Enhanced spatial resolution in third-harmonic microscopy through polarization switching

Enhanced spatial resolution in third-harmonic generation (THG) microscopy is demonstrated through manipulation of the polarization state across the focal field of a microscope. Enhancements in resolution of up to a factor of 2 are observed for a focal field linearly polarized at the center and switched to circularly polarized at the beam edges. As THG scattering is suppressed for circular polarization, the THG signal diameter is reduced, improving spatial resolution. (C) 2009 Optical Society of America