CO2 lasers are used in commercial and military applications and produce laser light in the infra-red region of the spectrum at around the 1000nm (10µm) wavelength. Some designs include incorporation of a ceramic 'bore', which acts as the optical wave-guide for the laser radiation and confines the electrical discharge. The ceramic therefore requires a very straight and accurate central hole with the outside having electrical contacts and the ends being designed to join to mirrors etc. The bores may be round or square and the device may be straight, Z-folded (i.e. several straight lengths).
Alumina Laser Wave Guides
Morgan Advanced Ceramics (MAC) Aluminas are particularly suitable for producing laser wave-guides since they provide the required combination of dielectric properties, thermal conductivity and optical reflectivity. Straight bores can be manufactured using ultrasonic drilling up to 250mm in length. Alumina grades are available that are particularly suitable for these parts and where additional metallising and brazing are required to form the complete assembly. Alternatively the development of square bores has been achieved using glazing or thermo-diffusion bonding techniques. Morgan Advanced Ceramics has all the facilities to manufacture these parts up to 1 metre in length including grinding, polishing, thermo-diffusion bonding and subsequent molybdenum-manganese metallising.
Thermo-Diffusion Bonded Assemblies for FIR CO2 Lasers
Morgan Advanced Ceramics’ ability to produce thermo-diffusion bonded assemblies offers excellent flexibility for the manufacturer of FIR CO2 lasers. The basic technique allows for two pieces of alumina to be cohesively bonded together such that there is no apparent joint and for all intents and purposes the resulting component is monolithic in nature. Using this technique, waveguides comprising complex assemblies of high precision component parts can be manufactured to form a homogenous alumina structure with bore widths and surface finishes maintained to very tight tolerances. The joint is completely homogenous, stress free, non-porous and visible except by high power microscopy.
Properties and Applications of Thermo-Diffusion Bonded Laser Assemblies
The resultant device is rugged and gas tight with the integrity of the gas seals proven over periods of time in excess of 5 years and is capable of being further processed at high temperatures e.g. during brazing. The ability to develop high output powers from miniaturised devices makes this technology extremely useful in the further development of these lasers for use in robotic, medical or defence applications.