12/05/2025
By Sreeja Purkait

The Kennedy College of Science, Department of Physics and Applied Physics, invites you to attend a Master’s thesis defense by Sreeja Purkait on “Design and Analysis of Compact Resonant Mid-IR Detectors."

Candidate Name: Sreeja Purkait
Degree : Master’s
Defense Date: Friday, Dec. 12, 2025
Time : 3 to 5 p.m.
Location :Olney Hall, Department of Physics Conference room

Thesis/Dissertation Title: Design and Analysis of Compact Resonant Mid-IR Detectors

Committee:

  • Advisor: Viktor Podolskiy, Ph.D., Department of Physics and Applied Physics, UMass Lowell
  • Hugo Ribeiro,Dr. rer. nat., Department of Physics and Applied Physics, UMass Lowell
  • Timothy Cook,Ph.D., Department of Physics and Applied Physics, UMass Lowell
  • Daniel Wasserman, Ph.D., Chandra Department of Electrical & Computer Engineering, UT Austin

Brief Abstract: 

Mid-wave infrared (MWIR) spectral region (free-space wavelength of λ0 ∼ 3 . . . 5μm) is vital for multiple applications in sensing, thermal imaging, and security. The majority of these applications rely on photodetectors, devices that convert incoming MWIR photons into electronic signals. This work presents an algorithm for optical design of several types of MWIR photodetectors with ultra-thin absorber regions, from large-scale periodic structures relying on guided mode resonance (GMR) to truly compact structures that combine GMR with cavity resonances. We apply this algorithm to design practical GMR detectors that are optimized for a given working wavelength and absorber material and thickness, for both substrate- and surface- side illumination. We demonstrate confinement of MWIR light in 250 nm and 150 nm thick absorbers. We next explore the performance of finite detectors and propose a truly compact detector design. This design, resonant pixel, couples light to both GMR and lateral cavity resonance, achieving deep sub-wavelength thickness and lateral dimensions of the order of ∼ 2λ0, with predicted external quantum efficiency ∼ 50%.