Epsilon Near Zero Optical Limiter

Optical sensor protection against laser threats has been a critical part of the Army’s S&T portfolio, especially with the advancement and availability of laser weapon systems. One particularly threatening system is a pulsed laser system using short (nanosecond) pulses with high fluence that could permanently damage the optical sensor. Typically, these treats are mitigated with optical limiter (OL) devices that protect optical sensors from laser induced damage. These devices transmit low intensity input light (in the PASS state) and limit the light transmission when exposed to light above the sensor damage threshold (in BLOCK state). Therefore, solutions for ultrafast, passive optical limiters where protection is activated by the incoming radiation are needed. Epsilon-near-zero (ENZ) materials provide extreme optical nonlinear response, offering a means to create these passive optical limiters. However, no practical designs exist that meet the stringent requirements for sensor protection. In this Phase I effort, we will explore designs that incorporate ENZ/metamaterial structures to create a reflective optical limiter. The ENZ material enables low activation threshold and the reflective protection strategy significantly increases damage threshold when compared to absorptive methods. Success in this effort will pave the way for a new generation of optical limiting devices.