We investigate an ability of wavefront aberration analysis with multi-order diffractive optical elements which are matched with Zernike polynomial basis. Numerical simulations reveal that phase aberration Zernike polynomials weight coefficients can be successfully recognized with considered diffractive optical element if the meaning of the phase aberration does not exceed 0.8π. Nevertheless, further increasing of phase aberration leads to impossibility of Zernike weight coefficient of wavefront aberrations estimation.
In this paper we provide 3d full-vector static electromagnetic simulation of silicon micro-ring resonator operating. We show that geometrical and scalar approaches are not sufficiently accurate for calculating resonator parameters. Quite strong dependence of ring resonator radius on waveguide width is revealed.
The work is a numerical and experimental study of closely spaced light spot production using diffractive optical elements (DOE). It is shown that low indexed Hermite–Gaussian mode formers coupled with an objective can be utilized for the production of contrasting closely spaced small light spots in objective focus. Using a tunable laser (EKSPLA NT 242), we demonstrate that low indexed mode forming is quite resistant to chromatic dispersion, but is extremely sensitive to shifting axes of the incident beam and the element.
We consider nanofocusing of electromagnetic field in the near-field using sharp metallic and dielectric particles with little radius of surface curvature. An ability of extraordinary field confinement is shown theoretically using integral equations and modelling in Comsol. We have offered the scheme of focusing, which consists of prefocuser and nanofocuser. We consider different composition of prefocuser and nanofocuser. It is shown that a size of a focal spot extremely depends on radius of surface curvature. A refractive axicon can be used as prefocuser and metal or silicon nanoparticle can be used as nanofocuser. If the radius of aluminum spherical nanofocuser is 20 nm the radius of the focal spot is λ 400 . That is smaller than it is achieved in previous works.
A helical intensity distribution was created in a near-field when Gaussian laser beam was focused by a binary phase
spiral axicon with high numerical aperture. It was shown by 3D-simlation using the Comsol software and natural
experiments with near-field microscope NT-MDT Integra Spectra. Experimental measurements and numerical
simulations are in good agreement.
We conduct a theoretical and experimental study of the distribution of the electric field components in the focal plane when rotating a zone plate with a π- phase jump placed in the focused beam. By comparison of the theoretical and experimental results, the analysis of the polarization sensitivity of different types of metal-coated aperture probes is conducted. It is demonstrated that with increasing diameter of the non-metal-coated tip part there occurs an essential redistribution of sensitivity in favor of the transverse electric field components and the increase of the probe’s energy throughput. We obtain that the probe response is similar to the transverse component of electric field in the case of Gaussian beam focusing however in the case of Hermite-Gaussian beam focusing the probe response is similar to gradient of electric longitudinal component.