Active Laser Protection System

Rugged and compact laser systems operating in the visible and infrared spectrum with output powers sufficient to damage the eye are becoming increasingly more accessible. In addition, ultra-short (femtosecond) laser systems with peak powers in the terawatts are now commercially available. Laser eye protection (LEP) for a wide range of laser wavelengths and pulse duration is important. Passive devices in which protection is activated by the incoming radiation is considered one of the best approaches to counter frequency agile and short pulse laser threats. There is considerable interest in the application of the nonlinear optical properties of materials for optical limiting. An ideal optical limiter will have high transmittance for low energy laser light and block energies above a threshold to clamp the output at some constant energy value. An ideal optical limiter will have a rapid, broadband response (picoseconds and e.g. the visible spectrum), and a large dynamic range. We propose to build optical limiters from metal-dielectric thin-film stacks using the nonlinear properties of metals and/or semiconductors. These stacks are usually very thin (microns) and built using standard thin-film equipment on common substrates. They can be integrated into optical systems with very little modification of the system optics.