Group - TEA laser

The CO2 TEA laser was invented in the late 1960s by Dr Jacques Beaulieu working at the Defence Research Establishment, Valcartier, in Quebec, Canada. The development was kept secret until 1970 when brief details were published. C K N Patel, working at the Bell Telephone Laboratories in 1963, first demonstrated laser output at 10.6 µm from a low pressure RF excited CO2 gas discharge. With the addition of nitrogen and helium and using a DC electrical discharge, CW powers of around 100 W were achieved. By pulsing the discharge using higher voltages or Q-switching using a rotating mirror, pulse powers of a few kilowatts could be obtained, but this was the practical limit. Higher peak powers could only be achieved by increasing the density of excited CO2 molecules. The capacity for stored energy per unit volume of gas increases linearly with density and thus gas pressure, but the voltage needed to achieve gas breakdown and couple energy into the upper laser levels, increases at the same rate. The practical solution avoiding very high voltages was to pulse the voltage transversely to the optical axis (rather than longitudinally as was the case for low pressure lasers), limiting the breakdown distance to a few centimetres. This allowed the use of manageable voltages of a few tens of kV. The problem was how to initiate and stabilize a glow discharge at these much higher gas pressures, without the discharge degenerating into a bright high-current arc, and how to achieve this over a useful volume of gas.