《Advanced Optical Materials》2017,5(14)

Conventional all‐dielectric metasurfaces made from high‐index and low‐loss materials (such as Si or GaAs) can achieve high optical efficiencies as well as broadband characteristics, mostly for the infrared (IR) light. However, maintaining the bandwidth and efficiency for conventional all‐dielectric metasurfaces for visible or near‐IR light becomes challenging, due to the limitations from material selection as well as fabrication techniques. In this paper, the idea of heterogeneous all‐dielectric metasurfaces is proposed for a better metasurface design in shorter‐wavelength ranges. An ultra‐broadband reflector, as a proof‐of‐principle demonstration, is presented in this paper, both numerically and experimentally. The broadband reflector demonstrates a good optical efficiency, a broadband reflectance, as well as a great manufacturability. Nanoimprint lithography patterning process and advanced etching recipes are developed for the large‐area and low‐cost heterogeneous metasurface fabrication.  相似文献   

    

《Advanced Optical Materials》2017,5(9)

The optimum reflection of the solar spectrum at well‐defined incident directions as well as its durability in time are, both, fundamental requirements of the optics of thermosolar and photovoltaic energy conversion systems. The stringent high performance needed for these applications implies that, almost exclusively, second face mirrors based on silver are employed for this purpose. Herein, the possibility to develop solar mirrors using other metals, such as copper and aluminum, is theoretically and experimentally analyzed. It is found that reflectors based on these inexpensive metals are capable of reflecting the full solar spectrum with efficiencies comparable to that of silver‐based reflectors. The designs herein proposed are based on aperiodic metal‐dielectric multilayers whose optimized configuration is chosen employing a code based on a genetic algorithm that allows selecting the best one among 10⁸ tested reflectors. The use of metals with wider spectral absorption bands is compensated by the use of multilayered designs in which metal absorption is almost suppressed, as the analysis of the electric field intensity distribution demonstrates. The feasibility of the proposed mirrors is demonstrated by their actual fabrication by large area deposition techniques amenable for mass production.  相似文献   

    

《Advanced Optical Materials》2017,5(3)

The advent of holography metasurfaces unlocks a plethora of exciting opportunities for rapid progress at the frontiers of various branches of science and engineering. However, the holography metasurfaces are constrained by sophisticated design and fabrication procedures and are less compatible with dynamic functionalities as well as unequal across the electromagnetic spectrum. Here, a new approach is proposed to fabricate speckle image holography metasurfaces with chaotic carrier fringes for broadband photon management. Using this holography metasurfaces structure allows to sculpt wavefronts of light almost at will. As a proof‐of‐concept, the incorporation of these structures into white organic light‐emitting diodes realizes tunable regional concentrated radiation patterns without spectral distortion. Moreover, the fabricated optical diffusers with the proposed structures also exhibit controllable broadband light softening, resulting in drastically enhanced extra optical gain than that of conventional diffusers. It is hoped that the effort can provide an alternative pathway for precisely broadband beam sculpting and can enable the integration of various optoelectronic systems for practical application.  相似文献   

    

《Advanced Optical Materials》2017,5(22)

Metasurfaces provide a novel strategy to manipulate electromagnetic (EM) waves by controlling the local phase of subwavelength artificial structures within the wavelength scale. So far, many exciting devices have been developed and most of them are based on passive metasurface, which can only perform a specific functionality. It is still very challenging to simultaneously achieve multiple EM functionalities and real‐time reconfigurability in one design. This study reports a reconfigurable metasurface for multifunctional control of EM waves. By controlling tunable elements, the proposed metasurface can dynamically change its local phase distribution to generate predetermined EM responses. Here, the metasurface can generate beam‐splitting performance that can be used to reduce backward scattering waves, and its scattering reduction frequency is tunable. In addition, such metasurface can also achieve dynamical beam deflection and polarization transformation through reconfigurable design of the phase distribution. The above EM functionalities have been experimentally demonstrated at microwave frequencies, which can be switched in real time by a computer‐controlled voltage source. This study paves the way toward the realization of multifunctional metadevices with real‐time and programmable control, showing great potential in applications of smart materials and devices for EM‐wave manipulation.  相似文献   

