Size Of Light Beam Research Articles

A modern approach to diagnostic methods of the cornea and aqueous humor of anterior chamber of the eye in patients with anterior uveitis, associated with spondyloarthritis

Anterior uveitis is the dominant clinical extra-articular manifestation of spondyloarthritis associated with the carriage of the human leukocyte antigen allele (HLA-B27), which may precede joint and spinal involvement. In 20–30% of cases, uveitis occurs with frequent relapses – up to 5–6 exacerbations per year, often has a protracted character and is poorly amenable to local anti-inflammatory therapy, which leads to a decrease in vision and a deterioration in the quality of life. Timely and accurate assessment of the severity of intraocular inflammation plays an important role in making a diagnosis and in choosing the right treatment tactics for treating anterior uveitis in patients with HLA-B27-associated spondyloarthritis. The current standard clinical approach to assessing inflammation is the presence and number of inflammatory cells in the anterior chamber aqua humor according to the SUN classification using slit lamp imaging. However, the assessment of SUN is very subjective. Moreover, the individual variability in anterior chamber cell count, which is the main diagnostic criterion for uveitis, can be exacerbated by certain testing conditions, such as the brightness of the slit lamp light bar, light beam size calibration, light source intensity. Advances in optical imaging technology, the application of the latest technologies and the improvement of already known methods offer new opportunities for an objective, accurate and quantitative assessment of inflammation. The article describes the possibilities of studying the cornea and the anterior chamber of the eye using anterior segment optical coherence tomography, confocal microscopy of the cornea and keratotopometry.

Effect of incident light beam conditions on firing characteristics of the radial-firing optical fiber tip

Effect of the incident light beam conditions, such as the beam profile, the beam size, and the incident angle on the beam propagation and the firing characteristics of the radial-firing optical fiber tip comprised of conically shaped air pocket was investigated by the simulation using the ray-tracing method. Regardless of the different Gaussian profiles of the incident beam, no significant difference in the maximum firing angle but a little increase in the firing power was found with the increase of the axial distance of the Gaussian profile. With the increase of the incident beam size, no significant difference in the maximum firing angle was found but the relative firing power decreased and the extent of the power decrease depended on the numerical aperture (NA) of the fiber. On the other hand, the incident beam angle (BA) dependence of the firing power was significant, decreased to 65.9% and 31.9% for the RFF tip of NA 0.12 and NA 0.22, respectively, with the increase of the incident BA from 0 deg to 12 deg but the maximum firing angles did not show much decrease, smaller than 5 deg. The present modified simulation considering the incident light beam size and angle clearly showed the very close power distribution of the firing beam with respect to the firing angle obtained by the experimental results.

Transverse Beam Emittance Measurement by Undulator Radiation Power Noise.

Generally, turn-to-turn power fluctuations of incoherent spontaneous synchrotron radiation in a storage ring depend on the 6D phase-space distribution of the electron bunch. In some cases, if only one parameter of the distribution is unknown, this parameter can be determined from the measured magnitude of these power fluctuations. In this Letter, we report an absolute measurement (no free parameters or calibration) of a small vertical emittance (5-15nm rms) of a flat beam by this method, under conditions, when it is unresolvable by a conventional synchrotron light beam size monitor.

21.3: Invited Paper: Non‐destructive testing for uniformity evaluation of thin film plate polarizers

Due to high technology requirements for modern display devices such as flexible, high resolution, thinner and higher transmission of polarizations, non‐destructive testing methods for evaluating quality of thin film plate polarizers are in high demand. In this paper, a system which can be used to observe defects and inhomogeneity of these thin film plate polarizers such as wide grid polarizers and thin film coating polarizers is proposed. This system consists of a collimated backlight light source, an afocal system, a polarizer, a rotation stage and a CCD camera. The collimated backlight is used to produces a collimating beam to pass through a sample under test. The afocal system shrinks the size of light beam from sample to pass through the polarizer. Based on Malus’s law, intensity of each pixel of images on CCD camera varies with the angle between the transmission axes of sample and polarizer, which is controlled by the rotation stage. Uniformity of thin film plate polarizers can be defined as polarization extinction ratio. This paper is to introduce the configuration and measurement theory, perform a setup used to implement it and present the experimental results from the uses of the setup. The results not only verify the validity but also confirm the feasibility of the proposed systems.

Vplyv sta¬tychnoho elektrychnoho polya na histerezys svitloindukovanoho perekhodu Frederiksa v nematychniy komirtsi

The influence of an external dc electric field on the hysteresis of the light-induced Fr´eedericksz transition in a nematic liquid crystal cell in the field of a light beam with a finite diameter has been studied. The external electric field orientations perpendicular to the cell surface and along it, in the direction of the incident light polarization, are considered. The dependences of the Fr´eedericksz transition thresholds for the increasing and decreasing intensities of the incident light on the electric field strength and the transversal light beam size are obtained numerically. The values of transversal light beam size and electric field strength, for which the Fr´eedericksz transition has a hysteretic character, are found. The hysteresis loop width is shown to increase if the dc electric field perpendicular to the cell surface grows. At the same time, the hysteresis loop width decreases, if the electric field is oriented along the cell surface.

Adjusting diffraction spectrum of an echelon-like grating influenced by surface plasmon of nanomaterials.

