Showing papers in "Optica Applicata in 2020"
TL;DR: In this paper, the analytical expressions describing experimental data of silver, gold, copper and aluminum dielectric permittivity in a wide spectral range are presented, and a comparison of samples production techniques, the measurement methods and the experimental data from different authors led to the conclusion that the most valid data are given by MCPEAK et al. (ACS Photonics 2(3), 2015, pp. 326-333) and BABAR et al (Appl. Opt. 54(3, 2015, p. 477-481), which are close to each
Abstract: In this work, the analytical expressions describing experimental data of silver, gold, copper and aluminum dielectric permittivity in a wide spectral range are presented. A comparison of samples production techniques, the measurement methods and the experimental data of different authors led to the conclusion that the most valid data are given by MCPEAK et al. (ACS Photonics 2(3), 2015, pp. 326–333) and BABAR et al. (Appl. Opt. 54(3), 2015, pp. 477–481), which are close to each other. Thus, the analytical expressions for silver, gold, copper and aluminum dielectric permittivity spectral dependences are based on it. The spectral range in which the dielectric permittivity is represented by the corresponding analytical expression is divided into several intervals. There is a specific function for each wavelength range.
7 citations
TL;DR: In this article, the influence of using InGaN waveguides on blue laser diodes was theoretically studied using 1D drift diffusion model and 2D optical mode calculation, and it was found that an increase of injection efficiency allows to reduce the doping level in an electron blocking layer and take advantage of decreased optical losses.
Abstract: The influence of using InGaN waveguides on blue laser diodes was theoretically studied using 1D drift diffusion model and 2D optical mode calculation. Despite of the known effect of increased confinement of an optical mode, especially for long wavelengths, an unexpected influence on the efficiency of carrier injection into the active region is discussed. It is found that InGaN-AlGaN interface is crucial to achieving high injection efficiency. A numerical model is created, which describes the influence of InGaN waveguide and Mg doping of electron blocking layer on basic properties of laser diodes. It is found that an increase of injection efficiency allows to reduce the doping level in an electron blocking layer and take advantage of decreased optical losses.
6 citations
TL;DR: In this paper, a nanoslotted microring resonator with enhanced light-matter interaction has been designed, which can be used for high sensitive refractive index sensing.
Abstract: A nanoslotted microring resonator (NSMR) with enhanced light-matter interaction has been designed, which can be used for high sensitive refractive index sensing. The performance of the device is investigated theoretically based on a three-dimensional finite-difference time-domain (3D-FDTD) method. In order to achieve high figure of merit sensing, the nanoslot geometry is exploited to make the optical field strongly localized inside the low index region and overlap sufficiently with the analytes. By using the 3D-FDTD method, the proposed NSMR sensor device achieves a high Q-factor (Q > 105) and sensitivity ~100 nm/RIU (RIU – refractive index unit). Moreover, the strong light confinement introduced by the nanoslot in NSMR results in the sensor figure of merit as high as 6.73 × 103. Thus, the design we proposed is a promising platform for refractive index-based biochemical sensing and lab-on-a-chip applications.
5 citations
TL;DR: A new method of MRTD measurement without drawbacks of other methods is presented, based on a three steps measurement concept using semi-automatic objective measurements and computer simulation, which offers higher measurement speed, lower cost and typically better accuracy in comparison with the typical M RTD measurement method.
Abstract: Minimum resolvable temperature difference (MRTD) is considered as the most important parameter of thermal imagers. A new method of MRTD measurement without drawbacks of other methods is presented in this paper. Proposed MRTD measurement method coded as virtual MRTD is based on a three steps measurement concept using semi-automatic objective measurements and computer simulation. First, objective parameters of the tested thermal imager are measured. Second, software simulates this tested thermal imager and generates the image of 4-bar target of specified spatial frequency (size) and contrast (temperature difference). Third, a human observer analyses the images of the 4-bar target generated by the software on the screen of PC set and measures MRTD of the simulated thermal imager at specified set of spatial frequencies. The proposed method offers higher measurement speed, lower cost and typically better accuracy in comparison with the typical MRTD measurement method.
5 citations
TL;DR: It is shown that the Monte Carlo algorithm can provide valid and accurate results but, due to its convergence properties, it might be difficult to apply for problems with large volumes or refractive indices of scattering objects.
