Recent Advances in Optical Metasurfaces
Editor: Cheng Zhang, Din-Ping Tsai
Optical metasurfaces, composed of planar arrays of sub-wavelength dielectric or metallic structures that collectively mimic the operation of conventional bulk optical elements, have revolutionized the field of optics by their potential in constructing high-efficiency and multi-functional optoelectronic systems with a compact form factor. By engineering the geometry, placement and alignment of its constituent elements, an optical metasurface arbitrarily controls the magnitude, polarization, phase, angular momentum, or dispersion of an incident light. The study of metasurface now spans various multidisciplinary fields in both fundamental research on light-matter interaction, and emerging applications from solid-state LiDAR to compact imaging and spectroscopy devices. To highlight the exciting developments in this field and to promote the diverse applications of metasurfaces, Prof. Cheng Zhang (Huazhong University of Science and Technology, China) and Prof. Din-Ping Tsai (The Hong Kong Polytechnic University, China) are organizing a special issue on Recent Advances in Optical Metasurfaces
This special issue cover recent progress in both the physics and applications of optical metasurfaces operating from the microwave to the ultraviolet spectral range. Topics include, but not limited to: 
➣ Design and optimization of optical metasurfaces
➣ Light manipulation and wavefront shaping using metasurfaces
➣ Active and tunable metasurfaces
➣ Nonlinear optical metasurfaces
➣ Novel material platforms for optical metasurfaces
➣ Metasurface technology for shorter wavelength regions, such as the ultraviolet (UV), deep-UV or vacuum UV region
➣ Emerging applications of metasurfaces
➣ Low-cost and large-area fabrication of metasurfaces
Article types include: review, research, letter, perspective, and comment.

Guest Editors: 
Prof. Cheng Zhang, Huazhong University of Science and Technology, China
Prof. Din-Ping Tsai, The Hong Kong Polytechnic University, China

Publication years
Loading ...
Article types
Loading ...
  • Select all
    Chunyu LIU, Yanfeng LI, Xi FENG, Xixiang ZHANG, Jiaguang HAN, Weili ZHANG
    Frontiers of Optoelectronics, 2021, 14(2): 201-210.

    The applications of terahertz (THz) technology can be greatly extended using non-diffractive beams with unique field distributions and non-diffractive transmission characteristics. Here, we design and experimentally demonstrate a set of dual non-diffractive THz beam generators based on an all-dielectric metasurface. Two kinds of non-diffractive beams with dramatically opposite focusing properties, Bessel beam and abruptly autofocusing (AAF) beam, are considered. A Bessel beam with long-distance non-diffractive characteristics and an AAF beam with low energy during transmission and abruptly increased energy near the focus are generated for x- and y-polarized incident waves, respectively. These two kinds of beams are characterized and the results agree well with simulations. In addition, we show numerically that these two kinds of beams can also carry orbital angular momentum by further imposing proper angular phases in the design. We believe that these metasurface-based beam generators have great potential use in THz imaging, communications, non-destructive evaluation, and many other fields.

    Zhilu YE, Minye YANG, Liang ZHU, Pai-Yen CHEN
    Frontiers of Optoelectronics, 2021, 14(2): 211-220.

    In this paper, we introduce an ultra-sensitive optical sensing platform based on the parity-time-reciprocal scaling (PTX)-symmetric non-Hermitian metasurfaces, which leverage exotic singularities, such as the exceptional point (EP) and the coherent perfect absorber-laser (CPAL) point, to significantly enhance the sensitivity and detectability of photonic sensors. We theoretically studied scattering properties and physical limitations of the PTX-symmetric metasurface sensing systems with an asymmetric, unbalanced gain-loss profile. The PTX-symmetric metasurfaces can exhibit similar scattering properties as their PT-symmetric counterparts at singular points, while achieving a higher sensitivity and a larger modulation depth, possible with the reciprocal-scaling factor (i.e., X transformation). Specifically, with the optimal reciprocal-scaling factor or near-zero phase offset, the proposed PTX-symmetric metasurface sensors operating around the EP or CPAL point may achieve an over 100 dB modulation depth, thus paving a promising route toward the detection of small-scale perturbations caused by, for example, molecular, gaseous, and biochemical surface adsorbates.

    Dong Kyo OH, Taejun LEE, Byoungsu KO, Trevon BADLOE, Jong G. OK, Junsuk RHO
    Frontiers of Optoelectronics, 2021, 14(2): 229-251.

