Department of Physics

Professor Armstrong's research is primarily nonlinear optics. Rather than study the nonlinearities themselves, Armstrong is more interested in their dependence on the type of media, in particular on novel classes including nanostructured, micro-structured, and fractal media. A well known example of a medium effect on a nonlinear optical process, second harmonic generation, is forbidden in symmetric bulk media, but permitted in nanostructured media. In particular, Armstrong's interests lie in exploiting the novel optical sensors and optical amplifiers. In the sensor development area, resonant properties, characteristic of many of these media, have led to the development of ultra-sensitive optical sensors that may be used to detect spectral emissions from extremely low, (including single-molecule-level) concentrations of molecular species. If the sensor is fabricated using nanostructured metallic particle using Surface Enhanced Raman Scattering (SERS), provides additional sensor gain.