scholarly journals Intrinsically core-shell plasmonic dielectric nanostructures with ultrahigh refractive index

2016 ◽  
Vol 2 (3) ◽  
pp. e1501536 ◽  
Author(s):  
Zengji Yue ◽  
Boyuan Cai ◽  
Lan Wang ◽  
Xiaolin Wang ◽  
Min Gu
Keyword(s):  
Refractive Index ◽  
High Performance ◽  
Topological Insulators ◽  
Near Infrared ◽  
Surface States ◽  
Core Shell ◽  
Frequency Range ◽  
Plasmonic Nanostructure ◽  
Edge Surface ◽  
Infrared Frequency Range

Topological insulators are a new class of quantum materials with metallic (edge) surface states and insulating bulk states. They demonstrate a variety of novel electronic and optical properties, which make them highly promising electronic, spintronic, and optoelectronic materials. We report on a novel conic plasmonic nanostructure that is made of bulk-insulating topological insulators and has an intrinsic core-shell formation. The insulating (dielectric) core of the nanocone displays an ultrahigh refractive index of up to 5.5 in the near-infrared frequency range. On the metallic shell, plasmonic response and strong backward light scattering were observed in the visible frequency range. Through integrating the nanocone arrays into a-Si thin film solar cells, up to 15% enhancement of light absorption was predicted in the ultraviolet and visible ranges. With these unique features, the intrinsically core-shell plasmonic nanostructure paves a new way for designing low-loss and high-performance visible to infrared optical devices.

scholarly journals Mode Sensitivity Exploration of Silica–Titania Waveguide for Refractive Index Sensing Applications

Sensors ◽  
2021 ◽  
Vol 21 (22) ◽  
pp. 7452
Author(s):  
Muhammad A. Butt ◽  
Andrzej Kaźmierczak ◽  
Cuma Tyszkiewicz ◽  
Paweł Karasiński ◽  
Ryszard Piramidowicz
Keyword(s):  
Refractive Index ◽  
High Performance ◽  
Near Infrared ◽  
Sol Gel ◽  
Cost Effective ◽  
Dip Coating ◽  
Infrared Wavelength ◽  
Refractive Index Sensing ◽  
Sensing Applications ◽  
Coating Method

In this paper, a novel and cost-effective photonic platform based on silica–titania material is discussed. The silica–titania thin films were grown utilizing the sol–gel dip-coating method and characterized with the help of the prism-insertion technique. Afterwards, the mode sensitivity analysis of the silica–titania ridge waveguide is investigated via the finite element method. Silica–titania waveguide systems are highly attractive due to their ease of development, low fabrication cost, low propagation losses and operation in both visible and near-infrared wavelength ranges. Finally, a ring resonator (RR) sensor device was modelled for refractive index sensing applications, offering a sensitivity of 230 nm/RIU, a figure of merit (FOM) of 418.2 RIU−1, and Q-factor of 2247.5 at the improved geometric parameters. We believe that the abovementioned integrated photonics platform is highly suitable for high-performance and economically reasonable optical sensing devices.

scholarly journals Plasmonic Sensing Characteristics of Gold Nanorods with Large Aspect Ratios

Sensors ◽  
2018 ◽  
Vol 18 (10) ◽  
pp. 3458 ◽  
Author(s):  
Chao Zhuang ◽  
Yifan Xu ◽  
Ningsheng Xu ◽  
Jinxiu Wen ◽  
Huanjun Chen ◽  
...  
Keyword(s):  
Refractive Index ◽  
Gold Nanorods ◽  
High Performance ◽  
Near Infrared ◽  
High Refractive Index ◽  
Surface Enhanced Raman Spectroscopy ◽  
Sers Substrate ◽  
Refractive Index Sensitivity ◽  
Aspect Ratios ◽  
Plasmonic Sensing

Plasmonic gold nanorods play important roles in nowadays state-of-the-art plasmonic sensing techniques. Most of the previous studies and applications focused on gold nanorods with relatively small aspect ratios, where the plasmon wavelengths are smaller than 900 nm. Gold nanorods with large aspect ratios are predicted to exhibit high refractive-index sensitivity (Langmir 2008, 24, 5233–5237), which therefore should be promising for the development of high-performance plasmonic chemical- and bio-sensors. In this study, we developed gold nanorods with aspect ratios over 7.9, which exhibit plasmon resonances around 1064 nm. The refractive index (RI) sensitivity of these nanorods have been evaluated by varying their dielectric environment, whereby a sensitivity as high as 473 nm/RIU (refractive index unit) can be obtained. Furthermore, we have demonstrated the large-aspect-ratio nanorods as efficient substrate for surface enhanced Raman spectroscopy (SERS), where an enhancement factor (EF) as high as 9.47 × 108 was measured using 4-methylbenzenethiol (4-MBT) as probe molecule. Finally, a type of flexible SERS substrate is developed by conjugating the gold nanorods with the polystyrene (PS) polymer. The results obtained in our study can benefit the development of plasmonic sensing techniques utilized in the near-infrared spectral region.

