Optimizing power extraction in stretched-pulse fiber ring lasers

A variable output coupling scheme is described for a stretched-pulse polarization additive pulse mode-locked (APM) fiber ring laser. The scheme allows the coupling percentage to be changed while the laser is running and allows for the maximum possible power extraction before cavity losses inhibit mode-locked operation. We describe how the nonlinear pulse dynamics change to compensate the change in cavity loss. Compared to high power output coupling schemes that use the APM rejection port, this method provides cleaner output pulses at comparable output powers. Pulse energies of 0.39 nJ are obtained at 48% output coupling in a diode-pumped system. 88 fs pulses with time-bandwidth products of 0.49 are obtained after output chirp compensation using a silicon prism pair. (C) 1995 American Institute of Physics.