Optical Near-field Interactions Research Articles

History-dependent nano-photoisomerization by optical near-field in photochromic single crystals

The history dependence of physical systems is promising for solving complex problems. To exploit spontaneous nanometre-scale optical memory for computation, the history dependence must be elucidated. Here, we demonstrate history-dependent or dynamic nano-photoisomerization through the sequential formation of multiple memory pathways in photochromic crystals via optical near-field interactions. Incident photons passing through photoisomerization memory pathways are observed using a double-probe optical near-field microscope, with one probe located on the front surface for local excitation and the other on the rear surface for near-field observations. By performing localised near-field excitation twice but at spatially different positions, negatively correlated near-field output patterns are observed between the first and second memory pathways. We also confirm that the first memory pathway is preserved after the formation of the second memory pathway. This result indicates that photoisomerization using an optical near field in diarylethene crystals has a history dependence, leading to brain-like dynamic information memorisation.

Probing the optical near-field interaction of Mie nanoresonators with atomically thin semiconductors

Optical Mie resonators based on silicon nanostructures allow tuning of light-matter-interaction with advanced design concepts based on complementary metal–oxide–semiconductor (CMOS) compatible nanofabrication. Optically active materials such as transition-metal dichalcogenide (TMD) monolayers can be placed in the near-field region of such Mie resonators. Here, we experimentally demonstrate and verify by numerical simulations coupling between a MoSe2 monolayer and the near-field of dielectric nanoresonators. Through a comparison of dark-field (DF) scattering spectroscopy and photoluminescence excitation experiments (PLE), we show that the MoSe2 absorption can be enhanced via the near-field of a nanoresonator. We demonstrate spectral tuning of the absorption via the geometry of individual Mie resonators. We show that we indeed access the optical near-field of the nanoresonators, by measuring a spectral shift between the typical near-field resonances in PLE compared to the far-field resonances in DF scattering. Our results prove that using MoSe2 as an active probe allows accessing the optical near-field above photonic nanostructures, providing complementary information to sophisticated near-field microscopy equipment.

Nano-Photonic Metrics: Fundamentals and Experimental Demonstration

As the popularity of Internet of Things (IoT) increases, there is a considerable demand for the improvement of physical security, owing to the increase in edge devices. However, fabrication and measurement techniques used by attackers are also improving continuously, and hence, it is becoming increasingly difficult to ensure the security of each device using conventional approaches. To counter variable attacks in this context, the concept of nano-photonic metrics has been proposed, which is based on a functional collaboration between existing physical security and near-field optical techniques. In this approach, the optical signals obtained from optical near-field interactions, which are induced between the target with nano-scale structures and the tip of the scanning probe as the reader, are defined as the unique features of each device to be authenticated. When attackers attempt spoofing, they must fabricate not only clones of original nano-scale structures but also the scanning probe; otherwise, they cannot impersonate regular users. Moreover, the estimation of the nano-scale structures of the target and the characteristics of the probe is typically a complex, inverse problem. Therefore, a novel authentication is expected to be performed. In this paper, we report the results of the quantitative evaluations of the performance from the viewpoint of physical security and the experimental verification of the practicality of the proposed approach.

Renormalization group analysis of near-field induced dephasing of optical spin waves in an atomic medium

While typical theories of atom–light interactions treat the atomic medium as being smooth, it is well-known that microscopic optical effects driven by atomic granularity, dipole–dipole interactions, and multiple scattering can lead to important effects. Recently, for example, it was experimentally observed that these ingredients can lead to a fundamental, density-dependent dephasing of optical spin waves in a disordered atomic medium. Here, we go beyond the short-time and dilute limits considered previously, to develop a comprehensive theory of dephasing dynamics for arbitrary times and atomic densities. In particular, we develop a novel, non-perturbative theory based on strong disorder renormalization group (RG), in order to quantitatively predict the dominant role that near-field optical interactions between nearby neighbors has in driving the dephasing process. This theory also enables one to capture the key features of the many-atom dephasing dynamics in terms of an effective single-atom model. These results should shed light on the limits imposed by near-field interactions on quantum optical phenomena in dense atomic media, and illustrate the promise of strong disorder RG as a method of dealing with complex microscopic optical phenomena in such systems.

