The copper vapour (neutral metal) laser is the most useful in the class of pulsed metal vapour lasers. The primary wavelengths for this laser are 510 and 578nm, and over 100W can be generated in the green and yellow part of the visible spectrum. The copper vapour laser is unusual with respect to its high power and high efficiency in this region and in that its normal operation is at pulse repetition rates of several tens of kilohertz. (The internal physics of this laser prevents CW (Continuous Wave) operation) In neutral metal vapour lasers, a fast electric discharge directly excites metal atoms, the high repetition rates permitting high average power output. The copper vapour comes from pieces of copper placed in the discharge tube, which is heated to about 1500°C to produce vapour at about 0.1mbar pressure. Several mbars of neon are added as a buffer gas to prevent window contamination and loss of copper. Overall wall plug efficiency is about 1% for these lasers, the highest for visible gas lasers. Fig.1. shows the schematic construction of a copper vapour laser.
The copper vapour laser tube is usually sealed with flat glass windows, the rear mirror is a total reflector, with 90% transmission chosen for the output window, which does not need to be specially coated. Beams from copper vapour lasers can be from about 10mm diameter to 50mm diameter, beam divergence for a stable (output window) type resonator is 3-5mradians. In the visible part of the spectrum, beam focusing is performed using glass optics.