Nonlinear Lens Research Articles

Sorting infrared optical vortices with a nonlinear angular lens.

Analogous to the regular lens, which spatially maps plane waves in the space domain to distinct points in the Fourier domain, the angular lens establishes the mapping relations between an angular mode and angular position, thus providing an effective toolkit for detecting an optical vortex. However, using the angular lens to sort infrared optical vortex modes via nonlinear optical processes remains relatively unexplored. Here, we design a nonlinear optical version of the angular lens to map the various infrared optical vortex modes to different angular positions in the visible region. We successfully sort nine infrared optical vortex modes of different topological charges with a visible camera, showing the cost-effective ability to sort infrared vortices compared to a relatively expensive infrared camera. Our scheme holds promise for infrared remote sensing, infrared vortex-encoded optical communications, and so on.

Enhancing Camera Calibration for Traffic Surveillance with an Integrated Approach of Genetic Algorithm and Particle Swarm Optimization.

Recent advancements in sensor technologies, coupled with signal processing and machine learning, have enabled real-time traffic control systems to effectively adapt to changing traffic conditions. Cameras, as sensors, offer a cost-effective means to determine the number, location, type, and speed of vehicles, aiding decision-making at traffic intersections. However, the effective use of cameras for traffic surveillance requires proper calibration. This paper proposes a new optimization-based method for camera calibration. In this approach, initial calibration parameters are established using the Direct Linear Transformation (DLT) method. Then, optimization algorithms are applied to further refine the calibration parameters for the correction of nonlinear lens distortions. A significant enhancement in the optimization process is achieved through the integration of the Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) into a combined Integrated GA and PSO (IGAPSO) technique. The effectiveness of this method is demonstrated through the calibration of eleven roadside cameras at three different intersections. The experimental results show that when compared to the baseline DLT method, the vehicle localization error is reduced by 22.30% with GA, 22.31% with PSO, and 25.51% with IGAPSO.

Electrical, Thermal Lens and Optical Study of Fluorescein Film for Application As Organic Photovoltaic Devices.

This article is devoted to the study of various dielectric and optoelectrical parameters nonlinear optic behaviors, thermal lens and self-diffraction parameters of Fluorescein (FLs) doped polymethyl methacrylate (PMMA) films. The films were prepared with 60mM. These studies are based on the calculated values of refractive, absorption coefficient, energy gap, extinction coefficient and nonlinear Refraction index . The polymer films were prepared using the casting technique. All samples were previously investigated by UV-Vis-NIR spectrophotometric measurements and Optical microscopy SEM and ATM. Utilizing thermal lens spectrometry, an investigation of the thermo-optical characteristics as well as the nonlinear refractive index was carried out. In this method, a pump beam and a probe beam were brought into collinear alignment with one another. To determination the nonlinear Refraction index . High values of nonlinear refractive index predict a bright future for materials in optical applications. These results indicate that the new dye is a promising candidate for applications in nonlinear optical devices. Investigations were carried out on organic photovoltaic devices in addition to devices consisting of active layers with conducting polymer of PHPP:P3HT film and PHPP:P3HT/Fls. The methods of polymer and dyes synthesis are presented and their physical properties are given.

Nonlinear Metasurfaces for Health-Monitoring Magnetic Induction-Based SWIPT Base Stations

Metasurfaces based on periodic arrays of high- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> coils have been used as artificial lenses to boost the power transfer efficiency of magnetic induction (MI)-based power transmission systems. In conventional linear topologies, the metamaterial (MTM) focalization effect is physically limited to an extremely narrow bandwidth (BW) due to the high- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> of MTM cells. Through accurate large-signal numerical simulations and experimental measurements, this article demonstrates that nonlinear MTM lenses inspired by the Duffing resonator can produce a substantial and stable gain (up to 16 dB) over a two-times wider BW compared to the linear case. With modulated excitations (quadrature phase shift keying (QPSK) signals), such a gain reaches 17 dB. Furthermore, the proposed lens is proven to reduce the peak-to-average power ratio (up to 4 dB) and the magnetic channel attenuation as a function of the data rate. The proposed MTM lenses are believed to have great potential in developing high-performance, low-cost MI-based base stations for simultaneous wireless information and power transmission in health-monitoring wireless body area networks.

All-optical information conversion in Rb vapor based on the spatial cross-phase modulation.

