Abstract
This study presents the theoretical design and analysis of a new surface micro-machined tuneable Fabry-Perot (FP) infrared filter for adaptive infrared photon detectors. The proposed structure uses broad spectral range, high reflectivity distributed Bragg reflector (DBR) mirrors based on amorphous Si/air layers, resulting in very high finesse filters. The device utilises three sacrificial layers to define the air-gap in the DBR mirrors, the resonant cavity spacer, and the separation of the top mirror from the supporting flexures. The flexures are fabricated from low-temperature plasma-enhanced chemical vapour deposited (PECVD) silicon nitride (SiN x ) and Au thin films. Separation of the top mirror from the supporting flexures allows for improved fill-factors (up to 79%), as well as increased tuning range. Optical and finite element modelling of the device has shown large wavelength tuning ranges are achievable (1.5- 2.5 ?m) at low actuation voltages (≪15 V), whilst still maintaining high cavity finesse.
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