Generation of Two‐Cycle Light Bullets With 2.0 mJ Energy via Self‐Compression of 5‐µm Pulses in Zinc Sulfide

Abstract Using ZnS as a nonlinear medium, solitonic self‐compression of 2.5 mJ pulses at 5‐µm wavelength is investigated. The spectral broadening in the self‐compression scheme is demonstrated with a reduction of pulse durations from 80 to 37 fs. The compression regime appears below the onset of small‐scale filamentation, yielding two‐cycle pulses with 2.0 mJ energy. The resulting high throughput of 80% is accompanied by a nearly undisturbed beam profile. Excellent spectral homogeneity across the beam profile is further demonstrated, which sets the scheme apart from other bulk compression schemes. Transformation of the Gaussian input profile into a Townes profile is observed, which acts as the mechanism for maintaining a high spatio‐temporal homogeneity and translates into a peak power increase that is nearly inversely proportional to the pulse duration reduction. The resulting peak power of 45 GW in a 1 kHz pulse train constitutes a new record value beyond 4 µm wavelength. The limiting effect of multiphoton absorption is additionally explored, and high harmonics are recorded up to 8th order. These harmonics support a >2‐octave supercontinuum spectrum in the visible and short‐wave IR spectral region with sizable 0.1 mJ pulse energy.