Date of Award
Doctor of Philosophy (PhD)
Advances in fabrication technology have enabled the development of compact, rigid polarization image sensors by integrating pixelated polarization filters with standard image sensing arrays. These compact sensors have the capability for allowing new applications across a variety of disciplines, however their design and use may be influenced by many factors. The underlying image sensor, the pixelated polarization filters, and the incident lighting conditions all directly impact how the sensor performs.
In this research endeavor, I illustrate how a complete understanding of these factors can lead to both new technologies and applications in polarization sensing. To investigate the performance of the underlying image sensor, I present a new CMOS image sensor architecture with a pixel capable of operation using either measured voltages or currents. I show a detailed noise analysis of both modes, and that, as designed, voltage mode operates with lower noise than current mode. Further, I integrated aluminum nanowires with this sensor post fabrication, realizing the design of a compact CMOS sensor with polarization sensitivity. I describe a full set of experiments designed as a benchmark to evaluate the performance of compact, integrated polarization sensors. I use these tests to evaluate for incident intensity, wavelength, focus, and polarization state, demonstrating the accuracy and limitations of polarization measurements with such a compact sensor. Using these as guides, I present two novel biomedical applications that rely on the compact, real-time nature of compact integrated polarimeters. I first demonstrate how these sensors can be used to measure the dynamics of soft tissue in real-time, with no moving parts or complex optical alignment. I used a 2 megapixel integrated polarization sensor to measure the direction and strength of alignment in a bovine flexor tendon at over 20 frames per second, with results that match the current method of rotating polarizers. Secondly, I present a new technique for optical neural recording that uses intrinsic polarization reflectance and requires no fluorescent dyes or electrodes. Exposing the antennal lobe of the locust Schistocerca americana, I was able to measure a change in the polarization reflectance during the introduction of the odors hexanol and octanol with the integrated CMOS polarization sensor.
Shantanu Chakrabartty, Roger Chamberlain, Spencer Lake, Barani Raman, William Richard