Abstract: The light scattering process can be modeled mathematically using the Fredholm integral equation. This equation is usually solved after its discretization and transformation into the system of algebraic equations. Volume integral equations can be also solved without discretization using the Monte Carlo algorithm, but its application to the light scattering simulations has not been sufficiently studied. Here we present the implementation of this algorithm for oneand three-dimensional light scattering computations and discuss its applicability in this field. We show that the Monte Carlo algorithm can provide valid and accurate results but, due to its convergence properties, it might be difficult to apply for problems with large volumes or refractive indices of scattering objects.
5 citations
TL;DR: This study presents a further analytical investigation into the point-ahead angle in complex satellite maneuvering environment and shows that the 2nd order point- Ahead angle has a significant detrimental impact on link stability in long distance links.
Abstract: The static bias error angle obviously affects pre-pointing links’ stability in the presence of vibration in intersatellite laser communication. The 2nd order point-ahead angle is a source of misalignment which was ignored in most solutions, and this is the concern of our paper. In this study, we present a further analytical investigation into the point-ahead angle in complex satellite maneuvering environment. Static bias error angle induced by the 2nd order point-ahead angle has been studied under different intersatellite links. The probability density function of the pre-pointing links’ outage has been derived in the presence of pointing jitter taking consideration of the static bias angle, and the link budget has also been analyzed. Simulation model of link stability has been established to verify the numerical results by the Monte Carlo method in Matlab-Simulink environment. The results have shown that the 2nd order point-ahead angle has a significant detrimental impact on link stability in long distance links. It is a neglectable factor. This work is dedicated to intersatellite laser communication system design.
5 citations
TL;DR: In this paper, the authors theoretically investigated the tight focusing of radially polarized circular partially coherent (RPCPC) beams through a high numerical aperture objective and obtained the sub-wavelength super-long optical needle and dark channel near the focus by engineering the source coherent length of the incident RPCPC beams.
Abstract: We theoretically investigate the tight focusing of radially polarized circular partially coherent (RPCPC) beams through a high numerical aperture objective. The sub-wavelength super-long optical needle and dark channel can be obtained near the focus, by engineering the source coherent length of the incident RPCPC beams. The length of the optical needle and the dark channel can be adjusted, and the obtained maximal lengths of the optical needle and the dark channel are both 22λ. The full width at half maximum of the optical needle and the dark channel are 0.6λ and 0.48λ, respectively.
4 citations
TL;DR: In this article, the authors theoretically investigate power-induced lasing state switching and bistability in a two-state quantum dot laser subject to optical injection, and they show that the injection power required for the state switching depends on the scanning route of injection power.
Abstract: We theoretically investigate power-induced lasing state switching and bistability in a two-state quantum dot laser subject to optical injection. The simulated results show that, for a free-running two-state quantum dot laser operating at the ground state under low current, a power-induced lasing state switching between the ground state and the excited state can be achieved through introducing optical injection with a frequency (winj) close to the lasing frequency of excited state (wES). The injection power required for the state switching depends on the scanning route of injection power, i.e. there may exist state bistability for the injection power within a certain region. For forward scanning injection power, with the increase of frequency detuning (ΔΩ = winj – wES), the injection power required for the state switching shows a decreasing trend accompanied by slight fluctuations. However, for backward scanning injection power, the injection power required for the state switching exhibits obvious fluctuations with the increase of ΔΩ. The width of the hysteresis loop fluctuates with ΔΩ, and the fluctuation amplitude is increased with the increase of the injection current. Additionally, the influences of the inhomogeneous broadening factor and the electron escape rate on the bistability performances are analyzed.
4 citations
TL;DR: The GARPFrMT is a nonlinear transformation used for eliminating potential insecurity existing in the linear image encryption system and is feasible and capable of withstanding several common attacks.
Abstract: An image encryption scheme based on a Gaussian apertured reality-preserving fractional Mellin transform (GARPFrMT) is proposed. The GARPFrMT was realized in the diffraction domain. The Gaussian aperture, like a soft aperture, improved the amount of light that passed through the lens compared to a hard aperture and reduced the light leakage at the edge of the lens, assisting to some extent in resisting direct attacks. In the proposed scheme, the reality-preserving transform was constructed in the diffraction domain to ensure that the cipher-text is real. The GARPFrMT is a nonlinear transformation used for eliminating potential insecurity existing in the linear image encryption system. In order to further enhance the security of the encryption system, an Arnold transform, and a bitwise XOR operation were employed for permutation and scrambling in the encryption process. Simulation results and theoretical analysis show that the proposed algorithm is feasible and capable of withstanding several common attacks.
