High-energy low-repetition broadband ultrafast lasers empowered by hollow-core fiber

Low-repetition-rate ultrafast lasers with high peak power and broadband spectrum are critical for applications such as industrial processing, lidar, imaging and spectroscopy, but a key missing element is a low-nonlinearity, low-dispersion single-mode waveguide suitable for mass production. Here we show that inserting a homemade anti-resonant hollow-core fiber with nonlinear coefficient 1.97×10⁻⁷ W^-1m^-1 and single transverse mode low-loss transmission into a simple compact mode-locked cavity yields a turn-key single-pulse all-fiber laser at 2.63 MHz repetition, 103 kW peak power, and 35 nm bandwidth. The stable phase across wavelengths generates highly coherent swept signals with frequency noise of 97 Hz²/Hz via time stretching, which is useful for coherent detection, and enables swept-source optical coherence tomography with 1.6 m range and MHz frame rate, vibration sensing up to 113.2 kHz, and dispersive Fourier transform spectrometry at 1.54 pm resolution. Our scheme provides a perspective for developing high-performance low-repetition-rate mode-locked lasers and applications.