Active Tuning of Spontaneous Emission by Mie-Resonant Dielectric Metasurfaces

Bohn, Justus; Bucher, Tobias; Chong, Katie E.; Komar, Andrei; Choi, Duk‐Yong; Neshev, Dragomir N.; Kivshar, Yuri S.; Pertsch, Thomas; Staude, Isabelle

doi:10.1021/acs.nanolett.8b00475

Cited by 128 publications

(128 citation statements)

References 43 publications

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“…Later, Komar et al demonstrate electrical tuning of the transmission with similar structures, in which a voltage of 70 V is used to obtain a modulation depth of 75%. More recently, LCs are also used for beam‐steering and controlling the spontaneous emission in Mie‐resonant dielectric metasurfaces . Controlling the efficiency of diffraction into certain orders is realized by a spatially varying silicon nanodisk array infiltrated with LCs .…”

Section: Tuning Via Phase Transitionsmentioning

confidence: 99%

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Tunable Metasurfaces Based on Active Materials

Cui

Bai

Sun

2019

Adv Funct Materials

215

111

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Metasurfaces, planer artificial materials composed of subwavelength unit cells, have shown superior abilities to manipulate the wavefronts of electromagnetic waves. In the last few years, metasurfaces have been a burgeoning field of research, with a large variety of functional devices, including planar lenses, beam deflectors, polarization converters, and metaholograms, being demonstrated. Up to date, the majority of metasurfaces cannot be tuned postfabrication. Yet, the dynamic control of optical properties of metasurfaces is highly desirable for a plethora of applications including free space optical communications, holographic displays, and depth sensing. Recently, much effort has been made to exploit active materials, whose optical properties can be controlled under external stimuli, for the dynamic control of metasurfaces. The tunability enabled by active materials can be attributed to various mechanisms, including but not limited to thermo‐optic effects, free‐carrier effects, and phase transitions. This short review summarizes the recent progress on tunable metasurfaces based on various approaches and analyzes their respective advantages and challenges to be confronted with. A number of potential future directions are also discussed at the end.

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Section: Tuning Via Phase Transitionsmentioning

confidence: 99%

“…The input laser beam can be deflected to 12° with an efficiency of 50% by heating the sample. Moreover, Bohn et al fabricate a silicon nanodisk array on the top of a fluorescent substrate, as shown in Figure c . By properly controlling the temperature of the LCs, the emission intensity doubles at the wavelength of 900 nm.…”

Section: Tuning Via Phase Transitionsmentioning

confidence: 99%

Tunable Metasurfaces Based on Active Materials

Cui

Bai

Sun

2019

Adv Funct Materials

215

111

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“…This allowed switching between two different modes by simply setting the polarization with the alignment of the LC layer. In other studies, liquid crystals have been used to actively enhance the nonlinear response of a metasurface and more recently for active control of spontaneous emission from a fluorescent substrate …”

Section: Adaptive Metasurfacesmentioning

confidence: 99%

Optical Metasurfaces: Evolving from Passive to Adaptive

Hail

Michel

Poulikakos

et al. 2019

Advanced Optical Materials

121

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of ultrathin, artificial surfaces, so-called metasurfaces, for manipulating the propagation of light at will. [1,2] Metasurfaces control the propagation of light by abruptly changing its phase, amplitude, polarization, or spectrum at a surface and within a thin (quasi-2D) layer using large arrays of optical scatterers with subwavelength separation. Ideally, each scatterer can be independently engineered in order to locally influence the wavelets of the impinging light, and therefore, arbitrarily reform the wavefront. This concept has been exploited to create a variety of flat optical elements such as beam deflectors, [3][4][5] lenses, [6][7][8] and holograms. [9,10] As compared to bulky refraction-based optical elements, these surfaces are of subwavelength or wavelength-scale thickness, which enables their integration into compact devices. A main feature of the majority of such flat optical elements is that they are passive, and once fabricated, their optical functionalities are invariable. A beam deflector of this kind will direct light of a certain wavelength and direction always into the same direction, or a lens will focus light always to the same focal point. A broad range of new applications could be enabled if it were possible to actively and reversibly change the functionality of metasurfaces after their fabrication. With such "adaptive" metasurfaces beam deflectors with adjustable angle of deflection, metalenses with variable focal length or dynamic holograms may be realized. Advances toward such active devices are highly relevant for applications such as light detection and ranging [11] (LIDAR) sensing for driverless cars, dynamic zoom lenses for miniaturized camera systems [12] (e.g., in smartphones), or holographic displays for augmented reality devices. [13] An adaptive metasurface allows for the dynamic adjustment of an optical functionality of the surface. As shown in Figure 1, for the specific case of a metalens, these surfaces can be categorized based on their degree of dynamic adaptivity. While a passive surface has a fixed functionality, a switchable metasurface allows for switching back and forth between two (or more) predefined states (e.g., switching between different focal lengths, deflection angles, or hologram images). A continuously tunable metasurface enables continuous adjustment of a property within a range (e.g., tunable focal length or deflection angle). Finally, a freely tunable metasurface allows for continuous, arbitrary adjustment of a property, for example, 3D adjustment of the focal point of the metalens shown in Figure 1. Adaptive functionalities can be added to metasurfaces with different methods, for example, by mechanically rearranging the scatterers on the surface with respect to each other, or modifying

