Mechanical tuning of two-dimensional photonic crystal cavity by micro Electro mechanical flexures

A nano-displacement sensing method for micro-opto-electro-mechanical-systems (MOEMS) is proposed. The method is based on a square lattice photonic crystal (PC) made of dielectric silicon posts, mounted on a micro mechanical flexure. The flexure is fixed at one end and is free to move at the other, to enable elastic deformations that, by being transferred to the photonic crystal array, modify its periodicity and the pertinent transmission characteristics. A missing-post defect is deliberately introduced in the photonic crystal, opening a narrow pass band within the band gap. The pass band wavelength is sensitive to dilatation of the micro mechanical flexure. The flexure Poisson ratio (PR) can be designed according to specific requirements to gain desired sensitivity. Simulations show high sensitivity of 12.3 nm band pass shift for every 1% flexure strain for flexure of a material with a Poisson ratio of −1. An inverted honeycomb based micro-electro-mechanical-systems (MEMS) flexure, with a Poisson ratio of −1, was fabricated in silicon and characterized.