Low-threshold high-dynamic range optical limiter for 100-fs laser pulses

Summary form only given. We present the first practical optical limiter for ultrashort, /spl sim/100 fs, laser pulses. Optical limiters show decreased transmittance with increasing laser pulse energy so that the transmitted energy is kept small. These devices are characterized by the onset-of-limiting energy E/sub on/ (pulse energy at which the transmittance T has fallen to T/sub lin//2, T/sub lin/ transmittance in the linear regime), the "dynamic range" = E/sub D//E/sub on/ (E/sub D/ damage energy), and the maximum transmitted output energy E/sub max/. A practical device for the protection of the human eye or sensitive photodetectors combines a low E/sub on/ with a high dynamic range, small E/sub max/, and a large linear transmittance. With our concept, a low threshold E/sub on/ = 11 nJ, a large dynamic range of 10750, and sufficient linear transmittance T/sub lin/ = 28% are obtained. Moreover, the transmitted energy E/sub max/ is restricted to 1.3 /spl mu/J. Our concept builds on two-photon absorption (TPA) and refractive index effects in ZnSe.