Tempest Nd:YAG Laser Operator’s Manual
36
7) Remove the interlock defeat and reinstall the Tempest laser head
cover.
The third harmonic generator (THG) crystal may be used to provide UV
radiation at 355 nm. The third harmonic generation process is Type I in
BBO, created with horizontally polarized fundamental and second
harmonic light. A half wave plate for the second harmonic is mounted
on the input to the THG housing. The third harmonic output is vertically
polarized. The THG housing may be installed by the end user. THG
generation requires that the SHG crystal has been installed and is
aligned.
1) Remove the Tempest laser head.
2) Insure that the second harmonic generator is installed according to
the preceding instructions.
3) Install the third harmonic generator using the second set of alignment
pins and screw holes. Insure that the harmonic generator housing is
installed such that it is against the second alignment pin.
4) Install the 355 nm dichroic separation mirrors using the alignment
pins and screw holes closest to the beam exit.
5) Adjust the wave plate on the second harmonic generator housing to
maximize the 355 nm energy.
6) Adjust the external screw on the THG housing to optimize the crystal
angle, maximizing 355 nm energy.
7) Reinstall the harmonic generator housing cover.
NOTE: DO NOT DISASSEMBLE THE HARMONIC
GENERATOR. THE CRYSTAL INSIDE IS HYGROSCOPIC.
DUST, DIRT AND HUMIDITY WILL DESTROY THE CRYSTAL.
The fourth harmonic generator is used to produce ultraviolet radiation at
266 nm by doubling the second harmonic output in BBO. A half wave
plate for the second harmonic is mounted on the input to the fourth
harmonic housing. The fourth harmonic output is vertically polarized.
Fourth harmonic generation (4HG) requires that the SHG crystal has
been installed and is aligned. Use the following procedure to install the
fourth harmonic generator.
1) Remove the Tempest laser head cover.
Third Harmonic
Installation
Fourth Harmonic
Installation
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