Broadband and Tunable 920-nm Femtosecond Pulse Generated by an All-Fiber Er:Fiber Laser System

Fiber-optic Cherenkov radiation (FOCR) is a promising nonlinear process that is widely used for nonlinear wavelength conversion. In this study, an all-fiber 920-nm femtosecond pulse source is experimentally demonstrated by using Cherenkov radiation. The 4-nJ 150-fs 1550-nm amplified seed pulse source ensures highly efficient 920-nm pulse generation. Cherenkov radiation is stimulated by inputting the high-energy ultrashort pulse to a highly nonlinear fiber. The dispersion values of the highly nonlinear fiber (HNLF) are carefully chosen to generate CR pulses at 920 nm. The generated pulse has a 150-pJ single pulse energy and a 232-fs pulse duration. The typical 30-nm bandwidth can support a sub-50-fs transform-limited pulse duration. The pump current can be adjusted to tune the central wavelength of the pulse source over 905-930 nm. This very simple approach can generate 920-nm femtosecond pulses. The wavelength range is useful for a wide range of applications, such as two-photon microscopy (TPM) in bio-imaging and so on.