High-energy femtosecond stretched-pulse fiber laser with a nonlinear optical loop mirror

Summary form only given. Fiber lasers have two primary drawbacks: environmental stability is not sufficient for operation outside the laboratory owing to uncontrolled birefringence and pulse energy is limited by excessive nonlinear phase shifts. Stretched-pulse lasers utilizing nonlinear polarization evolution (NPE-SPL) currently offer the best performance. Environmentally-stable lasers could be built with polarization maintaining (PM) fiber, but then NPE cannot be used. Nonlinearity limits pulse energy through soliton dynamics and by saturation of NPE. We consider the use of a nonlinear optical loop mirror (NOLM) to address the latter issue. We present the highest-energy femtosecond pulses obtained to date with a laser that uses NOLM (NOLM-SPL). The main benefits are two-fold: NOLM can function with PM fiber, and saturation of NOLM can be prevented through the choice of proper fiber length. NOLM operation derives from the nonlinear loop only, whereas the entire cavity contributes in the case of NPE.