SBS mitigation by sinusoidal phase modulation of a 1572 nm all-fiber amplifier for lidar CO2 sensing

Abstract

Lidar CO2 sensing can be performed by 1572 nm pulsed laser sources. This work presents the development of a fiber amplifier at this wavelength emitting 1 µs FWHM Gaussian pulses at a repetition rate of 7.5 kHz. We obtain the mitigation of stimulated Brillouin scattering (SBS) by shaping the seed laser spectrum into a frequency comb with sinusoidal phase modulation. This frequency comb is compatible with a coherent dual-comb spectroscopy (DCS) method for a targeted lidar CO2 sensing application. The effect of the harmonics spacing and relative intensity on the SBS threshold is studied. Laser pulses are amplified up to 182 µJ (182 W peak power) from a single-mode erbium (Er) and ytterbium (Yb) co-doped fiber. Those results hold promise for seeding large mode area Er-Yb co-doped fiber power amplifiers.