Near-field optical data storage using a solid immersion lens

TLDR

The solid immersion lens is a truncated glass sphere that increases the optical system’s numerical aperture by n², where n is the lens material’s refractive index. Using a solid immersion lens made from n = 1.83 glass and 780 nm illumination, the authors achieved a 317 nm spot, resolved a 500 nm period grating, wrote and read 350 nm magnetic domains, and anticipate a 125 nm spot with blue light.

Abstract

A near-field optical technique, using a new type of solid immersion lens (SIL), has been developed and applied to the writing and reading of domains in magneto-optic material. The SIL is a truncated glass sphere which serves to increase the numerical aperture of the optical system by n2, where n is the index of refraction of the lens material. Using a SIL made from n=1.83 glass and illuminating with 780 nm light, we have achieved a 317 nm spot size. We have resolved a 500 nm period grating, and written and read 350 nm diameter magnetic domains. The technique should be capable of a 125 nm focused spot size using blue light.