scholarly journals Spatio-spectral decomposition of complex eigenmodes in subwavelength nanostructures through transmission matrix analysis

Nanophotonics ◽  
2022 ◽  
Vol 0 (0) ◽  
Author(s):  
Young-Ho Jin ◽  
Juntaek Oh ◽  
Wonshik Choi ◽  
Myung-Ki Kim
Keyword(s):  
Near Field ◽  
Effective Means ◽  
Matrix Analysis ◽  
Mode Analysis ◽  
Excitation Wavelength ◽  
Plasmonic Nanostructures ◽  
Transmission Matrix ◽  
Electromagnetic Simulations ◽  
Value Decomposition ◽  
20 Nm

Abstract Exploiting multiple near-field optical eigenmodes is an effective means of designing, engineering, and extending the functionalities of optical devices. However, the near-field optical eigenmodes of subwavelength plasmonic nanostructures are often highly multiplexed in both spectral and spatial distributions, making it extremely difficult to extract individual eigenmodes. We propose a novel mode analysis method that can resolve individual eigenmodes of subwavelength nanostructures, which are superimposed in conventional methods. A transmission matrix is constructed for each excitation wavelength by obtaining the near-field distributions for various incident angles, and through singular value decomposition, near-field profiles and energy spectra of individual eigenmodes are effectively resolved. By applying transmission matrix analysis to conventional electromagnetic simulations, we clearly resolved a set of orthogonal eigenmodes of single- and double-slot nanoantennas with a slot width of 20 nm. In addition, transmission matrix analysis leads to solutions that can selectively excite specific eigenmodes of nanostructures, allowing selective use of individual eigenmodes.

scholarly journals Direct visualization of phase-matched efficient second harmonic and broadband sum frequency generation in hybrid plasmonic nanostructures

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Zhe Li ◽  
Brian Corbett ◽  
Agnieszka Gocalinska ◽  
Emanuele Pelucchi ◽  
Wen Chen ◽  
...  
Keyword(s):  
Conversion Efficiency ◽  
Second Harmonic ◽  
Effective Means ◽  
Sum Frequency Generation ◽  
Mode Analysis ◽  
Plasmonic Nanostructures ◽  
Integrated Photonics ◽  
Direct Visualization ◽  
Sum Frequency ◽  
Frequency Generation

Abstract Second harmonic generation and sum frequency generation (SHG and SFG) provide effective means to realize coherent light at desired frequencies when lasing is not easily achievable. They have found applications from sensing to quantum optics and are of particular interest for integrated photonics at communication wavelengths. Decreasing the footprints of nonlinear components while maintaining their high up-conversion efficiency remains a challenge in the miniaturization of integrated photonics. Here we explore lithographically defined AlGaInP nano(micro)structures/Al2O3/Ag as a versatile platform to achieve efficient SHG/SFG in both waveguide and resonant cavity configurations in both narrow- and broadband infrared (IR) wavelength regimes (1300–1600 nm). The effective excitation of highly confined hybrid plasmonic modes at fundamental wavelengths allows efficient SHG/SFG to be achieved in a waveguide of a cross-section of 113 nm × 250 nm, with a mode area on the deep subwavelength scale (λ2/135) at fundamental wavelengths. Remarkably, we demonstrate direct visualization of SHG/SFG phase-matching evolution in the waveguides. This together with mode analysis highlights the origin of the improved SHG/SFG efficiency. We also demonstrate strongly enhanced SFG with a broadband IR source by exploiting multiple coherent SFG processes on 1 µm diameter AlGaInP disks/Al2O3/Ag with a conversion efficiency of 14.8% MW−1 which is five times the SHG value using the narrowband IR source. In both configurations, the hybrid plasmonic structures exhibit >1000 enhancement in the nonlinear conversion efficiency compared to their photonic counterparts. Our results manifest the potential of developing such nanoscale hybrid plasmonic devices for state-of-the-art on-chip nonlinear optics applications.

