We demonstrate chopped-cw lasing in a Ce:LiCAF oscillator directly generating deep-UV light around 290 nm. The cw output was achieved by asynchronous pumping of a Ce:LiCAF oscillator by a mode-locked frequency quadrupled Nd:YVO4 laser that generates 23 ps pulses of 266 nm light at a repetition rate of 80 MHz. The pump laser was chopped with 8.3% duty cycle to minimize thermal effects in the frequency quadrupling stage. The maximum output power achieved was 384 mW when pumped with 3.3 W of pulsed 266 nm light, with a slope efficiency of 33%. The laser output was tunable from 286 to 295 nm with the potential to be broadened over the full gain bandwidth of Ce:LiCAF from 280 to 315 nm.

We analyze the dynamics of mode-locked pumped solid-state lasers focusing on the transition between mode-locked and CW behavior. Where the ratio of the pump and laser cavity lengths is a rational number, 'rational-harmonic mode-locking' is obtained. When the cavity length is detuned away from such resonances, modulated continuous output is generated. The transition from mode-locked to modulated CW operation is explored experimentally for a Ce:LiCAF laser operating at 290 nm and pumped by a 78.75 MHz mode-locked frequency quadrupled Nd:YVO(4) laser. Both CW output and mode-locked output with pulse repetition rates up to 1.1 GHz were achieved. A rate equation model is developed to predict optimum cavity lengths for achieving CW output with minimized modulation.

We report birefringent tuning using single and multiple magnesium fluoride (MgF(2)) Brewster tuning plates in a mode-locked pumped continuous-wave Ce:LiCAF laser. Depending on the thickness of the MgF(2) plates used, continuous tuning over a range of up to 13 nm from 284.5 to 297.5 nm with a full width at half-maximum linewidth of 14 pm (50 GHz) was achieved. By combining MgF(2) plates with etalons, the linewidth of the laser was narrowed down to 0.75 pm (2.7 GHz). This generated narrowband output is suitable for many applications in spectroscopy, cold-atom manipulation, and sensing.

No abstract