Optical Wave Field Research Articles

Using the dispersion model of a chiral metamaterial to calculate the characteristics of homogeneous and heterogeneous reflective and waveguide structures

Currently, metamaterials are actively used in the creation of microwave and optic devices for various purposes. This is due to their non-traditional properties, compared to dielectric, conductive and other materials. One type of metamaterial is chiral media, which contain conductive microelements of mirror asymmetric shape. Such metamaterials have dispersion and, as a consequence, it is necessary to take it into account when developing various microwave structures. The work demonstrates taking into account the dispersion of the dielectric constant and the chirality parameter for calculating waveguide and reflecting structures with homogeneous and inhomogeneous chiral layers. The work carried out an electrodynamic analysis of the reflective properties of an inhomogeneous chiral layer and a rectangular waveguide, with a homogeneous layer of chiral metamaterial located in the transverse plane. The work has developed a method for calculating the reflection and transmission coefficients of an optical wave from the inhomogeneous chiral structure under consideration, which is based on the use of the differential sweep method. When constructing a mathematical model, we took into account the cross-polarization of the optical wave field, which consists in the appearance of orthogonal components during the interaction of the field with a chiral metamaterial. The solution to the problem was reduced to a matrix differential equation for the unknown reflection coefficients of the main and cross-polarized components of the optical field. The work examined chiral metamaterials with linear and parabolic inhomogeneity profiles. The results of the work can be applied in the design of new microwave and optics devices with layers of metamaterial, which can expand their functionality.

Higher-Order Harmonics in Hexagonal Graphene Quantum Dots

We have considered the high-order harmonic generation in plane graphene quantum dots of hexagonal shape by the independent quasiparticle approximation-tight binding model. We have investigated how such a nonlinear effect is affected by a strong optical wave field, quantum dot typical band gap and lateral size, and dephasing processes. The equation of motion for the density matrix is solved by performing the time integration with the eight-order Runge–Kutta algorithm. If the optical wave frequency is much less than the quantum dot intrinsic band gap, the main aspects of multiphoton high harmonic emission in quantum dots are revealed. In such case dependence of the cutoff photon energy on the strength of the optical pump wave is almost linear. But when the wave frequency is comparable to the bandgap of the quantum dot, the cutoff photon energy shows saturation behavior with an increase in the wave field strength.

Controlling self-healing of optical field based on moiré dual-microlens arrays

Optical self-healing is a repairing phenomenon of a beam in the propagation, as it is perturbed by an opaque object. In this work, we demonstrate experimentally and theoretically that the moiré distributed dual-microlens array enables to generate optical fields with better healing ability to withstand defects than their counterparts of a single microlens array. By utilizing the double parameter scanning method, the self-healing degree of the optical field is significantly affected by both the interval distance and the relative angle of the dual-microlens arrays. The self-healing level is decreased significantly by lengthening the interval between the two microlens array with a small twist angle, while increasing the angle enhances the self-healing degree. Further study manifests the self-healing process with respect to the size and central location of the obstacle. The research results provide a simple and effective method to generate self-healing optical wave fields, which have potential applications including optical communication, assisted imaging technology, and even intense laser physics.

High-performance full-color imaging system based on end-to-end joint optimization of computer-generated holography and metalens.

Metasurface has drawn extensive attention due to its capability of modulating light with a high degree of freedom through ultrathin and sub-wavelength optical elements, and metalens, as one of its important applications, promises to replace the bulky refractive optics, facilitating the imaging system light-weight and compact characteristics. Besides, computer-generated holography (CGH) is of substantial interest for three-dimensional (3D) imaging technology by virtue of its ability of restoring the whole optical wave field and re-constructing the true 3D scene. Consequently, the combination of metalens and CGH holds transformative potential in enabling the miniaturization of 3D imaging systems. However, its imaging performance is subject to the aberrations and speckle noises originating from the metalens and CGH. Inspired by recent progress that computational imaging can be applied to close the gap, a novel full-color imaging system, adopting end-to-end joint optimization of metalens and CGH for high imaging quality, is proposed in this paper. The U-net based network as the pre-processing adjusts weights to make the holographic reconstruction offset imaging defects, incorporating the imaging processing into the step of generating hologram. Optimized by deep learning, the proposed imaging system is capable of full-color imaging with high fidelity in a compact form factor, envisioned to take an essential step towards the high-performance miniaturized imaging system.