First Nano-Infrared Spectroscopy and Imaging Measurements of Single Phospholipid Bilayers

2018 ◽  
Author(s):  
Adrian Cernescu ◽  
Michał Szuwarzyński ◽  
Urszula Kwolek ◽  
Karol Wolski ◽  
Paweł Wydro ◽  
...  
Keyword(s):  
Infrared Spectroscopy ◽  
Ir Spectroscopy ◽  
Absorption Band ◽  
Spectral Region ◽  
Near Field ◽  
Phospholipid Bilayers ◽  
Model Systems ◽  
Absorption Bands ◽  
Protein Complement ◽  
20 Nm

<div><div>Scattering-mode Scanning Near-Field Optical Microscopy (sSNOM) allows one to obtain absorption spectra in the mid-IR region for samples as small as 20 nm in size. This configuration has made it possible to measure FTIR spectra of the protein complement of membranes. (Amenabar 2013) We now show that mid-IR sSNOM has the sensitivity required to measure spectra of phospholipids in individual bilayers in the spectral range 800 cm<sup>-1</sup>–1400 cm<sup>-1</sup>. We have observed the main absorption bands of the dipalmitoylphosphatidylcholine headgroups in this spectral region above noise level. We have also mapped the phosphate absorption band at 1070 cm<sup>-1</sup> simultaneously with the AFM topography. We have shown that we could achieve sufficient contrast to discriminate between single and multiple phospholipid bilayers and other structures, such as liposomes. This work opens the way to further research that uses nano-IR spectroscopy to describe the biochemistry of cell membranes and model systems.</div></div><div></div>

scholarly journals Optical near-field mapping of plasmonic nanostructures prepared by nanosphere lithography

2018 ◽  
Vol 9 ◽  
pp. 1536-1543 ◽  
Author(s):  
Gitanjali Kolhatkar ◽  
Alexandre Merlen ◽  
Jiawei Zhang ◽  
Chahinez Dab ◽  
Gregory Q Wallace ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Hot Spots ◽  
Near Field ◽  
Nanosphere Lithography ◽  
Plasmonic Nanostructures ◽  
Far Field ◽  
Optical Images ◽  
Spatial Frequencies ◽  
Comparison Of The Results ◽  
Non Destructive

We introduce a simple, fast, efficient and non-destructive method to study the optical near-field properties of plasmonic nanotriangles prepared by nanosphere lithography. Using a rectangular Fourier filter on the blurred signal together with filtering of the lower spatial frequencies to remove the far-field contribution, the pure near-field contributions of the optical images were extracted. We performed measurements using two excitation wavelengths (532.1 nm and 632.8 nm) and two different polarizations. After the processing of the optical images, the distribution of hot spots can be correlated with the topography of the structures, as indicated by the presence of brighter spots at the apexes of the nanostructures. This technique is validated by comparison of the results to numerical simulations, where agreement is obtained, thereby confirming the near-field nature of the images. Our approach does not require any advanced equipment and we suggest that it could be applied to any type of sample, while keeping the measurement times reasonably short.

Control of Heat and Mass Transfers Due to Tearing Mode-Based Magnetic Islands During Disruption Phase in IR-T1 Tokamak

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
R. Sadeghi ◽  
A. Salar Elahi ◽  
M. Ghoranneviss ◽  
M. K. Salem
Keyword(s):  
Energy Content ◽  
Singular Value ◽  
Mode Analysis ◽  
Magnetic Fluctuations ◽  
Magnetic Islands ◽  
Tearing Mode ◽  
Tearing Modes ◽  
Complete Disruption ◽  
Value Decomposition ◽  
Mass Transfers

A structural change of perturbed magnetic configurations (such as magnetic islands) during disruption phase in IR-T1 tokamak was studied. The singular value decomposition (SVD) mode analysis and the (m,n) modes identification were presented. We also presented the SVD technique to analyze the tokamak magnetic fluctuations, time evolution of magnetohydrodynamics (MHD) modes, spatial structure of each time vector, and the energy content of each modes. We also considered different scenarios for plasma from steady-state to predisruption, complete disruption, creation of tearing modes, and finally magnetic islands.

