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

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microscopy attempts to correlate relatively large changes in the nonlinear response
of a medium with local changes in electronic or structural properties. ~onli~c~r nptical
microscopy probes the local structure or symmetry of a medium by focusing
the fundamental beam to ",3 pm. Ideally, one probes structural changes that cannot
be observed by linear optical techniques. For example, because of its high spatial
sensitivity, the nonlinear optical microscope appears well suited to investigate the
nonlinear optical properties of carbon nanoropes. Measurements of a single carbon
nanorope have the potential to provide a more accurate determination of nanotube
nonlinear optical properties than measurements of a sample that consists of an ensemble
of tubes or nanoropes. In contrast to SHG experiments from a sample of
randomly oriented nanoropes, SHG microscopy may isolate susceptibility elements
from a single nanorope, or a dilute collection of oriented nanotubes.
This chapter is organized as follows. vVe first discuss the historical development
of nonlinear optical microscopy. \Ve then describe our nonlinear optical microscope.
This section includes a discussion on the detectability limits of the microscope and
determines an upper bound on the nonlinearity of the carbon nanotubes from this
limit.
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