Multiple quasi-phase-matched device using continuous phase modulation of /spl chi//sup (2)/ grating and its application to variable wavelength conversion

We propose a new multiple quasi-phase-matched wavelength converter based on the continuous phase modulation of a /spl chi//sup (2)/ grating for use in variable wavelength conversion. A numerical study shows that the proposed device exhibits a high conversion efficiency, flexible design, and robust fabrication tolerance. A waveguide device fabricated by annealed proton exchange agrees well with the numerical design. Fine-tuning the device enabled us to demonstrate variable wavelength conversion between signals on the standard optical frequency grid. Using the device, we also demonstrated fast (<100 ps) wavelength switching of 4-channel 40-Gb/s signals. The obtained results clearly show that the proposed multiple quasi-phase-matched devices will be useful when constructing future flexible photonic networks.     

Applications of highly nonlinear chalcogenide glass fibers inultrafast all-optical switches

Applications of chalcogenide glass fibers in ultrafast all-optical switches have been investigated. Ultrafast all-optical switching has been accomplished in an optical Kerr shutter configuration using As₂S₃-based glass fiber. The nonlinear refractive index of the As₂S₃-based glass is estimated to be n₂=4.0×10^-14 (cm²/W ), which is higher by two orders of magnitude than that of silica glass fiber. Nonlinear absorption due to two-photon absorption has been revealed to be negligible, and up to a 2π-phase shift has been obtained. Switching speed and switching power were investigated experimentally and through calculations. A switching time of 12 ps and a switching power of 5 W can be achieved using a 10-ps gate pulse and only a 1-m chalcogenide glass fiber. However, signal transformation due to cross-phase modulation and group velocity dispersion is not negligible for shorter gate pulses. Lower switching power is possible by reducing the transmission loss and the core area and by optimizing the driving conditions     

High-power mid-infrared wavelength generation using difference frequency generation in damage-resistant Zn:LiNb03 waveguide

High-power 3.4 mum difference frequency generation (DFG) using a quasi-phase-matched Zn:LiNbO₃ waveguide fabricated by direct bonding technology is presented. The high resistance of the waveguide to photorefractive damage allows high-power generation. A 65 mW mid-infrared output was obtained using a continuous-wave high- power fibre amplifier as pump source. The DFG source can access over 10 nm continuously simply by scanning the signal wavelength, and will be useful for real-time trace gas sensing.     

All-optical discrimination based on nonlinear transmittance of MQWsemiconductor optical gates

This paper proposes an all-optical regenerator utilizing a novel all-optical discriminator. The impacts of nonlinearity of optical gates on discrimination performance are estimated. The evaluation of discrimination performance shows that amplified spontaneous emission noise and wave form distortion in optical signals can be effectively suppressed. We experimentally demonstrate the suppression using a low-temperature-grown optical switch up to 10 Gb/s     

Ultrafast all-optical switching using highly nonlinear chalcogenideglass fiber

Ultrafast all-optical switching with a switching power of 14 W was demonstrated in a Kerr shutter configuration using a single-mode As₂S₃-based glass fiber only 48 cm long. The nonlinear refractive index of the fiber was evaluated from the switching characteristics to be n₂=4.2×10^-14 (cm²/W), which is higher by two orders of magnitude than silica glass fiber     

All-optical switching based on cascading of second-ordernonlinearities in a periodically poled titanium-diffused lithium niobatewaveguide

We report efficient all-optical switching by using a periodically poled titanium-diffused lithium niobate (Ti:PPLN) waveguide. The periodically domain inversion of the Ti:PPLN waveguide is achieved by electric field poling. The switching is driven by the second-order nonlinear effect of the cascading of phase-matched sum-frequency-generation and difference-frequency-generation processes. It is found that about 12% of the signal is switched by a 20-W gate power     

56 byte optical cell selection at 55 Gbit/s in bit-interleavemultiplexing photonic ATM switch

Experiments on selecting 56 byte optical cells out of a four-channel bit-interleave multiplexed 55 Gbit/s pulse stream are carried out using a nonlinear optical loop mirror (NOLM) including a chalcogenide glass fibre     

An ultrafast photonic ATM switch based on bit-interleavemultiplexing

An optical ATM switch is proposed in which cells from individual input channels are time-division multiplexed in a bit-interleave manner. This switch can easily handle multicast switching because it is based on a broadcast-and-select network. Compared to an alternative switch that uses a cell-interleave time-division multiplexing scheme, the proposed optical switch has a much simpler structure. It does not need a cell compressor at each input and a cell expander at each output, which greatly reduces hardware complexity. Feasibility analyzes showed that a 64×64 photonic ATM switch with 2.5 Gb/s input/output is possible using the proposed technology. In an experimental demonstration, 4 b cells were selected from a 55 Gb/s bit-interleave multiplexed cell stream by using a new nonlinear optical fiber switch. With its high switch throughput, our switch is a strong candidate for future large-capacity optical switching nodes     

Direct-bonded QPM-LN ridge waveguide with high damage resistance at room temperature

A direct-bonded 13 mm-long quasi-phase matched LiNbO/sub 3/ (QPM-LN) ridge waveguide is fabricated that exhibits a second-harmonic generation efficiency of 44%/W. The waveguide shows very high resistance to photorefractive damage at room temperature. The difference frequency generation with an efficiency of -17.6 dB in the 1550 nm wavelength band is also demonstrated.     

Compact and tunable mid-infrared laser using QPM-LN waveguide and TLA

A compact and tunable difference frequency generation mid-infrared laser for gas sensing is developed using a quasi-phase-matched LiNbO₃ (QPM-LN) waveguide and a tunable laser diode array (TLA). The absorption spectra of methane from the -third- to -fifth-order around 3.3 mum are observed by tuning the QPM-LN waveguide temperature and the TLA wavelength. The absorption line width is investigated with high spectral resolution scanning and the result is compared with that calculated from the HITRAN database.