Progress in ultrafast color center lasers

We report new ultrafast color center lasers operating in the near infrared spectral range. Using newly developed KCl and KBr (F2+)H and (F2+)AH color center systems and synchronous mode-locking we realize picosecond and subpicosecond color center laser operation for the first time in the 1.8-2.4 μm wavelength range. Using semiconductor saturable absorbers we passively mode-lock NaCl (F2+)H and KCl FA (Tl) color center lasers in single- and coupled-cavity configurations. This results in mode-locked laser operation in the 1.5-1.7 μm range with shortest obtained transform-limited pulses of ∼ 150 femtosecond duration and pulse energies as high as several nJ. As a step toward infrared spectral continuum generation we amplify these nJ-level pulse energies by a factor of ∼ 103 using KCl FA(Tl) amplifier crystals.