Megawatt peak-power, single-mode, mid-infrared femtosecond pulse delivery at 5-6 μm via silica-based anti-resonant hollow core fiber

We demonstrate the first, to our knowledge, delivery of megawatt peak power, single-mode mid-infrared (MIR) femtosecond pulses at 5-6 μm using a silica-based anti-resonant hollow core fiber (AR-HCF). Benefiting from the light confinement inside the hollow core, the AR-HCF exhibits high damage thresholds, reliable power stability, efficient spatial beam self-cleaning, and pulse shape preservation. Pumped by a homemade LGS-based two-stage optical parametric amplifier generating high-power ∼200 fs pulses, the fiber achieves a maximum delivered peak power of 4 MW at 5.1 μm and 5 MW at 6.1 μm, with peak intensities reaching 100 GW/cm2, despite fiber losses exceeding 2 dB/m. This flexible, meter-scale delivery system demonstrates exceptional potential for addressing the challenges of high peak power MIR laser delivery in precise, minimally invasive interventional ablation, particularly at resonant peaks such as amide-I (6.1 μm) and cholesterol esters (5.75 μm).