Studies of buried interfaces by optical second-harmonic generation

Mining the polarization-dependence of nonlinear optical measurements

The electromagnetic field strength present within the focal volume of a pulsed laser is routinely high enough to produce reasonably efficient nonlinear summing and mixing of optical frequencies. The polarization-dependence of the outgoing beam is a sensitive function of the polarization state(s) of the incident beam(s) and the structure, orientation, and symmetry of the sample. Mining this information hinges on two elements: (1) accurate and precise polarization-dependent measurements, and (2) reliable modeling to relate the measured responses back to local structure and orientation. The central focus of this review is on the first step. Experimental strategies for precise and accurate nonlinear optical ellipsometry (NOE) polarization measurements are summarized for the most common and simplest case of second harmonic generation (SHG), or the frequency doubling of light, although extension to higher-order nonlinear optical interactions is straightforward in most cases.

Discrete retardance second harmonic generation ellipsometry

A new instrument was constructed to perform discrete retardance nonlinear optical ellipsometry (DR-NOE). The focus of the design was to perform second harmonic generation NOE while maximizing sample and application flexibility and minimizing data acquisition time. The discrete retardance configuration results in relatively simple computational algorithms for performing nonlinear optical ellipsometric analysis. NOE analysis of a disperse red 19 monolayer yielded results that were consistent with previously reported values for the same surface system, but with significantly reduced acquisition times.