115-MHz Linear NPE Fiber Laser Using All Polarization-Maintaining Fibers

Abstract

We report on a robust, erbium-doped ultrafast fiber laser mode-locked by an artificial saturable absorber (SA) based on nonlinear polarization evolution (NPE). Unlike previous NPE fiber lasers, our cavity employs all polarization-maintaining (PM) fiber so that the laser is insensitive against environmental fluctuations. By incorporating a phase shifter in the NPE artificial SA, the oscillator possesses self-starting mode-locking ability. However, it is difficult to start pulsed operation without such a phase shifter. The simple and novel fiber laser scheme utilizing above mentioned design can directly generate 0.11 nJ, 1.20 ps ultrashort pulses at a repetition rate of 115 MHz, which is the highest repetition rate in this type of fiber lasers. We believe that this fiber oscillator offers a promising source for high repetition rate applications under less stable conditions.