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Usuki T.,Photonics Electronics Technology Research Association PETRA
2013 International Symposium on Electromagnetic Theory, EMTS 2013 - Proceedings | Year: 2013

We developed a frequency domain simulator using the Yee lattice, which is compatible with the FDTD method. An S-matrix approach for quantum physics was applied to this simulator for the first time, as far as we know. It can then obtain arbitrary S-matrix elements where the S-matrix always satisfies unitarity within numerical error less than 10-8 for double precision format. © 2013 IEICE. Source

Srivastava A.,NTT Electronics | Onaka H.,Photonics Electronics Technology Research Association PETRA
European Conference on Optical Communication, ECOC | Year: 2015

Low power DSP has enabled 100G and 400G coherent fiber optic systems. Photonic integration of optical components combined with optical impairment mitigation capability of DSP have led to smaller footprint MSA and CFP 100G modules for core and metro networks. © 2015 Viajes el Corte Ingles, VECISA. Source

Kim Y.,University of Tokyo | Fujikata J.,Photonics Electronics Technology Research Association PETRA | Takahashi S.,Photonics Electronics Technology Research Association PETRA | Takenaka M.,University of Tokyo | Takagi S.,University of Tokyo
Optics Express | Year: 2015

We demonstrate a strained SiGe variable optical attenuator (VOA) with a lateral pin junction which exhibits record-low injectioncurrent for 20-dB attenuation. We optimize the distance between the highly doped p + and n + regions in the lateral pin junction to effectively inject electrons and holes, taking into account the propagation loss. In conjunction with the enhanced free-carrier absorption in strained SiGe, the SiGe VOA with the optimized lateral pin junction exhibits 20-dB attenuation by 20-mA/mm injection current, which is 1.5 times lower current density than that of the Si VOA. The SiGe VOA also shows better RF response than the Si VOA due to the short carrier lifetime in SiGe, allowing us to achieve efficient and fast attenuation modulation simultaneously. Furthermore, 2-GHz switching and error-free transmission of 4 × 12.5 Gbps WDM signal have been also achieved. © 2015 Optical Society of America. Source

Fukamachi T.,Opnext Japan Inc. | Adachi K.,Hitachi Ltd. | Adachi K.,Photonics Electronics Technology Research Association PETRA | Shinoda K.,Hitachi Ltd. | And 6 more authors.
IEEE Journal on Selected Topics in Quantum Electronics | Year: 2011

High-speed 1.3-μm directly modulated lasers (DMLs) have been developed to support sharply rising optical communications traffic. The most crucial requirement for these lasers is the ability to operate over a wide temperature range with no power-consuming electric cooler. Due to poor temperature characteristics resulting from its poor electron confinement in the multiquantum well, DMLs with InGaAsP material systems have been replaced by DMLs with InGaAlAs material systems, which have stronger electron confinement. In this paper, progress in uncooled 25-Gb/s 1.3-μm InGaAlAs DMLs is summarized. A 160-μm-long ridge-waveguide-type laser showed a lower threshold current Ith of 14.9 mA at high temperatures up to 95°C, and a small signal-frequency-response bandwidth f3dB of 14 GHz was achieved at a bias current of 60 mA at 95°C. Using this laser, clear 25-Gb/s operation was obtained at 95°C. In addition, stable operation was achieved for up to 4000 h at 85°C, indicating the basic applicability of the device to next-generation 25-Gb/s data communication systems. Furthermore, the developed technology was applied to a novel uncooled 25-Gb/s 1.3-μm surface-emitting laser for optical interconnects, in which a 45° mirror and a lens were integrated monolithically. © 2011 IEEE. Source

Horikawa T.,Photonics Electronics Technology Research Association PETRA | Horikawa T.,Japan National Institute of Advanced Industrial Science and Technology | Shimura D.,Photonics Electronics Technology Research Association PETRA | Mogami T.,Photonics Electronics Technology Research Association PETRA
MRS Communications | Year: 2016

Low-propagation-loss silicon wire waveguides are key components of optical integrated circuits. In this paper, we clarified, through assessment of the relationship between waveguide loss and fabrication technology that high-resolution lithography and an adjusted lithography process window are important for low-loss waveguides. The silicon wire waveguides fabricated by high-resolution lithography technology using ArF immersion lithography process showed world-record low propagation losses of 0.40 dB/cm for the C-band and 1.28 dB/cm for the O-band. Analysis with Barwicz and Haus's theory indicated that sidewall scattering is the main cause of propagation loss even in such low-loss waveguides. Copyright © Materials Research Society 2016 Source

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