Conference Agenda

We report on sub-picosecond pulses generation from mode-locked erbium-doped-fiber lasers operating at 2.8 µm and 3.5 µm using graphene-based saturable absorbers. The lasers produce stable 600 fs pulses at 2.8 µm and 700 fs at 3.5 µm. Our findings highlight graphene saturable absorber mirrors (G-SAM) as prime candidates for sub-picosecond operation for mid infrared fiber lasers.

Thanks to the low maximum phonon energy of fluoride glass, fiber lasers are no longer limited by the transmission limits of silica. This presentation reviews recent high-power milestones, including multi-watt continuous-wave emission approaching 4 µm and high-energy short-pulse amplifiers near 3 µm, alongside ongoing challenges in all-fiber integration.

This study focuses on mid-infrared and visible fibre laser systems based on fluoride fibres in linear cavity configuration with femtosecond-inscribed fibre Bragg gratings. Using Erbium-doped ZBLAN fibre as the gain medium, two laser configurations are demonstrated. The first is a visible upconversion laser operating at 543 nm, employing silica-based FBGs inscribed with 267 nm wavelength and Talbot interferometer technique. The second system operates at the wavelength of 2.75 µm, using a double-clad ZBLAN fibre and an FBG inscribed in passive fluoride fibre to form the laser cavity. Femtosecond laser inscription techniques enable highly reflective gratings essential for stable and compact resonators. These results highlight the effectiveness of FBG-based cavities in extending fibre laser operation into both visible and mid-infrared regions, supporting the development of robust and efficient fluoride fibre laser systems.

We demonstrate a new paradigm for high-efficiency, high-power mid-infrared (MIR) lasing in the 3 µm water vapor transmission window using a versatile random Raman fiber laser (RRFL) pump source. The RRFL offers broadband tunability (1560-1783 nm) and high power (>50 W). By upconversion pumping a Ho³⁺-doped ZrF₄ fiber at 1642 nm, we achieve 14.3 W at 2878 nm with a slope efficiency of 52.5% (~94% of the Stokes limit). For Dy³⁺-doped ZrF₄ fiber pumped at 1638 nm, we obtain 11.7 W at 3037 nm with a slope efficiency of 41.6% (~83% of the Stokes limit). Numerical modeling shows that reducing background loss could further improve the Dy³⁺ laser efficiency to ~94% of the Stokes limit. Thermal analysis confirms low heat generation and potential for scaling to >100 W output. This work provides a robust and efficient platform for MIR lasers in the 3 µm band, enabling advanced applications in spectroscopy, free-space communications, and medicine.