    Metasurfaces are composed of periodic subwavelength nanostructures and exhibit optical properties that are not found in nature. They have been widely investigated for optical applications such as holograms, wavefront shaping, and structural color printing, however, electron-beam lithography is not suitable to produce large-area metasurfaces because of the high fabrication cost and low productivity. Although alternative optical technologies, such as holographic lithography and plasmonic lithography, can overcome these drawbacks, such methods are still constrained by the optical diffraction limit. To break through this fundamental problem, mechanical nanopatterning processes have been actively studied in many fields, with nanoimprint lithography (NIL) coming to the forefront. Since NIL replicates the nanopattern of the mold regardless of the diffraction limit, NIL can achieve sufficiently high productivity and patterning resolution, giving rise to an explosive development in the fabrication of metasurfaces. In this review, we focus on various NIL technologies for the manufacturing of metasurfaces. First, we briefly describe conventional NIL and then present various NIL methods for the scalable fabrication of metasurfaces. We also discuss recent applications of NIL in the realization of metasurfaces. Finally, we conclude with an outlook on each method and suggest perspectives for future research on the high-throughput fabrication of active metasurfaces.

    Xiao FU, Haowen LIANG, Juntao Li
    Frontiers of Optoelectronics, 2021, 14(2): 170-186.

    Lens is a basic optical element that is widely used in daily life, such as in cameras, glasses, and microscopes. Conventional lenses are designed based on the classical refractive optics, which results in inevitable imaging aberrations, such as chromatic aberration, spherical aberration and coma. To solve these problems, conventional imaging systems impose multiple curved lenses with different thicknesses and materials to eliminate these aberrations. As a unique photonic technology, metasurfaces can accurately manipulate the wavefront of light to produce fascinating and peculiar optical phenomena, which has stimulated researchers’ extensive interests in the field of planar optics. Starting from the introduction of phase modulation methods, this review summarizes the design principles and characteristics of metalenses. Although the imaging quality of existing metalenses is not necessarily better than that of conventional lenses, the multi-dimensional and multi-degree-of-freedom control of metasurfaces provides metalenses with novel functions that are extremely challenging or impossible to achieve with conventional lenses.

    Yu BI, Lingling HUANG, Xiaowei LI, Yongtian WANG
    Frontiers of Optoelectronics, 2021, 14(2): 154-169.

    The dynamic control of the metasurface opens up a vital technological approach for the development of multifunctional integrated optical devices. The magnetic field manipulation has the advantages of sub-nanosecond ultra-fast response, non-contact, and continuous adjustment. Thus, the magnetically controllable metasurface has attracted significant attention in recent years. This study introduces the basic principles of the Faraday and Kerr effect of magneto-optical (MO) materials. It classifies the typical MO materials according to their properties. It also summarizes the physical mechanism of different MO metasurfaces that combine the MO effect with plasmonic or dielectric resonance. Besides, their applications in the nonreciprocal device and MO sensing are demonstrated. The future perspectives and challenges of the research on MO metasurfaces are discussed.

    Lei WAN, Danping PAN, Tianhua FENG, Weiping LIU, Alexander A. POTAPOV
    Frontiers of Optoelectronics, 2021, 14(2): 187-200.

    Dielectric metasurfaces-based planar optical spatial differentiator and edge detection have recently been proposed to play an important role in the parallel and fast image processing technology. With the development of dielectric metasurfaces of different geometries and resonance mechanisms, diverse on-chip spatial differentiators have been proposed by tailoring the dispersion characteristics of subwavelength structures. This review focuses on the basic principles and characteristic parameters of dielectric metasurfaces as first- and second-order spatial differentiators realized via the Green’s function approach. The spatial bandwidth and polarization dependence are emphasized as key properties by comparing the optical transfer functions of metasurfaces for different incident wavevectors and polarizations. To present the operational capabilities of a two-dimensional spatial differentiator in image information acquisition, edge detection is described to illustrate the practicability of the device. As an application example, experimental demonstrations of edge detection for different biological cells and a flower mold are discussed, in which a spatial differentiator and objective lens or camera are integrated in three optical pathway configurations. The realization of spatial differentiators and edge detection with dielectric metasurfaces provides new opportunities for ultrafast information identification in biological imaging and machine vision.