Efficient and scalable scheme for overcoming the pulse energy bottleneck of single-cycle laser sources

We propose a novel scheme called advanced dual-chirped optical parametric amplification (DC-OPA) that employs two kinds of nonlinear crystals (BiB$_3$O$_6$ and MgO-doped lithium niobate) to overcome the bottleneck of pulse energy scalability for single-cycle mid-infrared (MIR) laser pulses. In experiments, the advanced DC-OPA scheme achieved carrier-to-envelope phase-stable MIR laser pulses for a bandwidth of over one octave (1.4-3.1 $\mu$m) with an output pulse energy of 53 mJ. The pulse duration was compressed to 8.58 fs, which corresponds to 1.05 cycles with a central wavelength of 2.44 $\mu$m and peak power of 6 TW. To our knowledge, the obtained values for the pulse energy and peak power are the highest achieved for optical parametric amplification of single-cycle MIR laser pulses. Thanks to the energy scalability of the advanced DC-OPA scheme, it is potentially applicable to multi-TW sub-cycle laser pulses.