Sub-Two Cycle Compression of Yb Laser Pulses using Rotational Nonlinearity Enhancement in Molecular Gases

Few-cycle pulse generation has largely been achieved through the nonlinear propagation of short (<10-cycle) pulses in noble gas-filled capillaries, where the ``instantaneous'' optical nonlinearity can be efficiently exploited to generate octave spanning bandwidths. At much longer input pulse durations (>100-cycle), generating comparable bandwidths using noble gases requires employing larger levels of nonlinearity, prolonged interaction lengths, or multiple compression stages. By instead using linear molecular gases, where the field-driven alignment of the molecular ensemble boosts the optical nonlinearity, multi-octave supercontinua supporting sub-cycle durations can be generated. We demonstrate the enhanced supercontinuum generation by propagating 280 fs pulses in N₂, N₂O, and CO₂ filled hollow-core fiber. We compress pulses below two-optical cycles and use them to generate high-order harmonics.

This material is based on research supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES) under Award No. DE-SC0019291 and by the Air Force Office of Scientific Research (AFOSR) under Award No. FA9550-16-1-0149.