The coherent diffraction imaging method with three-dimensional spiral scanning is proposed for removal of an illumination background, high contrast and a wide field-of-view (FOV) with a limited amount of data. The pattern is moved in a conical spiral rather than axial multi-height measurements or lateral translation. In this way, each intensity pattern has axial and transverse phase modulation. Firstly, we can obtain the reconstructed object without an illumination background, which decreases the background noise and increases the contrast. Secondly, the image alignment process is omitted. In multi-height phase retrieval, image alignment is a key step. Once the consequence of alignment is imprecision, the image will fail to be reconstructed. Finally, the open illumination is employed so that a wide FOV can be obtained with several patterns. Compared with typical ptychography, the proposed method uses minimal patterns to realize the same size of FOV, which reduces the time required for data acquisition and processing. Overall, the proposed method combines the advantages of multi-height measurements and ptychography, which achieves a wide FOV, removing background, high contrast and high resolution at the same time. For pathological imaging, this method can perform label-free phase imaging, and it can directly obtain large-FOV imaging without the need for image stitching technology. Finally, this method provides a new method for medical pathological microscopy imaging.

Over the past two decades, optical fiber sensing technology has made considerable progress in sensor design, manufacturing process optimization, and system integration, and it has become an integral part of advanced sensing technologies. Various optical principles, such as interference, scattering, total internal reflection, and surface plasmon resonance, are applied in designing optical fiber (OF) sensors. As an emerging OF sensor device, nanostructured plasmonic OF sensors have attracted significant attention due to their superior performance and peculiar properties, realizing the Lab on fiber concept. As nanostructured plasmonic OF sensors feature the characteristics of both traditional OF sensors and plasmonic sensors, they exhibit unique advantages and can be used as powerful biochemical sensing tools or integrated photonic devices. A simple approach is also the use of metal nanoparticles in order to modify the side or end of the optical fiber to excite the surface plasmon resonance effect. One of the main branches in the "Lab on Fiber" field is optical-fiber based SERS, which seeks to combine the advantages of both SERS and optical fibers. This combination aims to create powerful, flexible, robust, and miniaturized spectroscopic tools for remote and highly sensitive detection of low-concentration molecular analytes in a variety of environments, including harsh conditions.

Introduction:

The time-course of the luminescence of a material after stopping the stimulating radiation characterizes the life-time of the radiative transitions that are converted after stimulation. And the yield of luminescence increases as the dose of stimulation increases, until reaching a saturation phase. Several experiments since 1993, however, have revealed that as the stimulation dose exceeds a saturation level, the luminescence yield may decline. And there is a lack of modelling-based understanding of this phenomenon. This work aims to present a model that may help understand the post-saturation decline of the luminescence yield.

Methods:

Spatially resolved delayed luminescence from yeast irradiated by ultraviolet-containing intense light was acquired by using a cooled CCD over a fixed duration (100 seconds) of exposure post photo-stimulation. The duration of the photo-stimulation varied over six orders of magnitude, from 1 millisecond to 1000 seconds. By using an irradiation–integration interleaved method [Piao, 2024], the yield of delayed luminescence of the yeast as a function of the irradiation dose was acquired in a total of five measurements. The dose–response of the yield of delayed luminescence consistently revealed a decline after saturation that is not explained by the common model of delayed luminescence. We propose a modification to the common three-level model of delayed luminescence to explain the post-saturation decline.

Results:

The decline in the integrated delayed luminescence observed by our measurements is equivalent to the decline in the commonly measured starting amplitude of the delayed luminescence commonly measured. By setting a limit to the number of the material’s atomic states that can be stimulated towards delayed luminescence, the common three-level model approach can lead to a reduction in the starting amplitude of the delayed luminescence after all pumpable states have been exhausted by the pumping dose.

Conclusions:

A model is proposed for the post-saturation decline of the luminescence yield of yeast. The insights may be relevant to pump-probe applications.

Dense colloidal suspensions, whose volume fraction is larger than 5%, are encountered in various research fields, such as slurry in chemical engineering, soymilk in food science, and intravenous fat emulsion in medical pharmacy. It is significant to assess non-destructively the particle properties of the suspensions, such as particle size distribution in the sub-micrometer scale and dispersion degree. Near-infrared spectroscopy has the potential to enable the assessment based on a relation between light scattering and particle properties. The suspensions strongly scatter light. However, the assessment is still under development because the relation has not been fully understood yet. In a dense suspension, the interference of the electric fields scattered by the particles strongly influences the light-scattering properties, the so-called interference effect. Since the 1980s, many researchers have studied the interference effect in suspensions at different volume fractions using the dependent scattering theory (DST), which is the electromagnetic theory. However, the mechanism of the effect needs to be clarified because of their complicated dependence on the particle size and its distribution, optical wavelengths, etc. We developed the DST in a polydisperse system to examine a relation between the particle size distribution and light scattering properties. Our numerical results showed that the logarithmic distribution strongly influences the scattering properties. We also developed an analytic model equation for the volume-fraction dependence of the scattering properties. The equation allowed us to evaluate the interference effects on the particle properties rapidly using a single parameter. Our results are indispensable for developing near-infrared spectroscopy using scattered light.

