Advances in mid-infrared fibre laser technologies

Fibre lasers have became increasingly important in applications such as polymer processing, laser surgery, defence and machining etc. The development of mid-infrared fibre lasers that can operate in robust environments in both continuous wave (CW) and pulsed mode is required. To date, there have only been few investigations in the development of mid-infrared light sources.

We report the experimental results for ultrashort-pulsed Er-doped fibre lasers at 2800 nm emission wavelength using the 2D nanomaterials MXene and platinum deselinide (PtSe₂). The semiconductor device SESAM was used as a benchmark for the evaluation of the performance of these nanomaterials. CW mode-locked operation at 2800 nm has been achieved using both MXene and PtSe₂. We have identified the optimum number of layers for ink-jet printed MXene saturable absorbers and have used this knowledge to realise the first monolithic CW mode-locked mid-infrared fibre laser. The calculated theoretical minimum pulsewidth for this laser is 11.4 ps.

In addition, we have also successfully demonstrated a Ho/Pr co-doped fibre laser operating in CWmode and emitting at the very longwavelength of 2.94 μm aimed for surgical applications. The slope efficiency is measured to be 7.78%. At 3.7W pump power, the output power of the laser is 256.7mW. The beam profile, which was measured using a CCD camera, confirms that the laser operates in the fundamental transverse mode. Stability tests have been conducted at 530.8 mW and 2.67 W pump powers over a period of two hours, and the laser has a very stable output power in both cases.