Dispersion Analysis and Control in a Yb-Doped Fiber Chirped Pulse Amplification System and Second-Harmonic Generation

We report a dispersion-controlled Yb-doped fiber chirped pulse amplification (CPA) system incorporating a tunable chirped fiber Bragg grating (CFBG) stretcher and a single-grating transmission compressor for dynamic compensation of power-dependent nonlinear effect. During the pulse amplification, the CFBG introduces adjustable third-order dispersion (TOD). By tuning the initial TOD provided by CFBG from −0.1965 ps³ at 2.37 W to −0.1791 ps³ at 9.65 W, residual TOD is efficiently compensated with the power-dependent nonlinear effect. As a result, by optimizing the dispersion balance at each output power, nearly constant femtosecond pulses with a duration of 250 fs are obtained over the entire power range, confirming effective control of nonlinear and dispersive effects in the amplification. The high-quality 1030 nm pulses enable efficient second-harmonic generation (SHG) in a type-I BBO crystal, producing 3.56 W femtosecond output at around 515 nm with a pulse duration of 190 fs, close to the Fourier transform limit. These results demonstrate a robust approach to generating high-power and temporal coherent ultrafast pulses suitable for precision micromachining and two-photon polymerization.