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

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polarization is negligible for Si (100) because it affects the nonlinear polarization by
the same mechanism as the standard fundamental polarization, i.e. both effects are
nonlocal effects, but the magnitude of the anomalous polarization is smaller than the
magnitude of the standard polarization. The anomalous polarization is significant
when it acts locally while the standard polarization acts nonlocally. e.g. nonlinear
microscopy of GaN [0001] at normal incidence, or when it is applied to unusual
geometries, e.g. rod-like nonlinear molecules at near normal incidence.
7.2.2 Detection
Due to the vast difference in the magnitudes of the linear and second-harmonic light.
we used two detection schemes. (Typically, the ratio of second-harmonic photons to
fundamental photons transmitted through the system was 1 to 10 12 .) Prior to the detection
apparatus, a small fraction of the light was reflected from a glass slide to a Si
photodiode. The output from the photodiode was measured by a Stanford Research
Systems SR530 lock-in amplifier. The measurement recorded the light reflected linearly
from the sample. The light transmitted through the glass slide was polarized
and the linear light was separated from the second-harmonic light by a short pass
filter. A monochrometer set to pass light at -l00 nm removed almost all of the background
light, while transmitting the second-harmonic light to a cooled Hamamatsu
side-on P~[T model R4220P. An image of the sample was formed by translating the
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