Abstract
Ultrafast lasers in the mid-infrared (mid-IR) range are attracting much attention because of their potential
applications to molecular spectroscopy, biomedical measurement, material processing, and attosecond
science. Among various ultrafast laser materials, chromium-doped chalcogenides are especially
promising for generating few-cycle mid-IR pulses because of their broad fluorescence spectra. In this
article, we review the history of mode-locked Cr:ZnS and Cr:ZnSe lasers and introduce our recent progress
in the development of the former. By using single-walled carbon nanotubes resonant in the mid-IR
wavelength, we achieved self-starting, mode-locked oscillation and 4.7-cycle pulse generation at a center
wavelength of 2.3 μm.