Real-Time Phase Imaging with an Asymmetric Transfer Function Metasurface

The conversion of phase variations in an optical wavefield into intensity information is of fundamental importance for optical imaging technology including microscopy of biological cells. While conventional approaches to phase-imaging commonly rely on bulky optical components or computational post processing, meta-optical devices have recently demonstrated all-optical, ultracompact image processing methods. Here we describe a metasurface that exploits photonic spin-orbit coupling to create an asymmetric optical transfer function for real time phase-imaging. The effect of the asymmetry on transmission through the device is demonstrated experimentally with the generation of high contrast pseudo-3D intensity images of phase variations in an optical wavefield without the need for post-processing. This non-interferometric method has potential applications in biological live cell imaging and real-time wavefront sensing.

Generalized Lorenz-Mie theory in the analysis of longitudinal photophoresis of arbitrary-index particles: On-axis axisymmetric beams of the first kind

The uniform plane wave is the reference solution of Maxwell’s equations when it comes to rigorous theoretical investigations of photophoretic forces from the Mie theory. Here, we address the theory of photophoresis for a more general class of on-axis axisymmetric beams of the first kind. To do so, the generalized Lorenz-Mie theory (GLMT) is introduced for the first time in the calculation of analytic and closed-form expressions for the asymmetry factor assuming arbitrary-index micro-sized spheres of arbitrary size parameters. The behavior of the asymmetry factor is illustrated for non-volatile particles illuminated by Gaussian and circularly symmetric zero-order Bessel beams. The theory here presented is valid for arbitrary size parameters and is a first attempt towards the incorporation of real optical wave fields into photophoresis of absorbing particles using the GLMT for arbitrary-shaped beams.

Multicolor Holographic Display of 3D Scenes Using Referenceless Phase Holography (RELPH)

In this paper, we present a multicolor display via referenceless phase holography (RELPH). RELPH permits the display of full optical wave fields (amplitude and phase) using two liquid crystal phase-only spatial light modulators in a Michelson-interferometer-based arrangement. Complex wave fields corresponding to arbitrary real or artificial 3D scenes are decomposed into two mutually coherent wave fields of constant amplitude whose phase distributions are modulated onto the wave fields reflected by the respective light modulators. Here, we present the realization of that concept in two different ways: firstly, via temporal multiplexing using a single setup, switching between wavelengths for temporal integration of the respective wavefields; secondly, using spatial multiplexing of different wavelengths with multiple Michelson-based setups; and finally, we present an approach to magnify the 3D scenes displayed by light modulators with limited space–bandwidth product for a comfortable viewing experience.

Diffraction model of a laser speckle interferometer for measuring micro-displacements of objects with scattering surface

On the basis of diffraction transformations of an optical wave field a mathematical model for the formation of speckle modulated interference patterns and signals at the output of a speckle interferometer is developed, which allows us to identify their properties and quantitative parameters. Speckle interferometers based on a Michelson arrangement are considered, where objects with scattering surfaces are used instead of mirrors in the reference and object arms. Results of numerical simulation of speckle modulated interference patterns on the basis of diffraction transformations of wave fields in an interferometer are discussed. Simulated images obtained at the output of the interferometer when focusing laser beams on the scattering surfaces of the controlled and reference objects are considered. Experimental results of using a speckle interferometer with a digital matrix photodetector for measuring the temperature micro-displacements of an object with a scattering surface and a quantitative comparison of experimental data with the results obtained by a numerical experiment using a diffraction model of a speckle interferometer are presented.

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.

Polarization contrast optical diffraction tomography.

We demonstrate large scale polarization contrast optical diffraction tomography (ODT). In cross-polarized sample arm detection configuration we determine, from the amplitude of the optical wavefield, a relative measure of the birefringence projection. In parallel-polarized sample arm detection configuration we image the conventional phase projection. For off-axis sample placement we observe for polarization contrast ODT, similar as for phase contrast ODT, a strongly reduced noise contribution. In the limit of small birefringence phase shift δ we demonstrate tomographic reconstruction of polarization contrast images into a full 3D image of an optically cleared zebrafish. The polarization contrast ODT reconstruction shows muscular zebrafish tissue, which cannot be visualized in conventional phase contrast ODT. Polarization contrast ODT images of the zebrafish show a much higher signal to noise ratio (SNR) than the corresponding phase contrast images, SNR=73 and SNR=15, respectively.

Field theory of monochromatic optical beams: I. Classical fields

We study monochromatic, scalar solutions of the Helmholtz and paraxial wave equations (PWEs) from a field-theoretic point of view. We introduce appropriate time-independent Lagrangian densities for which the Euler–Lagrange equations reproduces either Helmholtz and PWEs with the z-coordinate, associated with the main direction of propagation of the fields, playing the same role of time in standard Lagrangian theory. For both Helmholtz and paraxial scalar fields, we calculate the canonical energy-momentum tensor and determine the continuity equations relating ‘energy’ and ‘momentum’ of the fields. Eventually, the reduction of the Helmholtz wave equation to a useful first-order Dirac form, is presented. This work sheds some light on the intriguing and not so acknowledged connections between angular spectrum representation of optical wavefields, cosmological models and physics of black holes.

