Tm-doped ultrafast fiber laser chirped-pulse amplification at 1900 nm with second-harmonic-generation

A compact thulium-doped (Tm) chirped-pulse-amplification (CPA) fiber system is demonstrated that generates 360 fs short pulses centered at a wavelength of 1901 nm with high pulse energies larger than 200 nJ (repetition rate of 9.26 MHz). In an additional second-harmonic generation setup with a periodically poled lithium niobate crystal, pulses centered at 950 nm with a pulse energy of 73 nJ and a transform-limited duration of 300 fs are produced. Such a frequency-doubled Tm-doped CPA system operating around a wavelength of 950 nm can offer an attractive ultrafast source for two-photon microscopy.