Experimental demonstration of random walk by probability chaos using single photons

In our former work, we demonstrated chaotic oscillation induced in a nanoscale system consisting of quantum dots between which energy transfer occurs via optical near-field interactions. It is intriguing that the chaotic behavior is associated with probability. Indeed, we previously examined such oscillating probabilities via diffusivity analysis by constructing random walkers driven by chaotically driven bias. Herein, we experimentally implemented the concept of probability chaos using a single-photon source that was chaotically modulated by an electro-optical modulator that directly yielded random walkers via single-photon observations. An evident signature was observed in the ensemble average of the time-averaged mean square displacement.

<p style="text-align: left;">History, current developments, and future directions of near-field optical science

This paper reviews the science of the optical near-field (ONF), which is created and localized in a nanometer-sized material (NM) or on its surface. It is pointed out that work on near-field optics was started in order to break through the diffraction limit in optical microscopy and had already come to an end without giving answers to the essential questions on the origin of the near-field optical interaction. However, recent studies have reincarnated these studies and identified the ONF as an off-shell quantum field. Based on this identification, a novel science called off-shell science has started on the basis that the dispersion relation between energy and momentum is invalid for the ONF. This quantum field is called the dressed photon because it is created as a result of the interaction between photons and electrons (or excitons) in a NM and, thus, it accompanies the energies of electrons or excitons. In reviewing current developments, this paper presents fifteen novel phenomena that are contrary to the common views in conventional optical science. Novel technologies developed by applying these phenomena are also reviewed. These include: nanometer-sized optical devices, nano-fabrication technology, and energy conversion technology. High-power Si light emitting diodes, Si lasers, and SiC polarization rotators are reviewed as examples of electrical to optical energy conversion. For future directions, this paper also reviews novel theoretical studies that have commenced recently by relying on physical and mathematical bases.

Period doubling and route to chaos in reduced graphene oxide, an experimental evidence

We use Nonlinear Schrödinger Equation (NLSE) to investigate chaotic dynamics inside a graphene-based optical system. Numerical results show that with increasing the control parameters, the character of Modulation instability (MI) is changed from convective to absolute. In consequence, a hyper-chaotic map is more expressive to explain the dynamical state of the system. It is also indicated that a reverse transition from the chaotic regime to the stable state can be resulted if the optical input intensity is further increased. The optical input intensity and feedback strength are distinguished as the two control parameters of the system. We then use Reduced Graphene Oxide (RGO) dispersion with large nonlinear refractive index to verify if a transition to instability and chaotic behavior is experimentally realized for the visible input light wave. The observation begins with saturation in the nonlinear response followed by an Optical Bistability (OB) phenomena. Afterward, a quasi-periodic fluctuations appear expressing the absolute MI. In agreement with our simulation result based on the period doubling bifurcation diagram, this quasi-periodic state is recognized as a route to the chaos. We infer that the graphene Quantum Dots (QDs) which are formed as a result of reduction process are responsible for energy transfer through the optical near-field interactions and thus, strengthen the required feedback.

Optical near-field mapping with a superconducting nanowire detector

Optical near-fields are interesting from a theoretical perspective and of importance for practical applications, such as high-resolution imaging, sensing, and antenna-coupled quantum light sources. In this work, we use a custom-designed superconducting nanowire single-photon detector to directly read out the near-field interaction between a source and a detector. We use a subwavelength-sized aperture at the end of an optical fiber to record spatial near-field maps and to measure the distance dependence of the optical near-field interaction. Our measurements can be well described by a superposition of evanescent source fields with no noticeable probe-sample coupling. Our approach is a first step towards the development of near-field imaging techniques with single quantum sensitivity.

Parallel mapping of optical near-field interactions by molecular motor-driven quantum dots.

In the vicinity of metallic nanostructures, absorption and emission rates of optical emitters can be modulated by several orders of magnitude1,2. Control of such near-field light-matter interaction is essential for applications in biosensing3, light harvesting4 and quantum communication5,6 and requires precise mapping of optical near-field interactions, for which single-emitter probes are promising candidates7-11. However, currently available techniques are limited in terms of throughput, resolution and/or non-invasiveness. Here, we present an approach for the parallel mapping of optical near-field interactions with a resolution of <5 nm using surface-bound motor proteins to transport microtubules carrying single emitters (quantum dots). The deterministic motion of the quantum dots allows for the interpolation of their tracked positions, resulting in an increased spatial resolution and a suppression of localization artefacts. We apply this method to map the near-field distribution of nanoslits engraved into gold layers and find an excellent agreement with finite-difference time-domain simulations. Our technique can be readily applied to a variety of surfaces for scalable, nanometre-resolved and artefact-free near-field mapping using conventional wide-field microscopes.