scholarly journals High-sensitivity refractive index of Au@Cu2−xS core–shell nanorods

RSC Advances ◽  
2018 ◽  
Vol 8 (61) ◽  
pp. 35005-35013 ◽  
Author(s):  
Pengfei Cao ◽  
Huizhen Chen ◽  
Hailong Zhang ◽  
Lin Cheng ◽  
Tiaoming Niu
Keyword(s):  
Refractive Index ◽  
Near Infrared ◽  
High Sensitivity ◽  
High Refractive Index ◽  
Core Shell ◽  
Refractive Index Sensitivity ◽  
Index Sensitivity

A high refractive index sensitivity of Au@Cu2−xS core–shell nanorods working in the near-infrared is theoretically demonstrated.

scholarly journals Non-Hermiticity and topological invariants of magnon Bogoliubov–de Gennes systems

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Hiroki Kondo ◽  
Yutaka Akagi ◽  
Hosho Katsura
Keyword(s):  
Hall Effect ◽  
Topological Insulators ◽  
Three Dimensional ◽  
Surface States ◽  
Theoretical Models ◽  
Topological Invariant ◽  
Topological Invariants ◽  
Topological Phases ◽  
Ideal Candidate ◽  
Edge Surface

Abstract Since the theoretical prediction and experimental observation of the magnon thermal Hall effect, a variety of novel phenomena that may occur in magnonic systems have been proposed. We review recent advances in the study of topological phases of magnon Bogoliubov–de Gennes (BdG) systems. After giving an overview of previous works on electronic topological insulators and the magnon thermal Hall effect, we provide the necessary background for bosonic BdG systems, with particular emphasis on their non-Hermiticity arising from the diagonalization of the BdG Hamiltonian. We then introduce definitions of $$ \mathbb{Z}_2 $$ topological invariants for bosonic systems with pseudo-time-reversal symmetry, which ensures the existence of bosonic counterparts of “Kramers pairs.” Because of the intrinsic non-Hermiticity of bosonic BdG systems, these topological invariants have to be defined in terms of the bosonic Berry connection and curvature. We then introduce theoretical models that can be thought of as magnonic analogs of two- and three-dimensional topological insulators in class AII. We demonstrate analytically and numerically that the $$ \mathbb{Z}_2 $$ topological invariants precisely characterize the presence of gapless edge/surface states. We also predict that bilayer CrI$$_3$$ with a particular stacking would be an ideal candidate for the realization of a two-dimensional magnon system characterized by a nontrivial $$ \mathbb{Z}_2 $$ topological invariant. For three-dimensional topological magnon systems, the magnon thermal Hall effect is expected to occur when a magnetic field is applied to the surface.

New Core/Shell Ta2O5-PMMA Nanocomposites for Applications as Polymer Waveguides

2007 ◽  
Vol 1056 ◽  
Author(s):  
Dorothée Vinga Szabó ◽  
Rolf Ochs ◽  
Sabine Schlabach ◽  
Eberhard Ritzhaupt-Kleissl ◽  
Thomas Hanemann
Keyword(s):  
Refractive Index ◽  
Polymer Nanocomposites ◽  
Near Infrared ◽  
Microwave Plasma ◽  
High Refractive Index ◽  
Organic Coating ◽  
Hybrid Nanoparticles ◽  
Core Shell ◽  
Polymer Waveguides ◽  
Shell Particles

ABSTRACTTo realize ceramic/polymer nanocomposites for polymer waveguides, PMMA-coated Ta2O5 nanoparticles are synthesized as core/shell particles. Therefor a gas-phase process is used: the Karlsruhe Microwave Plasma Process. The organic coating is supposed to reduce the agglomeration of the ceramic cores and should facilitate the incorporation into the polymer resin. TEM investigations of the nanoparticles exhibit crystalline and amorphous Ta2O5 with sizes around 3 to 6 nm, confirmed by electron diffraction. Although the polymer coating is not visible in TEM imaging, electron energy loss spectroscopy (EELS) exhibits a significant C-edge, proofing the organic coating. The Ta2O5/PMMA nanoparticles are incorporated with different weight fractions to a maximum of 1 wt% by a dissolver stirrer into PMMA resin. The optical properties (refractive index, transmission) are determined as a function of the nanoparticle content. Compared to the pure polymer, the refractive index of the modified composite, measured at 633 nm, is increased by 0.001 and 0.004 at 0.1 wt% and 0.7 wt%, respectively. A similar tendency is observed at 1550 nm. The transmission in the near infrared (NIR) is similar to that of PMMA up to a content of 0.3 wt%. At higher nanoparticle contents transmission is reduced. The reduction in transmission is due to the presence of agglomerates larger then 1/10 of the applied wavelength, confirmed by TEM. The concept of incorporating inorganic/organic hybrid nanoparticles with intrinsic high refractive index in polymer matrices is very promising. A suitable effect in refractive index for application of ceramic nanoparticle/polymer nanocomposites as polymer waveguides could be observed even with low particle concentration.

