A few-cycle mid-infrared (MIR) laser is demonstrated via nonlinear self-compression in solid thin plates. In this novel solution, the anomalous material dispersion in the MIR band and the chirp induced by self-phase modulation are mutually compensated, which can achieve self-compression. Finally, with the 4 µm laser injection with 4.8 mJ/155 fs and few-cycle pulses with 3.44 mJ, 29.4 fs are generated with a high efficiency of 71.7%, and the system maintains very good spectral stability in 10 days. Compared with other post-compression methods, this self-compression technique has the advantages of high efficiency and robust and large energy expansion scale, which can be further extended to MIR lasers with other wavelengths and higher peak power.

Temporal contrast directly affects the interaction between the ultraintense and ultrashort pulse laser with matter. Seed laser sources with broad bandwidth and high temporal contrast are significant for overall temporal contrast enhancement. The technique of cascaded nonlinear processes with optical parametric amplification (OPA) and second harmonic generation (SHG) is demonstrated for high temporal contrast seed source generation. Within 40 ps before the main pulse, the temporal contrast reaches over 10 11 . The pulse energy and duration of the high contrast pulse are 112 μJ and 70 fs, respectively. Considering its high beam quality and stability, this laser source can serve as a high-quality seed for Nd: glass-based ultraintense and ultrashort pulse laser facilities.