Tip-Nanoparticle Near-Field Coupling in Scanning Near-Field Microscopy by Coupled Dipole Method**Supported by the Start-Up Grant of Zhejiang University of Technology, the Zhejiang Provincial Key Laboratory of Information Processing, Communication and Networking, the Zhejiang University, and the National Natural Science Foundation of China under Grant No 61605171.

We use the couple dipole method to investigate the scanning near-field optical microscopy metallic tip-nanoparticle near-field interaction. Dependences of the local field intensity inside the nanoparticle on the nanosized tip shape, the tip open angle and the illumination angle are revealed. In combination with the previous results, we establish a complete model to understand the tip-nanoparticle near-field coupling mechanism.

Ultra-High-Efficiency Anomalous Refraction with Dielectric Metasurfaces

Anomalous refraction is a form of extreme waveform manipulation that can be realized with artificially structured nanomaterials, such as metamaterials or metasurfaces. While this phenomenon has been previously demonstrated for select input and output angles, its generalization to arbitrary angles with high efficiencies remains a challenge. In this study, we show that periodic dielectric metasurfaces can support ultra-high-efficiency anomalous refraction for nearly arbitrary combinations of incident and outgoing angles (>90% efficiency for angles up to 50°). Both polarization-dependent and polarization-independent device configurations can be realized, and the achieved metrics exceed the capabilities of conventional metasurfaces by a large margin. Many of the devices studied here utilize dielectric nanostructures that support strong near-field optical interactions with neighboring structures and complex optical mode dynamics. We envision that these concepts can be integrated with practical applications in ...

Destruction of Nano-Inhomogeneities of the Surface of Dielectrics Using the Optical Near-Field

The destruction of surface nano-inhomogeneities of a quartz substrate using the optical near-field dipole-dipole interaction of atomic chlorine with SiO2 is studied. A method to obtain atomic chlorine by the local photodissociation of molecular chlorine by the optical near-field of the quartz substrate nano-inhomogeneities is proposed. The polarization of chlorine atoms and SiO2 by means of an evanescent wave, which is generated on the substrate surface, is investigated. A method is proposed to obtain the most optimal orientation of the dipoles of atomic chlorine and SiO2, using the features of the optical near-field, to maximally efficiently destroy the quartz substrate nano-inhomogeneities. The application of the composite quasiparticle model describing the optical near-field interaction of dipoles is considered.

Nanoscale hierarchical optical interactions for secure information

AbstractThere is increasing demand for novel physical security that can differentiate between real and false specific artifact that have been added to bank bills, certifications, and other vouchers. The most simple and effective method for improving the security level is to scale down the elemental structures so that they cannot be duplicated by attackers. While there is a paradox that the achieved fabrication resolution by a defender can also be realized by an attacker, further improvement in security is possible by the functional fusion of artifact metrics and nanophotonics. The fundamental advantages of this concept are the high-level clone resistance and individuality of nanoscale artifacts, which are based on the super-resolution fabrication and nanoscale hierarchical structure of optical near-field interactions, respectively. In this paper, the basis for the fabrication of nanoscale artifacts by utilizing random phenomena is described, and a quantitative evaluation of the security level is presented. An experimental demonstration using a nano-/macro-hierarchical hologram is presented to demonstrate the fundamental procedure for retrieving nanoscale features as hidden information. Finally, the concept and a simple demonstration of non-scanning probe microscopy are described as a practical application of the retrieval and authentication of nanoscale artifact metrics.

Percolation of optical excitation mediated by near-field interactions

Optical excitation transfer in nanostructured matter has been intensively studied in various material systems for versatile applications. Herein, we theoretically and numerically discuss the percolation of optical excitations in randomly organized nanostructures caused by optical near-field interactions governed by Yukawa potential in a two-dimensional stochastic model. The model results demonstrate the appearance of two phases of percolation of optical excitation as a function of the localization degree of near-field interaction. Moreover, it indicates sublinear scaling with percolation distances when the light localization is strong. Furthermore, such a character is maximized at a particular size of environments. The results provide fundamental insights into optical excitation transfer and will facilitate the design and analysis of nanoscale signal-transfer characteristics.

