DESIGN AND DEMONSTRATION OF WEIGHTED-COUPLING DIGITAL Y-BRANCH OPTICAL SWITCHES IN INGAAS INGAALAS ELECTRON-TRANSFER WAVE-GUIDES/

We have designed and demonstrated the first semiconductor digital opti cal switches that use weighted-coupling Y-branches. Using the beam pro pagation method we model both conventional Y-branches as well as weigh ted-coupling, shaped Y-branches with two angles. Theoretically we find that optimal shaping of the branch can provide, for the same device l ength, enhanced crosstalk performance and voltage efficiency. These fe atures are confirmed by our experimental results on switches fabricate d in InGaAs/lnGaAlAs chopped quantum well electron transfer waveguides . In the shaped Y-branch switch, we measure a voltage-length product o f 4 V-mm with single-arm drive, while that for the conventional Y-bran ch is 8 V-mm. With dual arm drive in the push-pull configuration, the shaped switch only requires 3.7 V for a 550 mu m active length. This s witch also has polarization and wavelength insensitive switching chara cteristics, with less than 1.0 dB variation in crosstalk over a wide o perating range from 1.52 to 1.58 mu m wavelength.