Hideaki Okayama

1.5 μm band efficient broadband wavelength conversion by difference frequency generation in a periodically domain‐inverted LiNbO3 channel waveguide

Efficient 1.5 μm band wavelength conversion by difference frequency generation (DFG) in a periodically domain‐inverted LiNbO3 channel waveguide is demonstrated, and DFG efficiency as high as 40% W−1 cm−2 is obtained. Nearly constant wavelength conversion efficiency has been confirmed over a broad wavelength range of 30 nm, which is the largest value ever reported.

First demonstration of high density optical interconnects integrated with lasers, optical modulators, and photodetectors on single silicon substrate

Optical interconnects integrated with lasers, silicon optical modulators and germanium photodetectors on a single silicon substrate were demonstrated for the first time. A 5 Gbps line bit rate and 3.5 Tbps/cm2 transmission density were achieved.

Wavelength conversions ∼1.5 μm by difference frequency generation in periodically domain‐inverted LiNbO3 channel waveguides

Wavelength conversions ∼1.5 μm are realized by difference frequency generation in periodically domain‐inverted LiNbO3 channel waveguides for the first time. A wide wavelength conversion bandwidth, which is very important for future wavelength division multiplexing optical communication system, is demonstrated in this kind of devices.

12.5-Gb/s operation with 0.29-V·cm V π L using silicon Mach-Zehnder modulator based-on forward-biased pin diode

We present high-speed operation of pin-diode-based silicon Mach-Zehnder modulators that have side-wall gratings on both sides of the waveguide core. The use of pre-emphasis signals generated with a finite impulse response digital filter was examined in the frequency domain to show how the filter works for different filter parameter sets. In large signal modulation experiments, V(π)L as low as 0.29 V·cm was obtained at 12.5 Gb/s using a fabricated modulator and the pre-emphasis technique. Operation of up to 25-Gb/s is possible using basically the same driving configurations.

Optical switch matrix with simplified N*N tree structure

Optical switch matrices with compact size and excellent crosstalk characteristics are discussed. Novel architectures for optical switch matrices are obtained by condensing the structure of N*N tree structure. 4*4 switches fabricated on LiNbO/sub 3/ substrates are discussed. >

Second‐harmonic generation device with integrated periodically domain‐inverted regions and distributed Bragg reflector in a LiNbO3 channel waveguide

We propose a new structure of LiNbO3 guided wave second‐harmonic generation device, in which the fundamental light beam is sufficiently confined by two distributed Bragg reflectors (DBRs) formed at input and output ports. The 40% increase in the conversion compared with a conventional device without DBR was achieved under a quasi‐phase matching condition.

Photorefractive damage of LiNbO3 quasiphase matched wavelength converters

Photorefractive damage (PRD) of LiNbO3 quasiphase matched (QPM) wavelength converters is studied by a novel two-beam method, in which the second-harmonic generation (SHG) tuning curve of a broadband probe beam is monitored. The QPM condition and wavelength conversion efficiency, which are characterized by the peak wavelength and peak intensity of the SHG tuning curve respectively, are investigated in detail with respect to the irradiation power and irradiation time. It is found that the QPM condition and wavelength conversion efficiency change markedly even for low irradiation powers (<20 mW), indicating that the PRD effect is non-negligible in LiNbO3 QPM wavelength converters intended for practical applications.

Reflective waveguide array demultiplexer in LiNbO/sub 3/

Wavelength demultiplexer fabricated on electrooptic LiNbO/sub 3/ is demonstrated. Reflection structure was employed to halve the device length. The full width at half maximum of the transmission peak was around 1 nm. The crosstalk was -12 to -25 dB. Polarization independence was attained using a reflective quarter-wave plate.

Design of Polarization-Independent Si-Wire-Waveguide Wavelength Demultiplexer for Optical Network Unit

We report the design of a compact wavelength demultiplexer using a Si wire waveguide as an optical network unit. We use a Mach–Zehnder lattice interferometeric filter structure to attain a flat-top response. The large wavelength dispersion of the Si wire waveguide requires special design considerations for widely separated wavelength channels. Preliminary experimental results obtained by the device fabricated in a silicon-on-insulator wafer showed a flat-top filter response.

Two-module stage optical switch network

A large-scale optical switch array based on guided-wave technology using two-module-stage network architecture is proposed. Networks are derived from a generalized three-stage switch network. Two types of architecture are demonstrated. In the first, building blocks in each module are 1/spl times/n, n/spl times/m nonblocking switches or n/spl times/r switch that can route limited numbers of input signal. In the second, crossbar, Banyan, or four-stage wide-sense nonblocking network is used as building blocks. The interconnection is simpler than for the first type. Network architectures that use Banyan or wide-sense nonblocking network building blocks are classed as thinned-out Banyan networks.