Casimir and Optical Forces Acting on a Silicon NOEMS Device Based on Slot-Waveguide Structure

We investigate the effect of Casimir force on a silicon nano-opto-electro-mechanical system (NOEMS) device, based on a slot-waveguide structure and driven by optical forces. Light is strongly confined in the slot-waveguide, which enhances the optical force and reduces the optical power necessary to control the device. However, we predict that the Casimir force affects the device's critical points of stability, by reducing the critical optical power for the quasi-TE fundamental eigenmode, as well as imposing a critical power for the quasi-TM one. Casimir force also changes the initial NOEMS equilibrium position, pre-deforming the two sides of the slot-waveguide, even in the absence of optical forces; this establishes a minimal initial gap distance for the slot-waveguide, thus affecting the device's design parameters.