Fabrication and characterization of MEMS airgap-based optical filters for the UV spectral range

This paper presents the design, fabrication, and characterization of MEMS airgap-based optical filters designed for the ultraviolet (UV) spectral range. Optical design, process conditions, and material choice have been optimized for obtaining large-area and optically flat membranes. Several distributed Bragg reflectors centered at λ=400 nm were designed using silicon oxide and nitride layers as the membrane materials. Airgap Bragg reflectors with up to 80% fill-factor were fabricated in standard Si technology and the spectral reflectance of the reflectors were compared. The optical characterization demonstrated a high reflectance (up to 80%) with only a few number of layers over a bandwidth of up to 175 nm in the UV spectral range.