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“…All‐dielectric metasurfaces, in particular, which are composed of elements made of a high‐refractive index dielectric material, have been lately attracting more attention, as they show a very high diversity of exploitable properties, while being free from ohmic losses associated with the presence of metals . The potential of dielectric metasurfaces as a platform for low‐loss, compact, functional components has been extensively demonstrated in numerous applications, such as reflection/refraction control and wave‐front shaping, lensing, control of light emission or photoluminescence, polarization control and polarimetry, generation of vortex beams, highly selective filtering, or enhancement of nonlinear processes …”

Section: Introductionmentioning

confidence: 99%

All‐Dielectric Silicon Metasurface with Strong Subterahertz Toroidal Dipole Resonance

Zografopoulos

Ferraro

Algorri

et al. 2019

Advanced Optical Materials

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properties of propagating electromagnetic waves, such as wave front, polarization, intensity, or spectrum, in ways unachievable by bulk materials of the same subwavelength thickness. [1][2][3] The constituent elements of a metasurface can be either metallic or dielectric and they are usually patterned on a low-loss, dielectric substrate. All-dielectric metasurfaces, in particular, which are composed of elements made of a high-refractive index dielectric material, have been lately attracting more attention, as they show a very high diversity of exploitable properties, while being free from ohmic losses associated with the presence of metals. [4] The potential of dielectric metasurfaces as a platform for low-loss, compact, functional components has been extensively demonstrated in numerous applications, such as reflection/refraction control and wave-front shaping, [5][6][7][8] lensing, [9] control of light emission [10,11] or photoluminescence, [12,13] polarization control [14,15] and polarimetry, [16] generation of vortex beams, [17] highly selective filtering, [18,19] or enhancement of nonlinear processes. [20,21] In addition to offering novel solutions in practical applications, metasurfaces can also provide insight in theoretical physics, optics, and the investigation of phenomena based on particular light-matter interaction conditions. One such case is that of toroidal modes, which have been under intense investigation, thanks to their unusual electromagnetic properties. The toroidal dipole, the simplest toroidal mode, is generated by a current flowing in a solenoid, which is bent into a torus. Under certain conditions, the excitation of the toroidal dipole can interfere destructively with the electric dipole mode and cancel the far-field scattering radiation of dielectric particles, in the so-called "anapole" state. [22] Since decades ago, toroidal modes were employed in physics, for instance, to explain the parity violation of the weak interactions in atomic nuclei, [23] to propose models of stable atoms, [24] or to describe dark matter. [25] In recent years, though, the interest on electromagnetic toroidal moments is rapidly increasing as, apart from the fundamental physical insight, they can be harnessed in numerous applications. [26,27] Toroidal modes in individual dielectric particles or small clusters have been theoretically proposed for the excitation of toroidal response, [28] cloaking, [29] enhanced absorption, [30] and nanolasing [31] or experimentally demonstrated as nonradiating sources [32] and for the enhancement of nonlinear effects. [33,34] Moreover, it A single-layer, all-dielectric metasurface exhibiting a strong toroidal resonance in the low-atmospheric loss radio window of the subterahertz W-band is theoretically proposed and experimentally demonstrated. The metasurface is fabricated on a high-resistivity floating-zone silicon wafer by means of a singleprocess, wet anisotropic etching technique. The properties of the toroidal mode of both the constituent dielectric elements and the metasur...

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Active Tuning of Spontaneous Emission by Mie-Resonant Dielectric Metasurfaces

Cited by 128 publications

References 43 publications

Tunable Metasurfaces Based on Active Materials

Tunable Metasurfaces Based on Active Materials

Optical Metasurfaces: Evolving from Passive to Adaptive

All‐Dielectric Silicon Metasurface with Strong Subterahertz Toroidal Dipole Resonance

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