamanaka T., Kano F.
European Conference on Optical Communication, ECOC 2009.12
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：European Conference on Optical Communication, ECOC
High-performance 1.3-μm InGaAlAs electroabsorption modulator integrated with DFB laser module for metro-area 100-Gbi/s Ethernet system (100GBASE-ER4) has been realized. Long-reach (40 km) error-free transmission under 25-Gbit/s operation on SMF is achieved for the first time. © VDE VERLAG GMBH.
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Kobayashi W., Arai M., Yamanaka T., Fujiwara N., Fujisawa T., Ishikawa M., Tsuzuki K., Shibata Y., Kondo Y., Kano F.
IEEE Photonics Technology Letters 21 ( 15 ) 1054 - 1056 2009.12
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：IEEE Photonics Technology Letters
We have developed a 1.55-μm uncooled electroabsorption modulator (EAM) integrated distributed-feedback laser with an InGaAlAs multiple quantum-well active/absorption stripe. These two components were directly butt-jointed using a simplified fabrication process. We demonstrated an 80-km single-mode fiber (SMF) transmission at 10 Gb/s over an extremely wide temperature range of 125°C (25°C-100°C) by adjusting only the bias voltage of the EAM depending on the temperature while keeping the modulation voltage swing constant at 2.5 V. We achieved a dynamic extinction ratio of over 9 dB and an 80-km SMF transmission with a power penalty of less than 2 dB over a wide temperature range. © 2009 IEEE.
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Kobayashi W., Yamanaka T., Arai M., Fujiwara N., Fujisawa T., Tsuzuki K., Ito T., Kondo Y., Kano F.
Conference Proceedings - International Conference on Indium Phosphide and Related Materials 367 - 370 2009.10
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Conference Proceedings - International Conference on Indium Phosphide and Related Materials
A 2-km 40-Gb/s transmission from -15 to 80°C is demonstrated using a 1.55-μm InGaAlAs EML for the first time. A powerpenalty below 2 dB with a dynamic extinction ratio of over 8.2 dB is achieved at -15°C.
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Uncooled (25-85 °c) 10-GbPs operation of 1.3-μm-range metamorphic InGaAs laser on gaas substrate
Arai M., Tadokoro T., Kobayashi W., Fujisawa T., Nakashima K., Yuda M., Kondo Y.
Conference Proceedings - International Conference on Indium Phosphide and Related Materials 226 - 229 2009.10
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Conference Proceedings - International Conference on Indium Phosphide and Related Materials
We have realized the first 10-Gbps direct modulation of a 1.3-μm-range laser diode with an InGaAs metamorphic buffer on a GaAs substrate. A 200-μm-long device had threshold currents as low as 5.2 and 11.4 mA at 25 and 85 °C, respectively. The maximum operating temperature was 135 °C. This excellent performance is attributed to the high quality InGaAs metamorphic buffer. ©2009 IEEE.
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Arai M., Tadokoro T., Fujisawa T., Kobayashi W., Nakashima K.
IEEE Photonics Technology Letters 21 ( 18 ) 1344 - 1346 2009.9
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：IEEE Photonics Technology Letters
We have realized 10-Gb/s direct modulation up to 100 C using a metamorphic InGaAs multiple-qunatum well (MQW) laser on a GaAs substrate. The highly strained InGaAs quantum well (QW) and strain-compensated GaAs barrier layer allowed 1.3-μ m-range lasing and an increased number of QWs (six). This laser with a 200-μm-long short cavity and a narrow ridge had maximum relaxation oscillation frequencies of 13 and 6 GHz at 25° C and 100 °C, respectively. A 10-km single-mode fiber error-free transmission was successfully obtained at a temperature of 85 ° C. © 2009 IEEE.
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Kobayashi W., Yamanaka T., Arai M., Fujiwara N., Fujisawa T., Tsuzuki K., Ito T., Tadokoro T., Kano F.
IEEE Photonics Technology Letters 21 ( 18 ) 1317 - 1319 2009.9
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：IEEE Photonics Technology Letters
We present the uncooled operation of a 1.55-μm 40-Gb/s InGaAlAs electroabsorption modulator (EAM) integrated distributed-feedback (DFB) laser within a temperature range of 95 °C (-15 ° C to 80 °C). To the best of our knowledge, this is the largest temperature range reported so far for such a 40-Gb/s EAM integrated DFB laser. We designed the EAM to operate at high speed by reducing the electrical parasitics, and we achieved a 3-dB frequency bandwidth of over 39 GHz for an EAM length of less than 150 m. We demonstrated a 2-km single-mode fiber (SMF) transmission at 40-Gb/s over a wide temperature range of 15 °C to 80 °C by adjusting only the bias voltage to the EAM while keeping the modulation voltage swing constant at 2.0 V when the temperature changed. We achieved a dynamic extinction ratio of over 8.2 dB and a 2-km SMF transmission with a power penalty of less than 2 dB over a wide temperature range. © 2009 IEEE.
