Optical bistability and X-shaped hysteresis in laser diode amplifiers

Laser diode amplifiers exhibit optical bistability when biased just below lasing threshold, and have applications as optical memory elements and optical switches, due to their very low switching energy (fJ) and presence of optical gain. While LDAs operated in transmission have received much attention, the reflection mode of operation has been largely neglected. In this paper we present a detailed experimental and numerical investigation of Fabry Perot LDA (FP-LDA) behavior under light injection when operated in reflection. We observe transitions from anticlockwise to clockwise hysteresis with changing bias level or incident wavelength detuning. Moreover, we also report the first experimental observation of X-shaped (or butterfly hysteresis) in this system. Our results are in very good agreement with calculation