William Angerer - Department of Physics and Astronomy - University ...

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before their focal point. This facilitates overlapping of the beams. The nonlinear crystal
is centered on the overlap of the two beams. I rotate the crystal about the normal
to its face to max:imize the SHG from each individual beam. This procedure aligns
the beams' polarizations in the proper plane for type I phase matching. I adjust the
angle of incidence between the fundamental beams and the crystal normal to produce
an equal amount of SHG from each of the fundamental beams; this can be verified
visually. This ensures maximum SHG from the overlap of the beams. Finally, I place
the PMT directly between the SHG from the fundamental beams. Phase matching
ensures that the SHG from the overlap of the fundamental beams will propagate in
this direction. The fundamental beams may be approximately temporally overlapped
by constructing the arms of the interferometer to have equal distances. The overlap
of the fundamental pulses is detected by observing the signal from the P~IT on an
oscilloscope while the speaker is on.
3.5 Normalization
There are three components required of any properly normalized spectral measurement:
elimination of the effects of the temporal fluctuations of the source. compensation
for the spectral variations of the source, and compensation or elimination of
the inherent spectral response of the detection system. This section discusses the
experimental techniques that address these issues.
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