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The LaserVision, custom-built Optical Parametric Oscillator/Optical Parametric Amplifier
(OPO/OPA) is a powerful solid state source of broadly tunable coherent radiation. It converts
the one fundamental wavelength from the Nd:YAG laser into a continuously tunable wavelength
from about 2500-4000 cm-1. It achieves this magnificent feat through a series of nonlinear
spectroscopic, parametric processes. Parametric process are photon interactions in which one
high frequency photon is annihilated and two lower frequency photons are created, i.e.:
w(pump) =w(signal) +w(idler)
where photon energy is conserved. In addition, photon momentum is conserved by the wave
vectors:
kp = ks + ki
where (p)ump, (s)ignal, and (i)dler simply are the traditional assignments given to the input
photon, and generated photons of higher and lower energy, respectively. The specific pair of
frequencies that is produced is determined by this momentum-, or phase-matching condition.
To produce the visible and infrared light, the OPO/OPA is pumped by a the 1064 nm
fundamental light from a Nd:YAG laser. This beam is immediately split. Approximately 60% of
it is sent to the amplifier for difference frequency generation, and the remainder frequency
doubled in a KTP crystal. This newly created 532 nm light is split so that about 40% is sent
to the sample for the SFG experiment, and 60% is directed to the oscillator (OPO) stage. The
OPO generates tunable signal and idler waves by angle tuning two, counter-rotating KTP
crystals. The idler signal is sent to the amplifier (OPA) stage which contains two KTP crystals
in the same geometry as the OPO stage. Here, difference frequency generation with the pump
1064 nm beam and the idler beam from the OPO creates the mid-infrared light for the SFG
experiment.
© 2001 Shultz Research Group
Last Updated: 3/4/04
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