Abstract:A three-dimensional (3D) hollow spot is of great interest for a wide variety of applications such as microscopy, lithography, data storage, optical manipulation, and optical manufacturing. Based on conventional high-numerical-aperture objective lenses, various methods have been proposed for the generation of 3D hollow spots for different polarizations. However, conventional optics are bulky, costly, and difficult to integrate. More importantly, they are diffraction-limited in nature. Owing to their unique prop… Show more
“…[ 7,8 ] Based on the concept of superoscillation, [ 9–11 ] a variety of sub‐diffraction or super‐resolution optical devices have been demonstrated either theoretically or experimentally, including scalar super‐resolution metalenses [ 12–22 ] and vector super‐resolution metalenses. [ 23–33 ] Such super‐resolution devices have been successfully shown great potential in label‐free super‐resolution microscopy [ 13,21,34,35 ] and super‐resolution telescope. [ 36 ] However, most previously reported super‐resolution metalenses only work at one single wavelength [ 37 ] or several designed discrete wavelengths, [ 38,39 ] while broadband achromatic metalenses working in the visible [ 40–42 ] and near‐infrared spectrum [ 43–46 ] as well as THz regime [ 47 ] are restricted by the Abbe DL.…”
THz focusing and imaging include bulky dielectric refractive lenses and parabolic mirrors. Due to the diffraction effect, the resolution of conventional optics is limited by the Abbe diffraction limit (DL) of 0.5λ/NA, [5] where λ and NA are working wavelength and numerical aperture (NA), respectively. Recently, there has been a growing interest in developing far-field super-resolution optical devices, which can achieve point-spread-function (PSF) of size smaller than the Abbe DL without evanescent waves [6] at a distance far beyond the near-field regime. [7,8] Based on the concept of superoscillation, [9-11] a variety of sub-diffraction or super-resolution optical devices have been demonstrated either theoretically or experimentally, including scalar super-resolution metalenses [12-22] and vector super-resolution metalenses. [23-33] Such super-resolution devices have been successfully shown great potential in labelfree super-resolution microscopy [13,21,34,35] and super-resolution telescope. [36] However, most previously reported super-resolution metalenses only work at one single wavelength [37] or several designed discrete wavelengths, [38,39] while broadband achromatic metalenses working in the visible [40-42] and nearinfrared spectrum [43-46] as well as THz regime [47] are restricted by the Abbe DL. To achieve a broadband super-resolution imaging, recently, a broadband super-resolution scheme was proposed and experimentally demonstrated by adopting the combination of a super-oscillatory binary phase filter and a conventional bulk achromatic refractive convex lens. [48] Up to now, it is still a great challenge to realize a sub-diffraction achromatic metalens with a continuous broad bandwidth. To achieve broadband achromatic super-resolution focusing, similar to the conventional optics, dispersion compensation is required to ensure that the wave of different wavelengths is focused at the same focal point. In addition, wave front engineering is also required to achieve the super-resolution PSF. Recent fast development of metasurfaces [49-54] provides effective ways to manipulate the amplitude, [55,56] phase, [57-61] polarization [30,33,62-66] and dispersion properties [67,68] of light waves. To achieve wave front shaping without influences on dispersion, one possible way is to realize broadband achromatic super-resolution by adopting amplitude modulation. Conventionally, pupil filters [69-78] can be used to achieve super-resolution in traditional optical systems. Recently, there are growing interests in developing super-resolution metalenses for applications of focusing and imaging. On one hand, various sub-diffraction metalenses have been demonstrated; however, most of them only work at a single wavelength or multiple discrete wavelengths. On the other hand, the previously reported broadband achromatic metalenses are diffraction-limited, or their focal spots are larger than the corresponding Abbe diffraction limit, 0.5λ/NA, where λ and NA are the lens working wavelength and numerical aperture. In the present wo...
