UV Bandpass Optical Filter for Microspectometers

Abstract

This paper describes the design and modeling of a UV bandpass optical filter for microspectrometers. The materials used for fabricating the multilayer UV filter are: silicon dioxide (SiO2), titanium dioxide (TiO2) and yttrium oxide (Y2O3). The optical filter shows a bandpass response wavelength in the range 230-280 nm, with a transmittance higher than 80%. Such a device is extremely suitable for optical detection of biological molecules with optical absorption or/and fluorescence in the UV spectral range. This UV optical filter can be built using post- processing after integrated-circuit and UV photodiode fabrication in a bipolar or CMOS technology. The dielectric multi-layer stack can be deposited on top of the UV photodiode after the standard technology process has been completed. The number of layers was optimized for 11 with all layers of a thickness acceptable for reproducible fabrication. The materials used for fabricating the UV filter are silicon compatible. Applications presented are in DNA solutions (to measure the optical density of these solutions at 260 nm) and in the detection of a gas flame in the presence of ambient light based on the different emission spectra in the UV.