Catenary Optical Fields Research Articles

Catenary optics: a perspective of applications and challenges

Catenary optics is an emerging direction of subwavelength optics, which is indispensable in describing the electric fields and dispersion property of coupled metallic subwavelength structures, and designing broadband high-efficiency geometric-phase metasurfaces. It involves catenary optical fields and catenary structures, in which both ordinary and equal-length catenary functions play important roles. In recent years, catenary optics has realized a variety of exotic phenomena and optical applications, including broadband photonic spin-Hall effect, super-resolution lithography, broadband absorbers, and extreme-angle imaging. Here, we discuss developments of catenary optics, including a brief history, physical concept and properties, applications, and future perspectives.

Large-scale diamond silver nanoparticle arrays as uniform and sensitive SERS substrates fabricated by surface plasmon lithography technology

Surface-enhanced Raman scattering (SERS) is still treated as an ultrasensitive analytical tool in various applications. However, it remains to be a challenge in manufacturing large-scale and uniform substrates. Here, a novel fabrication method, surface plasmon lithography (SPL) technology, is developed to fabricate large-scale and uniform diamond silver nanoparticle (DSN) arrays with inter-nanoparticle gap of 30 nm. Experimentally, the fabricated SERS substrates are uniform within a large scale of 10 mm2. Besides, the enhancement factor (EF) larger than 107 is obtained via detecting Rhodamine 6G molecules, deriving from the enhanced electromagnetic (EM) field in the form of catenary optical fields between neighboring DSNs. Our work demonstrates that SPL technology is a straightforward approach for easily fabricating gap-controllable SERS substrates with large area, high uniformity and high sensitivity.

Subwavelength Artificial Structures: Opening a New Era for Engineering Optics.

In the past centuries, the scale of engineering optics has evolved toward two opposite directions: one is represented by giant telescopes with apertures larger than tens of meters and the other is the rapidly developing micro/nano-optics and nanophotonics. At the nanoscale, subwavelength light-matter interaction is blended with classic and quantum effects in various functional materials such as noble metals, semiconductors, phase-change materials, and 2D materials, which provides unprecedented opportunities to upgrade the performance of classic optical devices and overcome the fundamental and engineering difficulties faced by traditional optical engineers. Here, the research motivations and recent advances in subwavelength artificial structures are summarized, with a particular emphasis on their practical applications in super-resolution and large-aperture imaging systems, as well as highly efficient and spectrally selective absorbers and emitters. The role of dispersion engineering and near-field coupling in the form of catenary optical fields is highlighted, which reveals a methodology to engineer the electromagnetic response of complex subwavelength structures. Challenges and tentative solutions are presented regarding multiscale design, optimization, fabrication, and system integration, with the hope of providing recipes to transform the theoretical and technological breakthroughs on subwavelength hierarchical structures to the next generation of engineering optics, namely Engineering Optics 2.0.

Ultrathin Metalenses: High‐Efficiency and Wide‐Angle Beam Steering Based on Catenary Optical Fields in Ultrathin Metalens (Advanced Optical Materials 19/2018)

Ultrathin Metalenses: High‐Efficiency and Wide‐Angle Beam Steering Based on Catenary Optical Fields in Ultrathin Metalens (Advanced Optical Materials 19/2018)

Multi-band coherent perfect absorption excited by a multi-sized and multilayer metasurface

We propose a multi-band infrared coherent perfect absorber where four perfect absorption peaks can be obtained for antisymmetrical inputs. The FWHM is nearly four times larger than that of a single band absorber. In addition, the absorptivity of each peak can be independently tuned by phase modulation. Since only magnetic resonances in the form of catenary optical fields in the upper and lower dielectric layers can be excited for symmetrical inputs, the number of absorption peaks will be reduced by half at this time. The absorption frequency under symmetrical inputs can be flexibly selected from low frequency to high frequency by changing the material of the upper and lower dielectric layers. Moreover, the bandwidth in optimized broadband absorber is enhanced by 9 times while high absorbance is maintained. The characteristic of the enhancing absorption bandwidth and the selective absorption may allow our metasurface to be used in many applications such as optical switch and modulators.

High‐Efficiency and Wide‐Angle Beam Steering Based on Catenary Optical Fields in Ultrathin Metalens

AbstractRecent advances in artificial subwavelength structures promise the realization of ultrathin, lightweight, and flat metalens, providing a potential candidate for traditional bulky and curved lens. Nevertheless, most metalenses are generally suffering from serious off‐axis aberration, resulting in a limited field‐of‐view (FOV). Here, a methodology to extend the FOV of metalens is presented by exploring the local catenary optical fields and symmetry transformation from rotational symmetry to transversal symmetry. As a proof of the concept, a high efficiency (>80% even when the incidence angle is titled by 60°) and ultrathin (≈0.127 λ) metalens consisting of bilayer geometric metasurface is designed, fabricated, and characterized. The wide FOV of metalens benefiting from local catenary fields and symmetry transformation is numerically demonstrated by full‐wave simulation and ray tracing method. Moreover, the wide‐angle beam steering ability beyond ± 60° is experimentally demonstrated, which exhibits obvious advantages compared with previous beam steering transmitarrays. The novelty of the proposed methodology lies at the fact that both transversal and longitudinal local catenary fields are excited in a single component: the transversal catenary field is utilized for high efficiency spin–orbit interaction and phase modulation, while the longitudinal catenary field and symmetry transformation ensure wide‐angle operation.

Theory of microscopic meta-surface waves based on catenary optical fields and dispersion.

Surface waves bounded by subwavelength-structured surfaces have many exotic electromagnetic properties different from those supported by smooth surfaces. However, there is a long-standing misconception, claiming that these waves must propagate along the macroscopic interface. In this paper, we describe in detail the microscopic meta-surface wave (M-wave) in artificial subwavelength structures. It is shown that the waves penetrating macroscopic surfaces share the essence of most surface waves (i.e., they spread along the microscopic interfaces, formed by adjacent constitutive materials). Equivalent circuit theory and transfer matrix method have been adopted to quantitatively describe these M-waves with high accuracy in the form of catenary optical fields and dispersion. Based on these analyses, novel omnidirectional band-stop filters and wide-angle beam deflectors are designed with operational angles up to 88°. We believe these results may provide many new perspectives for both the understanding and design of functional subwavelength structures.

Revisitation of Extraordinary Young’s Interference: from Catenary Optical Fields to Spin–Orbit Interaction in Metasurfaces

Extraordinary Young’s interference is an anomalous phenomenon observed at metallic surface in 2004. The shrinkage of slit size into deep subwavelength scale introduces many novel effects that cannot be described by classic interference theory. In this paper, the Young’s interference excited by subwavelength slits is investigated via rigorous Maxwell’s equations. We reveal a universal spin–orbit interaction mechanism associated with the catenary optical fields in 2D isotropic metal-dielectric structures for the generation of optical vortex array and spin Hall effect. Based on the interference of vectorial vortex arrays with opposite topological charges, a simple yet powerful method for the fabrication of space-variant metasurfaces is proposed for the first time, which breaks the fundamental limit of traditional interference lithography. These results may provide numerous new perspectives on both the design of catenary metasurfaces and optical spin-controlled devices.