4 citations
TL;DR: In this paper, the cross-spectral density function of a multi-Gaussian Schell-model vortex (MGSMV) beam propagating through slanted atmospheric turbulence was derived, and the influence of the MGSMV beam parameter and slant atmospheric turbulence on the spreading properties of a Gaussian beam was studied.
Abstract: The cross-spectral density function of a multi-Gaussian Schell-model vortex (MGSMV) beam propagating through slanted atmospheric turbulence was derived, and the influences of the MGSMV beam parameter and slanted atmospheric turbulence on the spreading properties of a MGSMV beam are studied. One can find that a MGSMV beam propagating in slanted atmospheric turbulence can evolve into the flat-topped beam, and a MGSMV beam with larger index N and topological charge M propagating in slanted atmospheric turbulence will lose the dark hollow center and evolve into the Gaussian beam more slowly than the MGSMV beam with smaller index N and topological charge M. It is also found that a MGSMV beam propagating in slanted atmospheric turbulence with larger strucutre parameter C will evolve into Gaussian beam faster, but the influences of zenith angle α on the spreading properties of MGSMV beam in the far field can be ignored.
3 citations
TL;DR: In this article, a cyclic interferometric configuration is chosen to maintain the stability of the operation against external vibrations, and a wave plate is inserted into the common paths to introduce an intrinsic phase difference between the orthogonal polarized beams.
Abstract: An alternative polarization phase-shifting technique is proposed to determine the thickness of transparent thin-films. In this study, the cyclic interferometric configuration is chosen to maintain the stability of the operation against external vibrations. The incident light is simply split by a non-polarizing beam splitter cube to generate test and reference beams, which are subsequently polarized by a polarizing beam splitter. Both linearly polarized beams are orthogonal and counter -propagating within the interferometer. A wave plate is inserted into the common paths to introduce an intrinsic phase difference between the orthogonal polarized beams. A transparent thin-film sample, placed in one of the beam tracks, modifies the output signal in terms of the phase retardation in comparison with the reference beam. The proposed phase-shifting technique uses a moving mirror with a set of “fixed” polarizing elements, namely, a quarter-wave retarder and a polarizer, to facilitate phase extraction without rotating any polarizing devices. The measured thicknesses are compared with the measurements of the same films acquired using standard equipment such as the field-emission scanning electron microscope and spectroscopic ellipsometer. Experimental results with the corresponding measured values are in good agreement with commercial measurements. The system can be reliably utilized for non-destructive thickness measurements of transparent thin -films.
TL;DR: This paper verifies the practicability and reliability of the algorithm by designing the visible light indoor positioning system based on fire safety rescue in natural environment and smoke environment and shows that the positioning error does not exceed 0.70 cm in smoke environment.
Abstract: From the perspective of ensuring life safety, combined with the advantages of high-speed time response and energy conservation of white light emitting diodes (LEDs), the visible light indoor positioning algorithm based on fire safety is proposed in the paper. First, the model is designed which needs three LED lights arranged in a straight line and positioned in the geographically north direction on the top of the model. Then, the proposed algorithm is discussed and analyzed when the camera is located at the center of the model and facing north, when the camera is located at the center of the model and the angle is rotated, and when the camera is located at any position of the model, respectively. It can accurately calculate the current position of the camera, its response speed is fast and the positioning accuracy is high. Furthermore, this paper also verifies the practicability and reliability of the algorithm by designing the visible light indoor positioning system based on fire safety rescue in natural environment and smoke environment. The experimental results show that the positioning error does not exceed 0.70 cm in smoke environment.
TL;DR: An automatic classification method is proposed to distinguish DME images from normal images in optical coherence tomography (OCT) retinal fundus images, revealing the ability of fine-tuning models to train non-medical images, allowing them can be classified with limited training data.
Abstract: Diabetic macular edema (DME) is the dominant reason of diabetic visual loss, so early detection and treatment of DME is of great significance for the treatment of diabetes. Based on transfer learning, an automatic classification method is proposed to distinguish DME images from normal images in optical coherence tomography (OCT) retinal fundus images. Features of the DME are automatically identified and extracted by the pre-trained convolutional neural network (CNN), which only involves fine-tuning the VGGNet-16 network without any user intervention. An accuracy of 97.9% and a sensitivity of 98.0% are acquired with the OCT images in the Duke data set from experimental results. The proposed method, a core part of an automated diagnosis system of the DME, revealed the ability of fine-tuning models to train non-medical images, allowing them can be classified with limited training data. Moreover, it can be developed to assist early diagnosis of the disease, effectively delaying (or avoiding) the progression of the disease, consequently.
