Sub 500 fs high power quasimonolithic FCPA laser using an all-solid step-index flexible PM VLMA Yb-doped fiber amplifier

We report on the design of a quasi-monolithic fiber chirped pulse amplification (FCPA) system operating at 1040 nm. Chirped-pulse amplification has been achieved using an all-solid step-index PM VLMA Yb-doped fiber, designed and drawn at Photonics Bretagne. The amplifier is integrated to the system through an internally developed mode field adapter (MFA), and bended with a 14 cm diameter, giving a truly single-mode behavior. 540 fs pulses are obtained without any fiber length optimization. An average power of 50 W has been achieved at the fundamental repetition rate of the laser, but also energies up to 41 mu J per pulse at lower repetition rate, pump power limited. The pulses are stretched using a thermally-controlled tunable chirped fibered Bragg grating (CFBG), allowing fine dispersion tuning, and compressed using a chirped volume Bragg grating (CVBG).