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Reuven Gordon

Publications and source records attributed to Reuven Gordon.

15 recordsLinked to original sources
arXiv2022

Coupling Perovskite Quantum Dot Pairs in Solution using Nanoplasmonic Assembly

Perovskite quantum dots (PQDs) provide a robust solution-based approach to efficient solar cells, bright light-emitting devices, and quantum sources of light. Quantifying heterogeneity and understanding coupling between dots is critical for these applications. We use double-nanohole optical trapping to size individual dots and correlate to emission energy shifts from quantum confinement. We were able to assemble a second dot in the trap, which allows us to observe the coupling between dots. We observe a systematic red-shift of 1.1 $\pm$ 0.6 meV in the emission wavelength. Theoretical analysis shows that the observed shift is consistent with resonant energy transfer and is unusually large due to moderate-to-large quantum confinement in PQDs. This demonstrates the promise of PQDs for entanglement in quantum information applications. This work enables future in situ control of PQD growth as well as studies of the coupling between small PQD assemblies with quantum information applications in mind.

cond-mat.mes-hall↗
arXiv2022

Roadmap for Optical Tweezers

Optical tweezers are tools made of light that enable contactless pushing, trapping, and manipulation of objects ranging from atoms to space light sails. Since the pioneering work by Arthur Ashkin in the 1970s, optical tweezers have evolved into sophisticated instruments and have been employed in a broad range of applications in life sciences, physics, and engineering. These include accurate force and torque measurement at the femtonewton level, microrheology of complex fluids, single micro- and nanoparticle spectroscopy, single-cell analysis, and statistical-physics experiments. This roadmap provides insights into current investigations involving optical forces and optical tweezers from their theoretical foundations to designs and setups. It also offers perspectives for applications to a wide range of research fields, from biophysics to space exploration.

physics.optics↗
arXiv2021

Watching Single Unmodified Enzymes at Work

Many proteins undergo conformational changes during their activity. A full understanding of the function of these proteins can only be obtained if different conformations and transitions between them can be monitored in aqueous solution, with adequate temporal resolution and, ideally, on a single-molecule level. Interrogating conformational dynamics of single proteins remains, however, exquisitely challenging and typically requires site-directed chemical modification combined with rigorous minimization of possible artifacts. These obstacles limit the number of single-protein investigations. The work presented here introduces an approach that traps single unmodified proteins from solution in a plasmonic hotspot and makes it possible to assign changes in refractive index to changes in protein conformation while monitoring these changes for minutes to hours with a temporal resolution at least as fast as 40 microseconds. The resulting single molecule data reveals that adenylate kinase employs a hidden enzymatic sub-cycle during catalysis, that citrate synthase populates a previously unknown intermediate conformation, which is more important for its enzymatic activity than its well-known open conformation, that hemoglobin transitions in several steps from its deoxygenated and rigid T state to its oxygenated and flexible R state, and that apo-calmodulin thermally unfolds and refolds in steps that correspond to conformational changes of individual protein domains.

physics.bio-ph↗
arXiv2020

Matters Arising: Modeling and observation of mid-infrared nonlocality in effective epsilon-near-zero ultranarrow coaxial apertures

In "Modeling and observation of mid-infrared nonlocality in effective epsilon-near-zero ultranarrow coaxial apertures" the authors perform infrared transmission measurements on coaxial aperture arrays in metal films. They claim that the blue-shift of the resonances is the result of nonlocality. They claim that roughness will not produce a shift. This is contrary to past results in plasmonics, to our simulations and to past published claims from some of the same authors. Furthermore, the effect of planarization that occurs for atomic layer deposition, as has been reported elsewhere, will produce a blue-shift. Finally, discrepancies between different nonlocal models, time-dependent density functional theory and other experimental observations all call into question the accuracy of the particular nonlocal model chosen for this regime.

physics.optics↗
arXiv2019

Molecular optomechanics in the anharmonic cavity-QED regime using hybrid metal-dielectric cavity modes

Using carefully designed hybrid metal-dielectric resonators, we study molecular optomechanics in the strong coupling regime ($g_{\rm }^2/ω_m {>} κ$), which manifests in anharmonic emission lines in the sideband-resolved region of the cavity-emitted spectrum ($κ{<}ω_m$). This nonlinear optomechanical strong coupling regime is enabled through a metal-dielectric cavity system that yields not only deep sub-wavelength plasmonic confinement, but also dielectric-like confinement times that are more than two orders of magnitude larger than those from typical localized plasmon modes. These hybrid metal-dielectric cavity modes enable one to study new avenues of quantum plasmonics for single molecule Raman scattering.

cond-mat.mes-hall↗
arXiv2019

Generating and Detecting High Frequency Liquid-Based Sound Resonances with Nanoplasmonics

We use metal nanostructures (nanoplasmonics) excited with dual frequency lasers to generate and detect high frequency (> 10 GHz) sound wave resonances in water. The difference frequency between the two lasers causes beating in the intensity, which results in a drop in the transmission through the nanostructure when an acoustic resonance is excited. By observing the resonance frequency shifts with changing nanostructure size, the transition from slow to fast sound in water is inferred, which has been measured by inelastic scattering methods in the past. The observed behavior shows remarkable similarities to a simple Debye model (without fitting parameters). The ability to directly excite high-frequency sound waves in water may unlock the secret of how the nanofluidic environment, that is typically considered to be extremely viscous, can efficiently support the energetic dynamics of life via protein vibrations at the nanometer scale.

