Field Of Light Wave Research Articles

A Hybrid Lens to Realize Electrical Real‐Time Super‐Resolution Imaging

AbstractReal‐time dynamic super‐resolution focusing technology is crucial for various imaging applications. However, the diffraction limit significantly impedes the achievement of real‐time dynamic super‐resolution imaging. Prior studies within this domain, such as super‐resolution fluorescence imaging and structured illumination microscopy, heavily rely on fluorescent labels and intricate algorithms. This article proposes a novel approach to achieving real‐time dynamic super‐resolution imaging at microwave frequency by integrating the Mikaelian lens derived from conformal transformation optics with the space‐time‐coding metasurface antenna. Real‐time dynamic super‐resolution focusing with a resolution ranging from 0.3λ to 0.4λ is demonstrated at the periphery of the Mikaelian lens with a numerical aperture (NA) of 0.54. The proposed hybrid lens exhibits the capacity to discern features separated by about one‐third of a wavelength with high precision. The work offers a universal solution for achieving dynamic real‐time super‐resolution imaging electrically, which can be extended to terahertz waves, visible light, and other wave fields, such as acoustic and flexural waves.

Multi-zone resonance spectrometry of inelastic electron scattering of light and the manifestation of strong spin-orbit interaction in nanostructures with quantum dots

Highly sensitive methods of inelastic light scattering spectrometry have been developed to detect individual photons in the visible and near-infrared spectral ranges (0.4-1.35) μm. Precision optical measurements of vibrational and electronic states of nanostructures with quantum objects are performed, using the example of quantum-dimensional nanoheterostructures (311)In si-GaAs/InAs with InAs quantum dots. A distinctive attractive feature of such structures with a degenerate valence band of symmetry 8 is the presence of a strong spin-orbit interaction. In this case, the intrinsic moment of the holes can effectively interact with the electric field of the incident light wave. It was found that such interaction causes intense luminescence and inelastic scattering of the light wave in the IR region of the 0.9-1.35 μm spectrum. Effective generation of nonequilibrium electron-hole (e-h) plasma with concentrations n=p=1.0·1017 cm-3 and T_e=T_h=25 K,was revealed under resonant excitation conditions, while the lattice temperature T_L=5.1 K. New mechanisms have been discovered for the formation of an abnormally intense integration spectrum of multiplex inelastic light scattering of a rather complex shape formed by various separable resonant contributions of the processes of quasi-elastic scattering by charge carriers, light scattering by acoustic plasmons of electron-hole plasma, as well as inelastic intra- and inter-band light scattering by heavy holes. It has been established that the anomalous intensity gain of such multi-zone selective resonant light scattering is more than 105 times higher than the intensity of Thomson light scattering on individual charge carriers. There is agreement between the estimated calculated and experimental spectra, and for the most part for the difficult-to-interpret significant width of the observed light scattering line. It is shown that new mechanisms of various contributions to the formation of scattered photon radiation are important diagnostic elements that are clearly manifested in the spectra of the resulting enhanced inelastic light scattering. Keywords: nanostructures, quantum objects, resonant scattering of light by charge carriers, exchange interaction, plasma diagnostics.

A Study of Resolution Improvement in Noncoherent Optical Coherence Imaging

Noncoherent light, as a common light source in life, can effectively avoid problems such as scattering noise caused by optical components incoherent light imaging, and through the design of the optical path can also trigger interference and holographic imaging of objects, allowing holography to be used in more fields. Various techniques have emerged for recording holograms using incoherent light sources as technology has developed. A recording method has been proposed that exploits the correlation between the object wave information and the Fresnel band sheet to achieve incoherent hologram recording. Using a spatial light modulator (SLM) loaded with a bit-phase mask with multiplexed lens function, the incident light wavefield is phase-modulated to achieve diffraction spectroscopy and phase shifting. And holograms with different phase shifts can be obtained and combined with phase-shifting techniques to eliminate the effects of twin images caused by coaxial holography in the reproduction process. Based on the study of this incoherent holographic imaging system, the influence of the characteristics of the main components of the system and the corresponding parameters on the resolution of the recorded and reproduced holograms is investigated, and optimization methods are given from both theoretical and experimental studies. The empirical analysis of the FINCH imaging system is carried out. The observed optical path is designed, and the method of making a bit-phase mask loaded on a spatial light modulator is presented. The effect of the focal length and recording distance of the dislocation mask on the resolution of the system is investigated by both computer simulation and experimental operation.

