Functional-Graded Index Metasurfaces for Infrared Radiation and Guiding

Farmahini-Farahani, Mohsen; Mosallaei, Hossein

doi:10.1109/tnano.2014.2365554

Cited by 13 publications

(5 citation statements)

References 25 publications

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“…Other work can be found that spatially varied the lattice spacing [22,23], the orientation of the unit cells [24][25][26][27], the pattern within the unit cell [28][29][30], the symmetry of the lattice [31] and combinations of these [32][33][34][35]. The concept of spatially variant lattices applies equally well to metasurfaces and work can be found in the areas of leaky-wave antennas [36], radiation and guiding [37], phase gradient metasurfaces [38,39], Luneberg lenses [40][41][42] and more [38,39,43].…”

Section: Introductionmentioning

confidence: 99%

Spatially variant periodic structures in electromagnetics

Rumpf

Pazos

Digaum

et al. 2015

Phil. Trans. R. Soc. A.

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Section: Introductionmentioning

confidence: 99%

Spatially variant periodic structures in electromagnetics

Rumpf

Pazos

Digaum

et al. 2015

Phil. Trans. R. Soc. A.

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“…We optimize one quarter of the binary pattern with 10 × 10 pixels. Compared to the Metal-Insulator-Metal (MIM) patch widely employed for this application 17 , 18 , the binary nano-antenna of Fig. 2 has a resolution of 25 nm and is much more resilient to fabrication imperfections.…”

Section: Resultsmentioning

confidence: 99%

“…They therefore find applications in vast areas including: optical beam-steering 8 , 9 , lensing 5 , 10 , 11 , imaging 12 , 13 , and holography 14 , 15 . The de facto approach in designing metasurfaces has been to choose a canonical meta-element based on some considerations regarding the problem at hand, and then performing a systematic study to form a pre-compiled library of sub-wavelength nano-antennas that ideally cover the whole required range of optical responses, in terms of scattering phase and/or amplitude 16 – 18 . The library elements can then be employed to realize the intended phase and amplitude profiles for wavefront-forming and holography applications.…”

Section: Introductionmentioning

confidence: 99%

Adaptive Genetic Algorithm for Optical Metasurfaces Design

Jafar‐Zanjani

Inampudi

Mosallaei

2018

Sci Rep

Self Cite

202

116

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As optical metasurfaces become progressively ubiquitous, the expectations from them are becoming increasingly complex. The limited number of structural parameters in the conventional metasurface building blocks, and existing phase engineering rules do not completely support the growth rate of metasurface applications. In this paper, we present digitized-binary elements, as alternative high-dimensional building blocks, to accommodate the needs of complex-tailorable-multifunctional applications. To design these complicated platforms, we demonstrate adaptive genetic algorithm (AGA), as a powerful evolutionary optimizer, capable of handling such demanding design expectations. We solve four complex problems of high current interest to the optics community, namely, a binary-pattern plasmonic reflectarray with high tolerance to fabrication imperfections and high reflection efficiency for beam-steering purposes, a dual-beam aperiodic leaky-wave antenna, which diffracts TE and TM excitation waveguides modes to arbitrarily chosen directions, a compact birefringent all-dielectric metasurface with finer pixel resolution compared to canonical nano-antennas, and a visible-transparent infrared emitting/absorbing metasurface that shows high promise for solar-cell cooling applications, to showcase the advantages of the combination of binary-pattern metasurfaces and the AGA technique. Each of these novel applications encounters computational and fabrication challenges under conventional design methods, and is chosen carefully to highlight one of the unique advantages of the AGA technique. Finally, we show that large surplus datasets produced as by-products of the evolutionary optimizers can be employed as ingredients of the new-age computational algorithms, such as, machine learning and deep leaning. In doing so, we open a new gateway of predicting the solution to a problem in the fastest possible way based on statistical analysis of the datasets rather than researching the whole solution space.

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“…As a proof of concept, we are interested in designing a meta-array where the electrical addressability and individual control over each subwavelength ITO-integrated GMRM unit cell give us the opportunity to realize the desired gradient phase delay for beam forming/shaping. The mechanism is similar to having control over a surface wave by utilizing the holography technique, in which any desired beam-forming (e.g., focusing and bending) can be achieved through introducing a spatial modulation of refractive index at the interface. − The proposed metasurface enables the excitation of counter-propagating guided modes with a plane wave illumination across the whole metasurface plane. The guided modes can be decoupled into free space at the place of each grating nanobar, and their properties can be altered by electrically modifying the refractive index of ITO.…”

Section: Tunable Beam Steering With Ito-integrated Gmrm Meta-arraymentioning

confidence: 99%

Electro-optical Amplitude and Phase Modulators Based on Tunable Guided-Mode Resonance Effect

Forouzmand

Mosallaei

2019

ACS Photonics

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Here, electrically tunable amplitude and phase modulators are designed by the hybridization of indium tin oxide (ITO) into a guided-mode resonance mirror (so-called GMRM), which consists of a high-index silicon (Si) nanograting placed on top of a Si guiding core followed by a silicon dioxide optical buffer layer and a highly reflective substrate. The physical mechanism is based on the intriguing optical characteristics of GMRMs and integration of a dual-gated ITO with the capability of charge carrier modulation into the Si nanograting. A gate-tunable amplitude modulator with a modulation depth as high as ∼0.80 is realized by careful selection of structural parameters, excitation of a strongly coupled guided-mode resonance, and modifying the external bias voltage. This design can also be adjusted only by changing the thickness of its optical buffer layer and moderating the strength of the guided-mode resonance to serve as an efficient active phase modulator. The phase variation of ∼210° and relatively high reflection amplitude in the 0.45–0.6 range are accomplished when the applied bias voltage alters from −15 V to +24 V. This reflection phase tuning mainly originates from the carrier depletion and accumulation inside the incorporated 5-nm-thick ITO layer. The accurate modeling and numerical calculation of the optical response of the proposed unit cell for different applied external voltages are carried out through linking the electrostatics device physics model and rigorous coupled wave analysis optical simulation. The design rules and physical principles behind the dual-gated ITO-integrated GMRM unit cell are discussed in-depth by investigation of the structural parameters, the nature of supported resonances, and voltage-dependent effects of inhomogeneous carrier distributions in both ITO and Si layers. The electrical addressability and individual control over pixelated subwavelength unit cells provide the opportunity for realizing an actively reconfigurable metasurface with the desired gradient phase delay.

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Functional-Graded Index Metasurfaces for Infrared Radiation and Guiding

Cited by 13 publications

References 25 publications

Spatially variant periodic structures in electromagnetics

Spatially variant periodic structures in electromagnetics

Adaptive Genetic Algorithm for Optical Metasurfaces Design

Electro-optical Amplitude and Phase Modulators Based on Tunable Guided-Mode Resonance Effect

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