TL;DR: Theoretical analysis and simulation demonstrate that the proposed image encryption scheme is feasible with a high efficiency and a strong ability of resisting various common attacks, and there are not any round-off errors in computation over finite fields, thus guaranteeing a strictly lossless image encryption.
Abstract: In this paper, we propose an image encryption algorithm based on a permutation polynomial over finite fields proposed by the authors. The proposed image encryption process consists of four stages: i) a mapping from pixel gray-levels into finite field, ii ) a pre-scrambling of pixels’ positions based on the parameterized permutation polynomial, iii ) a symmetric matrix transform over finite fields which completes the operation of diffusion and, iv) a post-scrambling based on the permutation polynomial with different parameters. The parameters used for the polynomial parameterization and for constructing the symmetric matrix are used as cipher keys. Theoretical analysis and simulation demonstrate that the proposed image encryption scheme is feasible with a high efficiency and a strong ability of resisting various common attacks. In addition, there are not any round-off errors in computation over finite fields, thus guaranteeing a strictly lossless image encryption. Due to the intrinsic nonlinearity of permutation polynomials in finite fields, the proposed image encryption system is nonlinear and can resist known-plaintext and chosen-plaintext attacks.
TL;DR: In this article, an optical signal coupling scheme for slab waveguide surface grating coupler sensors is proposed based on the use of polymer microlenses, and the feasibility of the proposed scheme is demonstrated by the experimental investigation into the optical signal couplings to the test structure of TiO2-SiO2 slab waveguera surface coupler using both types of lenses.
Abstract: We present an optical signal coupling scheme for slab waveguide surface grating coupler sensors. The proposed solution is based on the use of polymer microlenses. In this work we analyze two types of compact polymer lenses: the aspheric plano-convex lenses and Fresnel lenses. The feasibility of the proposed scheme is demonstrated by the experimental investigation into the optical signal coupling to the test structure of TiO2-SiO2 slab waveguide surface grating coupler using both types of lenses.
TL;DR: The experiment results demonstrate that the proposed image deblurring approach outperforms the existing methods for the images that are seriously blurred in direction motion.
Abstract: Sharp images ensure success in the object detection and recognition from state-of-art deep learning methods. When there is a fast relative motion between the camera and the object being imaged during exposure, it will necessarily result in blurred images. To deblur the images acquired under the camera motion for high-quality images, a deblurring approach with relatively simple calculation is proposed. An accurate estimation method of point spread function is firstly developed by performing the Fourier transform twice. Artifacts caused by image direct deconvolution are then reduced by predicting the image boundary region, and the deconvolution model is optimized by an α-confidence statistics algorithm based on the greyscale consistency of the image adjacent columns. The proposed deblurring approach is finally carried out on both the synthetic-blurred images and the real-scene images. The experiment results demonstrate that the proposed image deblurring approach outperforms the existing methods for the images that are seriously blurred in direction motion.
TL;DR: In this paper, a high-repetition-frequency Q-switched laser is realized through adopting a Nd:LaMgAl11O19 (Nd:LMA) disordered crystal as the gain material, a laser diode lasing at 796 nm as the pumped source, and a semiconductor saturable absorber mirror (SESAM) as the Qswitched device.
Abstract: High-repetition-frequency Q-switched laser is realized through adopting a Nd:LaMgAl11O19 (Nd:LMA) disordered crystal as the gain material, a laser diode lasing at 796 nm as the pumped source, and a semiconductor saturable absorber mirror (SESAM) as the Q-switched device. The output characteristics are analyzed under using different transmittance T plane mirrors as an output coupler. Without adopting SESAM, the laser is operating at a CW state, and a relatively high transmittance is helpful for achieving high output power, slope efficiency and light-to-light efficiency. For T = 7.5% and an absorbed power of 6.17 W, the output power arrives at its maximum of 1160 mW, and the corresponding slope efficiency and light-to-light efficiency are 20.71% and 18.78%, respectively. After introducing SESAM into the cavity, the laser operates at a passively Q-switched state, and the largest slope efficiency is 13.14% under T = 5.0%. Adopting five different output couplers, with the increase of the absorbed power, the pulse repetition frequencies, the pulse energies and the peak powers will ascend while the pulse widths will decline. The observed narrowest pulse width, the maximum pulse repetition frequency, the highest pulse energy and peak power are 1.745 μs, 175.88 kHz, 3.21 μJ and 1.84 W, respectively.
