MWIR TPA Notch Filter

EPIR proposes to develop a HgCdTe (MCT)-based notch filter that is capable of autonomously attenuating pulses from an incoming mid-wavelength infrared (MWIR) laser threat while simultaneously transmitting scene energy critical to the normal operation of the imaging system. This filter uses two-photon absorption (TPA) nonlinear response of narrow bandgap semiconductor materials to attenuate high laser photon flux. The response time of the filter is in picosecond range, and the recovery time is equally fast. The increase in size, weight and power consumption (SWaP) of the imaging system is minimal. The design of TPA filter includes a MCT-based pn junction that not only significantly increases the TPA coefficient, but also allows monitoring of the electrical impedance of the filter, so that additional protection to the imaging system (e.g. electromechanical or electrochromic shutters) can be implemented. EPIR plans to design and fabricate a TPA notch filter to block laser threats with intensity of ~MW/cm2, with no restriction on acceptance angles, no moving parts, and no polarization sensitivity. By the end of the Phase I project, detailed design along with preliminary experimental characterization results will be delivered.