Reprogrammable multifocal THz metalens based on metal–insulator transition of VO2-assisted digital metasurface

Kargar, Roya; Rouhi, Kasra; Abdolali, Ali

doi:10.1016/j.optcom.2020.125331

Cited by 38 publications

(22 citation statements)

References 69 publications

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“…With the advent of metasurfaces, a new generation of 2D computational interfaces has emerged to spatially shape the optical fields over deeply sub-wavelength volumes [36]- [38]. Several characterization frameworks based on local tensorial scattering coefficients [39]- [46], surface impedance formulation [47], [48], generalized sheet transition conditions (GSTCs) by susceptibility tensors [49], [50] as well as individual/effective polarizabilities [35], [51]- [53], have been fostered to represent metasurfaces in their general bianisotropic forms. These methods do consider normal components; however, in most studies the normal components are omitted.…”

Section: Theoretical Investigationmentioning

confidence: 99%

Reciprocal Metasurfaces for On-Axis Reflective Optical Computing

Momeni

Rajabalipanah

Rahmanzadeh

et al. 2021

IEEE Trans. Antennas Propagat.

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Analog computing has emerged as a promising candidate for real-time and parallel continuous data processing. This paper presents a reciprocal way for realizing asymmetric optical transfer functions (OTFs) in the reflection side of the onaxis processing channels. It is rigorously demonstrated that the presence of Cross-polarization Exciting Normal Polarizabilities (CPENP) of a reciprocal metasurface circumvents the famous challenge of Green's function approach in implementation of on-axis reflective optical signal processing while providing dual computing channels under orthogonal polarizations. Following a comprehensive theoretical discussion and as a proof of concept, an all-dielectric optical metasurface is elaborately designed to exhibit the desired surface polarizabilities, thereby reflecting the first derivative and extracting the edges of images impinging from normal direction. The proposed study offers a flexible design method for on-axis metasurface-based optical signal processing and also, dramatically facilitates the experimental setup required for ultrafast analog computation and image processing.

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Section: Theoretical Investigationmentioning

confidence: 99%

Reciprocal Metasurfaces for On-Axis Reflective Optical Computing

Momeni

Rajabalipanah

Rahmanzadeh

et al. 2021

IEEE Trans. Antennas Propagat.

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“…A number of mechanical tuning techniques have been developed such as stretching the metalens on the elastic substrate [21][22][23], MEMs-actuated silicon metasurface lens [24], MEMsactuated axially moving metasurface doublet lens [25], manually-actuated [26][27] or MEMs-actuated [1] laterally moving two cubic phase metasurfaces of an Alvarez lens, and controlling the angular orientation of the metalens doublets [28][29][30]. Furthermore, other forms of tuning such as incorporating tunable materials into metasurfaces for changing focal position have been studied [20,[31][32][33][34][35][36][37][38][39][40][41][42][43]. These include but are not limited to the use of anisotropic liquid crystals [31][32], thermo-optical materials [20,[33][34], phase change and phase transition materials like GST [35][36][37]/GSST [38]/VO2 [39][40], graphene [41][42][43], etc.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, other forms of tuning such as incorporating tunable materials into metasurfaces for changing focal position have been studied [20,[31][32][33][34][35][36][37][38][39][40][41][42][43]. These include but are not limited to the use of anisotropic liquid crystals [31][32], thermo-optical materials [20,[33][34], phase change and phase transition materials like GST [35][36][37]/GSST [38]/VO2 [39][40], graphene [41][42][43], etc.…”

Section: Introductionmentioning

confidence: 99%

Inverse Design of On-Chip Thermally Tunable Varifocal Metalens Based on Silicon Metalines

Zarei

Khavasi

2021

IEEE Access

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High-contrast transmitarray (HCTA) metasurfaces, named as metalines in this article, a category of lithographically defined on-chip diffractive elements with minimized scattering loss, enables parallel on-chip optical signal processing. While high-performance devices with different functionalities are reported, most of them are static, and their optical functions are fixed after fabrication. However, dynamically tunable metasurfaces are of essential need in many modern optical systems. Here, we employ an inverse design method, combining FDTD parameter sweep with Fourier-optics simulations, to design thermally-controlled varifocal metalenses. Thermal tunability is accomplished through the thermo-optical effect of silicon. Maximum focal length tunability of 12% and 24% are demonstrated for 400µm and 200µm aperture varifocal metalens doublets at the wavelength of 1.55µm, respectively. The focusing efficiency is more than 74% for the whole temperature range. The 400µm and 200µm aperture metalenses are able to concentrate the input beam to spot sizes less than one wavelength and two wavelengths, respectively. This paves the way for dynamically controlled silicon photonics computational chips.

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“…Among these, flat lens or metalens, as one of the most fundamental optical elements, has attracted significant research interest in recent years. Hitherto, on the one hand, various reflective and transmissive metalenses have been demonstrated in the terahertz (THz) [ 23 , 24 ], IR [ 25 , 26 , 27 ] and visible [ 28 , 29 , 30 ] wavelength range. On the other hand, however, metalens operating in the UV wavelength range is rare—despite this, UV optics have plenteous applications in the fields of high-resolution photolithography [ 31 ], imaging [ 32 ] and chemical/biological sensing [ 33 ].…”

Section: Introductionmentioning

confidence: 99%

Design of Polarization-Independent Reflective Metalens in the Ultraviolet–Visible Wavelength Region

et al. 2021

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Flat lens or metalens, as one of the most important application branches of metasurfaces, has recently been attracting significant research interest. Various reflective and transmissive metalenses have been demonstrated in the terathertz, infrared and visible wavelength range. However, metalens operating in the ultraviolet (UV) wavelength range is rare. Moreover, the development of reflective UV metalens, the important counterpart of transmissive ones, falls far behind. In this work, with thorough investigation of material properties, we propose a reflective metalens based on silicon dioxide (SiO2) and aluminum (Al) that operates in the vacuum ultraviolet (VUV) to visible wavelength region. Four reflective metalenses were designed and optimized for wavelengths of 193, 441, 532 and 633 nm, and prominent focusing capability was observed, especially for the VUV wavelength of 193 nm. Dispersion characteristics of the metalenses were also studied within ±50 nm of the design wavelength, and negative dispersion was found for all cases. In addition, the SiO2 + Al platform can be, in principle, extended to the mid-infrared (IR) wavelength range. The reflective VUV metalens proposed in this work is expected to propel miniaturization and integration of UV optics.

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Reprogrammable multifocal THz metalens based on metal–insulator transition of VO2-assisted digital metasurface

Cited by 38 publications

References 69 publications

Reciprocal Metasurfaces for On-Axis Reflective Optical Computing

Reciprocal Metasurfaces for On-Axis Reflective Optical Computing

Inverse Design of On-Chip Thermally Tunable Varifocal Metalens Based on Silicon Metalines

Design of Polarization-Independent Reflective Metalens in the Ultraviolet–Visible Wavelength Region

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