TL;DR: In this article, a new type of X-ray source was introduced, which was expected to generate multiple characteristic lines and achieve wavelength division multiplexing technology in Xray band.
Abstract: After the concept of X-ray communication was proposed, its application in complex electromagnetic environment has received more attention, such as data transmission in re-enter special electromagnetic condition. In this article, a new type of X-ray source was introduced firstly, which was expected to generate multiple characteristic lines and achieve wavelength division multiplexing technology in X-ray band. Then an experimental platform was built for analyzing transmission characteristics of X-ray photon in various plasma media. Finally, the calculation model for a link power equation was given. Experiment results show that transmittance of 8–18 keV X-ray signal is relatively stable, atomic numbers from 29 to 42 are the most suitable materials for wavelength division multiplexing, the X-ray communication system is expected to realize about 200 kbps data transmission rate in adjacent space.
TL;DR: In this paper, the plasmonic characteristics of SiO2-Ag and hollow core Ag nanoparticles placed on dielectric substrates are investigated and tuned to the NIR wavelength spectrum for biological applications.
Abstract: In this article, plasmonic characteristics of SiO2-Ag and hollow core Ag nanoparticles placed on dielectric substrates are investigated and tuned to the NIR wavelength spectrum for biological applications. It is shown that by placing the core-shell Ag nanoparticles on a dielectric substrate and exciting the normal plasmon mode of the nanoparticle, it is possible to obtain strong plasmon resonances at wavelengths as long as λ = 700 nm which exhibits a red shift of more than 300 nm compared to the resonance of freestanding pure Ag nanoparticles at which normal plasmon resonance wavelength shows a sensitivity of approximately 100 nm/RIU in respect to the substrate refractive index change. “SiO2-Ag and hollow core Ag nanoparticles on silicon” are optimized to exhibit a strong normal plasmon resonance at λ = 633 nm while preserving the plasmonic field enhancement intact. Finally, a three dimensional substrate for surface-enhanced Raman spectroscopy (SERS) is designed and numerically investigated. The substrate is composed of Si nanorod array decorated with the designed nanoparticles which exhibits superior characteristics such as a uniform and gapless field enhancement and an electromagnetic enhancement factor of more than 3 × 106, an order of magnitude higher than the enhancement factor for a similar structure decorated with Au nanoparticles.
TL;DR: In this article, the authors present an implementation of resonance coupling between a unidirectional air waveguide and two cavities with one-way rotating state in a two-dimensional dielectric photonic crystal and a magneto-optical photonic lattice.
Abstract: In the paper we present an implementation of resonance coupling between a unidirectional air waveguide and two cavities with one-way rotating state in a two-dimensional dielectric photonic crystal and a magneto-optical photonic crystal. We theoretically calculate the dispersion curves of the line defect waveguide and the dispersion curves of waveguide-cavity interaction, respectively. Numerical simulations show that, via waveguide-cavity coupling, a series of interesting resonance phenomena can be generated in the system. By modifying direction of the applied external magnetic field, storing and discharging of photonic energy can be realized. Our work may provide a practical and useful guidance for optical communications.
TL;DR: Raw data from the ORA enables definition and numerical analysis of new parameters, characterizing every measurement, which can be successfully used for describing an individual eye and differentiating between some specific groups of patients.
Abstract: Purpose: Presented study describes new parameters calculated from the Ocular Response Analyzer (ORA) raw data. Such an approach can increase the applicability of the ORA in ophthalmic diagnosis. Among many proposed and examined by us parameters from raw data of the air pressure and applanation curves, only a few were chosen and then applied for characterizing a selected group of patients. Methods: The study included healthy subjects in a control group and patients divided into 2 groups: suspect and glaucoma. A series of four ORA measurements were taken from each subject. The raw ORA data were numerically analyzed and new parameters were calculated from the ORA curves for each measurement. Comparative analysis was carried out for the newly proposed parameters (and original parameters from the ORA device). Results: This interesting finding is that the new parameters showed a statistically significant ability to distinguish the glaucoma suspect group from healthy and glaucomatous patients. Moreover comparable or higher repeatability than for IOPg and CH was obtained. Conclusion: Raw data from the ORA enables definition and numerical analysis of new parameters, characterizing every measurement, which can be successfully used for describing an individual eye and differentiating between some specific groups of patients.
