Optical Limiters Based on PT-Symmetry Breaking of Reflectionless Modes

Abstract

We report optical limiting of single 532-nm 6-ns laser pulses by two coupled optical cavities with a PT-symmetric spectrum of reflectionless modes at fluences above 10 mJ/cm2. The optical limiting is related to broken PT symmetry due to light-induced changes in one of the cavities. At the limiting threshold, the optical limiter quickly becomes highly reflective rather than absorbing, thereby protecting itself from laser-induced damage.