Optical Limiting with Nanocrystalline Materials

Broadband visible optical limiting filters will be an essential element for soldier protection in the future battlefield environment. New materials are required that provide protection for the eye for pulses >0.5 mJ. We propose to use suspensions ofunaggregated absorbing nanoparticles for optical limiting. Such nanoparticles can exhibit optical limiting by several mechanisims, including charge trapping inducing plasmon and donor/acceptor absorption, and local heating leading to formation of lightscattering microplasmas. In Phase I, using new synthetic methods for semiconductor nanoparticles we prepared a selection of broad band absorbing monodisperse (1-10 nm diameter) particles of several candidate semiconductors and evaluated their opticallimiting behavior in comparison to polydisperse C suspensions. A multiwavelength nanosecond characterization facility was established at EIC with capabilities of measuring between 225 nm to 1625 nm over six orders of input fluence. Several newnanocrystalline systems were identified that provide substantial advantages over prior art for broadband protection. Phase II will entail adding improved automation and imaging capabilities to the instrumentation, synthesizing an expanded group ofnanomaterials and size distributions, developing the concept of sensitized nanocrystals for wide dynamic range optical limiting, and developing solid matrices for creating filter elements with a low damage threshold.The new filters have government marketsfor eye protection of military personnel, including individual eyewear and inclusion in sights and periscopes, as well as for sensor protection in terrestrial and satellites imaging systems. Commercial markets include laser safety eyewear and as protectionfor cameras and optical instruments.