“…[ 7,8 ] Based on the concept of superoscillation, [ 9–11 ] a variety of sub‐diffraction or super‐resolution optical devices have been demonstrated either theoretically or experimentally, including scalar super‐resolution metalenses [ 12–22 ] and vector super‐resolution metalenses. [ 23–33 ] Such super‐resolution devices have been successfully shown great potential in label‐free super‐resolution microscopy [ 13,21,34,35 ] and super‐resolution telescope. [ 36 ] However, most previously reported super‐resolution metalenses only work at one single wavelength [ 37 ] or several designed discrete wavelengths, [ 38,39 ] while broadband achromatic metalenses working in the visible [ 40–42 ] and near‐infrared spectrum [ 43–46 ] as well as THz regime [ 47 ] are restricted by the Abbe DL.…”
THz focusing and imaging include bulky dielectric refractive lenses and parabolic mirrors. Due to the diffraction effect, the resolution of conventional optics is limited by the Abbe diffraction limit (DL) of 0.5λ/NA, [5] where λ and NA are working wavelength and numerical aperture (NA), respectively. Recently, there has been a growing interest in developing far-field super-resolution optical devices, which can achieve point-spread-function (PSF) of size smaller than the Abbe DL without evanescent waves [6] at a distance far beyond the near-field regime. [7,8] Based on the concept of superoscillation, [9-11] a variety of sub-diffraction or super-resolution optical devices have been demonstrated either theoretically or experimentally, including scalar super-resolution metalenses [12-22] and vector super-resolution metalenses. [23-33] Such super-resolution devices have been successfully shown great potential in labelfree super-resolution microscopy [13,21,34,35] and super-resolution telescope. [36] However, most previously reported super-resolution metalenses only work at one single wavelength [37] or several designed discrete wavelengths, [38,39] while broadband achromatic metalenses working in the visible [40-42] and nearinfrared spectrum [43-46] as well as THz regime [47] are restricted by the Abbe DL. To achieve a broadband super-resolution imaging, recently, a broadband super-resolution scheme was proposed and experimentally demonstrated by adopting the combination of a super-oscillatory binary phase filter and a conventional bulk achromatic refractive convex lens. [48] Up to now, it is still a great challenge to realize a sub-diffraction achromatic metalens with a continuous broad bandwidth. To achieve broadband achromatic super-resolution focusing, similar to the conventional optics, dispersion compensation is required to ensure that the wave of different wavelengths is focused at the same focal point. In addition, wave front engineering is also required to achieve the super-resolution PSF. Recent fast development of metasurfaces [49-54] provides effective ways to manipulate the amplitude, [55,56] phase, [57-61] polarization [30,33,62-66] and dispersion properties [67,68] of light waves. To achieve wave front shaping without influences on dispersion, one possible way is to realize broadband achromatic super-resolution by adopting amplitude modulation. Conventionally, pupil filters [69-78] can be used to achieve super-resolution in traditional optical systems. Recently, there are growing interests in developing super-resolution metalenses for applications of focusing and imaging. On one hand, various sub-diffraction metalenses have been demonstrated; however, most of them only work at a single wavelength or multiple discrete wavelengths. On the other hand, the previously reported broadband achromatic metalenses are diffraction-limited, or their focal spots are larger than the corresponding Abbe diffraction limit, 0.5λ/NA, where λ and NA are the lens working wavelength and numerical aperture. In the present wo...