All-optical information conversion, conveying optical signals without electro-optical transformation, plays a vital role in the all-optical devices and optical communication. We achieve the all-optical information conversion in Rb vapor by utilizing the spatial cross-phase modulation. The refractive index of atomic medium is spatially modulated by the strong switch laser beam, which makes it as a nonlinear focusing lens for the weak signal laser beam. As a result, the far-field diffraction ring patterns of the signal laser beam interacted with atoms can effectively carry the nonlinear phase shift information of the switch laser beam. The channel numbers, channel capacities and channel storage densities of information transmission from switch laser beam to signal laser beam are investigated in the terms of switch laser intensity and vapor temperature. Finally, a special "sxu" alphabetic string, encoded by ASCII code, is introduced to verify this all-optical information conversion scheme. This work paves the way for studying optical information processing and all-optical networking with atomic ensembles.

Nonlinear beam tapering and two-dimensional ring solitons.

We examine a possibility to exploit the nonlinear lens effect-the initial stage of self-focusing to localize initially broad field distribution into the small central area where wave collapse is arrested-the nonlinear beam tapering. We describe two-dimensional localized solitary waves (ring solitons) in a physical system that presents a linear medium in the central core, surrounded by the cladding with the focusing Kerr nonlinearity. The standard variational analysis demonstrates that such solitons correspond to the minimum of the Hamiltonian.

Tunable high-order Bessel-like beam generation based on cross-phase modulation.

Nonlinear atomic media are promising substitutes for spatial light modulators (SLMs) owing to the high tunability and fast response. We demonstrate the generation of high-order Bessel-like beam based on cross-phase modulation in 85Rb atoms. The atomic medium, whose refractive index is spatially modulated by the focused Gaussian pump beam, acts as a nonlinear focusing lens for the Laguerre-Gaussian probe beam. As a result, the probe beam carries the nonlinear phase shift and is converted into a Bessel-like mode in far-field diffraction. The superior self-healing ability of the generated high-order Bessel-like beam is verified by inserting an obstruction in the beam path, and its high tunability is investigated in terms of the pump beam power and vapor temperature. Furthermore, this novel beam is used in an obstruction-immune rotation sensor to measure the angular velocity. Nonlinear atomic medium as a novel SLM promises considerable application prospects in modulating the light field structure.

Envelope time reversal with a nonlinear time lens based on accelerating quasi-phase-matching

We show theoretically and numerically that a time-reversed replica of the pump pulse envelope in a frequency converted signal can be achieved using a nonlinear time lens realized with an accelerating spatiotemporal quasi-phase-matching (QPM) modulation. The nonlinear process depends on a suitable combination of the input and output dispersion and acceleration rate of a quadratic spatiotemporal QPM modulation.

Third-order nonlinear optical properties and thermal lens effect of 5-hydroxyquinoline azo dyes

In this research, the third-order nonlinear characteristics of some novel azo dyes based on 5-hydroxyquinoline (containing quinoline skeleton in their structure) were studied via Z-scan technique and by means of a continuous wave of a diode-pumped laser at the wavelength 532 nm with an intensity of 38.72 × 103 W/m2. The nonlinear absorption coefficient and nonlinear refractive index (β and n2, respectively) were calculated by fitting the theoretical model and experimental data obtained from the Z-scan technique. The open aperture component of this technique illustrated reverse saturable absorption phenomenon. Thermal nonlinear phase shift affected the shapes of closed-aperture Z-scan curves, and they did not fit well with the common theoretical models. The forms of peak-to-valley in these plots did behave like a modified aberrant thermal lens model. The substituent effect on the values of β and n2 was also investigated and demonstrated that the azo dyes bearing electron-withdrawing groups offer higher values of β and n2 than the other azo dyes with or without electron-donating groups. The calculated values of third-order susceptibility of these azo dyes were from the order 10-6esu, indicating their potential capability for the use in optical devices.

Nonlinear Metamaterial Lenses for Inductive Power Transmission Systems Using Duffing-Resonator Based Unit Cells

Metamaterials (MTMs) based on a periodic array of resonant coils have been shown to behave as μ-negative (MNG), enabling the focusing of magnetic flux. The phenomenon has been deployed by designers to boost the efficiency of many inductively coupled systems, such as magnetic resonance imaging, underwater and underground communications, and charging base stations (CBS) for consumer electronics and implanted devices. However, due to their dependency on high-Q unit cells, linear MNG-like MTMs have limited bandwidth, restricting their use in many applications, notably in near-field simultaneous wireless information and power transmission (NF-SWIPT) systems. To improve the tight constraints of the amplitude-bandwidth trade-off of artificial magnetic lenses, this paper presents a theoretical analysis of nonlinear MTMs based on a lattice of Duffing resonators (DRs). Additionally, it introduces a criterium for the quantification and evaluation of the amplitude-bandwidth enhancement. The analytical results are based on a circuit model and further verified by numerical simulations using commercial software. The preliminary findings in this paper open up possibilities for nonlinear MTM lenses and can be applied to enhance the linear amplitude-bandwidth limit.

