A carrier-envelope-phase-stable near-single-cycle mid-infrared laser based on optical parametric chirped pulse amplification and hollow-core fiber compression is demonstrated. A 4 μm laser pulse with 11.8 mJ energy is delivered from a KTA-based optical parametric chirped pulse amplification (OPCPA) with 100 Hz repetition rate, and compressed to 105 fs by a two-grating compressor with efficiency over 50%. Subsequently, the pulse spectrum is broadened by employing a krypton gas-filled hollow-core fiber. Then, the pulse duration is further compressed to 21.5 fs through a CaF bulk material with energy of 2.6 mJ and energy stability of 0.9% RMS, which is about 1.6 cycles for a 4 μm laser pulse. The carrier envelope phase of the near-single-cycle 4 μm laser pulse is passively stabilized with 370 mrad.

We demonstrate in this Letter the generation of carrier-envelope-phase (CEP)-stabilized laser pulses at 910 nm with simultaneously high-temporal-contrast, broad spectral bandwidths and few-cycle pulse durations. Through combining the techniques of cascaded optical parametric amplification (OPA) and second-harmonic generation (SHG) in the laser setup, a pulse temporal contrast as high as > 10 12 has been obtained at the laser output. During the OPA and SHG processes, both the pulse chirp and gain bandwidth are perfectly optimized, leading to the generation of 170 µJ pulses with > 200 n m bandwidth and ∼ 15 f s pulse duration. Moreover, the CEP of the laser is stabilized passively to a noise level of less than 340 mrad. This high-quality pulsed light source, as the seed laser of the deuterated potassium dihydrogen phosphate (DKDP)-based 100 PW system, will be integrated into the Station of Extreme Light facility in the near future.

A femtosecond mid-infrared optical vortex laser can be used for high harmonic generation to extend cutoff energy to the kilo-electron-volt range with orbital angular momentum, as well as other secondary radiations. For these, we demonstrate a high-energy femtosecond 4 μm optical vortex laser based on optical parametric chirped pulse amplification (OPCPA) for the first time. The optical vortex seed is generated from a femtosecond 4 μm laser by a silicon spiral phase plate with the topological charge l of 1 before the stretcher. Through using a two-stage collinear OPCPA amplifier, the chirped vortex pulse is amplified to 12.4 mJ with 200 nm full width at half-maximum bandwidth. After compression, the vortex laser pulse with 9.53 mJ, 119 fs can be obtained. Furthermore, the vortex characteristics of the laser beam are investigated and evaluated. This demonstration can scale to generate a higher-peak-power vortex mid-IR laser and pave a new way for high field physics.

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