Compact Tm-doped fibre laser pumped by a 1600 nm Er-doped fibre laser designed for environmental gas sensing

•An all-fibre linear Tm-doped fibre laser is created pumped by Er-doped fibre laser.•Both of them are optimized as per the fluorescence property of Er and Tm ions.•Outputs are 35.5 mW and 10.6 mW respectively at wavelength of 1874 nm and 1995 nm.•These wavelengths align well with the absorption spectra of environmental gases.•CO2 sensing can be done by this compact system ideally suited to in-the-field use.

In this work, the compact all-fibre linear Erbium (Er)-doped fibre lasers, operating at wavelengths of 1584 nm and 1600 nm have been described and optimized, with an aim to achieve better pumping conditions for a Thulium (Tm)-doped fibre laser. Optimization of the system has been carried out involving the studies on the different lengths of the Er-doped fibre and the different grating pairs used to achieve 173.5 mW of laser power at 1600 nm under bidirectional pumping at 980 nm. The designed Er-doped fibre laser at 1600 nm has been utilized successfully to pump longer wavelength Tm-doped fibre laser. The obtained laser power (output of Tm-doped fibre laser) of 35.5 mW at 1874 nm and 10.6 mW at 1995 nm is effective for environmental gas sensing, as these wavelengths align well with the absorption spectra of greenhouse gases such as CO2. The laser offers high power (tens of milliWatts), good directionality and a compact overall packaging with the diode pumping, making them ideally suited to ‘in-the-field’ use.