Parabola-Like Gold Nanobowtie on Sapphire Substrate as Nano-Cavity

Plasmonic metallic nanostructures have attracted much interest for their ability to manipulate light on a subwavelength scale and for their related applications in various fields. In this work, a parabola-like gold nanobowtie (PGNB) on a sapphire substrate was designed as a nano-cavity for confining light waves in a nanoscale gap region. The near-field optical properties of the innovative PGNB structure were studied comprehensively, taking advantage of the time-resolved field calculation based on a finite-difference time-domain algorithm (FDTD). The calculation result showed that the resonance wavelength of the nano-cavity was quite sensitive to the geometry of the PGNB. The values that related to the scattering and absorption properties of the PGNB, such as the scattering cross section, absorption cross section, extinction cross section, scattering ratio, and also the absorption ratio, were strongly dependent on the geometrical parameters which affected the surface area of the nanobowtie. Increased sharpness of the gold tips on the parabola-like nano-wings benefited the concentration of high-density charges with opposite electric properties in the narrow gold tips with limited volume, thus, resulting in a highly enhanced electric field in the nano-cavity under illumination of the light wave. Reduction of the gap size between the two gold nano-tips, namely, the size of the nano-cavity, decreased the distance that the electric potential produced by the highly concentrated charges on the surface of each gold nano-tip had to jump across, therefore, causing a significantly enhanced field in the nano-cavity. Further, alignment of the linearly polarized electric field of the incident light wave with the symmetric axis of the PGNB efficiently enabled the free electrons in the PGNB to concentrate on the surface of the sharp gold tips with a high density, thus, strongly improving the field across the nano-cavity. The research provides a new insight for future design, nanofabrication, and characterization of PGNBs for applications in devices that relate to enhancing photons emission, improving efficiency for energy harvesting, and improving sensitivity for infrared detection.

Comparative study of the electronic structure and optical properties of the Heusler alloys Co2MGa and Co2MAl (M = Fe and Ni)

The electronic structure and optical properties of the Heusler alloys Co2NiGa, Co2NiAl, Co2FeGa, and Co2FeAl are reported and compared in this work. In the Fe-based alloys, Co2FeGa and Co2FeAl, the electronic structure is found to have 100% spin polarization with the indirect energy gap in the [Formula: see text]-[Formula: see text] direction, whereas in Co2NiGa and Co2NiAl, the density of states is metallic in both spin projections with spin polarization of 55% (Co2NiGa) and 37% (Co2NiAl). Total and Co partial magnetic moments of all Heusler alloys for the optimized lattice parameters were found in a good agreement with previous calculations and experimental data. The frequency dependence of the real and imaginary parts of the complex dielectric constant for the Heusler alloys is studied in the spectrum region of 0.08–5 eV. The research results are discussed based on the performed calculations of the electronic structure. It was found that the character of variations of the spectral parameters of the alloys is typical for media with the metallic conductivity. In the IR region, the mechanism of the intraband acceleration of electrons by the light wave field dominates. The significant changes in the optical spectrum, magnetic moment, spin polarization and electronic structure were revealed in Co2MGa and Co2MAl for different M atoms which motivate further investigations of the Co-based Heusler alloys as promising materials for spintronics.

Multiphoton intersubband transitions in an armchair graphene nanoribbon

We present an analytical approach to the problem of the interband transitions in an armchair graphene nanoribbon (AGNR), exposed to the time-periodic electric field of strong light wave, polarized parallel to the ribbon axis. The two-dimensional Dirac equation for the massless electron subject to the ribbon confinement is employed. In the resonant approximation the probability of the transitions between the valence and conduction size-quantized subbands are calculated in an explicit form. We trace the dependencies of the Rabi frequency for these transitions on the ribbon width and electric field strength for both the multiphoton-assisted and tunneling regimes relevant to the fast oscillating and practically constant electric field, respectively. Estimates of the expected experimental values for the typically employed AGNR and laser technique facilities show that the Rabi oscillations can be observed under laboratory conditions. The data, corresponding to the intersubband tunneling, makes the AGNR a 1D condensed matter analog, in which the quantum electrodynamic vacuum decay can be detected by the employment of the attainable electric fields.

Influence of far-red light coherence on the functional state of plants.

