CO2 Laser Output Windows
A common problem for windows used in
high-power lasers is that of thermal distortion of
the beam caused by thermally induced refractive
index gradients as the window is heated by the
transmitted beam. This issue is minimised by the
use of optical CVD diamond as the window
material has a high thermal conductivity, a low absorption coefficient and a low value of the
temperature coefficient of the refractive index. This enables diamond products like exit
windows, output couplers, beamsplitters and lenses for high power Co2 - -
lasers. The extreme high laser damage treshold allows more compact systems with diamond
optics and enables maintenance free optics because of the very long lifetime of the optic. The
following table compares the values of these quantities for diamond and ZnSe at 10.6μm wave
length.
The potential advantages of diamond for this application are further illutrated in the pictures,
which show the result of 2-D computational
modelling of the thermal and refractive index
gradients of a diamond and a ZnSe window
both AR coated on both surfaces and cooled
at the edge when traversed by a 10.6μm
wavelength, 5kW Co2 laser beam.-