Focusing of continuous and pulsed laser beams by microsphere

We have considered the focusing of continuous and pulsed beams using polystyrene ( n = 1.59) microsphere with diameter of 5 μm. It was shown that it is possible to overcome the diffraction limit in both cases. Simulation using commercial software FullWave showed that the smallest diameter of the focus equals to FWHM = (0.55 ± 0.08) λ in the case of focusing of the CW beam (a plane wave with a wavelength of 633 μm), and equals to FWHM = (0.54 ± 0.08) λ in the case of focusing of the pulsed beam duration of 1.25 fs. Numerical results obtained using FullWave consistent with the results obtained using the MEEP and using own implementation of BOR-FDTD method, and are also in agreement with the experimental data.