Low-threshold high-dynamic-range optical limiter for ultra-short laser pulses

We demonstrate an optical limiter for ultra-short (similar to 100-fs) laser pulses. The device has a dynamic range (= damage energy/ onset-of-limiting energy) of more than 10000 and an onset-of-limiting energy of only similar to 10nJ. The output-pulse energy is kept below 1.3 muJ. The limiting mechanism is based on two-photon absorption and refractive nonlinearities in a 20-mm piece of ZnSe. We discuss the importance of the different nonlinearities, damage issues, and guidelines for the construction of the device.