Operation
39
6) Fire laser #2 and note the position of the beam on the mirror, relative
to the beam from laser #1. Adjust the fold mirror #1 to overlap the
two visible beams immediately after the second harmonic generator.
7) Observe the overlap of the two beams at a point 1-2 meters away
from the laser head.
8) Adjust the polarizer assembly mount to optimize the overlap of the
two beams.
9) Repeat steps 5 – 8 to get the optimal overlap between the beams from
laser #1 and laser #2. The overlap can be observed along the beam
line from the laser head exit for several meters.
10) Turn off both lasers and reinstall the secondary head cover. Check
the alignment with both lasers operating at the desired energy.
An optional configuration of Gemini includes an extetnded base plate that
allows installation of a third or fourth harmonic generator to produce UV
wavelengths. In this configuration the Gemini can operate at 532 nm or 266 nm
using both laser heads or at 355 nm using only one laser head. The green (532
nm) wavelength is generated as in the standard Gemini. The UV wavelength
(355 nm or 266 nm) is generated by placing the third (355 nm) or fourth (266
nm) harmonic generator in the beam path just before the dichroic mirror set near
the exit aperture. See Figure 4-8.
Figure 4-8: Gemini with Extended Base Plate for UV Operation
Gemini UV
Operation
Third (355
nm) or fourth
(266 nm)
harmonic
generator
355 nm or 266
nm dichroic
mirror set
Optical
Attenuator
(optional)
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