All-polarization-maintaining figure-of-9 soliton and dispersion-managed Er-doped fiber oscillators

Abstract

We first demonstrate a self-starting, environmentally stable, all-polarization-maintaining (PM) fiber based figure-of-9 erbium-doped fiber laser using a nonlinear amplifying loop mirror (NALM) mode-locked in the soliton regime. Stable single pulse operation can be achieved at a center wavelength of 1572 nm with a 3 dB bandwidth of 11 nm. The output pulses have an average power of 11.5 mW and a repetition rate of 52.5 MHz, and the pulse duration is 420 fs after compression. We then add a spool of PM dispersion-compensation fiber to compensate the cavity dispersion. Stretched pulse mode-locking could then be achieved with a center wavelength of 1560 nm and a 3 dB bandwidth of 39.5 nm, which is, to our knowledge the broadest spectrum measured from an all-fiber all-PM NALM-based oscillator. The pulse can be further compressed down to 95 fs, nearly transform limited. Therefore, these sources are ideally suitable for ultrafast optics applications such as ultrafast spectroscopy and nonlinear microscopy.