    

《Advanced Optical Materials》2017,5(22)

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《Advanced Optical Materials》2017,5(21)

As a revolutionary three‐dimensional (3D) optical imaging technique, optical holography has attracted wide attention for its capability of recording both the amplitude and phase information of light scattered from objects. Holograms are designed to transform an incident wave into a desired arbitrary wavefront in the far field, which requires ultimate complex phase control in each hologram pixel. Conventional holograms shape the wavefront via the phase accumulation effect during the wave propagation through bulky optical elements, suffering issues of low‐resolution imaging and high‐order diffraction. Recently, metasurfaces, 2D metamaterials with ultrathin thickness, have emerged as an important platform to reproduce computer‐generated holograms due to their advantages in manipulating light with well‐controlled amplitude, phase, and polarization. In this article, the latest research progress in various types of metasurface holograms is reviewed from their design principles to versatile functional applications. At the end, more potential applications of metasurface holograms are discussed and some future research directions are also provided.  相似文献   

    

Yaxin Zhang  Jinjin Jin  Mingbo Pu  Qiong He  Yinghui Guo  Xiong Li  Xiaoliang Ma  Xiangang Luo 《固体物理学:研究快报》2020,14(5)

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Yichao Liu  Jichao Fu  Hongguang Dong  Chengsheng Gong  Fei Sun  Sailing He 《固体物理学:研究快报》2020,14(3)

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Ali Forouzmand  Hossein Mosallaei 《Laser u0026amp; Photonics Reviews》2020,14(6)

Herein, a tunable semiconductor‐based metasurface, based on electro‐optical modulation of an array of geometrically‐fixed silicon (Si) nanobars, sandwiched between two distributed Bragg reflectors (DBRs) is proposed. A flat‐top transmission spectrum with a steep phase profile, which turns out to be essential to realize a highly‐efficient spatial light modulator in transmission mode, is formed by excitation of two spectrally close Fabry‐Pérot‐type and guided‐mode resonances. The refractive‐index of Si nanobars is electrically modulated by the injection of electrons and holes using a P–I–N junction configuration, considered along each nanobar. It is theoretically demonstrated that wide phase agility of 215° and transmission amplitude higher than 0.6 (with an average of ≈0.83) can be accomplished at the operating wavelength of ≈1.55 µm. This wide‐range tunability is realized by introducing free electron and hole carrier densities of ∆N = ∆P = 5 × 10¹⁸ cm⁻³ accompanied with Si refractive‐index‐change of ∆n_Si = 0.01. The transmission phase of each unit cell can be separately controlled, which in turn allows to design a tunable meta‐array with real‐time beam control. As a proof of concept, a dynamic focusing metalens with an adjustable focal length is designed and numerically investigated.  相似文献   

    

Xuyue Guo  Peng Li  Jinzhan Zhong  Sheng Liu  Bingyan Wei  Wei Zhu  Shuxia Qi  Huachao Cheng  Jianlin Zhao 《Laser u0026amp; Photonics Reviews》2020,14(3)

Tailoring the spatial structure of light field in multiple degrees of freedom is a research hotspot in recent years. The topology of light field, as one of the most fascinating structures, such as vortex knots and links associated with the phase singularities, is evoking increasing attention both in fundamental research and practical application. Here, an all‐dielectric metasurface device is proposed and experimentally demonstrated that can construct vortex knots and links in light field at the micro scale. These two distinct topological configurations can be switched by changing the incident polarization. Utilizing the digital holographic interference method, these topological configurations of vorticity lines are accurately characterized in three‐dimensions, and the topology‐preserving evolution of such ultra‐small fields is demonstrated. These two classical configurations exemplify the capability of multichannel manipulating topology by compact metadevice. The work may promote the application of structured light filed at the micro scale and even the creation of other physical fields with ultra‐small size.  相似文献