Abstract

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, with 100-fs long, ~1 nJ pulses routinely achievable.¹ 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 have recently proposed the use of nonlinearity management to address the former issue.² We now consider the use of a nonlinear optical loop mirror (NOLM) to address the latter. We present the highest-energy femtosecond pulses obtained to date with a laser that uses NOLM (NOLM-SPL). The main benefits are two-fold: (a) NOLM can function with PM fiber, (b) 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.

© 2002 Optical Society of America