Linearly Chirped Microwave Waveform Generation Based on an Unbalanced Chirped Pulse Amplifier in a Mode-Locked Laser

We propose and demonstrate an approach to generating linearly chirped microwave waveform (LCMW) based on an unbalanced chirped pulse amplifier (CPA) in a mode-locked laser (MLL). The MLL pulses are extracted from the laser cavity after experiencing different amounts of dispersion in the CPA, resulting in two optical pulses with same spectral range but different temporal durations. The two temporally stretched optical pulses are sent to a photodetector (PD) to generate an LCMW beat signal. Our study shows that the generated LCMW signal can have a large time-bandwidth product (TBWP) and a tunable central frequency by optimizing the dispersion coefficients of the CPA and tuning the time delay between the optical pulses. The incorporation of the unbalanced CPA in the MLL enables the generation of optical pulses with high optical power, eliminates the requirements for external dispersive device for pulse stretching and features a simple structure and a low cost.