Michael A. Reagan

Electric charging and nanostructure formation in polymeric films using combined amplitude-modulated atomic force microscopy-assisted electrostatic nanolithography and electric force microscopy

A hybrid technique, combining lithography which exploits atomic force microscope tip manipulation with modified electric force microscopy was used to study surface electric charging (deposition and evolution) of polymethyl methacryalate and polystyrene films. Upon charging the films past a threshold voltage, two distinct regimes were observed: (1) stable feature formation related to electric breakdown and mass transport resulting in stable film deformation due to the negative surface charging (negative tip bias) and (2) no stable feature formation regime attributed to viscoelastic deformation of polymer surface followed by the surface relaxation in the case of positive surface charging (positive tip bias).

Running gratings in photoconductive materials

Starting from the three-dimensional version of a standard photorefractive model (STPM), we obtain a reduced compact set of equations for an electric field based on the assumption of a quasi-steady-state fast recombination. The equations are suitable for evaluation of a current induced by running gratings at small-contrast approximation and also are applicable for the description of space-charge wave domains. We discuss spatial domain and subharmonic beam formation in bismuth silicon oxide (BSO) crystals in the framework of the small-contrast approximation of STPM. The experimental results confirming holographic current existence in BSO crystal are reported.

Smart photogalvanic running-grating interferometer

Photogalvanic effect produces actuation of periodic motion of macroscopic LiNbO3 crystal. This effect was applied to the development of an all-optical moving-grating interferometer usable for optical trapping and transport of algae chlorella microorganisms diluted in water with a concentration of 27×104ml−1.