Adiabatic mode transformation in width-graded nano-gratings enabling multiwavelength light localization

Shayegannia, Moein; Montazeri, Arthur O.; Dixon, Katelyn; Prinja, Rajiv; Kazemi-Zanjani, Nastaran; Kherani, Nazir P.

doi:10.1038/s41598-020-79815-9

Cited by 5 publications

(3 citation statements)

References 33 publications

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“…Typically, chirped gratings refer to structures with varying periods wherein changing the pitch opens exciting avenues for manipulating the dispersion relation and shaping the plasmonic response. [64,65] The pitch of a nano-grating can be modulated either by chirping the groove-to-groove separation, grading the groove width, or both. Each of these types and topologies of chirped nano-gratings avail distinct mechanisms to trap multiwavelength plasmonic modes.…”

Section: Plasmonic Gratingsmentioning

confidence: 99%

Rainbows at the End of Subwavelength Discontinuities: Plasmonic Light Trapping for Sensing Applications

Farid

Dixon

Shayegannia

et al. 2021

Advanced Optical Materials

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Surface plasmon polaritons (SPPs) which exist at the metal-dielectric interface are guided by the coupling of electromagnetic waves to oscillations in the electron gas plasma created at metal surfaces. Plasmonics, a subset of the field of nanophotonics pertaining to all things beyond the diffraction limit, has flourished and evolved significantly over the past decade offering practical utility to a variety of applications. [1] Notwithstanding the ohmic loss in metals and commensurate limited propagation lengths of SPPs, the ability to effectively concentrate light in nanoscale volumes and generate extremely high electric field intensities at discontinuities or subwavelength patterned surfaces offers unique opportunities to enhance lightmatter interactions for a diverse range of functionalities. [2] Trapping broadband electromagnetic radiation over a range of deep subwavelength guided modes in a given structure provides opportunities for light-matter interactions at the nanoscale. Use of materials-commonly metals-that exhibit negative dielectric permittivity (ε < 0) at optical frequencies provide an optimum solution for light localization. Nanometallic light concentrators, in contrast to their dielectric counterparts, can squeeze and localize light into subwavelength volumes with greater control and higher efficiency. [3] Such plasmonic light concentration can be achieved by either resonant or non-resonant structures. In resonant structures, SPPs are created by time-varying electric fields that exert a force on the negatively charged electron gas inside a metal. These oscillations are resonantly driven leading to a strong charge displacement at specific optical frequencies and concentration of the light field within the structures. [4] For non-resonant light concentration effects, Schuller et al. demonstrated subwavelength light localization by introducing a feed gap in the metal structure for retardation-based resonators. The gap builds up opposite charges across it whereby SPPs encounter a longitudinal electric field component causing strong sub-wavelength light localization. [2] The focus of this article is plasmonic devices that enable rainbow light trapping, a specific modality of nanoscale field enhancement in which trapped light is spatially separated This article presents recent advances in plasmonic multiwavelength rainbow light trapping, a field that has evolved over the last decade and today is an active area of research interest encompassing a manifold of potential applications which include optical biosensing, photodetection, spectroscopy, and medicine. Conventional plasmonic devices are designed and optimized to enhance optical performance at single wavelengths, and as such are not suitable for applications that require electromagnetic field localization at multiple frequencies or broad frequency ranges of interest. To overcome these limitations, the ability to slow and trap light at multiple wavelengths and at different spatial locations has attracted significant scientific attention and opened up n...

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Section: Plasmonic Gratingsmentioning

confidence: 99%

Rainbows at the End of Subwavelength Discontinuities: Plasmonic Light Trapping for Sensing Applications

Farid

Dixon

Shayegannia

et al. 2021

Advanced Optical Materials

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“…The significance of the resonator spacing s lies in the control over adiabatic transfer of resonant energy within the bullseye structures, as greater distance between grooves optimizes energy flow between adjacent resonators, albeit at the expense of increased Ohmic losses. [ 26 ] In this work, we hold the width of the central groove and the length of all grooves fixed at 25 nm and 115 nm respectively, while varying Δ w from 3 to 9 nm and s from 150 to 300 nm for a total of 16 bullseye structures. Figure 1b shows a scanning electron microscopy (SEM) image of these 16 bullseyes along with a high magnification image of a single structure.…”

Section: Resultsmentioning

confidence: 99%

Plasmonic Bullseye Nanocavities for Broadband Light Localization and Multi‐Wavelength SERS

Dixon

Hasham

Shayegannia

et al. 2023

Advanced Optical Materials

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Plasmonic nanostructures capable of broadband light trapping and field enhancement have promising applications in a wide range of fields. This study presents a platform for broadband, polarization‐independent field enhancement in the visible regime through the use of width‐graded nanocavities in a bullseye configuration. The fabrication procedure utilizes electron beam lithography (EBL) to achieve fine control over the nanocavity geometry and template stripping to enable rapid and low‐cost production. The utility of these devices as substrates for multi‐wavelength surface enhanced Raman spectroscopy (SERS) is demonstrated through molecular detection in a 10 μM solution at two excitation wavelengths. The impact of bullseye geometry on both the broadband spectral response and multi‐wavelength SERS performance is examined. The measured SERS enhancement factor (EF) is shown to depend primarily on the plasmonically active surface area of the device, regardless of the local electromagnetic field strength within the nanocavities. These results highlight not only the utility of the width‐graded bullseye as a broadband platform for SERS and other applications but also provide design guidelines to optimize the enhancement factor and broadband performance of similar devices.

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“…The width and height of the gratings are considered as w g and h 1 , h 2 , h 3 , h 4 , and h 5 , which vary from 50 to 250 nm. Fabrication of proposed SCs is feasible via meticulous lithographic techniques, facile multi-layer sputter-deposition of thin metal-dielectric layers, tapered-side wall mold technique, or mold cast techniques based on the electrolytic growth of silver [31].…”

Section: Introductionmentioning

confidence: 99%

Absorption enhancement of Perovskite solar cells using multiple gratings

2023

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Perovskite Solar Cells have very low absorption in the near-infrared region. In this paper, in order to enhance the absorption in this region, a new technique has been presented based on multiple excitations of plasmonic modes through the gratings on the backside of the cell. Gratings on the backside of the active layer lead to absorption enhancement by exciting localized surface plasmons and light scattering, and since the resonance of surface plasmons is highly dependent on the dimensions of the gratings, the resonance wavelength can be adjusted by accurately determining the dimensions of the gratings. In order to simultaneously increase in several wavelengths, multiple gratings have been used on the backside of the cell. In using multiple gratings, the absorption in the near-infrared region has been increased many times by choosing the appropriate dimension of gratings. The highest average absorption of 68.46% has been achieved using five gratings which is a 50% increase compared to the structure without gratings. The simulation results under incident angles from 0 to 85 degrees indicate that gratings enhance light absorption up to an angle of 45 degrees. Meanwhile, the structure with five gratings degrees has an average absorption close to 70% up to an angle of ±45 degrees and is not sensitive to the incident angle. These multiple nanostructures have the ability to trap more light inside the active layer and thus promise a high-efficiency solar cell.

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Adiabatic mode transformation in width-graded nano-gratings enabling multiwavelength light localization

Cited by 5 publications

References 33 publications

Rainbows at the End of Subwavelength Discontinuities: Plasmonic Light Trapping for Sensing Applications

Rainbows at the End of Subwavelength Discontinuities: Plasmonic Light Trapping for Sensing Applications

Plasmonic Bullseye Nanocavities for Broadband Light Localization and Multi‐Wavelength SERS

Absorption enhancement of Perovskite solar cells using multiple gratings

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