The influence of the coherence of far-red (730 nm) light on the functional activity of plants was studied. Blackberry explants cultivated in vitro on an artificial nutrient medium served as a biological model. The explants were irradiated with light beams with different spatial and temporal coherence. The average cell size D was taken as the discrimination threshold for the coherence length L_{coh} and the correlation radius r_{cor}. The results of irradiation were judged by the length and number of shoots formed on each explant. The greatest photoinduced effect was observed when the conditions L_{coh}, r_{cor}>D were fulfilled, i.e., when the cell fit completely in the coherence volume of the light wave field. Significant differences in growth parameters were also observed in the variants of the experiment with a constant frequency spectrum of radiation (fixed L_{coh}), but different r_{cor}. It is concluded that the correlation properties of radiation affect photoregulatory processes.

Deep Coded Aperture Design: An End-to-End Approach for Computational Imaging Tasks

Covering from photography to depth and spectral estimation, diverse computational imaging (CI) applications benefit from the versatile modulation of coded apertures (CAs). The lightwave fields as space, time, or spectral can be modulated to obtain projected encoded information at the sensor that is then decoded by efficient methods, such as the modern deep learning decoders. Although the CA can be fabricated to produce an analog modulation, a binary CA is preferred since more straightforward calibration, higher speed, and lower storage are achieved. As the performance of the decoder mainly depends on the structure of the CA, several works optimize the CA ensembles by customizing regularizers for a particular application without considering the critical physical constraints of the CAs. This work presents an end-to-end (E2E) deep learning-based optimization of CAs for CI tasks. The CA design method aims to cover a wide range of CI problems, easily changing the loss function of the deep approach. The designed loss function includes regularizers to fulfill the widely used sensing requirements of the CI applications. Mainly, the regularizers can be selected to optimize the transmittance, the compression ratio, and the correlation among measurements. At the same time, a binary CA solution is encouraged, and the performance of the CI task is maximized in applications such as restoration, classification, and semantic segmentation.

Acceleration and expansion of a photorealistic computer-generated hologram using backward ray tracing and multiple off-axis wavefront recording plane methods

Holograms can reconstruct the light wave field of three-dimensional objects. However, the computer-generated hologram (CGH) requires much calculating time. Here we proposed a CGH generation algorithm based on backward ray tracing and multiple off-axis wavefront recording planes (MO-WRP) to generate photorealistic CGH with a large reconstruction image. In this method, multiple WRPs were placed parallelly between the virtual object and the hologram plane. Virtual rays were emitted from the pixel of WRPs and intersect with the object. The complex amplitude of WRPs is then determined by illumination module, such as Phong reflection module. The CGH was generated by the shifted Angular Spectrum Propagation (ASP) from WRPs to the hologram plane. Experimental results demonstrate the effectiveness of this method, and the CGH generation rate is 37.3 frames per second (1 WRP) and 9.8 frames per second (2×2 WRPs).

Lightwave terahertz quantum manipulation of nonequilibrium superconductor phases and their collective modes

We present a gauge-invariant density matrix description of non-equilibrium superconductor (SC) states with spatial and temporal correlations driven by intense terahertz (THz) lightwaves. We derive superconductor Bloch--Maxwell equations of motion that extend Anderson pseudo-spin models to include the Cooper pair center-of-mass motion and electromagnetic propagation effects. We thus describe quantum control of dynamical phases, collective modes, quasi-particle coherence, and high nonlinearities during cycles of carrier wave oscillations, which relate to our recent experiments. Coherent photogeneration of a nonlinear supercurrent with dc component via condensate acceleration by an effective lightwave field dynamically breaks the equilibrium inversion symmetry. Experimental signatures include high harmonic light emission at equilibrium-symmetry-forbidden frequencies, Rabi--Higgs collective modes and quasi-particle coherence, and non-equilibrium moving condensate states tuned by few-cycle THz fields. We use such lightwaves as an oscillating accelerating force that drives strong nonlinearities and anisotropic quasi-particle populations to control and amplify different classes of collective modes, e.g., damped oscillations, persistent oscillations, and overdamped dynamics via Rabi flopping. Recent phase-coherent nonlinear spectroscopy experiments can be modeled by solving the full nonlinear quantum dynamics including self-consistent light--matter coupling.

Simulation and Research of Light Path Optical Wave Field of Optical Voltage Sensor Based on Pockels Effect

This paper introduces the development status of optical voltage sensor based on Pockels effect at home and abroad. A research scheme of optical voltage sensor with optical path reciprocity is proposed and its reciprocity mechanism is expounded. Comsol Multiphysics, a multi-physical field coupling simulation software, is used to simulate the fluctuation of the transmission of incident polarized light in the electro-optic crystal, thus realizing the three-dimensional fluctuation simulation of the light wave field, which provides a new research idea and theoretical reference for analyzing and designing the optical path component unit of the optical voltage sensor.

