Enhanced peak power and short pulse operation of planar waveguide CO2 lasers

Abstract

We report a large peak power enhancement and reduction in pulse width for planar waveguide carbon dioxide lasers. Gain modulation through rf discharge power switching produces trains of laser pulses with peak power levels at up to 38 times the cw power level, with a pulse duration as low as 10 μs. Operation at repetition rates in the kHz region preserves the average power (100 W) of the normal cw/long pulse mode of operation. The laser is shown to operate close to the predicted boundaries dictated by thermal loading of the discharge.

Longitudinal coupled‐cavity scheme for microwave‐excited CO2 slab lasers

“…Future designs will have to maintain this efficiency throughout the operating power regime of this laser. As compared to RF-excited slab lasers, it should be noted that the typical electrooptic efficiency of the latter attains ϳ10% in both sealed and slow-flow schemes for CW and pulsed operation [14]. This efficiency level is not much higher than that obtained by the microwave-excited slow-flow CO 2 laser experiment presented in this paper.…”

“…This microwave-excited diffusion-cooled laser yielded ϳ0.5 W/cm 2 . Recently, an RF-excited scheme presented by Villarreal et al [14] introduced an enhanced peak-to-average laser power ratio of 38. The laser power density-per-slab area attains ϳ0.8 W/cm 2 .…”

High-peak-power CO 2 planar waveguide lasers for direct high-resolution machining

“…2. We have measured the variation of the fall time with pressure and mixture for a static gas fill that has reached dissociation equilibrium [2]. As may be expected from the storage ofvibrational energy in the N2 and CO molecules followed by energy transfer to C02, the response time decreases in relation to the partial pressure of CO2 in the mixture.…”

“…Fig. 2 shows typical enhanced pulses [2] using a 200 Hz pulse rate and 20 kW peak power with 180 ton of 1 : 1 :3 C02:N2 ;He +5%Xe. A peak power of 3 .5 kW is achieved in the 20 to 50 ps range.…”

CO2 laser drives extreme ultraviolet nano-lithography — second life of mature laser technology

“…These practically maintenance−free lasers operate usually with gas mix pressure 50-150 Torr and are capable of operating in a wide range of pulsing frequencies, from single−pulse mode to CW−mode of RF−discharge, producing pulses of 50-500 microseconds in optical beams of good quality delivered by various configurations of unstable−wa− veguide hybrid resonators [57]. The optimized designs could produce energetic pulses of duration down to few microseconds [59] achieved only by RF modulation. The multi−kW diffusion−cooled lasers based on the planar and annular discharge geometries, covering a power level range from few Watts to kiloWatts, have been present in the industry for many years and are commercially available from multiple vendors.…”