All-fiber chirp tuning of ultrashort pulses via long chirped fiber Bragg grating pair

Chirp tuning of ultrashort pulses is crucial for nonlinear fiber amplification and nonlinear dynamics investigations. Here we demonstrate all-fiber chirp tuning via chirped fiber Bragg grating (CFBG) pair. Two identical long CFBG were placed reversely to cancel out most of their huge dispersion (~40 ps/nm @1030 nm), while the controllable temperature gradient along them could be used for precise chirp tuning with a tuning range of ~ ps², verified by dispersion measurement and ultrashort pulse broadening. This relatively large chirp tuning could be used in prechirp management in nonlinear fiber amplifiers, exemplified by the optical spectrum tailoring therein. In addition, we also show this precise chirp tuning capability could be very helpful for pulse temporal quality diagnosis, which is indispensable for seed pulse optimization. We believe this all-fiber chirp tuning technique would find wide applications in nonlinear amplification and ultrafast nonlinear dynamics investigations.