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The PL – 3 CO operates sealed off on low gain CO
transitions in the range 5.2 to 6.0 microns with an output
power of 1Watt.
By changing the cavity optics and gas mixture the PL3 can
be converted into a tuneable CO2 laser covering 9-11
microns with 15W output power.
The PL3 uses a double discharge pyrex tube with a common
central high voltage nickel cathode and two symmetrically
placed tungsten ring anodes. The resonator has no internal
Brewster windows with the output coupler and diffraction
grating mounted within the vacuum envelope of the laser.
The pyrex discharge tube is terminated by
stainless steel flanges with copper gasket vacuum seals
providing high vacuum integrity for extended period
sealed-off operation.
The optical elements are stably
mounted within granite end blocks spaced by a four rod
invar frame. The high efficiency grating is held on an
intra-vacuum gimbal pivoted mount with line selection
achieved via a manual differential micrometer control.
The
high quality mirror mounts used ensures the laser operates
reliably for extended periods without need for cavity
alignment optimisation. The output mirror is mounted on a
thermally compensated cylindrical piezo-electric ceramic
for fine cavity length tuning. The latter can also be used
in the closed loop dither stabilisation system based on
the opto-galvanic effect.
The vacuum seal at the output
coupling end of the laser is a ZnSe Brewster window,
external to the cavity optics. The laser output is
horizontally plane polarised.
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