Optical interactions with a charged metallic nanoshell

The effect of extraneous charge on the optical interactions with metallic nanoshells is studied theoretically based on an effective medium model, with the electrodynamic theory also formulated to justify the accuracy of this model. Both optical far-field and near-field interactions will be studied. Furthermore, the hybridization model is generalized to include the charge effects yielding results for the multipole resonances consistent with those from the effective medium model. It is found that while the extraneous charges will lead to blueshifted resonances, their effect on the bonding modes will be most significant, especially for localized near-field sources. In addition, it is pointed out that the applicability of our theory can go beyond the metallic nanoshell to include graphene-coated core–shell particles studied recently in the literature.

Non-scanning optical near-field microscopy for nanophotonic security

We propose a novel method for observing and utilizing nanometrically fluctuating signals due to optical near-field interactions between a probe and target in near-field optical microscopy. Based on a hierarchical structure of the interactions, it is possible to obtain signals that represent two-dimensional spatial patterns without requiring any scanning process. Such signals reveal individual features of each target, and these features, when appropriately extracted and defined, can be used in security applications—an approach that we call nanophotonic security. As an experimental demonstration, output signals due to interactions between a SiO2 probe and Al nanorods were observed by using near-field optical microscopy at a single readout point, and these signals were quantitatively evaluated using an algorithm that we developed for extracting and defining features that can be used for security applications.

Phase effects on the optical near-filed interaction of a nanohole dimer milled in a gold film

The near-field optical interaction of a nanohole dimer milled in a gold film and illuminated by an optical plane-wave is investigated. Depending on the polarization direction of the incident light, two resonant peaks are generated, in the normalized transmission spectrum due to the strong interaction between the nanoholes. In order to elucidate the nature of the interaction between the nanohole dimer elements at the resonant peaks, the symmetry breaking idea is applied. It is found that, in contrast to the complementary metallic nanoparticle dimers, the short and long wavelength peaks of the transmission spectrum can be assigned to in-phase and out-of-phase interaction of two adjacent magnetic dipoles, respectively. Furthermore, it is shown that breaking the symmetry in line with the polarization of the incident magnetic field results in severely antiphase interaction, while breaking the symmetry in line with the polarization of the incident electric field results in slightly out-of-phase interaction, at the long wavelength peak. The numerical simulation results are verified with Magnetic Coupled Dipole Approximation (MCDA) method.

WITHDRAWN: Improvement in performance of three-input nanophotonic AND gate based on optical near-field interactions

WITHDRAWN: Improvement in performance of three-input nanophotonic AND gate based on optical near-field interactions

Dynamic near-field optical interaction between oscillating nanomechanical structures.

Near-field optical techniques exploit light-matter interactions at small length scales for mechanical sensing and actuation of nanomechanical structures. Here, we study the optical interaction between two mechanical oscillators—a plasmonic nanofocusing probe-tip supported by a low frequency cantilever, and a high frequency nanomechanical resonator—and leverage their interaction for local detection of mechanical vibrations. The plasmonic nanofocusing probe provides a confined optical source to enhance the interaction between the two oscillators. Dynamic perturbation of the optical cavity between the probe-tip and the resonator leads to nonlinear modulation of the scattered light intensity at the sum and difference of their frequencies. This double-frequency demodulation scheme is explored to suppress unwanted background and to detect mechanical vibrations with a minimum detectable displacement sensitivity of 0.45 pm/Hz1/2, which is limited by shot noise and electrical noise. We explore the demodulation scheme for imaging the bending vibration mode shape of the resonator with a lateral spatial resolution of 20 nm. We also demonstrate the time-resolved aspect of the local optical interaction by recording the ring-down vibrations of the resonator at frequencies of up to 129 MHz. The near-field optical technique is promising for studying dynamic mechanical processes in individual nanostructures.

Decision making based on optical excitation transfer via near-field interactions between quantum dots

Optical near-field interactions between nanostructured matters, such as quantum dots, result in unidirectional optical excitation transfer when energy dissipation is induced. This results in versatile spatiotemporal dynamics of the optical excitation, which can be controlled by engineering the dissipation processes and exploited to realize intelligent capabilities such as solution searching and decision making. Here, we experimentally demonstrate the ability to solve a decision making problem on the basis of optical excitation transfer via near-field interactions by using colloidal quantum dots of different sizes, formed on a geometry-controlled substrate. We characterize the energy transfer behavior due to multiple control light patterns and experimentally demonstrate the ability to solve the multi-armed bandit problem. Our work makes a decisive step towards the practical design of nanophotonic systems capable of efficient decision making, one of the most important intellectual attributes of the human brain.