Improving resolution of second harmonic generation microscopy via scanning structured illumination.

Second harmonic generation microscopy (SHGM) is a well-known technique for examining the noncentrosymmetric structures in biomedical research. However, without real-state transitions, fluorescence-based superresolution methods cannot be applied. To improve the resolution, fringe-scanning SHGM (FS-SHGM), which combines SHGM with structured illumination based on point-scanning, is introduced in this paper.

Transverse modes of a laser using volume Bragg grating as the cavity mirror.

A simulation and experiment were performed to demonstrate that a laser using volume Bragg grating as one of the cavity mirrors can achieve lasing even if the laser cavity length exceeds the traditional stable cavity condition. The laser transverse mode changes from a Gaussian beam into a ring-shaped mode as the laser cavity length increases from stable to unstable cavity conditions. At the same time, the effective modal reflectivity is reduced as the cavity length increases.

A liquid-crystal model for friction.

Rate-and-state friction is an empirical approach to the behavior of a frictional surface. We use a nematic liquid crystal in a channel between two parallel planes to model frictional sliding. Nematic liquid crystals model a wide variety of physical phenomena in systems that rapidly switch between states; they are well studied and interesting examples of anisotropic non-Newtonian fluids, characterized by the orientational order of a director field SE pointing arrow(x,t) interacting with the the velocity field u(x,t).