Ultra-high order harmonic mode-locking of a Raman fiber laser

Abstract

An ultra-high order harmonically mode-locked Raman fiber laser with a high signal-to-noise ratio has been proposed and demonstrated. We apply the nonlinear polarization rotation (NPR) technique as the mode-locker in the Raman fiber laser. The underlying harmonic mode-locking (HML) mechanism is discussed to achieve ultra-high order HML in the Raman fiber laser. Up to 5044th ultra-high order HML has been obtained with a signal-to-noise ratio of up to 42.5 dB. To the best of our knowledge, this is the highest order of passive HML achieved so far from a Raman fiber laser using NPR or similar techniques.

Raman Gain Square‐Wave Noise‐Like Pulse Laser Pumped by a Random Fiber Laser

“…[9][10][11] Most of these works used rare earth doped fibers to provide optical gain limited in particular wavelength range, while Raman fiber lasers can exactly make up for this weakness. [12,13] Therefore, generation of NLP in mode-locked fiber lasers using stimulated Raman scattering (SRS) to provide optical gain at flexible wavelengths, is drawing more and more attention, including high-order harmonic NLP generation, [14] NLP based on cascaded Raman scattering, [15,16] and rectangular NLP generation, [17] etc. However, a long cavity is commonly required to provide enough Raman gain in such systems, which conversely degrades the phase-matching condition of mode locking.…”