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Fujisawa T., Arai M., Yamanaka T., Kondo Y., Kano F.
Journal of Applied Physics 105 ( 11 ) 2009.7
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of Applied Physics
Material properties of highly strained GaInNAs quantum wells grown on GaInAs or quasi-GaInAs substrates are investigated by using microscopic theory together with a band structure calculation based on ten-band kp theory specially formulated for highly strained materials. It is shown that the material gain of GaInNAs quantum wells is reduced by incorporating N into a well layer although the strain in the well layer becomes small. The reduction can be compensated by properly choosing barrier materials. The performance of laser diodes, such as characteristic temperatures T 0 and differential gains, is also investigated, and the present results show that very high T 0 (≃140 K) and differential gain with moderate strain (≃1.6%) can be achieved by carefully designing quantum well structures, indicating the applicability of these lasers for high-temperature and high-speed operation. © 2009 American Institute of Physics.
DOI： 10.1063/1.3126522
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Arai M., Nakashima K., Fujisawa T., Tadokoro T., Kobayashi W., Yuda M., Kondo Y.
IEEE Journal on Selected Topics in Quantum Electronics 15 ( 3 ) 724 - 730 2009.5
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：IEEE Journal on Selected Topics in Quantum Electronics
In this paper, we have newly developed an InGaAs metamorphic buffer on a GaAs substrate grown by metalorganic vapor-phase epitaxy, and realized a fully relaxed quasi-InGaAs substrate with low threading dislocation density. We have also successfully developed a 1.3-μ m-range ridge waveguide laser with InGaP upper cladding and InAlGaAs lower cladding layers. This laser has achieved the highest continuous-wave operating temperature (173° C) reported for a metamorphic laser. We measured the relaxation oscillation frequency from the relative intensity noise and undertook a 10-Gb/s direct modulation experiment. © 2006 IEEE.
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Arai M., Tadokoro T., Fujisawa T., Kobayashi W., Nakashima K., Yuda M., Kondo Y.
Electronics Letters 45 ( 7 ) 359 - 360 2009.4
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Electronics Letters
The first direct modulation of a 1.3m-range metamorphic laser diode on a GaAs substrate has been realised. A 200m-long device had threshold currents as low as 5.2 and 11.4mA at 25 and 85°C, respectively. This laser also achieved 10Gbit/s direct modulation up to 85°C. © 2009 The Institution of Engineering and Technology.
DOI： 10.1049/el.2009.0263
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10-Gbps direct modulation using a 1.31-μm ridge waveguide laser on an InGaAs ternary substrate
Arai M., Kobayashi W., Fujisawa T., Yuda M., Tadokoro T., Kinoshita K., Yoda S., Kondo Y.
Applied Physics Express 2 ( 2 ) 2009.2
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Applied Physics Express
We have realized a high-performance ridge waveguide laser diode on an InGaAs ternary substrate. To improve the thermal conductivity, we chose a low indium content (In: 0.13) InGaAs substrate and realized a 1.31-μm emission using highly strained InGaAs multiple-quantum-wells. The improved thermal conductivity of the substrate enables continuous wave operation even with a reduced ridge width and a short cavity length (L = 200 μm). These improvements led to the first demonstration of a 10-Gbps data transmission using a laser on an InGaAs ternary substrate. © 2009 The Japan Society of Applied Physics.
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Kobayashi W., Arai M., Yamanaka T., Fujiwara N., Fujisawa T., Ishikawa M., Tsuzuki K., Shibata Y., Kondo Y., Kano F.
Conference on Optical Fiber Communication, Technical Digest Series 2009
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Conference on Optical Fiber Communication, Technical Digest Series
An 80-km SMF transmission at 10-Gb/s using a 1.55-μm, InGaAlAs EML was demonstrated over an extended temperature range (-25°C to 100°C). A dynamic extinction ratio of over 9 dB at -25°C was obtained. © 2009 OSA.
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Kikuchi N., Shibata Y., Tsuzuki K., Yasui T., Ishikawa M., Ishii H., Arai M., Sato T., Kawaguchi Y., Kano F.
Conference on Optical Fiber Communication, Technical Digest Series 2009
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Conference on Optical Fiber Communication, Technical Digest Series
A traveling-wave-electrode InP n-p-i-n Mach-Zehnder modulator monolithically integrated with a semiconductor optical amplifier was developed. Loss-less operation and full C-band 40-Gbit/s DPSK modulation with a low driving voltage of 3 Vpp was successfully demonstrated. © 2009 OSA.