Wavevector mismatch and Doppler-free three-dimensional atom localization

In the regime of the Raman–Nath approximation we show coherence control of three-dimensional atom localization with high precession and resolution via probe absorption when a five-level atomic system is cyclically driven by three orthogonal standing optical wave-fields together with one traveling optical wave-field and two microwave wave-fields in an optical cavity. We apply wavevector mismatch and subsequently the Doppler-free technique to the atom localization system to minimize the imprecision in the atom’s position in the standing wave-field caused by its high velocity in the cavity. The position of the single atom is freed from the two effects by collinear coupling of the driving fields with the atom in the cavity. The atomic position is controlled in the sub-wavelength domain of the standing wave-field with probability and high quality resolution by adjusting the relative phase and amplitude of the driving fields.

Inelastic interactions, numerical breathers and chaotic wave fields for a focusing Kundu–Eckhaus equation in a nonlinear optical fiber

Investigation is made on a focusing Kundu–Eckhaus equation in nonlinear/quantum optics and fluid mechanics, for describing the optical properties of the femtosecond lasers and femtochemistry objects, and for examining the stability of the Stokes waves in weakly nonlinear dispersive media. We derive the one and two optical breather solutions via the Darboux transformation. Inelastic interactions between two single-hump optical breathers and between a single-hump optical breather and a double-hump optical breather are depicted. Numerical optical breathers are obtained via the split-step Fourier method: β affects the speeds of the numerical optical breathers and space energy distribution, while β has no effects on the total energy, where β is a real constant representing the quintic nonlinearity. Optical chaotic wave fields via three initial conditions, including the plane wave, one soliton and one breather, are derived. Among them, the optical chaotic wave field via the one breather is the most orderless via the probability density function. Total energy of the optical chaotic wave field via the one breather is the largest.

Optical breathers and multiple rogue waves via the modulation instability for a complex Ginzburg–Landau equation in the mode-locked laser operation

Investigation is made on a complex Ginzburg–Landau equation for the mode-locked laser operation. Optical breathers are numerically derived via the split-step Fourier method. Effects of the modulation instability on the dynamic behaviors of the optical breathers are investigated: when the growth rate of the modulation instability increases, the optical breather splits into two optical breathers earlier, and the two optical breathers separate faster. Via the energy distributions of the optical breathers, we obtain that when the fission phenomenon occurs, the energy decreases more than that of the fusion phenomenon. Multiple rogue waves in the chaotic wave field are obtained via the modulation instability. It is observed that multiple rogue waves occur earlier as the growth rate of the modulation instability becomes larger. Occurrence of the rogue wave can be predicted via the spectrum of the optical chaotic wave field.

Optical breathers and rogue waves via the modulation instability for a higher-order generalized nonlinear Schrödinger equation in an optical fiber transmission system

For describing the propagation of ultrashort pulses in a high-speed, long-distance optical fiber transmission system with the fourth-order dispersion, cubic–quintic nonlinearity, self-steepening and self-frequency shift, a higher-order generalized nonlinear Schrodinger equation is investigated. We get the rogue-wave solutions. Effects of the modulation instability on the optical rogue waves are studied: Increasing the growth rate of the modulation instability makes the existence time of the optical rogue wave shorter. We numerically derive the optical breathers in the chaotic wave fields via the modulation instability. Spectrum of the optical chaotic wave field can be used to indicate the appearance of the optical breather in the chaotic wave field. Optical rogue waves in the chaotic wave fields are also gotten via the modulation instability.

Instantaneous Speckle Structures in a Partially Coherent Optical Wave Field with Broad Frequency and Angular Spectra

We consider the hypothesis of instantaneous volume speckle structures in a partially coherent optical wave field of frequency-broadband radiation from an extended light source. We discuss the spatiotemporal correlation properties of instantaneous speckle structures and the relation of these properties with the spatiotemporal coherent properties of the wave field. We show that the instantaneous speckle structures determine spatial fluctuations of the wave field and its spatial coherent properties. Using numerical calculations of the field of wave perturbations in the near-field diffraction region of the extended light source, we obtain images of instantaneous speckle structures in the longitudinal cross section of the wave field and investigate the correlation properties of the spatial distribution of the instantaneous intensity of the wave field in the direction of its propagation as functions of the width of the frequency spectrum and the width of the angular spectrum of the field. We show that the longitudinal length of instantaneous speckles can be determined either by the width of the frequency spectrum of the field, or the width of its angular spectrum, or, jointly, by the width of the frequency spectrum and the width of the angular spectrum of the field. We find conditions under which instantaneous speckle structures propagate, experiencing decorrelation changes during their propagation, to a distance that is determined by the width of the angular spectrum of the field.

