Microdisplacement sensor based on high-Q nanocavity in slot photonic crystal

A microdisplacement sensor formed by a fixed and mobile hole-array based slot photonic crystal (slot-PhC) components is demonstrated. The sensing technique is based on a nanoscale cavity with a high-Q factor in photonic crystals (PhCs). The high-Q nanocavity (H0-cavity) is formed by only laterally shifting two adjacent holes outwards slightly in the opposite direction. The properties of the microdisplacement sensor are analyzed theoretically and simulated using the finite-difference time-domain method. The simulation results indicate that with a proper operating frequency, a quasilinear measurement of microdisplacement is achieved with a sensitivity of 1.0a(-1) (a is the lattice constant) in the sensing range between 0.00a and 0.20a. Although other researchers such as Xu et al.(1) who demonstrated a micro displacement sensor possessing an equivalent sensitivity, the Q factor is only 40. In this paper, combined with harmonic analysis, we show numerically that an intrinsic Q value of up to 6x10(3) is achieved. In addition, it is worth mentioning that when the parameters of the H0-cavity are determined, the resonant frequency of the H0-cavity remains approximately constant as the mobile PhC segment shifts along the common axis. It will be easier and more accurate for measurements in practical applications. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3574528]