Electronic Structure and Optical Properties of the Co2NiAl Heusler Alloy

The frequency dependences of the real part e1(ω) and imaginary part e2(ω) of the complex dielectric constant of the Co2NiAl Heusler alloy are studied in a region of spectrum of 0.08–5 eV. It was found that the character of variations of the spectral parameters of the Co2NiAl ally is typical of media with metallic conductivity. In the IR region, the mechanism of intraband acceleration of electrons by the field of light wave dominates. The contribution of interband electron transitions is marked even at the energies E ≥ 0.15 eV. Results of the investigations are discussed based on the performed electronic structure calculations. It is shown that the main contribution to the resulting optical conductivity dependence is made by interband electron transitions in the band with spins opposite to the magnetization direction.

Discussion on Verdet constant solution model of paramagnetic magneto-optical materials

<sec> The Verdet constant is one of the key parameters to characterize the material magneto-optical properties. The quantum theory is usually used to study magneto-optical properties and calculate the Verdet constant of paramagnetic material. However, the traditional quantum theory only takes into account the influence of the electron transition dipole moments caused by the particle property of light, which therefore cannot formulate the Verdet constant of magneto-optical material accurately. </sec><sec> In view of the shortcomings of the existing theory, in this paper we propose is a wave-transition model of the Verdet constant. Due to the special wave-particle duality of light, the contribution of the non-transition dipole moment to the Verdet constant, caused by the electric field of light wave, should not be ignored. </sec><sec> According to the basic theory of magneto-optical effect, in this paper we first explore the intrinsic mechanism of the paramagnetic material’s Verdet constant at a microscopic level and analyze the deficiency of traditional quantum theory. Furthermore, the classical electronic dynamic theory and quantum theory are used to reveal the contribution of volatility and transition of the light to the electric dipole moment. The density operator and statistical algorithm are introduced to derive the polarizability tensor of the paramagnetic magneto-optical material, thus obtaining the Verdet constant expression of the paramagnetic magneto-optical material, from which the Verdet constant is formulated. Taking the paramagnetic magneto-optical material TGG for example, the splitting energy levels and wave function of Tb<sup>3+</sup> ions in the spin-orbit coupling, crystal field and effective field are calculated by the quantum method, and finally the Verdet constants under the traditional quantum theory and the volatility transition contribution model are obtained quantitatively. The comparative analysis shows that the results calculated by the wave-transition contribution model are more consistent with the experimental data and more accurate than the results calculated through the traditional quantum theory. The idea and method put forward in this paper will provide reference for further exploring the magneto-optical effect mechanism of paramagnetic magneto-optical materials. </sec>

Influence of Interaction Retardation and Radiation Reaction on the Fano Resonance Efficiency in the System of Nanoparticles

The system of metallic nanospheroids in the field of monochromatic light wave under conditions of manifestation of the Fano resonance is considered. The dimensions of the nanospheroids are much smaller than the wavelength of the incident radiation, but distances between them can be arbitrary. An analysis is made of the influence of the interparticle interaction and the reaction field on the inhomogeneity of the energy distribution of the collective oscillations of electrons in the system (the Fano resonance efficiency). It is shown that both the retardation and the reaction field contribute to an increase in the resonance efficiency.

Transparent conductive nanocomposite layers with polymer matrix and silver nanowires reinforcement

Purpose: The article deals with one of the completely new groups of composite inorganic nanostructured materials used in the form of surface layers, characterised by unique properties, such as transparency over 84.4% in the field of visible light waves, anti-reflective and electrical properties comparable to semiconductors. Design/methodology/approach: A technology for producing such layers containing not less than 5% of silver nanowires by mixing a colloid containing silver nanowires from fragmented agglomerates by ultrasound homogeniser with the polymer dissolved in chloroform with good bonding to the polymer matrix and of good quality was developed. Findings: It was shown that increasing the content of silver nanowires to 30% in composite layers causes an increase in the refractive coefficient from 1.9 to 2.2 and a decrease in light transmission from 88.1 to 81.9% and a decrease in the value of light reflection from 11.1% up to 6.7%. With an increased content of silver nanowires, these layers show better electrical properties, and the width of the energy gap is reduced from 3.93 eV to 1.60 eV. Composite layers with a mass fraction greater than 5% of silver nanowires show properties analogous to semiconductors despite the metallic nature of their conductivity. Research limitations/implications: The use of silver nanowires as a reinforcement of transparent nanocomposite layers with a poly(methyl methacrylate) PMMA matrix improves selected optical and electrical properties as a result of the uniform distribution of the reinforcing phase in the matrix material. Originality/value: The influence of the content of silver nanowires, layering conditions, applied methods of dispersing silver nanowires in the matrix material on the structure and properties of newly developed nanocomposite layers was determined.

