Mode-locked dysprosium fiber laser: picosecond pulse generation from 2.97 to 3.30 {\mu}m

TL;DR

This paper introduces the first broadly tunable mode-locked dysprosium fiber laser operating from 2.97 to 3.30 μm, achieving picosecond pulses with high energy, expanding mid-infrared laser capabilities for practical applications.

Contribution

It demonstrates a novel dysprosium-doped fiber laser using frequency shifted feedback, achieving unprecedented spectral tunability and pulse generation in the mid-infrared range.

Findings

Generated 33 ps pulses with up to 2.7 nJ energy.

Achieved 3000–3400 cm^-1 tunability from 2.97 to 3.30 μm.

First mode-locked fiber laser covering this spectral region.

Abstract

Mode-locked fiber laser technology to date has been limited to sub-3 {\mu}m wavelengths, despite significant application-driven demand for compact picosecond and femtosecond pulse sources at longer wavelengths. Erbium- and holmium-doped fluoride fiber lasers incorporating a saturable absorber are emerging as promising pulse sources for 2.7--2.9 {\mu}m, yet it remains a major challenge to extend this coverage. Here, we propose a new approach using dysprosium-doped fiber with frequency shifted feedback (FSF). Using a simple linear cavity with an acousto-optic tunable filter, we generate 33 ps pulses with up to 2.7 nJ energy and 330 nm tunability from 2.97 to 3.30 {\mu}m (3000--3400 cm^-1)---the first mode-locked fiber laser to cover this spectral region and the most broadly tunable pulsed fiber laser to date. Numerical simulations show excellent agreement with experiments and also offer new insights into the underlying dynamics of FSF pulse generation. This highlights the remarkable potential of both dysprosium as a gain material and FSF for versatile pulse generation, opening new opportunities for mid-IR laser development and practical applications outside the laboratory.