Sub-λ/10 spot size in semiconductor solid immersion lens microscopy

The angular spectrum of radially polarized Laguerre–Gaussian beams was tailored by an annular aperture in a semiconductor solid immersion lens microscope. The radii of two concentric rings in the amplitude aperture were optimized by a multi-objective particle swarm optimization algorithm. A GaAs solid immersion lens with NA=3.4 was used in the numerical calculation and a spot size of 98 nm (<λ/10<λ/10) at a wavelength of 1064 nm illumination was obtained.