Watt-level ultrafast 1.75 {\mu}m laser system based on thulium-doped core and terbium-doped cladding fluoride fibers

TL;DR

This paper presents a watt-level, ultrafast laser system at 1.75 μm using thulium and terbium-doped fluoride fibers, achieving femtosecond pulses suitable for multiphoton microscopy.

Contribution

It introduces a novel fiber laser system combining thulium and terbium doping to produce high-power, ultrafast pulses at 1.75 μm with efficient compression and tunability.

Findings

Generated ~250 nJ pulses with ~1 W average power

Achieved pulse duration of 217 fs after compression

System is suitable for multiphoton microscopy

Abstract

We report watt-level femtosecond pulses in the 1.75 $\mu$m region using a thulium-doped core, terbium-doped cladding fluoride (Tm:Tb:ZBLAN) fiber laser system. The seed pulse is generated through stimulated Raman scattering in a silica fiber pumped by an erbium-doped fiber laser. The soliton is subsequently amplified through a multi-stage Tm:Tb:ZBLAN amplifier. The tunability of our chirped fiber Bragg grating stretcher, matched with a Treacy compressor, compresses the pulse to 217 fs. Our system generates ~250 nJ of single-pulse energy, with a corresponding average power of ~1 W at a 4 MHz repetition rate. The laser system is suitable for multiphoton microscopy.