Stable Ultrashort Pulse Generation Using a Coiled and Tapered Few-Mode-Fiber Polarization Controller as a Saturable Absorber

Abstract

We present a coiled and tapered graded-index few-mode-fiber (FMF) polarization controller (PC) as a saturable absorber (SA) in an all-fiber laser. We obtain the 845 fs ultrashort pulse with a signal-to-noise ratio (SNR) of 65 dB, using a tapered graded-index FMF of 40 cm in the cavity. The spectrum is centered at 1588.2 nm with a 3 dB spectral bandwidth of 4.04 nm. Furthermore, a Q-switched mode-locked state is observed between 140 and 360 mW of the pump power in the cavity. The results further demonstrate the application of a coiled and tapered graded-index FMF PC as a SA for stable high-energy ultrashort pulse formation and provide a technical method for generating ultrashort pulses.