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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.


Baba T.,Photonics Electronics Technology Research Association PETRA | Baba T.,Japanese Institute for Photonics Electronics Convergence System Technology | Akiyama S.,Photonics Electronics Technology Research Association PETRA | Akiyama S.,Japanese Institute for Photonics Electronics Convergence System Technology | And 12 more authors.
Optics Express | Year: 2013

We achieved 50-Gb/s operation of a ring-resonator-based silicon modulator for the first time. The pin-diode phase shifter, which consists of a side-wall-grating waveguide, was loaded into the ring resonator. The forward-biased operation mode was applied, which exhibited a VπL as small as 0.28 V·cm at 25 GHz. The driving voltage and optical insertion loss at 50-Gb/s were 1.96 Vpp and 5.2 dB, respectively. © 2013 Optical Society of America.


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


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.


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.


Okayama H.,Oki Electric Industry Co. | Okayama H.,Photonics Electronics Technology Research Association PETRA | Onawa Y.,Oki Electric Industry Co. | Onawa Y.,Photonics Electronics Technology Research Association PETRA | And 6 more authors.
Optics Express | Year: 2014

We report polarization independent Bragg grating wavelength filter using polarization rotation. A non-vertical waveguide sidewall and antisymmetric grating structure can be used to generate the polarization rotation of the fundamental modes. The diffraction efficiencies and peaks becomes the same for two orthogonal input polarizations. The concept was verified by simulation and experiment. © 2014 Optical Society of America.


Uemura H.,Photonics Electronics Technology Research Association PETRA | Kurita Y.,Photonics Electronics Technology Research Association PETRA | Furuyama H.,Photonics Electronics Technology Research Association PETRA
European Solid-State Circuits Conference | Year: 2015

In order to realize reliable OOB (Out-of-Band) transmission which is a major problem in optically connected SATA (Serial ATA) or SAS (Serial Attached SCSI), 12.5 Gb/s driver and receiver ICs with a newly-developed double threshold AGC were fabricated by TSMC 90 nm CMOS process. The double threshold AGC realized the rejection of small noise in a transmission line in an idle condition and the suppression of long decay in the end of a burst, and highly reliable optical OOB transmission was achieved. Optically connected SATA 6 Gb/s system operation was demonstrated for the first time in the world. © 2015 IEEE.


Akiyama S.,Photonics Electronics Technology Research Association PETRA | Imai M.,Photonics Electronics Technology Research Association PETRA | Baba T.,Photonics Electronics Technology Research Association PETRA | Akagawa T.,Photonics Electronics Technology Research Association PETRA | And 7 more authors.
IEEE Journal on Selected Topics in Quantum Electronics | Year: 2013

We developed PIN-diode-based silicon Mach-Zehnder modulators, which have side-wall-gratings in the phase-shifter sections. Such passive waveguides with gratings were fabricated using ArF immersion lithography, which showed a small scattering loss of 0.4 dB/mm. We extensively investigated the forward-biased operation of the modulators by using equivalent circuit analysis and the measurement of the fabricated devices. We argue carrier recombination time only plays a minor role for the overall performance of the modulator. Dependences of the modulation efficiency on other various critical parameters are discussed. In particular, if we use relatively short phase shifter, the forward-biased operation provides smaller VπL than reversed one even at high frequency of 20 GHz, at the expense of the narrow bandwidth. Our approach enables high-speed operation up to 50 Gb/s, by using phase shifter as short as 250 μm and preemphasis signals. For 12.5-Gb/s operation, the modulator cell size was only 300 μm × 50 μm, which was suitable for the applications of high-density optical interconnects. © 1995-2012 IEEE.


Saito S.,Photonics Electronics Technology Research Association PETRA | Saito S.,Japanese Institute for Photonics Electronics Convergence System Technology | Saito S.,Hitachi Ltd. | Oda K.,Photonics Electronics Technology Research Association PETRA | And 7 more authors.
Applied Physics Letters | Year: 2011

We propose a germanium fin light-emitting diode for a monolithic light source on a Si photonics chip. The germanium fins were fabricated by the oxidation condensation of silicon-germanium sidewalls epitaxially grown on silicon fins. We found that a tensile stress is applied to the pure germanium fins by the difference of the thermal expansion coefficient with that of the surrounding oxide. The electroluminescence spectra were consistent with those expected from direct recombination in germanium with a tensile stress. The strong immunity of germanium fins against high current densities would be favourable to achieve population inversions by electrical pumping. © 2011 American Institute of Physics.


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.

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