This article aims to study the varying diffraction spectrum phenomenon influenced by surface plasmon of nanomaterials. Experiments used silver nanoparticles to build the echelon-like grating as test samples, where the grating spacing of line pattern is 10 μm and within the width of silver nanoparticles line is 5 μm alternately. In this work, the silver stripes with gradient thickness were first formed line pattern alternately with glancing angle deposition and photolithography, and then annealed at temperature of 250 °C for 3 mins to fabricate the silver nanoparticles as bowl-like forms. Thicknesses of the silver nanoparticles in the echelon-like grating increase from 0 nm to 40 nm and their diameters grow from 0 nm to 35 nm with quasilinear increment simultaneously. Analyzing the varying diffraction spectrum was focused on observing the first order diffraction by changing the beam size and the probe position of the incident light. The significant results show that the bigger the incident light beam size, the larger the peak wavelength difference (Δλ) of the two first order diffractions. Moreover, the peak spectrum is shifted to long wavelength and Δλ is diminished by probing area with big size of nanoparticles.

Effect of light beam on measurements of reflectance and transmittance of turbid media with integrating sphere: Monte Carlo simulation

Integrating sphere technique is widely used to measure the total reflectance and transmittance of turbid sample, but the unavoidable light loss induces some measuring error. It has never been reported whether the error depends on the shape and size of light beam. In this paper, a convolution for computing the responses to rectangular incident light beam based on the Monte Carlo method was presented. The effects of light beam shape and size, and optical properties of sample on the measurements were addressed. The results show that the light loss with rectangular incident light beam is larger than that with circular one with the same area. The more the area of light beam, the more the light loss. And the light loss induced by the optical properties of sample is much more significant than that by the shape and size of the incident light beam.

Filamentation length of high-power sharply focused femtosecond laser radiation in air. Effect of light beam size

The results of laboratory experiments on measurements of the length and position of the filamentation zone of femtosecond GW laser radiation at wavelengths of 800 and 400 nm propagating in air under conditions of sharp external focusing are presented. Dependencies of the length of the radiation filamentation zone on its initial radius and power are studied. Qualitatively new regularity is obtained, which consists in invariance of the observed length of the beam filamentation under variations in its diameter with the assumption of equality of the initial intensities. The feature is not typical for collimated radiation and is connected with the dominance of geometrical focusing over Kerr self-focusing of a beam during filament formation.

Numerical study of the properties of optical vortex array laser tweezers

Chu et al. constructed a kind of Ince-Gaussian modes (IGM)-based vortex array laser beams consisting of p x p embedded optical vortexes from Ince-Gaussian modes, IG(e)(p,p) modes [Opt. Express 16, 19934 (2008)]. Such an IGM-based vortex array laser beams maintains its vortex array profile during both propagation and focusing, and is applicable to optical tweezers. This study uses the discrete dipole approximation (DDA) method to study the properties of the IGM-based vortex array laser tweezers while it traps dielectric particles. This study calculates the resultant force exerted on the spherical dielectric particles of different sizes situated at the IGM-based vortex array laser beam waist. Numerical results show that the number of trapping spots of a structure light (i.e. IGM-based vortex laser beam), is depended on the relation between the trapped particle size and the structure light beam size. While the trapped particle is small comparing to the beam size of the IGM-based vortex array laser beams, the IGM-based vortex array laser beams tweezers are suitable for multiple traps. Conversely, the tweezers is suitable for single traps. The results of this study is useful to the future development of the vortex array laser tweezers applications.

Proposal of an Optical Linear Sensor Using One-Side Frosted Glass

Sensors that detect the distance and the position of an object are used in a lot of fields. Among of them, the sensors that measure the shift value of an object are a large scale system, furthermore, an accurate mounting of these sensors is required. To solve these problems, this paper proposes an optical linear sensor using one-side frosted glass. This sensor can detect the position of the light irradiation point only by putting it directly on the target. For a parallel light, it is irrelevant to the distance between this sensor and the source of light because the size of light beam is unchanged according to the distance. This sensor assumes that the sensor’s surface irradiated roughly vertical with the light, and does not need a high accurate mounting. Therefore, it can be easily used.

Choice of electrode geometry for accurate measurement of organic photovoltaic cell performance

The relationship between the performance and the electrode geometry of organic photovoltaic devices was investigated to establish the proper electrode geometry for reproducible and accurate performance measurement. Photovoltaic cells (ITO∕PEDOT:PSS∕P3HT+PCBM∕LiF∕Al) having crossbar-type and island-type electrode geometries were fabricated. The crossbar-type cells varied greatly in performance depending on the illuminated light beam size relative to the overlap area of the crossbar-type electrodes due to excess photocurrent generated from the cell region outside the overlapped electrode area, where PEDOT:PSS serves as anode. We systematically investigated the relationship between the conductivity of the PEDOT:PSS, the illumination area, and the amount of excess photocurrent generated.

Spectral Ellipsometry of Multilayer ZnS/ZnSe Heterostructures

By the method of spectral ellipsometry with binary modulation of the polarization state the dispersions of the refractive index n, absorption coefficient k, and layer thickness in ZnS/ZnSe multilayer structures grown by the chemical gas‐phase deposition method from heteroorganic compounds on GaGaAs‐substrates with ZnSe buffer layers have been determined. The efficiency of local ellipsometric measurements (with a light beam size less than 150 × 500 μm) permitting mapping of the parameters of structures with A2B6 layers up to a few microns thick has been demonstrated. The optical properties of oxide layers formed on the zinc selenide surface have been investigated. Multilayer structures (ZnSe/ZnS)n/ZnSe/GaAs with a pronounced exciton absorption and specific features in the reflection spectra coinciding in energy with exciton transitions, as well as Bragg mirrors with a reflection coefficient up to 99% in the blue region of the spectrum, have been studied.