Method of microcantilever deflection measurement utilizing mechanochromic effect in photonic crystals

In this paper we present a method for microcantilever deflection measurement utilizing a stress-tunable photonic crystal (Photonic Bandgap, PBG) waveguide. The method uses the mechanochromic effect, i.e. the modulation of transmissive properties by applied force. A 2D photonic crystal-based channel waveguide with a 90/spl deg/ band is used as sensitive element. The structure is monolithically integrated with the basis of the microcantilever where deflection-induced stress is maximal. Applied stress simultaneously causes a shift of the photonic bandgap edge and photoelastic refractive index change and this is used for amplitude modulation of light signal. The approach may be used in deflection or stress sensing in various other MEMS sensors.