Characterization and estimation of microsphere-lens misalignment from FTIR response data of microsphere-lens-enhanced MWIR SLS photo detectors

MWIR microsphere-lens-enhanced detectors have exhibited an increase in detector sensitivity. One factor affecting microsphere-lens-enhanced MWIR detectors sensitivity is the microsphere lens misalignment as we show in this work. Microsphere lens misalignment can cause reduced spectral responses. Modeling of all physical factors, including detector environment sources causing non-desired artifacts, is tedious and complex (not complete). There is a need for better empirical methods/signal processing/data analysis to try to accurately estimate and extract microsphere misalignment. This paper presents a novel signal processing and data analysis method based on a custom software filtering algorithm that involves a step based process consisting of FTIR boundary computation, wavelet de-noising, sensitivity normalization and quantitative computation to estimate microsphere misalignment directly from microsphere enhanced-lens detector FTIR signal responses. Multiple SLS detector sizes, microsphere-lens materials and microsphere sizes are analyzed. Results show microsphere misalignment, based on the data considered, generally increases with the diameter of the sphere, and decreases with respect to the size of the detector. This calls for new signal processing methods and data analysis methods to automatically detect and correct microsphere misalignment.