Abstract: An ultralow-energy electro-optical 2×2 cross-bar switch comprises an identical pair of semiconductor nanobeams that are incorporated in the central arms of a waveguided Mach-Zehnder interferometer. Each nanobeam includes a one dimensional “lattice” of holes along the nanobeam axis that defines a resonant cavity whose fundamental mode is the operating wavelength of the switch. A localized, lateral lengthwise extending portion of the semiconductor nanobeam is doped P type, while the other lateral half of the nanobeam wing is doped N type, forming a P-N junction in the body. Application of an electric potential across the P-N junction alters the effective index of refraction of the lengthwise extending portion and controls both the transmission and reflection of an incoming optical signal at the operating wavelength of the switch through the semiconductor nanobeam. Constructive and destructive interference of component signals within the interferometer controls the spatial routing of the incident light.

Abstract: An electro-optical switch implemented in coupled photonic crystal waveguides is disclosed. The switch is proposed and analyzed using both a finite-difference time-domain (“FDTD”) method and a plane wave expansion (“PWM) method. The switch may be implemented in a square lattice of silicon posts in air, as well as in a hexagonal lattice of air holes in a silicon slab. Switching occurs due to a change in the conductance in the coupling region between the photonic crystal waveguides, which modulates the coupling coefficient and eventually causes switching. Conductance may be induced electrically by carrier injection or optically by electron-hole pair generation. The electro-optical switch has low insertion loss and optical crosstalk in both the cross and bar switching states.