A Ph.D. student in the School of Electrical and Computer Engineering at Georgia Tech, Keilman is conducting research on photonic crystals with his Ph.D. advisor David S. Citrin (who is temporarily based at the Georgia Tech-Lorraine campus) and with researchers at École Polytechnique in Palaiseau, France.

Photonic crystals are periodic arrangements of dielectrics. Analogous to the band gap that may exist for electrons in solid materials, photonic crystals may exhibit a photonic band gap–a range of frequencies where light is unable to propagate through the structure. Thus, of the various applications of photonic crystals, one is to exclude light within a given frequency band.

Keilman's research is focused on how the properties of photonic crystals are degraded by the inevitable presence of disorder, such as uncontrolled variations in the dielectric constant and slight discrepancies in the position and size of the constituent parts. Disorder tends to permit light to propagate in the photonic band gap of the otherwise perfect photonic crystal.

Keilman is exploring structures that look ordered when one zooms in on a small region, but shows considerable disorder when one zooms out. Such structures may provide some of the benefits of ordered photonic crystals while relaxing the stringent requirements imposed in fabricating perfect structures.