Мгновенные спекл-структуры в частично когерентном оптическом волновом поле с широкими частотным и угловым спектрами

AbstractWe consider the hypothesis of instantaneous volume speckle structures in a partially coherent optical wave field of frequency-broadband radiation from an extended light source. We discuss the spatiotemporal correlation properties of instantaneous speckle structures and the relation of these properties with the spatiotemporal coherent properties of the wave field. We show that the instantaneous speckle structures determine spatial fluctuations of the wave field and its spatial coherent properties. Using numerical calculations of the field of wave perturbations in the near-field diffraction region of the extended light source, we obtain images of instantaneous speckle structures in the longitudinal cross section of the wave field and investigate the correlation properties of the spatial distribution of the instantaneous intensity of the wave field in the direction of its propagation as functions of the width of the frequency spectrum and the width of the angular spectrum of the field. We show that the longitudinal length of instantaneous speckles can be determined either by the width of the frequency spectrum of the field, or the width of its angular spectrum, or, jointly, by the width of the frequency spectrum and the width of the angular spectrum of the field. We find conditions under which instantaneous speckle structures propagate, experiencing decorrelation changes during their propagation, to a distance that is determined by the width of the angular spectrum of the field.

Optical wavefields measurement by digital holography methods

The phase distortions arise due to the atmospheric turbulence, the experimental conditions or a low quality of the imaging system. They can seriously limit the resolution of the image. Phase distortions can be spatially dependent, which means that a linear space-invariant transfer function cannot completely correct all phase errors in the field of view. Computer holography can be used to access a complex-valued optical field from an object under coherent illumination after detecting interference of intensity between the object and the reference beams. In this work, we developed approaches to improve image sharpness to measure phase distortions in computer holography using the example of defocus measurement. Image enhancement algorithms use a nonlinear optimization procedure to determine and measure phase distortions to form a reconstructed image at a high resolution. Our work was focused on numerical modelling, developing algorithms and conducting laboratory experiment.

Measuring the Phase of an Optical Field from Two Intensity Measurements: Analysis of a Simple Theoretical Model

Under the scalar paraxial approximation, an optical wavefield is considered to be complex function dependent on position; i.e., at a given location in space the optical field is a complex value with an intensity and phase. The optical wavefield propagates through space and can be modeled using the Fresnel transform. Lenses, apertures, and other optical elements can be used to control and manipulate the wavefield and to perform different types of signal processing operations. Often these optical systems are described theoretically in terms of linear systems theory leading to a commonly used Fourier optics framework. This is the theoretical framework that we will assume in this manuscript. The problem which we consider is how to recover the phase of an optical wavefield over a plane in space. While today it is relatively straightforward to measure the intensity of the optical wavefield over a plane using CMOS or CCD sensors, recovering the phase information is more complicated. Here we specifically examine a variant of the problem of phase retrieval using two intensity measurements. The intensity of the optical wavefield is recorded in both the image plane and the Fourier plane. To make the analysis simpler, we make a series of important theoretical assumptions and describe how in principle the phase information can be recovered. Then, a deterministic but iterative algorithm is derived and we examine the characteristics and properties of this algorithm. Finally, we examine some of the theoretical assumptions we have made and how valid these assumptions are in practice. We then conclude with a brief discussion of the results.

Recent Advances of the Polymer Micro/Nanofiber Fluorescence Waveguide.

Subwavelength optical micro/nanofibers have several advantages, such as compact optical wave field and large specific surface area, which make them widely used as basic building blocks in the field of micro-nano optical waveguide and photonic devices. Among them, polymer micro/nanofibers are among the first choices for constructing micro-nano photonic components and miniaturized integrated optical paths, as they have good mechanical properties and tunable photonic properties. At the same time, the structures of polymer chains, aggregated structures, and artificial microstructures all have unique effects on photons. These waveguided micro/nanofibers can be made up of not only luminescent conjugated polymers, but also nonluminous matrix polymers doped with luminescent dyes (organic and inorganic luminescent particles, etc.) due to the outstanding compatibility of polymers. This paper summarizes the recent progress of the light-propagated mechanism, novel design, controllable fabrication, optical modulation, high performance, and wide applications of the polymer micro/nanofiber fluorescence waveguide. The focus is on the methods for simplifying the preparation process and modulating the waveguided photon parameters. In addition, developing new polymer materials for optical transmission and improving transmission efficiency is discussed in detail. It is proposed that the multifunctional heterojunctions based on the arrangement and combination of polymer-waveguided micro/nanofibers would be an important trend toward the construction of more novel and complex photonic devices. It is of great significance to study and optimize the optical waveguide and photonic components of polymer micro/nanofibers for the development of intelligent optical chips and miniaturized integrated optical circuits.