Multi-Watt Long-Wavelength Infrared Femtosecond Lasers and Resonant Enamel Ablation

High average power broadband tunable long-wavelength infrared (LWIR) femtosecond lasers operating at fingerprint wavelengths of 7–14 µm hold significant promise across a range of applications, including molecular hyperspectral imaging, strong-field light-matter interaction, and resonant tissue ablation. Here, a 6–12 µm broadband tunable parametric amplifier based on LiGaS₂ or BaGa₄S₇, generating an output power of 2.4 W at 7.5 µm, and 1.5 W at 9.5 µm, pumped by a simple and effective thin-square-rod Yb:YAG amplifier producing 110 W 274 fs output pulses is presented. As a proof of concept, efficient resonant ablation and microstructure fabrication on enamel are showcased at the hydroxyapatite resonant wavelength of 9.5 µm, with a laser intensity two orders-of-magnitude lower than that required by non-resonant femtosecond lasers, which can foster more precision surgical applications with superior biosafety.