Fast Optical Limiters (OL) with Enhanced Dynamic Range

The proliferation of commercial, visible and infrared wavelength laser systems is increasingly becoming an existential threat to our warfighters, which drives the need for further EO/IR sensor and eye protection development. Current fielded sensor protection is limited to fixed wavelength filters. Broadband filters designed to circumvent multi-wavelength laser threats are plagued by low transmittance, which degrades the sensitivity and performance of the sensor. Future warfighter threats include frequency agile lasers and thus have the potential of defeating fixed filters. Self-activating (passive) devices where protection is activated by the incoming radiation (optical limiting) are the best approach to counter frequency agile and short pulse laser threats. Current state-of-the-art of optical limiters are hampered by low off-state transmittance and laser damage threshold, high activation laser fluence, and narrow field of view and bandwidth. We will design, fabricate and test an optical limiter concept based on metal-dielectric stacks that incorporate thin film phase change materials (VO2). The novel optical limiter devices have large angular acceptance, large band width, sub-nanosecond response times, high laser damage threshold, and short reset times. Typically less than 10 nano-layers are grown by physical deposition processes. The compact devices can be integrated into existing EO/IR sensors against laser threats.