Symmetric directional coupler switches

Operation and design considerations are described for a general class of symmetric directional coupler switches. Performance limitations are discussed in terms of asymmetries. Comparisons are made between various waveguide and electrode geometries. Measured devices operating at
\lambda = 0.83 \mu
m have a V
π
voltage length product under 30 V mm and an extinction ratio greater than 28 dB in each output state.