Electro-optic tuning of split ring resonators embedded in a liquid crystal

Atorf, Bernhard; Mühlenbernd, Holger; Muldarisnur, Mulda; Zentgraf, Thomas; Kitzerow, Heinz‐S.

doi:10.1364/ol.39.001129

Cited by 21 publications

(21 citation statements)

References 22 publications

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“…These structures proved less sensitive to surface anchoring due to their near‐field extending over larger distances and thus an interaction with a larger volume of the LCs. In the near‐IR spectral range the resonance of a split ring resonator‐based metamaterial was shifted by 1.2% with the realignment of LCs in an applied electric field . Here, the application of a thin organic silane layer on the metamaterial, which facilitated the alignment of the LCs and mitigated the surface anchoring, was crucial for the better performance compared to a previous study of a similar surface but without silane layer where no resonance shifts were measured .…”

Section: Adaptive Metasurfacesmentioning

confidence: 66%

Optical Metasurfaces: Evolving from Passive to Adaptive

Hail

Michel

Poulikakos

et al. 2019

Advanced Optical Materials

115

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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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Section: Adaptive Metasurfacesmentioning

confidence: 66%

Optical Metasurfaces: Evolving from Passive to Adaptive

Hail

Michel

Poulikakos

et al. 2019

Advanced Optical Materials

115

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“…Its resonance frequency ≈11.08 GHz undergoes a maximum shift of 210 MHz with an applied DC electric field of 0.3 V µm −1 . Subsequently, metallic metasurfaces have been integrated with LCs to obtain tunability over a wide spectral range from the visible to the THz frequencies . It is noteworthy that in the visible and NIR regimes, the metallic meta‐atoms have similar sizes compared to LC molecules and the efficiency of tuning is decreased due to the anchoring of LCs to the metallic surface .…”

Section: Tuning Via Phase Transitionsmentioning

confidence: 99%

Tunable Metasurfaces Based on Active Materials

Cui

Bai

Sun

2019

Adv Funct Materials

204

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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“…In liquid crystals, the birefringent molecules can be reoriented along the electric field direction, thereby creating a large refractive-index change possibly exceeding 0.3 [100]. By immersing metasurface structures in a liquid crystal cell, electrical tuning of resonances in plasmonic [101][102][103][104] and dielectric [105,106] resonator arrays has been demonstrated. Electrically tunable liquid crystal metasurfaces engineered using an inverse-design approach have demonstrated high-efficiency and wide-angle steering performances [107].…”

Section: Electro-refractive Switchingmentioning

confidence: 99%

Design for quality: reconfigurable flat optics based on active metasurfaces

et al. 2020

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Optical metasurfaces, planar subwavelength nanoantenna arrays with the singular ability to sculpt wavefront in almost arbitrary manners, are poised to become a powerful tool enabling compact and high-performance optics with novel functionalities. A particularly intriguing research direction within this field is active metasurfaces, whose optical response can be dynamically tuned postfabrication, thus allowing a plurality of applications unattainable with traditional bulk optics. Designing reconfigurable optics based on active metasurfaces is, however, presented with a unique challenge, since the optical quality of the devices must be optimized at multiple optical states. In this article, we provide a critical review on the active meta-optics design principles and algorithms that are applied across structural hierarchies ranging from single meta-atoms to full meta-optical devices. The discussed approaches are illustrated by specific examples of reconfigurable metasurfaces based on optical phase-change materials.

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Electro-optic tuning of split ring resonators embedded in a liquid crystal

Cited by 21 publications

References 22 publications

Optical Metasurfaces: Evolving from Passive to Adaptive

Optical Metasurfaces: Evolving from Passive to Adaptive

Tunable Metasurfaces Based on Active Materials

Design for quality: reconfigurable flat optics based on active metasurfaces

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