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

73
ing identical optical components in the sample and reference arms. The potentially
greatest cause of discrepancy is the beam splitter. Our beam splitter was optically
engineered to reflect 10% of a p-polarized incident beam at an angle of incidence
of 45°. I tested the relative spectral responses of the two arms by measuring the
SHG signal with y-cut quartz in both the sample and reference arm. For both the
p-polarized and s-polarized input Ti:AI 2 0 3 pulses, the relative response of the sample
arm to the reference arm varied repeatedly and predictably by less than 15%.
In order to fully eliminate both effects of the Ti:Ah03 pulse's characteristics
and the inherent spectral response of the detection system, nonlinear signals of
GaN / Ah03 are reported as
[ reported ( - 2 )­
GaN W - Wo -
SAN
[ s&mple( -'l )
w-~o
[r"'rence(w=2w )
quartz 0
[ s&mple ( -2w ) •
quartz w- 0
/reference(w=2w )
quartz 0
(3.2)
\"ote that I!:;:"/!le(w = 2wo) refers to the measured second-harmonic intensity of Ga.\"
in the sample arm. The first measurement in equation (3.2).
(3.3)
measures a relative value of the signal from GaN that is free of the spectral characteristics
of the laser source and fluctuations in the laser power. The second measurement.
I
sample( 2)
quartz W = Wo
[reference (W - 2w )'
quartz - 0
(3..!)
is also free of the spectral characteristics of the laser and fluctuations in laser power. In
addition, this measurement determines the response of the detection system. There-
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