Haruhiko Kuwatsuka

Large current MOSFET on photonic silicon-on-insulator wafers and its monolithic integration with a thermo–optic 2 × 2 Mach–Zehnder switch

n-channel body-tied partially depleted metal-oxide-semiconductor field-effect transistors (MOSFETs) were fabricated for large current applications on a silicon-on-insulator wafer with photonics-oriented specifications. The MOSFET can drive an electrical current as large as 20 mA. We monolithically integrated this MOSFET with a 2 × 2 Mach-Zehnder interferometer optical switch having thermo-optic phase shifters. The static and dynamic performances of the integrated device are experimentally evaluated.

First demonstration of ultra-low-energy hierarchical multi-granular optical path network dynamically controlled through NSI-CS for video related applications

We developed ODU-XC, CDC-ROADM, and silicon photonics switch, and built an eight-node network capable of 90Tbps based on NSI-CS standard protocol. Its energy consumption was orders of magnitude lower than that achievable with IP routers.

Ultrafast electron dynamics of intersubband excitation concerning cross-phase modulation in an InGaAs/AlAs/AlAsSb coupled double quantum well

The ultrafast electron dynamics accompanying intersubband excitation in an InGaAs/AlAs/AlAsSb double quantum well has been investigated by femtosecond pump-probe spectroscopy. The photoinduced changes in the refractive index that causes cross-phase modulation is dominated by a decreased number as well as increased temperature of the electrons in the lower conduction subbands. The change in the number of conduction electrons decays monotonically, whereas the change in the electron temperature exhibits a maximum at around 0.9 ps after the photoexcitation. Heating of the conduction electrons is caused by their excess energy after intersubband longitudinal-optical phonon scattering.

Sub-millisecond timing-jitter-free tuning of parametric dispersion compensator.

We demonstrate sub-millisecond tuning of a prototype parametric tunable dispersion compensator (P-TDC) based on cascaded polarization-diverse four-wave mixing (FWM) process with a fast tunable and highly wavelength-stable pump light source. The pump light source is developed using a tunable distributed amplification chirped sampled grating distributed reflector laser that is fully wavelength tunable by on-chip heaters with a 3-dB frequency response of 45 kHz, resulting in fast dispersion tuning of less than 50 μs without additional timing jitter. The P-TDC is developed as the first prototype to satisfy essential requirements for practical network uses: stable input-polarization diversity, input-wavelength preservation, and seamless dispersion tunability for entire C-band input wavelengths are simultaneously achieved.

Parametric Tunable Dispersion Compensation With Spectrally Noninverting Wavelength Conversion Using Quasi-Phase-Matched Adhered Ridge Waveguide

We develop a highly efficient quasi-phase-matched adhered ridge waveguide (QPM-ARW) in LiNbO3 as a nonlinear material, and demonstrate tunable wavelength conversion without spectral inversion (SI) and parametric tunable dispersion compensation for a single-mode fiber (SMF) link. The QPM-ARW module with a second harmonic generation efficiency of 700 %/W achieves tunable wavelength conversion with a wavelength-tuning range of at least 25 nm through cascaded sum- and difference-frequency generation (SFG-DFG) process in which the signal and pumps are located symmetrically around the phase matching wavelength. The power penalty of the wavelength conversion is less than 0.6 dB for 43-Gb/s nonreturn-to-zero on-off-keying (NRZ-OOK) signals. We then apply the tunable wavelength conversion without SI to the parametric tunable dispersion compensation scheme, and achieve successful optical tunable dispersion compensation in 43-Gb/s NRZ-OOK transmissions over 53.2-km SMF.

Dynamic parametric dispersion compensation using FPGA pump controller and dispersion monitor

We demonstrate an autonomous fast parametric dispersion compensator with a fast TDA-CSG-DR laser and a dispersion monitor based on spectral shearing interferometer. A response time of less than 17 ms, potentially sub millisecond, is achieved.

Optical-comb-line selection from a low-power/low-OSNR comb using a low-coherence semiconductor laser for flexible ultra-dense short range transceivers

6.25GHz-spaced optical-comb-line selection either by low-coherence injection-locked laser (LC-ILLD) or with a combination ultra-narrow-filter and low-noise-fiber-amplifier (UNF-FA) is assessed. In a 144Gbps DP-64QAM transmission the LC-ILLD outperforms the UNF-FA approach for comb-OSNR-levels below 30dB.

Dynamic optical path switching of 172-Gbit/s OTDM ultra-high definition video signals using fast channel-identifiable clock recovery and integratable devices

Dynamic optical switching was first demonstrated in 172-Gbit/s OTDM transmissions of real ultra-high definition video signals, using truly in-band clock distribution with channel identification and newly developed CMOS-based transceivers, quantum-dot SOAs, monolithic ISBT all-optical gate.

Full-band injection-locking properties of a monolithically integrated tunable laser with single stripe structure

Full-band injection-locking properties of a high power, low phase noise, tunable monolithically integrated CSG-DR-LD are investigated. An average injection-locking range of 2.5GHz at optical injection ratios of -22dB is obtained. These characteristics make the CSG-DR-LD a highly promising light source for future tunable coherent receivers.

Power-efficient gray-scale control of silicon thermo-optic phase shifters by pulse width modulation using monolithically integrated MOSFET

We first-time demonstrate gray-scale control by pulse-width modulation for silicon thermo-optic (TO) phase shifters using monolithic MOSFET. This work enables simple and power efficient control of TO modules without using DAC and analog current drivers.