Self-starting Cr2+:ZnSe femtosecond laser with 200 nm continuous tuning and 96.5 nm bandwidth at 2.2 µm.

Abstract

High-resolution optical diagnostics in the short wavelength infrared (SWIR II) region have gained significant attention in medical research, showing great potential for tissue spectroscopy and visualization due to the region's low water absorption and scattering coefficients. However, high-beam-quality sources covering an entire spectral range are limited. This paper presents the development of a femtosecond Cr²⁺:ZnSe laser with a 2.2 µm center wavelength, a pulse duration of 60 fs, a spectral width of 96.5 nm, and an energy of 4.5 nJ. The resulting source is expected to enable spectroscopy and the optical coherence tomography system for diagnosing collagen-rich tissues.