Mode expanded optical switch in resonant vertically coupled waveguides

We propose and demonstrate a novel expanded mode voltage controlled optical switch based on electrorefraction and electroabsorption in resonantly coup led tapered vertical waveguides, The device was grown in a single standard epitaxial growth and was processed using conventional fabrication technique s. A 200-mu m-long mode transformation region was used for expanding the mo de and optical switching. Greater than 20-dB switching contrast ratio was o btained with a reverse bias of less than 1 V. Reduced far-field divergence angles (8 degrees x 24 degrees) were also achieved. With good contrast rati o at low voltage bias and an inherent expanded mode, this device shows prom ise for low-cost optoelectronic switching applications.