We demonstrate an L-band all-fibre erbium-doped laser mode locked by nonlinear polarisation rotation and working in the stretched-pulse regime. The use of a single segment of gain fibre with appropriate length and dispersion and a Brewster fibre grating optimised for the L band as an in-fibre polariser enables the generation of pulses at 1.59-μm central wavelength, which can be linearly compressed to 64-fs duration. Numerical simulations of the laser model support our experimental findings. Our laser design gives a route towards low-cost and low-complexity fibre-integrated laser sources for applications requiring L-band ultrashort pulses.
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Funding: National Key Research and Development Program of China (2020YFB1805800); National Natural Science Foundation of China (61575120, 61975107); Natural Science Foundation of Shanghai (20ZR1471500); Overseas Expertise Introduction Project for Discipline Innovation (D20031); Key Laboratory of Space Active Opto-electronics Technology (2021-ZDKF-1); Engineering and Physical Sciences Research Council (EP/S003436/1 – PHOS).