Few-cycle, µJ-level pulses beyond 5 µm from 1-µm-pumped OPA's based on non-oxide nonlinear crystals

Nonlinear vibrational and strong-field spectroscopies can tremendously benefit from high-power few-cycle mid-infrared (MIR) laser pulses beyond 5 μm at repetition rates << 10 kHz. Here, we explore the potential of a novel non-oxide crystal, BaGa₄S₇ (BGS), for the direct coverage of the MIR beyond 5 µm starting from Yb-laser sources and report on a μJ-scale, sub-4-cycle, 100-kHz optical parametric amplifier (OPA) at 10 μm. We compare BGS with LiGaS₂ (LGS) with respect to performance in ultrafast MIR OPAs. The unique properties of BGS indicate great potential for nonlinear optical applications, especially due to the much faster development of its manufacturing processes and the larger achievable single-crystal sizes compared to LGS.