Tuning range extension of pulse repetition rate using chirped fiber Bragg gratings

We present a fiber femtosecond laser oscillator that incorporates a pair of chirped fiber Bragg gratings (CFBGs) to augment the cavity length elongation produced by a PZT actuator. With a magnification factor of 18.2, the CFBG pair offers a 4.44 mm cavity length extension, providing a 25.59 kHz tuning range of the repetition rate from a 41.56 MHz nominal value without loss of mode locking. The extended tuning range enhances the performance of comb stabilization in uncontrolled environments and pulse-to-pulse interferometry for step height measurements.