Realizing a terahertz far-field sub-diffraction optical needle with sub-wavelength concentric ring structure array

Ruan, Desheng; Li, Zeyu; Du, Liang-Hui; Zhou, Xun; Zhu, Li-Guo; Lin, Cuiping; Yang, Mengyu; Chen, Gang; Yuan, Weiqing; Liang, Gaofeng; Wen, Zhongquan

doi:10.1364/ao.57.007905

Cited by 23 publications

(13 citation statements)

References 29 publications

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“…A prescribed super-Gaussian function can be used to describe the extended longitudinal profile of an optical needle. Using optimization algorithms, the transmission function of a BA mask can be obtained by minimizing the difference between the actual field distribution and the merit function 114–117,124,159 . However, when applying these commonly used methods, one must calculate the diffraction patterns on the planes at different positions within the target optical needle at intervals that are smaller than one wavelength and then compare the calculated patterns with their merit profiles.…”

Section: Design Methodsmentioning

confidence: 99%

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Superoscillation: from physics to optical applications

2019

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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.

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Section: Design Methodsmentioning

confidence: 99%

“…The transverse size of the generated optical needle varied between 0.42λ and 0.49λ within the 12λ propagation distance 116 . Using a BP mask, a subdiffraction optical needle was experimentally generated with a length of 19.7λ at a THz wavelength of 118.8 μm 117 .…”

Section: Superoscillatory Optical Devicesmentioning

confidence: 99%

Superoscillation: from physics to optical applications

2019

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“…In this context, SOLs arise as an interesting and powerful alternative, as they can focus light into a subwavelength hotspot located further than 10 times the wavelength in free space. [ 37–42 ]…”

Section: Introductionmentioning

confidence: 99%

“…The focus size is usually evaluated by means of its full width at half maximum (FWHM), defined as the distance at which the power distribution has been reduced to half its maximum at the focal spot whereas the side lobe level (SLL) is defined as the ratio between the maximum power at the focal point and the maximum power of the first side lobe (more details about these parameters can be found in the Supporting Information); 4) obtain an ultrathin and compact lens, with a thickness < 0.04 λ 0 and diameter < 55 λ 0 ; the metaSOL becomes one to two orders of magnitude electrically smaller than the SOLs designed for the optical spectrum [ 48–50 ] and up to three times smaller than the SOLs reported in the THz range. [ 37 ]…”

Section: Introductionmentioning

confidence: 99%

Highly Efficient Focusing of Terahertz Waves with an Ultrathin Superoscillatory Metalens: Experimental Demonstration

Legaria

Teniente

Kuznetsov

et al. 2021

Advanced Photonics Research

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The performance of an ultrathin (thickness < 0.04λ 0) metasurface superoscillatory lens (metaSOL) is experimentally demonstrated in the terahertz (THz) range. The metaSOL is designed using two different hexagonal unit cells to improve the efficiency and properties of the conventional transparent–opaque zoning approach. The focusing metastructure produces, at a frequency f exp = 295 GHz, a sharp focal spot 8.9λ exp away from its output surface with a transversal resolution of 0.52λ exp (≈25% below the resolution limit imposed by diffraction), a power enhancement of 18.2 dB, and very low side lobe level (−13 dB). Resolution below the diffraction limit is demonstrated in a broad fractional operation bandwidth of 18%. The focusing capabilities of the proposed metaSOL show its potential use in a range of applications such as THz imaging, microscopy, and communications.

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“…For instance, in Reference 12, a silicon binary diffractive optical element—a focusing device of THz laser radiation from a Gaussian beam into a coaxial segment, has been investigated. In Reference 13, the possibility for creation of subdiffractive optical needle in the far zone with a planar lens in the THz range has been shown.…”

Section: Introductionmentioning

confidence: 99%

Control of tightly focused laser beams in the THz range

Degtyarev

Dubinin

Gurin

et al. 2021

Micro & Optical Tech Letters

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The possibility for control of tightly focused laser beams excited by the resonator modes of a THz laser based on a hollow circular dielectric waveguide is studied theoretically and experimentally. The wavelength of the radiation under study is 0.4326 mm corresponding to the generation line of the optically pumped HCOOH‐molecule THz laser. The focusing system is implemented by a short‐focus lens covered by absorbing masks in the central region. The focal area parameters were controlled by changing the size of the masks. The electric field components of the laser modes are calculated using the Rayleigh‐Sommerfeld integral transformations under non‐paraxial approximation. The use of absorbing masks made it possible to reduce the beam diameter in the focal region and increase the depth of focus of the linearly polarized EH11‐mode and azimuthally polarized TE01‐mode as well. In this case, despite of the presence of an absorbing mask, the distribution of the total field intensity of the TE01‐mode retained its annular shape, and the field maximum of the EH11‐mode is observed at center of the focal spot. The results of this work can be implemented in medical diagnostics, high‐speed communications, and environmental monitoring.

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Realizing a terahertz far-field sub-diffraction optical needle with sub-wavelength concentric ring structure array

Cited by 23 publications

References 29 publications

Superoscillation: from physics to optical applications

Superoscillation: from physics to optical applications

Highly Efficient Focusing of Terahertz Waves with an Ultrathin Superoscillatory Metalens: Experimental Demonstration

Control of tightly focused laser beams in the THz range

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