Development of a Color Center Laser in Sodium -

A powerful and stable color center laser based on a perturbed F_2^+ center has been demonstrated in additively colored NaCl:OH ^- crystals. Optical spectroscopy measurements indicate that this new laser active color center is an F_2^+ defect located beside an O^{2-} substitutional impurity ion. The perturbing O^{2 -} ion serves both as a stable electron trap as well as a spatial trap for the F_2^+ center. Excited state spectroscopy measurements of the center conclusively demonstrate its F_2 ^+-like character. The NaCl:OH^- (F _2^+:O^{2-} ) color center laser tunes smoothly over the 1.4 to 1.9 μm wavelength region, delivering output powers in excess of 1 Watt at the peak of the tuning curve. Laser operation has been monitored for periods of several weeks with no observable fading in output power. Modelocked operation of the NaCl:OH^- laser has generated tunable infrared pulses of 7 psec duration. High average modelocked powers in excess of 800 mW have been obtained at the peak of the laser tuning curve. Finally, stabilized enhanced modelocked operation of the NaCl:OH^- laser has been achieved utilizing an external nonlinear resonator coupled to the modelocked laser cavity. To date, this coupled cavity laser has generated tunable, subpicosecond pulses as short as 150 fsec, with high average powers.