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8 September 2011Reflection mode two-dimensional photonic-crystal-slab-waveguide-based micropressure sensor
Photonic crystals (PhCs) have recently been the focus for the developing micro- and nano-optical sensors, due to its
capability to control and manipulate light on planar devices. This paper presents a novel design of micro-optical pressure
sensor based on 2-dimensional PhC slab suspended on Si substrate. A line defect was introduced to the PhC slab to guide
and reflect light with frequency in the photonic bandgap in the plane of the slab. The structure, with certain surface
treatment, can be used in miro-scale pressure catheters in heart ablation surgeries and other biomedical applications. The
working principle of the device is to modify light reflection in the PhC line defect waveguide by moving a substrate
vertically in the evanescent field of the PhC waveguide. Evanescent field coupling is the critical step that affects light
transmission and reflection. High resolution electron-beam lithography and isotropic wet etching have been used to
realize the device on the top layer of a Si-On-Insulator (SOI) wafer. The PhC slab is released by isotropic wet etch of the
berried oxide layer. The output reflection spectrum of the device under different pressure conditions is simulated using
3-dimensional finite difference time domain (FDTD) method. The result showed that when the PhC slab is close enough
to the substrate (less than 400 nm), the reflected light intensity decreases sharply when the substrate moves towards the
PhC slab. Mechanical response of the sensor is also studied.