Secondary instability in thin film flows under an inclined plane: growth of lenses on spatially developing rivulets

The response of a thin film flowing under an inclined plane, modelled using the lubrication equation, is studied. The flow at the inlet is perturbed by the superimposition of a spanwise-periodic steady modulation and a decoupled temporally periodic but spatially homogeneous perturbation. As the consequence of the spanwise inlet forcing, the so-called rivulets grow downstream and eventually reach a streamwise-invariant state, modulated along the direction perpendicular to the flow. The linearized dynamics in the presence of a time-harmonic inlet forcing shows the emergence of a time-periodic flow characterized by drop-like structures (so-called lenses) that travel on the rivulet. The spatial evolution is rationalized by a weakly non-parallel stability analysis. The occurrence of the lenses, their spacing and thickness profile, is controlled by the inclination angle, flow rate, and the frequency and amplitude of the time-harmonic inlet forcing. The faithfulness of the linear analyses is verified by nonlinear simulations. The results of the linear simulations with inlet forcing are combined with the computations of nonlinear travelling lenses solutions in a double-periodic domain to obtain an estimate of the dripping length, for a large range of conditions.

Calculations of detuning with amplitude for the McMillan electron lens in the Fermilab Integrable Optics Test Accelerator (IOTA)

The McMillan electron lens will be one of the experimental implementations of nonlinear integrable lattices in the Fermilab Integrable Optics Test Accelerator (IOTA). We describe the physics of the nonlinear McMillan lens and calculate the tune dependence with amplitude from the experimental parameters. Some of the implications for the design of experiments in IOTA are discussed.

On the possibility of footprint compression with one lens in nonlinear accelerator lattice

Electromagnetic interaction of colliding beams along with other nonlinear fields often limits the beams' lifetimes and luminosities. Nonlinearities result in the spread of betatron frequencies (footprint) and, thus, may enhance dynamic diffusion of particles due to high order resonances. One of the possible ways to eliminate nonlinearities and overcome the corresponding difficulties is compensation of nonlinear forces, but, in practice, it is hardly possible to obtain exact linearity of the system. The compensation with a single nonlinear lens cannot cope with distributed nonlinearities, nonlinearities due to parasitic crossings, etc. In the article, we present a method to compute parameters of nonlinear element (lens) that eliminates both the footprint and resonance strength without achieving full compensation.

Interacting quantum mixtures for precision atom interferometry

We present a source engineering concept for a binary quantum mixture suitable as input for differential, precision atom interferometry with drift times of several seconds. To solve the non-linear dynamics of the mixture, we develop a set of scaling approach equations and verify their validity contrasting it to the one of a system of coupled Gross–Pitaevskii equations. This scaling approach is a generalization of the standard approach commonly used for single species. Its validity range is discussed with respect to intra- and inter-species interaction regimes. We propose a multi-stage, non-linear atomic lens sequence to simultaneously create dual ensembles with ultra-slow kinetic expansion energies, below 15 pK. Our scheme has the advantage of mitigating wave front aberrations, a leading systematic effect in precision atom interferometry.

Cascaded nonlinearity induced spatial domain effects in a high power femtosecond optical parametric oscillator.

We have investigated the effect of cascaded optical nonlinearity on the spatial beam properties of a femtosecond optical parametric oscillator (OPO). The OPO was operated with a tunable phase mismatch by varying the angle of the nonlinear crystal. The cascaded nonlinearity induced self-focusing and defocusing changed resonator's stability and impacted mode properties. With tuning of a phase mismatch, the calculated parabolic part of cascaded nonlinearity lens focal length changes from f ∼ 30 mm (D ∼ 33 m-1 at Δθ ∼ -0.5o) to infinity and back to f ∼ -110 mm (D ∼ -9 m-1 at Δθ ∼ 0.9o) in the LBO nonlinear crystal. Such high power nonlinear lenses in a cavity operated near its stability limit promoted the generation of axially asymmetric or pass-to-pass unstable resonator modes. It was shown that phase mismatched optical parametric oscillation changes the physical character of the resonator from linear to ring-like with two nonlinear crystals having two different focusing powers. Calculations showed that the QCN induced spatial nonlinear phase should lead to severe longitudinal chromatic aberrations for broad spectrum pulses. A numerical simulation in XYZ spatial domain and calculations using ABCD matrix approach confirmed the physical mechanisms underlying the experimental results and allowed for the interpretation of the observed effects.

