When an optical lens is illuminated by a plane wave, the generated focal spot is given by the Abbe diffraction limit. However, arbitrary small spots, surrounded by additional lobes, can be obtained by illuminating the lens with a suitable light pattern. This is a manifestation of super-oscillation (SO), since the far field intensity pattern is band-limited by the ratio of the lens numerical aperture and the wavelength, but nevertheless the light beam at the focal plane can oscillate locally at much higher frequency. Here, we investigate a systematic method to structure the small lobes of SO function, by using Gaussian, Hermite-Gaussian, Laguerre-Gaussian and Airy functions. After experimentally realizing the subwavelength focusing of these structured super-oscillating optical beams we showed their capabilities to achieve high localization of nano-meter sized particles and observed unprecedented localization accuracy and trapping stiffness, significantly exceeding those provided by standard diffraction limited beams. Further, we envisage that the method of structuring super-oscillating functions shown here can be used in other fields, e.g. STED microscopy, nonlinear frequency conversion, lithography, plasmonics as well as in the time domain for structuring light pulses for supertransmission and for time-dependent focusing
We study, theoretically and experimentally, the concept of non-diffracting super-Airy beam, where the main lobe of the beam is observed to be nearly half in size and with increased intensity compared to the main lobe of the Airy beam. However, reducing the main lobe size does not affect the transverse acceleration and non-spreading features of the beam. Furthermore, we observed that during propagation, super Airy main lobe shows faster self-reconstruction after an obstruction than the Airy main lobe. Therefore, we envision that specifically, a beam with a smaller lobe size and higher intensity can out-perform the Airy beam for applications such as nonlinear optics, curved plasma generation, laser micromachining, and micro- particle manipulation, while the faster reconstruction property of the super-Airy main lobe can surpass the Airy beam in applications of scattering and turbulent media.
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