Performance of Field-Induced Directional Coupler Switches

Switching in a GaAs field-induced, three-waveguide straight directional coupler is studied theoretically. This device can be tuned externally by changing the voltage across the waveguides. Because of this tunability, the device has some very attractive features as a switching element. The performance change due to variations in the device parameters such as length, waveguide separation, waveguide width, and wavelength of operation is numerically computed. The effect of material absorption, input and output coupling, and asymmetric excitation are included in the performance evaluation. For a device length of 1400 μm, a crosstalk of-34 dB and a power transfer efficiency of–2 dB is predicted, while for the same device size a two-guide directional coupler is predicted a crosstalk of-13.4 dB. The device has a 400 nm voltage tunable bandwidth with a maximum crosstalk penalty of 3 dB.