Subject of study . The absorption coefficient of fused silica plates is investigated. Aim of study. The aim is to measure the absorption coefficient of fused silica at a wavelength of 793.4 nm and investigate the spatial nonuniformity of the absorption coefficient within the aperture of optical samples. Method. The absorption coefficient is measured using a photothermal method with a Shack–Hartmann sensor. The measurement technique is based on monitoring the wavefront of radiation transmitted through a sample subjected to local thermal loading induced by laser irradiation, followed by the creation of a digital twin of the sample. Numerical simulations of the heating and deformation processes in the samples are performed using the finite-element method. The relative measurement error is 20%. Main results. The mean absorption coefficient of the three samples ranges from 0.6×10 −5 cm −1 to 1.5×10 −5 cm −1 . One of the samples exhibits pronounced spatial nonuniformity of absorption. In this sample, the ratio of the maximum to minimum absorption is 1.7. Practical significance. The obtained results can be used for the calculation of thermal aberrations in near-infrared laser optical systems employing optical elements composed of fused silica.
Subject of study. The effect of the thickness of Yb:Y 2 O 3 +ZrO 2 optical ceramics on the luminescence decay kinetics of the excited 2 F 5/2 state of Yb 3+ ions is investigated. Aim of study. The aim is to establish the relationship between the luminescence lifetime of the excited state of Yb 3+ ions in yttrium oxide optical ceramics with zirconium oxide addition and the ceramic thickness. Method. A wedge-shaped sample is selected for the experimental investigation of the effect of the transparent-ceramic thickness on the photoluminescence-decay kinetics, which substantially simplifies the study. The theoretical interpretation of the experimental results is based on the Biberman–Holstein integro-differential equation. Main results. The saturation of the photoluminescence-decay time in 5Yb:Y 2 O 3 +ZrO 2 optical ceramics as a function of sample thickness is experimentally observed. The saturation value of the luminescence-decay time reaches 1270 µs at a sample thickness of 1.2 mm. A qualitative explanation of the luminescence-lifetime saturation effect is presented on the basis of the Biberman–Holstein integro-differential equation. Practical significance. Saturation of the luminescence lifetime of the excited 2 F 5/2 state of Yb 3+ ions in 5Yb:Y 2 O 3 +ZrO 2 optical ceramics as a function of sample thickness is revealed. To achieve high laser conversion efficiency in 5Yb:Y 2 O 3 +ZrO 2 optical ceramics, the selection of sample thicknesses that do not lead to the saturation of the luminescence-decay time is recommended.
Subject of the study. This study investigates the role of the visible spectrum of everyday lighting in causing myopia in adolescents. Aim of the study . The aim of the study is to investigate the effects of narrow spectral compositions of everyday light on eye growth. Induced changes in the morphology and mechanical properties of the sclera are identified using a rapidly developing biological model. Moreover, the possibility of preventing the development of myopia in children and adolescents is determined based on experimental data. Methods. This study was conducted using Japanese quails. LEDs with narrow spectral ranges [blue (450±25nm), red (630±25nm), and yellow (560±50nm)] were used as light sources. The sizes and morphological features of the structural elements of the eye along the optical axis were studied in the native state using high-resolution acoustic methods and in vitro using light and electron microscopy. The mechanical properties of the sclera were studied using a tensile testing machine. Main results. The main results were obtained at a physiological level of illumination from birth to fertile age (45–65 days). Narrow-spectrum-induced changes in the anteroposterior axis length, especially in lens thickness, morphology, and mechanical properties of the sclera, were revealed in laboratory animals (Japanese quails) as they matured. Experimental data confirmed the formation of ametropia in the eyes when the spectrum of daily lighting shifted toward blue or red light. Practical significance. The results of the study draw attention to the spectral characteristics of everyday lighting sources, including display devices, which significantly affect the formation of ametropia in children and adolescents. Recommendations for ametropia prevention are also provided.
Subject of study. This study proposes a multispectral microscope module. Aim of study . The aim of this study is to develop and validate a multispectral device that is compatible with a standard optical microscope and provides simultaneous acquisition of spectral images of microobjects. Methods . The multispectral camera consists of identical miniature lenses that simultaneously form images of the same object on different regions of a single matrix sensor. Spectral filtering was performed using narrow-band filters placed behind each lens. The multispectral camera and microscope were optically coupled using a special coupling system. Main results . The optical system of the multispectral module was designed. The module forms eight spectral images of the same object on a single sensor in the spectral range 450–800 nm. The multispectral module was then fabricated. Agreement between the theoretically calculated and experimentally measured image-quality parameters was demonstrated. Practical significance . The developed multispectral module can be used both for spectral imaging and for analyzing the spatial distribution of the spectral properties of various microobjects. Spectral images can be acquired without scanning, enabling the use of the module for studying fast processes and recording weak signals with long exposure times.
Subject of study . This study investigates the thin films of standard and reduced graphene oxide. Aim of study. The aim of this work is to determine the dependence of the optical and morphological parameters of the films on the state of graphene oxide (standard or reduced) using ellipsometry. Method. The components of the polarization vectors were measured, and the ellipsometric angles ψ and Δ were determined. The ellipsometric equation was solved to determine the dispersion dependences of the extinction coefficient k and refractive index n and to estimate the thickness and surface roughness of the films studied. Main results. The dispersion dependences of the parameters n and k in the visible range were determined for thin films of standard and reduced graphene oxide. The thickness and roughness of the graphene-oxide films were shown to decrease after reduction. Practical significance . The ellipsometry results obtained in this work for thin films of standard and reduced graphene oxide enable the use of standard films as antireflection coatings because of their relatively low refractive index and reduced films as reflecting and absorbing electrical contacts because of their increased refractive index ( n up to 2.6) and extinction coefficient ( k up to 1.3). In addition, the proposed method can be used to determine the degree of material reduction.
