Kiyohide Sakai

Planar-waveguide quasi-phase-matched second-harmonic-generation device in Y-cut MgO-doped LiNbO3

A planar-waveguide quasi-phase matched second-harmonic generation device, which consists of a Y-cut periodically poled MgO-doped LiNbO3 core and SiO2 claddings, provides 1-W green light with 30-% conversion efficiency at room temperature.

Blue light generation in a ridge waveguide MgO:LiNbO3 crystal pumped by a fiber Bragg grating stabilized laser diode.

We report cw blue light generation by using a periodically poled MgO:LiNbO(3) crystal with a ridge waveguide pumped by a fiber Bragg grating stabilized laser diode with 0.25 nm spectrum width in the coherent collapse regime. Blue light generation of 73 mW with 27% conversion efficiency and a wide temperature tolerance of 5.7 degrees C were attained.

Master-oscillator power-amplifier scheme for efficient green-light generation in a planar MgO:PPLN waveguide

We developed a new master-oscillator power-amplifier scheme consisting of a tapered semiconductor amplifier and a fiber-grating-stabilized laser diode for efficient green-light generation in a planar MgO:PPLN waveguide, and demonstrated cw green-light generation of 346 mW.

A 95% efficient inverter with 300-W power output for 6.78-MHz magnetic resonant wireless power transfer system

We developed a high-power Class-E inverter for a 6.78-MHz magnetic resonant wireless power transfer system. The inverter consisted of six synchronized coupled low-power inverters; the outputs were combined after the corresponding matching circuit. We attained a drain efficiency of 94.6% at the power output of 315 W. In addition, we demonstrated a wireless power transfer system consisting of the Class-E inverter, a pair of magnetic resonant coils 200 mm in diameter separated at an air-gap distance of 42 mm, and a diode bridge rectifier. The system achieved a dc-dc efficiency of 84.7% at a power output of 301 W.

Coaxial high-current photodiode module for analog optical links

We fabricated a coaxial high-current InGaAs/InP p-i-n photodiode module using a small-sized TO-can package with a diameter of 4.8 mm, and demonstrated an RF power output of 25.2 dBm at a frequency of 5 GHz.

Planar-waveguide quasi-phase matched second-harmonic generation device in Y-cut MgO-doped LiNbO 3

A planar-waveguide quasi-phase matched second-harmonic generation device, which consists of a Y-cut periodically poled MgO-doped LiNbO 3 core and SiO 2 claddings, provides 1-W green light with 30-% conversion efficiency at room temperature.

Uncooled DFB lasers for CATV

Strained-layer MQW-DFB lasers at a wavelength of 1.3 micrometers operating from -40 degree(s)C to 85 degree(s)C without any coolers are demonstrated. On the basis of the leakage current analysis, a laser structure including the active layer and the current blocking layer is chosen to achieve low distortion over wide-temperature-range. Extremely low threshold current of 17 mA at 85 degree(s)C and operation current of 37 mA at 5 mW and 85 degree(s)C are obtained. The lasers realize low distortion of less than -50 dBc at 65 degree(s)C in 78-channel CSO measurements. Furthermore, a fabricated laser module with a coaxial package also achieved low CSO values of -55 dBc under 16-channel loading in the temperature range from -40 degree(s)C to 85 degree(s)C. This uncooled DFB laser module is very useful for return path application in CATV systems.