KEYWORDS: Axicons, Near field optics, Binary data, Polarization, Diffraction, Near field, Optical components, Near field diffraction, Ions, Electron beam lithography
We analytically and numerically show that by introducing the asymmetry into the axicon design it becomes possible to generate the longitudinal electric field (E-field) component on the optical axis for linearly and circularly polarized incident beams. Binary axicons with high numerical aperture (NA) are fabricated in three configurations – axisymmetric and spiral ones, and bi-axicon – by electron beam lithography. Experimental measurements for the near-field diffraction of most common and easy to implement incident beams – linearly and circularly polarized – are conducted. The experimental results agree with the theoretical analysis.
KEYWORDS: Polarization, Near field scanning optical microscopy, Objectives, Near field, Molecules, Microscopy, Zone plates, Gaussian beams, Fiber optics, Microscopes
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.
We propose and analyze new polarization converters to transform the linearly polarized laser modes into axially symmetric modes, which show more promise in various applications, as well as generating various inhomogeneously polarized configurations. Designed converters are based on the coherent composition of the modal beams with different amplitude-phased distribution and polarization states. What makes the systems simple and universal is the use of diffractive optical elements (DOEs) to generate required mode patterns with specific space orientation alongside the simultaneous generation of different beams with different transverse mode content, which can be subsequently combined. The numerical modeling of the polarization mode converters has made it possible to analyze its performance and capabilities. The DOEs in question have been designed and fabricated. Natural experiments that demonstrate the generation of vector higher-order cylindrical beams have been conducted.
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