Polarization Dynamics in Mode-Locked Fiber Lasers

Abstract

The ground-breaking scientific and technological impact of optical frequency combs (OFC) – a bunch of equidistantly spaced narrow spectral lines or pulse train with the stabilized period produced by mode-locked laser – has been recognized by the scientific community sinFce 2005 when Theodor W. Hänsch was awarded the Nobel Prize in Physics. The recent Nobel Prize (2018) in physics corroborates the power of lasers in the context of pulse-shaping techniques for generating high-intensity laser pulses (Gérard Mourou and Donna Strickland: chirped pulse amplification). Though OFC and pulse-shaping techniques have already revolutionized a range of science and technological fields, there are still challenges related to unlocking new vector waveforms based on fast and slowly evolving state of polarization (SOP) in the pulse train. Harnessing vector waveforms will advance OFC-based technologies for applications in optical telecommunications, high-resolution spectroscopy, medical diagnostics, metrology and autonomous driving (LIDARs). Given advantages of the mode-locked fiber lasers vs bulk counterpart, e.g., confinement of pump and signal beams, long interaction length, and control of the propagation properties by the waveguide, make such lasers an ideal testbed for mastering different vector waveforms. This chapter summarizes our recent research results on the experimental characterization of vector waveforms generated by mode-locked fiber lasers in the time scales ranging from a few pulse widths (soliton molecules) to round-trip time (soliton rain, harmonic mode locking). Experimental results on slow and fast fundamental soliton polarization dynamics are presented in the first two sections. Experimental study of multipulsing polarization dynamics in the form of complex of pulses, soliton molecules, soliton rain, and vector rogue waves is described in the next four sections. Next, the experimental characterization of new vector mechanisms of fundamental and harmonic mode-locking is outlined. Finally, the theoretical characterization of the vector dynamics is described.