“…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. Due to their comparative large sidelobes, those super‐resolution lenses are not suitable for direct imaging.…”
the concept of superoscillation, [13,14] there has been growing interest in developing optical super-resolution devices for far-field operation without evanescent waves. [15,16] According to this concept, an arbitrary small point-spread function (PSF) can be achieved by engineering the wave front of the incident wave through a properly designed amplitude-phase mask. [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][23][24] and vector wave superoscillatory lenses. [25][26][27][28][29][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. Due to their comparative large sidelobes, those super-resolution lenses are not suitable for direct imaging. In most traditional optical imaging systems, super-resolution PSF usually leads to relatively large sidelobes, which carry a decent amount of energy and might restrict further improvement in the spatial resolution. However, in a confocal microscope, the sidelobes of a super-resolution illumination lens can be effectively suppressed by a conventional optical objective lens, because the PSF of the entire confocal optical system is the product of the two PSFs of the illumination lens and the collection lens. [32] Although their focusing efficiency is only several percentages, super-resolution lenses have demonstrated promising potentials in the application Recently, developments in superoscillatory optical devices have allowed for label-free far-field optical super-resolution technology by allowing engineering of optical point-spread functions beyond the traditional Abbe diffraction limit. However, such superoscillatory optical devices are optimized for the normalincident operation, which inevitably leads to a comparatively slow imaging acquisition rate in the application of super-resolution microscopy. Here, a super-resolution metalens is demonstrated with a high numerical aperture that can focus oblique incident light into a hot spot with a size smaller than the diffraction limit at the visible wavelength. This super-resolution metalens has a numerical aperture of as large as 0.97, a focal length of 38.0 µm, a radius of 151.9 µm, and a field of view of 4° that enables super-resolution focusing on the focal plane at a wavelength of λ = 632.8 nm. In a 5.6λ × 5.6λ field of view on the focal plane, the size of the focal spot is smaller than 0.45λ, which is only 0.874 times the corresponding Abbe diffraction limit. The super-resolution metalens offers a promising way toward fast-scanning labelfree far-field super-resolution microscopy.
“…Both theoretical and experimental results have indicated that this optical lever results in significant attenuation of the longitudinal component in the image field 64 . The absence of longitudinal polarization was verified in later experimental investigations of focused superoscillation optical fields 139,161 , which showed clear deviations of image fields from the theoretically predicted electric fields and satisfactory agreement was observed between the image fields and the transverse components that were obtained via numerical simulation.Fig. 11Superoscillation optical field characterization systems. a The superoscillatory fields are obtained by a high-NA microscope with an objective lens mounted on a 1D nanopositioner (1D NP), where the camera is used to obtain the 2D intensity distribution of the diffraction pattern.…”
Section: Characterization Of Superoscillatory Optical Fieldsmentioning
confidence: 74%
“…11b, to measure the longitudinal electric components, the fibre tip axis must be set perpendicular to the polarization direction or at an angle at which the tip can respond to the longitudinal polarization to a certain extent 88,130 . A titled tip can be used to map the entire electric field within the plane of a tilted nanofibre with satisfactory similarity to the theoretical result of the entire field 130,139 , and the distortion that is caused by the polarization selectivity can be minimized with a tilt angle of 45°.…”
Section: Characterization Of Superoscillatory Optical Fieldsmentioning
confidence: 76%
“…As shown in Fig. 8, a 3D hollow spot was experimentally created with a transverse inner FWHM of 0.546λ (0.496λ/NA) and an axial inner FWHM of 1.585λ at a wavelength of 632.8 nm 139 . Further investigation showed that both the transverse and axial sizes can be significantly reduced by independently modulating the radial and azimuthal components of the incident waves using birefringent metasurfaces.…”
The resolution of conventional optical elements and systems has long been perceived to satisfy the classic Rayleigh criterion. Paramount efforts have been made to develop different types of superresolution techniques to achieve optical resolution down to several nanometres, such as by using evanescent waves, fluorescence labelling, and postprocessing. Superresolution imaging techniques, which are noncontact, far field and label free, are highly desirable but challenging to implement. The concept of superoscillation offers an alternative route to optical superresolution and enables the engineering of focal spots and point-spread functions of arbitrarily small size without theoretical limitations. This paper reviews recent developments in optical superoscillation technologies, design approaches, methods of characterizing superoscillatory optical fields, and applications in noncontact, far-field and label-free superresolution microscopy. This work may promote the wider adoption and application of optical superresolution across different wave types and application domains.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
