Graphene based widely-tunable and singly-polarized pulse generation with random fiber lasers

TL;DR

This paper demonstrates a novel method for generating widely tunable, singly-polarized pulses using cavity-free random lasers enhanced by monolayer graphene's polarization selectivity and broadband saturable absorption, enabling stable, high-extinction pulsed laser output.

Contribution

It introduces a graphene-based approach for coherent pulse generation in cavity-free random lasers, achieving broad tunability, polarization control, and pulse stability, which was not previously possible.

Findings

Achieved broadly tunable pulsewidths down to 900 ps.

Demonstrated tunable repetition rates up to 3 MHz.

Produced highly polarized pulses with 41 dB extinction ratio.

Abstract

Pulse generation often requires a stabilized cavity and its corresponding mode structure for initial phase-locking. Contrastingly, modeless cavity-free random lasers provide new possibilities for high quantum efficiency lasing that could potentially be widely tunable spectrally and temporally. Pulse generation in random lasers, however, has remained elusive since the discovery of modeless gain lasing. Here we report coherent pulse generation with modeless random lasers based on the unique polarization selectivity and broadband saturable absorption of monolayer graphene. Simultaneous temporal compression of cavity-free pulses are observed with such a polarization modulation, along with a broadly-tunable pulsewidth across two orders of magnitude down to 900 ps, a broadly-tunable repetition rate across three orders of magnitude up to 3 MHz, and a singly-polarized pulse train at 41 dB extinction ratio, about an order of magnitude larger than conventional pulsed fiber lasers. Moreover, our graphene-based pulse formation also demonstrates robust pulse-to-pulse stability and wide-wavelength operation due to the cavity-less feature. Such a graphene-based architecture not only provides a tunable pulsed random laser for fiber-optic sensing, speckle-free imaging, and laser-material processing, but also a new way for the non-random CW fiber lasers to generate widely tunable and singly-polarized pulses.