Passively mode locked femtosecond color center lasers in the erbium gain band

Using semiconductor saturable absorbers, we passively mode lock two color center lasers (CCL) to generate femtosecond pulses at wavelengths within the gain band of erbium-doped fiber amplifiers. For the first time to our knowledge, we passively mode lock a KCl, FA(Tl) CCL in a single cavity to generate near transform limited Gaussian pulses as short as 315 fs with pulse energies up to 600 pJ. We also extend the tuning range for a NaCl, (F 2+)H CCL to include the 1.5–1.6 μm wavelength range and generate pulses as short as 280 fs by addition of a low-loss intracavity prism filter and proper crystal preparation. The performance of the two lasers are compared as a function of wavelength.