Surface and bulk second-harmonic responses from a glass slide using tightly focused radially polarized light

The radially polarized beam is tightly focused by a high numerical aperture microscope objective with adjustable cover glass correction. The intensities of a second-harmonic (SH) signal as a function of the focal position inside a glass slide for different settings of cover glass correction are measured. As compared to linear polarization illumination, the surface responses at the two surfaces of the glass slide are more easily observed in the case of radial polarization. For the first time, to the best of our knowledge, we present the experimental demonstration that surface and bulk SH responses from solid centrosymmetric materials can be separately addressed by adjusting the cover glass correction thickness and the position of the focal exciting field.