Advanced Photonics Nexus, Volume. , Issue , ()
635 nm femtosecond fiber laser oscillator and amplifier [Early Posting]
Fiber femtosecond mode-locked oscillator as an ideal laser solution has achieved great success in the 0.9-3.5 µm infrared wavelengths, but remains an outstanding challenge in the visible spectrum (390-780 nm). Here, we tackle this challenge by introducing a visible-wavelength mode-locked femtosecond fiber oscillator along with an amplifier. This fiber femtosecond oscillator, which emits red light at 635 nm, employs a figure-nine cavity configuration, applies a double-clad Pr3+-doped fluoride fiber as the visible gain medium, incorporates a visible-wavelength phase-biased nonlinear amplifying loop mirror (PB-NALM) for mode-locking, and utilizes a pair of customized high-efficiency and high-groove-density diffraction gratings for dispersion management. Visible self-starting mode-locking established by the PB-NALM, directly yields red laser pulses with a minimum pulse duration of 196 fs and a repetition rate of 53.957 MHz from the oscillator. Precise control of the grating pair spacing can switch the pulse state from dissipative soliton, stretched-pulse soliton to conventional soliton. A chirped-pulse amplification system built alongside the oscillator in addition immensely boosts the laser performance, resulting in an average output power over 1 W, a pulse energy of 19.55 nJ, and a dechirped pulse duration of 230 fs.
Manuscript Accepted: Feb. 6, 2024
Posted: Feb. 6, 2024