Introduction

The dyes and pigments widely used in coloring methods are often toxic, chemically unstable at high temperatures, prone to fading under ultraviolet rays, and cannot easily color objects of sub-micron size or smaller. Photonic crystals and dielectric multi-layers have limited spatial resolution, a low refractive index, and limited coloration. In order to solve these issues, we computationally demonstrate that dynamic wavelength tuning via the photothermal deformation of a metal semi-shell on a self-assembling nanoparticle can achieve a wide color gamut.

Methods

The calculation includes the shape of the structure, thickness of the metal of the semi-shell on a core, wavelength, angle of incidence, polarization, chromaticity coordinates, and evaluation index by area on the chromaticity diagram. From the reflectance spectra calculated using the discrete dipole approximation, the tristimulus values XYZ of the light are plotted in CIELuv space. The area enclosed by all coordinate points of all the tristimulus values is determined.

The core material is fused silicon oxide, the substrate material is aluminum, and the deposition material is silver, which is known as a thermally deformable plasmonic metal. The nanosphere diameter is 100 nm, the substrate thickness is 40 nm, and the deposition thicknesses are 15, 20, and 25 nm. The semi-shell capping angle varies from 30° to 90°.

Results

The color coordinates were calculated from the reflectance spectra of nanospheres with the silver semi-shells of 15, 20, and 25 nm in thickness, plotted in CIELuv space, and yielded the gamut area of 2.3x10^-2, 2.6x10^-2, and 2.2x10^-2, respectively, at the two-dimensional density of 19.8 μm^–2.

Conclusions

Silver semi-shells of 20 nm thickness showed the largest gamut area for nanospheres with 100 nm diameters at a density of 19.8 μm^–2 on Al substrate. Further investigations at various densities will be conducted to determine the optimal structure.

Arrays of non-diffractive beams, such as Bessel beams, are important for applications in emerging fields of microscopy, photonics, nonlinear optics, optical trapping, beam shaping, laser fabrication, etc. Our study focused on the generation of an array of zero-order Bessel beams, primarily using passive optical elements, i.e., an axicon lens, telescope, and a nanosecond laser-fabricated grating. At first, one-dimensional and two-dimensional gratings of periods in the range of 120 to 800 µm and a fill factor of 0.5 were fabricated using a diode-pumped solid-state nanosecond pulsed laser with a central wavelength of 1064 nm, a nominal pulse width of 2 ns, and a maximum pulse energy of 1 mJ. The efficacy of thus-fabricated gratings in generating a Bessel beam array was then evaluated using a beam imaging setup. To do so, a Gaussian laser beam with a central wavelength of 532 nm was incident on thegrating, followed by an axicon lens and a telescope, to generate an array of micro-Bessel beams. The generated Bessel beam array was then characterised by a 4f imaging system. The radial beam profiles of micro-Bessel beams were recorded all along the beam propagation direction and were subsequently processed using MATLAB software. The retrieved physical characteristics of Bessel beams generated with an axicon only (i.e., without grating) are as follows: Bessel central core FWHM of 0.9 µm, longitudinal FWHM of 220 µm. When gratings were employed, diverging Bessel beam arrays of dimensions up to [5 x 5] were obtained. After a certain propagation distance, depending on the period of grating, zero- and first-diffraction-order Bessel beams in the array emerged, with visible Bessel characteristics. It was also observed that the characteristics of Bessel beams in an array format remained invariant from isolated Bessel beams.

The exchange bias (EB) is a unidirectional anisotropy in ferro-/antiferromagnetic (FM/AFM) systems which primarily leads to a horizontal shift of the magnetic hysteresis loop after field-cooling through the Néel temperature of the AFM. After being discovered in Co/CoO core-shell nanoparticles, it is nowadays investigated in diverse material systems. Co/CoO thin film systems are among those most widely studied. Here, we report measurements at different temperatures, below and above the Néel temperature of CoO, for different sample orientations with respect to the external magnetic field. The samples were produced by a molecular beam epitaxy growth of 8 nm Co on CoO(100) substrates after the substrates had been irradiated by heavy ions (xenon or uranium) to induce defects in the AFM. While the EB was relatively small, measurements of the bulk magnetization at low temperatures revealed unusually shaped hysteresis loops. Measurements of the magneto-optic Kerr effect, on the other hand, in which laser light interacts only with the surface magnetic layer, showed simple, nearly rectangular hysteresis loops. The transverse magnetization component was examined by changing the laser’s linear polarization direction. In this way, differences between magnetization reversal processes in xenon and uranium-irradiated samples could be shown. This study underlines the possibility to optically detect the magnetization at a sample surface, as opposed to other techniques which measure the bulk magnetization, and thus the advantage of complementary information on surface and bulk magnetization from optical and non-optical measurement methods.