scholarly journals Near-field Strong Plasmonic Resonances in Bi1.5Sb0.5Te1.8Se1.2 Topological Insulator Film

2021 ◽  
Author(s):  
Baoshan Guo ◽  
Huan Yao ◽  
Ningwei Zhan ◽  
Lan Jiang
Keyword(s):  
Topological Insulator ◽  
Electromagnetic Waves ◽  
Near Infrared ◽  
Near Field ◽  
Surface States ◽  
Field Energy ◽  
Hole Array ◽  
Infrared Range ◽  
Plasmonic Material ◽  
Edge Surface

Abstract Topological insulators are a new class of quantum materials with metallic (edge) surface states and insulating bulk states. They exhibit various novel electronic and optical properties that make them highly promising electronic, spintronic, and optoelectronic materials. Our report confirms that the topological insulator Bi 1.5 Sb 0.5 Te 1.8 Se 1.2 (BSTS) is also an effective plasmonic material in the visible and near-infrared range. A BSTS film can effectively control transmission and reflection characteristics by changing the period of the hole array. This study determined that a strong resonant surface plasmonic mode at the resonance peak can confine approximately 80% of the electromagnetic field energy is demonstrated. Higher-order (second- and third-order) resonance peaks were also found, which is critical for controlling electromagnetic waves and research into new optoelectronic devices.

Light-trapping enhanced ZnO–MoS2 core–shell nanopillar arrays for broadband ultraviolet-visible-near infrared photodetection

2018 ◽  
Vol 6 (26) ◽  
pp. 7077-7084 ◽  
Author(s):  
Ling Ning ◽  
Tianhao Jiang ◽  
Zhibin Shao ◽  
Ke Ding ◽  
Xiujuan Zhang ◽  
...  
Keyword(s):  
High Performance ◽  
Near Infrared ◽  
Light Trapping ◽  
Core Shell ◽  
Trapping Effect ◽  
Infrared Photodetection ◽  
Nanopillar Arrays

High-performance ZnO–MoS2 core–shell nanopillar (NP) array-based photodetectors are fabricated by taking advantage of the light trapping effect of ZnO NP array.

Quantum spin Hall effect and topological insulators

2017 ◽  
Author(s):  
S. Murakami ◽  
T. Yokoyama
Keyword(s):  
Topological Insulators ◽  
Surface States ◽  
Two Dimensions ◽  
Quantum Spin ◽  
Three Dimensions ◽  
Pure Spin ◽  
Topological Order ◽  
Edge States ◽  
Edge Surface ◽  
Quantum Spin Hall

This chapter begins with a description of quantum spin Hall systems, or topological insulators, which embody a new quantum state of matter theoretically proposed in 2005 and experimentally observed later on using various methods. Topological insulators can be realized in both two dimensions (2D) and in three dimensions (3D), and are nonmagnetic insulators in the bulk that possess gapless edge states (2D) or surface states (3D). These edge/surface states carry pure spin current and are sometimes called helical. The novel property for these edge/surface states is that they originate from bulk topological order, and are robust against nonmagnetic disorder. The following sections then explain how topological insulators are related to other spin-transport phenomena.

Core-mediated synthesis, growth mechanism and near-infrared luminescence enhancement of α-NaGdF4@β-NaLuF4:Nd3+ core–shell nanocrystals

CrystEngComm ◽  
2020 ◽  
Vol 22 (8) ◽  
pp. 1359-1367 ◽  
Author(s):  
Qinqin Shao ◽  
Chao Yang ◽  
Xiaoxu Chen ◽  
Hong Zhang ◽  
Guoying Feng ◽  
...  
Keyword(s):  
Growth Mechanism ◽  
Emission Intensity ◽  
High Performance ◽  
Near Infrared ◽  
Infrared Emission ◽  
Core Shell ◽  
Luminescence Enhancement ◽  
Infrared Luminescence ◽  
Near Infrared Emission

High-performance α-NaGdF4@β-NaLuF4:Nd3+ nanocrystals have been constructed based on a core-mediated method. Their near-infrared emission intensity was eventually enhanced by more than 2 times.

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