High aperture focusing through a spherical interface: Application to refractive solid immersion lens (RSIL) for subsurface imaging

The effects of on-axis spherical aberration and defocus on focusing across a spherical interface between two materials of mismatched refractive index are discussed. A vectorial integral representation for high aperture focusing in this configuration is formulated and an analytical expression for the spherical aberration function is derived. Numerical simulations are performed to analyse the effects of the spherical interface on both the transverse and axial intensity profiles. The results from these numerical simulations are important industrially in understanding the resolution enhancements from solid immersion lens technology, as well as being of more fundamental interest in calculating the distribution at the focal plane under different solid immersion lens configurations.