CO2 laser with 65MW pulses and 100kW power: concept and first steps of development

Abstract

From theoretical considerations it is well known that pulsed CO2 lasers with beam peak powers of 50 MW and a pulse length of 20 μs should be able to launch small satellites. To overcome limitations from ultra high power densities in a single laser source, a new concept proposes a beam source which consists of several individual laser systems. Short laser pulses emitted by 16 Q-switched CO2 laser sources with more than 50 MW power, as of coaxial electrode geometry with excellent beam power to volume ratio, will be combined on a common optical beam path to form a longer single pulse as required. Coaxial lasers have already been built successfully, although without Q-switching. As a main component of the above concept a new optical beam switching element - a "plasma mirror" - which can withstand ultra high power densities that must serve as a Q switch and as a beam path switch is proposed. From the literature it is well known that very dense plasmas are able to reflect an incoming laser beam totally if the plasma frequency, depending on the electron density, equals the laser radiation frequency. As a first step for the development of such a device the absorptivity and reflectivity of iron argon plasmas for CO2 laser beams has been studied theoretically and experimentally by the authors with the result, that for plasma electron densities of 1017 cm-3 nearly 100% are absorbed due to "inverse bremsstrahlung", but that the plasma frequency and thus reflectivity can not be reached, since the electron density is too small in plasmas as contained in electrical arcs.