Ken Ueki

Polarization- and wavelength-insensitive guided-wave optical switch with semiconductor Y junction

A polarization- and wavelength-insensitive semiconductor guided-wave optical switch with a Y junction is proposed. The switch exhibits a digital response with respect to current, allowing its use as a wavelength-insensitive 1*2 optical switch. The switching characteristics are analyzed by using the beam propagation method, and a design example is given. The polarization- and wavelength-insensitive switching operation has been confirmed with a fabricated GaAs/GaAlAs switch at wavelengths of 1.3 and 1.55 mu m, and the on/off ratio exceeded 20 dB at an injection current of 250 mA at these wavelengths. >

Broad-band high-silica optical waveguide star coupler with asymmetric directional couplers

A broadband optical waveguide star coupler with asymmetric directional couplers is proposed. A coupling or splitting ratio of the coupler is flattened with respect to wavelength by choosing appropriate values for Delta beta and complete power transfer length. The wavelength characteristics of uniform and alternating Delta theta b directional couplers are investigated, and their broadband operation is shown theoretically. To demonstrate the feasibility of the new proposal, 8*8 star couplers composed of such asymmetric directional couplers are fabricated by using high-silica waveguides on a silicon chip. A star coupler composed of asymmetric directional couplers exhibited 2-dB loss variation in the wavelength range of 1.3-1.55 mu m, and this value was almost one fourth of that of a star coupler composed of symmetric directional couplers. >

Polarization and Wavelength Independent Four-Port Optical Routing Switch with Semiconductor Y-Junction Optical Cross-Points

We propose a polarization and wavelength independent four-port routing switch with semiconductor Y-junction optical switching cross-points, and report the performance of the fabricated routing switch.