scholarly journals Metal–dielectric hybrid nanoantennas for efficient frequency conversion at the anapole mode

2018 ◽  
Vol 9 ◽  
pp. 2306-2314 ◽  
Author(s):  
Valerio F Gili ◽  
Lavinia Ghirardini ◽  
Davide Rocco ◽  
Giuseppe Marino ◽  
Ivan Favero ◽  
...  
Keyword(s):  
Frequency Conversion ◽  
Near Infrared ◽  
Strong Field ◽  
Second Harmonic ◽  
Near Field ◽  
Field Enhancement ◽  
High Refractive Index ◽  
Plasmonic Nanostructures ◽  
Ohmic Losses ◽  
Order Of Magnitude

Background: Dielectric nanoantennas have recently emerged as an alternative solution to plasmonics for nonlinear light manipulation at the nanoscale, thanks to the magnetic and electric resonances, the strong nonlinearities, and the low ohmic losses characterizing high refractive-index materials in the visible/near-infrared (NIR) region of the spectrum. In this frame, AlGaAs nanoantennas demonstrated to be extremely efficient sources of second harmonic radiation. In particular, the nonlinear polarization of an optical system pumped at the anapole mode can be potentially boosted, due to both the strong dip in the scattering spectrum and the near-field enhancement, which are characteristic of this mode. Plasmonic nanostructures, on the other hand, remain the most promising solution to achieve strong local field confinement, especially in the NIR, where metals such as gold display relatively low losses. Results: We present a nonlinear hybrid antenna based on an AlGaAs nanopillar surrounded by a gold ring, which merges in a single platform the strong field confinement typically produced by plasmonic antennas with the high nonlinearity and low loss characteristics of dielectric nanoantennas. This platform allows enhancing the coupling of light to the nanopillar at coincidence with the anapole mode, hence boosting both second- and third-harmonic generation conversion efficiencies. More than one order of magnitude enhancement factors are measured for both processes with respect to the isolated structure. Conclusion: The present results reveal the possibility to achieve tuneable metamixers and higher resolution in nonlinear sensing and spectroscopy, by means of improved both pump coupling and emission efficiency due to the excitation of the anapole mode enhanced by the plasmonic nanoantenna.

scholarly journals Near-field transmission matrix microscopy for mapping high-order eigenmodes of subwavelength nanostructures

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Eunsung Seo ◽  
Young-Ho Jin ◽  
Wonjun Choi ◽  
Yonghyeon Jo ◽  
Suyeon Lee ◽  
...  
Keyword(s):  
Near Field ◽  
High Order ◽  
Transmission Matrix

scholarly journals Mapping bound plasmon propagation on a nanoscale stripe waveguide using quantum dots: influence of spacer layer thickness

2015 ◽  
Vol 6 ◽  
pp. 2046-2051 ◽  
Author(s):  
Chamanei S Perera ◽  
Alison M Funston ◽  
Han-Hao Cheng ◽  
Kristy C Vernon
Keyword(s):  
Quantum Dots ◽  
Laser Beam ◽  
Layer Thickness ◽  
Near Field ◽  
Surface Distance ◽  
Spacer Layer Thickness ◽  
Spacer Layer ◽  
20 Nm ◽  
Mode A ◽  
Plasmon Propagation

In this paper we image the highly confined long range plasmons of a nanoscale metal stripe waveguide using quantum emitters. Plasmons were excited using a highly focused 633 nm laser beam and a specially designed grating structure to provide stronger incoupling to the desired mode. A homogeneous thin layer of quantum dots was used to image the near field intensity of the propagating plasmons on the waveguide. We observed that the photoluminescence is quenched when the QD to metal surface distance is less than 10 nm. The optimised spacer layer thickness for the stripe waveguides was found to be around 20 nm. Authors believe that the findings of this paper prove beneficial for the development of plasmonic devices utilising stripe waveguides.

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