Unravelling Saturable Absorption of Thulium-doped Fibres for New Level of Integrated Femtosecond Pulse Generation

TL;DR

This paper demonstrates a highly integrated all-fibre femtosecond laser using Thulium-doped fibres as a saturable absorber, achieving stable, ultrashort pulses with potential for compact laser systems.

Contribution

It introduces a simple, highly integrated all-fibre saturable absorber based on Thulium-doped fibres, enabling ultrashort pulse generation without complex cavity designs.

Findings

Achieved 350 fs pulse duration at 45 MHz repetition rate

Demonstrated stable operation with ~1% power fluctuation

Used a saturable absorber with 23% modulation depth

Abstract

The ultrashort pulse laser operation is crucially defined by engaging explicit modulators. Conventionally, they are laborious to incorporate into an all-fibre design or involve the design of sophisticated cavities. We exploit Thulium-doped fibre as the gain and simple, highly integrated saturable absorber with a modulation depth of 23% and a high thermal damage threshold. Hence, pulses as short as 350fs carrying 1nJ energy at a repetition rate of 45MHz have been demonstrated. The laser average output power showed long-term stability with ~1%. The utilised concept of all-fibre saturable absorber provides technological grounds for a down-scaled, highly integrated laser architecture.