Electro-nanomechanically actuated integrated-optical interferometric intensity modulators and 2×2 space switches

Abstract

Electro-nanomechanically actuated integrated-optical (IO) interferometric intensity modulators and 2×2 space switches with switching times of about 50 μs are demonstrated (at wavelength λ=633 nm). By a successful combination of micromechanics and integrated optics in silicon technology, Mach–Zehnder interferometers with either Y-junctions or multimode-interference (MMI) couplers as light splitters and combiners, and, consequently, with either a single or two input and output ports are fabricated with monomode Si 3N 4 rib waveguides on oxidized silicon wafers. The effective-refractive-index-shifting element E is microstructured from an oxidized silicon wafer in the form of a cantilever; it is attached to the waveguide chip by optical contact bonding with the cantilever protruding over the rib waveguide in one leg of the Mach–Zehnder interferometer. The effective-refractive-index changes Δ N required for IO device operation are induced by elastic deflection of the cantilever under electrostatic forces thus varying the width of the air gap between the element E and the waveguide. A slow drift effect of the electro-nanomechanical devices was eliminated and stable device operation was achieved by surface treatment (silanization) of the waveguide chip and of the element E, which made their surfaces hydrophobic. Potential applications of the 2×2 space switches are envisaged in telecommunication networks, after scaling of the devices from the visible demonstration wavelength used to the telecommunication wavelengths λ=1.3 and 1.55 μm. The electro-nanomechanical IO switches with switching times in the microseconds to several tens of microsecond regime have the attractive features of requiring low switching voltages, low switching energies and no holding power.