Sub-50 nm focusing of a 405 nm laser by hemispherical silicon nanolens

Abstract

In this work, we study the light focusing behaviors of a sub-micrometer Si hemispherical nanolens in theory. Results show that the width and depth of the focus spot light at 405 nm can reach 42 nm (approximately λ / 10 ) and 20 nm ( λ / 20 ), respectively. Theoretical analysis indicates that this nanofocusing phenomenon comes from two reasons, the high refractive index of Si and the sub-micrometer size of the lens, which considerably decrease the influence of material losses. The focusing capability of the Si nanolens is comparable with the current extreme ultraviolet technique but with a low cost, providing an alternative approach towards super-resolution photolithography and optical microscopy.