Metasurface-Coupled HgCdTe Alloys for Nonreciprocal Optical Limiting

Optical limiting (OL) has been widely used to protect human eyes and valuable electronic devices from intense laser radiation. For many strategically important DoD applications, it is desirable that OL is initiated only when the laser radiation comes from adversaries (forward direction), but not when our soldiers try to use laser for communication, laser range finding or laser-based countermeasures (reverse direction). In this proposed project, Sivananthan Laboratories, together with our SBIR partner, Vanderbilt University, will demonstrate nonreciprocal optical limiting using metsurface-coupled HgCdTe (MCT) alloys. In this approach, we exploit the metsurface’s capability of concentrating laser’s electric field spatially in MCT alloys with intrinsically strong two-photon absorption. Compared to technologies involving phase-change materials like VO2, our approach takes advantage of rapid and hysteresis-free nonlinear optical response and eliminates slow thermally induced phase-change processes. The spatially asymmetric concentration of laser’s electric field due to the metasurface would further enhance the nonlinear optical absorption in MCT. Our preliminary results indicate that our metasurface-coupled MCT alloys can achieve a strong nonreciprocity greater than 10 dB over a broad wavelength range. In Phase I we will perform modeling to design the optimal device structure(s), fabricate the designed device, and characterize the device’s nonreciprocity and insertion loss in OL.  A comprehensive report with recommended materials and designs as well as a path for improved device performance in terms of bandwidth, insertion loss, nonreciprocal power range, and incident angles range for Phase II will be provided.