Pulse combination and compression in hollow-core fiber for few-cycle intense mid-infrared laser generation

The generation of high-peak-power, few-cycle mid-infrared (MIR) pulses using coherent beam combination and nonlinear pulse compression techniques simultaneously is demonstrated. The two pulses, with identical pulse energy of 2.8 mJ and pulse duration of 160 fs, are coherently combined at the input end of a krypton-filled hollow-core fiber (HCF), and then the bandwidth of the combined pulse is broadened to near an optical octave due to strong phase modulations, and the temporal width is compressed into a few-cycle regime. Finally, a 2.7 mJ, 22.9 fs, 20 Hz laser at 4 μm can be obtained, and the pulse peak power is greatly enhanced compared with that of conventional single-channel optical parametric chirped pulse-amplification systems. Furthermore, the peak power generated from this system has the prospect of further scaling up through use of more channels of coherent combination, which can pave a way to generate higher peak power ultra-intense MIR pulses for strong-field physics.