Nonlinear microscope objective using thin layer of organic dye for optical tweezers

The microscope objective for optical tweezers requires a high resolving power and a large numerical aperture. For these purposes, the oil immersion objective can be improved. However, the index of the oil immersion objective and glass cover-slip must be matched resulting in a limit to enhance numerical aperture, and then optical trap efficiency. The optical trap efficiency can be enhanced by using a thin layer of organic dyelike an added nonlinear lens. To improve the resolving power and the optical trap efficiency of nonlinear tweezers, a thin layer of organic dye glued by microscope objective like the nonlinear microscope objective is proposed in this paper. The explicit expressions of the focal length, numerical aperture, axial optical trap efficiency of nonlinear microscope objective are theoretically derived. Some interesting properties of particular nonlinear microscope objective used like nonlinear optical tweezersare numerically observed. The obtained results show that the numerical aperture and optical trap efficiency are significantly improved. Our proposed nonlinear microscope objective has advantages such as more compact and smooth focal shift in the range of micrometers suitable to stretch DNA molecules in comparison with the previous ones.

Navigated non-contact fluorescence tomography

A non-contact approach for diffuse optical tomography (DOT) has been developed for on-demand image updates using surgical navigation technology. A stereoscopic optical tracker provides real-time localization of reflective spheres mounted to a laser diode and near-infrared camera. Standard camera calibration is combined with tracking data to determine the intrinsic camera parameters (focal length, principal point and non-linear lens distortion) and the tracker-to-camera transform. Tracker-to-laser calibration is performed using images of laser beam intersection with a tracked calibration surface. Source and detector positions for a finite-element DOT implementation are projected onto the boundary elements of the tissue mesh by finding ray-triangle intersections. A multi-stage model converts camera counts to surface flux by accounting for lens aperture settings, fluorescence filter transmittance, photodetector quantum efficiency, photon energy, exposure time, readout offset and camera gain. The image-guidance framework was applied to an in-house optical tomography system configured for indocyanine green (ICG) fluorescence. Mean target registration errors for camera and laser calibration were less than 1 mm. Surface flux measurements of total reflectance and fluorescence in Intralipid-based fluorescence phantoms (0–2 μg ml−1) had mean errors of 3.1% and 4.4%, respectively, relative to diffusion theory predictions. Spatially-resolved reflectance measurements in a calibrated optical phantom agreed with theory for radial distances up to 25 mm from the laser source. Inverse fluorescence reconstructions of a sub-surface fluorescence target confirmed the localization accuracy (average target centroid error of 0.44 mm). This translational research system is under investigation for clinical applications in head and neck surgery, including oral cavity tumor resection, lymph node mapping and free-flap perforator assessment.

PC-VINS-Mono: A Robust Mono Visual-Inertial Odometry with Photometric Calibration

&lt;p&gt;Feature detection and Tracking, which heavily rely on the gray value information of images, is a very importance procedure for Visual-Inertial Odometry (VIO) and the tracking results significantly affect the accuracy of the estimation results and the robustness of VIO. In high contrast lighting condition environment, images captured by auto exposure camera shows frequently change with its exposure time. As a result, the gray value of the same feature in the image show vary from frame to frame, which poses large challenge to the feature detection and tracking procedure. Moreover, this problem further been aggravated by the nonlinear camera response function and lens attenuation. However, very few VIO methods take full advantage of photometric camera calibration and discuss the influence of photometric calibration to the VIO. In this paper, we proposed a robust monocular visual-inertial odometry, PC-VINS-Mono, which can be understood as an extension of the opens-source VIO pipeline, VINS-Mono, with the capability of photometric calibration. We evaluate the proposed algorithm with the public dataset. Experimental results show that, with photometric calibration, our algorithm achieves better performance comparing to the VINS-Mono.�&lt;/p&gt;

Three-Dimensional Printing of Nonlinear Optical Lenses.

In the current paper, a series of nonlinear optical (NLO) active devices was prepared by utilizing stereolithographic three-dimensional printing technique. Microcrystalline NLO active component, urea, or potassium dihydrogen phosphate was dispersed in a simple photopolymerizable polyacrylate-based resin and used as the printing material to fabricate highly efficient transparent NLO lenses. The nonlinear activity of the printed lenses was confirmed by second-harmonic generation measurements using a femtosecond laser-pumped optical parametric amplifier operating at a wavelength of 1195 nm. The three-dimensional printing provides a simple method to utilize a range of NLO active compounds without tedious crystal growing and processing steps. Furthermore, introducing NLO additives in the printing material provides an easy and cost-efficient way to manufacture lenses with NLO functionality.

Self-focusing of the light in transparent nanosuspension

It was analyzed the self-focusing regime of the Gaussian beam in transparent nanosuspension with electrostrictive nonlinearity. The theoretical analysis of the light-induced mass transfer in the nanosuspension was carried out for large intensities of the Gaussian beam radiation, when the concentration change is comparable to the primary value. The nonlinear lens in this mode is the nonlinear function of the incident light intensity. It is shown that the critical power value decreases significantly for high intensity beam. The results are relevant to the study of the radiation self-action in the nanosuspension and optical diagnostics of such materials.