High-dynamic-range cascaded-focus optical limiter

We report experimental results of using an f/5, cascaded-focus optical geometry for a high-dynamic-range optical limiter. The device consists of a a-cm-thick CS2 cell at the first focus and a reverse saturable-absorber dye in a thin cell (0.1 mm) at the second focus. The strong self-focusing in the CS2 that is due to the ac Kerr effect and electrostriction keeps the energy at the second cell below its damage threshold. Using lead phthalocyanine in chloroform as the reverse saturable-absorption material, we clamped the maximum output energy below 1 mu J for input energies up to 14.5 mJ without damage. We used a frequency-doubled, Q-switched 5-ns (FWHM) Nd:YAG laser operating at a 10-Hz repetition rate. of the device is at least 7500. (C) 2000 Optical Society of America OCIS codes: 260.5950, 190.0190.