Applications of digital adaptive filters to time-resolved optical microscopy
Date
2020
Authors
Gupta, Saurabh, author
Wilson, Jesse W., advisor
Pezeshki, Ali, committee member
Thamm, Douglas, committee member
Journal Title
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Volume Title
Abstract
Phosphorescence lifetime imaging is used on several fronts, such as, skin cancer or melanoma diagnosis, and estimation of tissue oxygenation among others. Oxygen profiling is critical for mapping brain activity, apart from its use to monitor several metabolic activities, and often employs oxygen tagging molecules/probes. In this work, we describe a novel technique to recover phosphorescence lifetime using a real-time digital adaptive filter running on a field-programmable gate array (FPGA) and conclude with an important takeaway. We also describe our strategy to mitigate relative intensity noise (RIN) in ultrafast fiber lasers, which are an attractive alternative to bulk lasers for non-linear optical microscopy due to their compactness and low cost. The high RIN of these lasers poses a challenge for pump-probe measurements such as transient absorption and stimulated Raman scattering, along with modalities that provide label-free contrast from the vibrational and electronic structure of molecules. Our real-time approach for RIN suppression uses a digital adaptive noise canceller implemented on a FPGA. We demonstrate its application to transient absorption spectroscopy and microscopy and show compatibility with a commercial lock-in amplifier. Lastly, we report the noise estimates specific to our current setup.