Multi-Dimensional Optical Fiber Sensing Enabled by Digital Coherent Optical Technologies

Optical fiber sensing (OFS) systems can be used to accurately measure temperature, strain, pressure, and other physical parameters by detecting the change in the field of lightwave. As they are used in more application areas, a new type of OFS with the ability of providing multi-dimensional, highly sensitive, ultra-fine, and real-time measurement is necessary. This is possible with the application of digital coherent optical technologies in the OFS systems. In this paper, we show that many aspects of OFS systems can be replaced or enhanced by digital coherent optical technologies. For example, digital optical frequency comb (DOFC) can replace the sweeping laser source, and the digital coherent optical receiver can replace the direct detection receiver to enable simultaneous detection of all the dimensions of lightwave. Based on these techniques, we present our research progresses on OFS with multi-dimensional, real-time, ultra-fine spectral analysis, and single-shot Brillouin optical time-domain analysis based DOFC for distributed OFS. We show that the OFS systems can be bought to a whole new level with the capabilities of real-time time–frequency analysis, ultra-fine spectral resolution, and ultra-low sensitivity. Opportunities and challenges of using digital coherent optical technologies in OFS systems are also discussed.

Relation between dichroism of photoalignment azo dyes and their orientation under light wave field

AbstractTo date, azo dyes are widely used for liquid crystal photoalignment in flat panel displays. The relation of dichroism of azo dyes with their orientation under intensive light wave field is considered. Values of a parameter, which characterizes orientation order of both molecules and dimers, were obtained as well as energy of their orientation process. Number of cooperatively oriented dye molecules was estimated. The angles distribution functions for different dimers were derived. Dipole electrical transition moments directed on angles close to 90° to the direction of maximal polarizability of dimers were revealed.

Surgical correction of biliary hypertension in patients with complicated forms of chronic pancreatitis

We calculate the temperature of the atoms in the field of counter-propagating stochastic light waves (the chaotic-field model). We show that the temperature of the atomic ensemble depends on the autocorrelation time of the waves, their intensity and the detuning of the carrier frequency of the waves from the atomic transition frequency. The field can form a one-dimensional trap for atoms, as is readily seen from our previous investigation of light-pressure force on an atom in counter-propagating stochastic light waves [V. I. Romanenko, B. W. Shore, L. P. Yatsenko, Opt. Commun. 268 (2006) 121–132]. We carry out numerical simulation of the atomic ensemble using parameters appropriate for sodium atoms. Analyzing the known investigation of the light-pressure force on atoms and their motion in the counter-propagating polychromatic waves, we suggest an hypothesis that any polychromatic counter-propagating waves that have a discrete spectrum, or waves described by a stationary stochastic process, one of which repeats the other, can form a trap for atoms.

Theory of liquid crystal orientation under action of light wave field and aligning surfaces

Theoretical models developed in the MRSU group under leadership of Professor Artem Dadivanyan in area of the LC orientation and photo-induced effects are presented. Angular distribution functions of the dye and liquid crystal molecules under action of intensive light beam have been derived. The number of molecules in cluster is estimated. A model of dimers formation in the photoalignment dye is suggested that explains influence of the dye molecular structure on both polar and azimuthal anchoring energy.

Tamm plasmon-polaritons structures with Bi-substituted garnet layers

New original Tamm plasmon-polaritons (TPP) structures with Bi-substituted iron garnet and Au plasmonic layers were proposed, synthesized and investigated. The structures with single and double garnet layers were modelled to form a TPP mode at the center of photonic band gab. The top Au layer has the gradient thickness varied in the range from 0 to 65.2 nm. It was found the features of TPP resonances as a function of the thickness of metal coating. The resonances on TPP have the maximum optical quality factor and transmission at the vicinity of Au thickness of 30 nm. These configurations are optimum to form the highest intensity of electric field of light wave in the area of the magnetic layers. It was found the spectral blue and red shifts of TPP mode with increasing of Au thickness. The blue and red shifts can be explained respectively by structural and thickness changes of Au coating. The maximum resonant values of Faraday rotation were –2.1° at 664 nm and –12.3° at 645 nm for structures with single and double garnet layers, respectively, and thickness of Au coating of 65.2 nm.