Design and Demonstration of Weighted-Coupling Digital Y-Branch Optical Switches in InGaAs/InGaA1As Electron Transfer Waveguides

We have designed and demonstrated the first semiconductor digital optical switches that use weighted-coupling Y-branches. Using the beam propagation method we model both conventional Y-branches as well as weighted-coupling, shaped Y-branches with two angles. Theoretically we find that optimal shaping of the branch can provide, for the same device length, enhanced crosstalk performance and voltage efficiency. These features are confirmed by our experimental results on switches fabricated in InGaAs/InGaA1As chopped quantum well electron transfer waveguides. In the shaped Y-branch switch, we measure a voltage-length product of 4 V-mm with single-arm drive, while that for the conventional Y-branch is 8 V-mm. With dual arm drive in the push-pull configuration, the shaped switch only requires 3.7 V for a 550 µm active length. This switch also has polarization and wavelength insensitive switching characteristics with less than 1.0 dB variation in crosstalk over a wide operating range from 1.52 to 1.58 µm wavelength.