Micro displacement sensor based on line-defect resonant cavity in photonic crystal

A micro displacement sensor and its sensing technique based on line-defect resonant cavity in photonic crystals (PhCs) are presented. The line-defect resonant cavity is formed by a fixed and a mobile PhC segments. With a proper operating frequency, a quasi-linear measurement of micro-displacement is achieved with sensitivity of 1.15 a(-1) ( a is the lattice constant) and Q factor of 40. The sensitivity can be adjusted easily by varying either Q factor or operating frequency of the sensing system. In addition, the sensing range can be broadened to -0.55 a ~0.60 a by using multiple operating frequencies. The properties of the micro displacement sensor are analyzed theoretically and simulated using finite-difference time-domain (FDTD) method.