physics.app-ph↗
arXiv2016

Theory for the Acoustic Raman Modes of Proteins

We present a theoretical analysis that associates the resonances of extraordinary acoustic Raman (EAR) spectroscopy [Wheaton et al., Nat Photon 9, 68 (2015)] with the collective modes of proteins. The theory uses the anisotropic elastic network model to find the protein acoustic modes, and calculates Raman intensity by treating the protein as a polarizable ellipsoid. Reasonable agreement is found between EAR spectra and our theory. Protein acoustic modes have been extensively studied theoretically to assess the role they play in protein function; this result suggests EAR as a new experimental tool for studies of protein acoustic modes.

physics.bio-ph↗
arXiv2016

Modal theory of modified spontaneous emission for a hybrid plasmonic photonic-crystal cavity system

We present an analytical modal description of the rich physics involved in hybrid plasmonic-photonic devices that is confirmed by full dipole solutions of Maxwell's equations. Strong frequency-dependence for the spontaneous emission decay rate of a quantum dipole emitter coupled to these hybrid structures is predicted. In particular, it is shown that the Fano-type resonances reported experimentally in hybrid plasmonic systems, arise from a very large interference between dominant quasinormal modes of the systems in the frequency range of interest. The presented model forms an efficient basis for modelling quantum light-matter interactions in these complex hybrid systems and also enables the quantitativ prediction and understanding of non-radiative coupling losses.

cond-mat.mes-hall↗
arXiv2015

Raman Spectroscopy of Single Nanoparticles in a Double-Nanohole Optical Tweezer System

A double nanohole in a metal film was used to trap nanoparticles (20 nm diameter) and simultaneously record their Raman spectrum using the trapping laser as the excitation source. This allowed for the identification of characteristic Stokes lines for titania and polystyrene nanoparticles, showing the capability for material identification of nanoparticles once trapped. Increased Raman signal is observed for the trapping of multiple nanoparticles. This system combines the benefits of nanoparticle isolation and manipulation with unique identification.

physics.optics↗
arXiv2014

Nanoplasmonic Tweezers Visualize Protein p53 Suppressing Unzipping of Single DNA-Hairpins

Here we report on the use of double-nanohole (DNH) optical tweezers as a label-free and free-solution single-molecule probe for protein-DNA interactions. Using this approach, we demonstrate the unzipping of individual 10 base pair DNA-hairpins, and quantify how tumor suppressor p53 protein delays the unzipping. From the Arrhenius behavior, we find the energy barrier to unzipping introduced by p53 to be $2\times 10^{-20}$ J, whereas cys135ser mutant p53 does not show suppression of unzipping, which gives clues to its functional inability to suppress tumor growth. This transformative approach to single molecule analysis allows for ultra-sensitive detection and quantification of protein-DNA interactions to revolutionize the fight against genetic diseases.

physics.bio-ph↗
arXiv2014

Dynamic Variation in Protein-Small Molecule Interaction Observed by Double-Nanohole Optical Trapping

The interaction of proteins with small molecules is fundamental to their function in living organisms and it is widely studied in drug development. Here we compare optical trapping dynamics of streptavidin and biotinylated streptavidin using a double nanohole optical trap in a metal film. Consistent and clearly distinct behavior is seen between the protein with and without the small molecule binding. The real-time dynamics at the single protein level are accessible with this technique, which also has advantages of not requiring tethering to a surface or the need for exogeneous markers.

physics.bio-ph↗
arXiv2011

Limits for superfocusing with finite evanescent wave amplification

Perfect lensing using negative refractive index materials and radiationless electromagnetic interference both provide extreme subwavelength focusing by "amplifying" evanescent wave components that are usually lost. This paper provides a relation between the achievable focus spot size, the amplification available and the focal length. This may be considered as a revised version of Abbe's diffraction limit for focusing systems that have evanescent wave amplification. It is useful in comparing the amplification achieved in various subwavelength focusing implementations, as well as determining when it is better to use existing near-field techniques, such as simple diffraction from an aperture or slit, than to attempt complicated superfocusing.

physics.optics↗
arXiv2008

Proposal for Optical Super-Focusing with a Metal-Dielectric Waveguide Array

In this paper, super-focusing using radiationless electromagnetic interference is extended to the visible regime. It is shown that the highest-order mode of a specifically designed metal-dielectric waveguide array can provide the rapidly oscillating source field for radiationless interference. Using finite-difference time-domain simulations, an example structure is demonstrated. This structure provides focusing to 0.21 of the optical wavelength at a distance of half the optical wavelength from the source.

physics.optics↗
arXiv2007

Plasmonic Bragg Reflectors for Subwavelength Hole Arrays in a Metal Film

We present plasmonic Bragg reflectors for increasing the extraordinary optical transmission through periodic arrays of subwavelength apertures in a metal film. The increase in transmission arises by preventing loss at the edges of the array. The plasmonic Bragg reflectors have periodicity of half the usual array's periodicity. Nano-hole arrays flanked thus by reflectors exchibited double the transmission as compared to the arrays without reflectors. These structures may also be used to isolate devices in plasmonic integrated circuits.

physics.optics↗