Generation of a sub-diffraction hollow ring by shaping an azimuthally polarized wave

Abstract

The generation of a sub-diffraction optical hollow ring is of great interest in various applications, such as optical microscopy, optical tweezers, and nanolithography. Azimuthally polarized light is a good candidate for creating an optical hollow ring structure. Various of methods have been proposed theoretically for generation of sub-wavelength hollow ring by focusing azimuthally polarized light, but without experimental demonstrations, especially for sub-diffraction focusing. Super-oscillation is a promising approach for shaping sub-diffraction optical focusing. In this paper, a planar sub-diffraction diffractive lens is proposed, which has an ultra-long focal length of 600 λ and small numerical aperture of 0.64. A sub-diffraction hollow ring is experimentally created by shaping an azimuthally polarized wave. The full-width-at-half-maximum of the hollow ring is 0.61 λ, which is smaller than the lens diffraction limit 0.78 λ, and the observed largest sidelobe intensity is only 10% of the peak intensity.

High‐Numerical‐Aperture Dielectric Metalens for Super‐Resolution Focusing of Oblique Incident Light

“…[ 17 ] This opens an alternative way toward far‐field optical super‐resolution. In the past several years, various types of superoscillatory lenses have been demonstrated, including linear‐focusing lenses, [ 18,19 ] spot‐focusing lenses, [ 20,21 ] long‐depth‐of‐focusing lenses, [ 22–24 ] and vector wave superoscillatory lenses. [ 25–30 ] So far, the smallest PSF that has ever been experimentally demonstrated has a full‐width‐at‐half‐maximum (FWHM) value of 0.33λ, [ 31 ] where λ is the working wavelength.…”

Large-scale high-numerical-aperture super-oscillatory lens fabricated by direct laser writing lithography

“…A SOL is a nanostructured mask and on illumination with a coherent light source, it creates a sub-Abbe-Rayleigh diffraction limit focus at a distance in the optical far-eld region. [1][2][3] This is related to the fact that band-limited functions are able to locally oscillate arbitrarily faster than their highest Fourier component, and this is a counter-intuitive physical phenomenon now known as super-oscillation. 2 By delicate interference of multiple propagating waves, a SOL can also form a needle-like focused beam with extremely long depth of focus in the propagation plane while keeping the sub-diffraction features in the transverse plane.…”

“…7,8 Linearly, radially and azimuthally polarized light can be focused to form a needle-like shape with sub-diffraction spot size by diffraction from a phase or amplitude-modulated SOL mask. 3,[9][10][11][12][13][14][15][16] Achromatic SOLs in the visible range were also proposed recently. 1,17 Furthermore, visible-range recongurable bi-chromatic and multi-focus SOLs and Fresnel zone plates have also been demonstrated.…”

Generation and propagation characteristics of a localized hollow beam

“…Various approaches to the generation of LHBs have been proposed since the demonstration of this beam was first realized by using the destructive interference between two light beams at the focus [16]. They were generated by the use of nonparaxial light [17][18][19], holograms [16,20], binary phase plates [21][22][23][24], conical refraction [25][26][27][28][29], a uniaxial crystal [30], partially coherent beams [31,32], a spatial light modulator (SLM) [33], surface plasmon polaritons [34,35], and a photon sieve [36], to form a desirable hollow axial structure. In phase modulation methods, the diffractive optical elements, such as the π-phase plate, are constructed by the binary elements or the binary bitmap of the SLM.…”