Super-Broadband Noise-Like Pulse Erbium-Doped Fiber Ring Laser With a Highly Nonlinear Fiber for Raman Gain Enhancement

We present a compact all-fiberized erbium-doped fiber ring laser, which generates linearly polarized picosecond pulses with a maximum bandwidth of 135 nm and excellent spectral flatness. The pulse energy and width are reconfigurable from 0.7 to 1.1 nJ and from 6.5 to 220 ps, respectively, via controlling the pumping power and/or the cavity finesse. We also analyze the relative intensity noise (RIN) characteristics of the source that results in ${-}{\rm 97}~{\rm dB}$ at low frequencies (up to 100 kHz) and ${-}{\rm 104}~{\rm dB}$ at high frequencies (up to 5 MHz), respectively. In particular, the high-frequency RIN is attributed to the spontaneous Raman scattering generated in the laser and of a comparable level with that of a commercial supercontinuum source based on a mode-locked fiber laser.