Wavelength division multiplexer with photoinduced Bragg gratings fabricated in a planar-lightwave-circuit-type asymmetric Mach-Zehnder interferometer on Si

A planar-lightwave-circuit (PLC)-type wavelength division multiplexer with photoinduced Bragg gratings is successfully fabricated on Si. The Bragg gratings are formed in the arms of an asymmetric four-port Mach-Zehnder interferometer (MZI). We demonstrate that signals with three wavelengths can be demultiplexed to three output ports. Heaters are used to compensate for the phase error in the MZI and to switch the output ports. An insertion loss at a Bragg wavelength of 1534.78 nm can be changed from 1.5 to about 19 dB by controlling the heater, indicating that photoinduced Bragg gratings are useful for expanding PLC functions.