ADIABATIC 3-DB COUPLERS, FILTERS, AND MULTIPLEXERS MADE WITH SILICA WAVE-GUIDES ON SILICON

We report the performance of adiabatic 3-dB couplers and y-branches. These devices are broad-band and divide power equally. They have no observable polarization dependence. Typical excess losses relative to a straight waveguide is 0.1-0.2 dB for the 3-dB couplers and about 0.4 dB for the y-branches. Fiber to fiber insertion loss of 0.31 dB was measured for a 2.5-cm straight waveguide. The devices were used to fabricate transmission filters peaked at 1.55 half arrow pointing up and to the right m and power combiners having two channels at 1.48 and 1.55 half arrow pointing up and to the right m. The device fabrication was improved by use of a flowable top cladding layer containing boron and phosphorous which easily filled-in between closely spaced waveguides.