Magnetization reversal processes and magnetization dynamics in general are of utmost importance for many spintronics applications. Such ultrafast dynamics can be measured, e.g., using pump–probe experiments with pulsed lasers, in which a strong pump laser excites a sudden change in the magnetization vector, leading to a precession (measured by the weak probe laser) until the relaxed state is reached again. Such measurements, however, are challenging due to the necessary overlap of both laser beams on the sample. An easier approach would be modeling this process. Such a model has been developed based on the micromagnetic simulation MagPar. Using simulated ultra-short laser pulses, we investigated a matrix of separate ferromagnetic cylindrical cells to prototype possible memory applications. The cells made of FePt were immersed in an MgO layer to satisfy adequate thermal conditions. The heat-transport problem was solved using the two-temperature model. Simulations were performed using the micromagnetic Landau–Lifshitz–Bloch (LLB) equation and the finite element method (FEM) to mimic realistic shapes of material objects as well as to include magneto-optic and thermal fields. The calculations were carried out for different distances between cells and a variety of laser pulse durations and intensities. The obtained results provide information about stability conditions for magnetization states and the possible spatial density of such memory devices.

It is commonly known that the interplay of linear and nonlinear effects
gives rise to solitons, i.e., self-trapped localized structures, in a wide range of physical
settings, including optics, Bose--Einstein condensates (BECs), hydrodynamics,
plasmas, condensed-matter physics, etc. Nowadays, solitons are considered as an
interdisciplinary class of modes, which feature diverse internal structures.
While most experimental realizations and theoretical models of solitons
have been elaborated in one-dimensional (1D) settings, a challenging issue is
the prediction of stable solitons in 2D and 3D media. In particular, multidimensional
solitons may carry an intrinsic topological structure in the form of vorticity. In
addition to the "simple" vortex solitons, fascinating objects featuring complex
structures such as hopfions, i.e., vortex rings with internal twist, have been predicted too.
A fundamental problem is the propensity of multidimensional solitons
to be unstable (naturally, solitons with a more sophisticated structure, such as
vortex solitons, are more vulnerable to instabilities). Recently, novel perspectives for the
creation of stable 2D and 3D solitons were brought to the attention of researchers in
optics and BEC. The present talk aims to provide an overview of the main results
and ongoing developments in this vast field. An essential conclusion is the benefit
offered by the exchange of concepts between different areas, such as optics, BEC, and
hydrodynamics.
A thorough survey of the topic is provided in a new book:
B. A. Malomed, "Multidimensional Solitons" (American Institute of Physics, Melville, NY, 2022).

Zopiclone is a Cyclopyrrolone sedative hypnotic drug, which considerably increases the normal transmission of gamma-aminobutyric acid (GABA) in the Central Nervous System, via modulating GABA-A-type receptors. The aim of this research was to exactly find and quantify the amount of pure Zopiclone, as an active substance in tablets. Zopiclone as a pure active substance was dissolved in Dioxane p.a. as a solvent to obtain a standard solution, 1.2 µg / mL, which showed an absorption maximum in the Ultraviolet (UV) range A = 0.231 that has corresponded to ƛ = 282 nm. Prepared pure standard solution absorbances for the studied concentration range between 0.60 μg/mL and 16.80 μg/mL were read out at the maximum absorption wavelength λ. = 282 nm of Zopiclone solutions in Dioxane p.a. as a solvent. The amount of pure Zopiclone calculated on a pharmaceutical tablet was found to be 7.214322 mg, very close to the officially stated active substance content (7.5 mg). The average allowed percentage deviation value found was (+) 3.80904 %, below the maximum official value of ± 10% stated by the Romanian, European, and International Pharmacopoeias Rules. The spectrophotometric UV analysis method was subjected to the statistical validation procedure. Sandell Sensitivity, the interference test, stability of prepared standard solutions, system precision, method precision, and analysis accuracy were found within the normal range of values. The statistical analysis has revealed a very good linearity of the UV proposed method, in the standard concentration range from 0.60 μg / mL to 16.80 μg / mL. Linear regression coefficient R² = 0.9997386 and correlation coefficient R= 0.9998693; R² > 0.9990 and R > 0.9990 were located within the normal official range of values. Standard error of the linear regression was SE = 0.0027056, SE <<1. Detection Limit LOD = 0.2848 μg / mL and Quantitation Limit LQ = 0.9493 μg / mL were found to be within the normal range of values.