TL;DR: In this paper, the effect of emulsion concentration on the possibility of its objective characterization using synchronous fluorescence spectra was studied and the similarity of spectra at various oil concentrations was analyzed.
Abstract: The development of petroleum extraction and transport technology does not ensure complete isolation of these substances from the natural environment. This problem is exacerbated by the location of mining equipment on the sea shelf and the fact that numerous submarine pipelines, tankers and handling terminals can also emit oil pollution. Therefore, the possibility of detecting oil dispersed in the water is particularly important. This paper reports the efforts to identify methods of characterization of the water containing the crude oil emulsion in a very low concentration (a few to several tens of ppm). Due to this, the effect of emulsion concentration on the possibility of its objective characterization using synchronous fluorescence spectra was studied. The similarity of spectra at various oil concentrations was analysed. It has been shown that the stabilization of the shape of synchronous fluorescence spectra occurs at relatively low oil concentrations.
TL;DR: In this article, a double-layer three-port grating was proposed for beam splitter with high efficiency under TE polarization and TM polarization, where the incident grating region was composed of fused silica and Ta2O5.
Abstract: In this paper, a novel double-layer three-port grating is described. The incident grating structure is in the second-order Littrow configuration. The grating region is composed of fused silica and Ta2O5. The designed grating beam splitter has high efficiency under TE polarization and TM polarization, respectively. The efficiency of two polarizations is more than 90%. In addition, compared with a single-layer three-port grating, this new beam splitter has good fabrication tolerance and incident bandwidth. Therefore, the optimized structure has a good application value.
TL;DR: In this article, the influence of the quantum well and barrier thicknesses on optical properties of InGaAs/AlInAs superlattices was reported, where six different structures of In0.53Ga0.47As/ Al0.48In0.52As were grown by low pressure metal organic vapour phase epitaxy (MOVPE).
Abstract: In the presented work, the influence of the quantum well and barrier thicknesses on optical characteristics of InGaAs/AlInAs superlattices was reported. Six different structures of In0.53Ga0.47As/ Al0.48In0.52As superlattices lattice-matched to InP were grown by low pressure metal organic vapour phase epitaxy (LP-MOVPE). Optical properties of the obtained structures were examined by means of photoluminescence spectroscopy. This technique allows quick, simple and non-destructive measurements of radiative optical transitions in different semiconductor heterostructures. The analysis of recorded photoluminescence spectra revealed the influence of the quantum well and barrier thicknesses on the emission line energy.
TL;DR: In this article, the authors presented the idea to use diffractive structures designed to work for the substantially increased THz frequency range, and analyzed mono and multi-focal lenses forming pointlike foci as well as axicon and light sword optical elements focusing THz radiation into line segments located along the optical axis.
Abstract: Thin and lightweight achromatic focusing elements with F-number close to 1 are desirable in many practical applications. We present the idea to use diffractive structures designed to work for the substantially increased THz frequency range. The paper analyses monoand multi-focal lenses forming point-like foci as well as axicon and light sword optical elements focusing THz radiation into line segments located along the optical axis. We consider diffractive elements in a form of the first and the second order kinoforms having various thicknesses. Designed and fabricated elements were numerically and experimentally examined to verify their achromatic functioning. We present point spread functions (XY scans) and 2D energy maps (XZ scans) for different THz frequencies. Moreover, a diagram of chromatic aberration is created by registering energy distribution along the optical axis for different frequencies. The distance corresponding to the highest energy is chosen for each frequency. Therefore, we can compare broadband working of designed structures. The spherical lens coded as kinoform of the second order provides the best broadband functioning, however it is two times thicker than structures providing extended depth of focus (light sword and axicon) working with slightly smaller efficiency but being much thinner.
TL;DR: The results show that merit function SMD2 to determine the depth of objects is more accurate and suitable for real-time application.
Abstract: We proposed a method using a merit function to determine the depth of objects in computational integral imaging by analyzing the existing methods for depth extraction of target objects. To improve the resolution of reconstructed slice images, we use a digital camera moving in horizontal and vertical direction with the set interval to get elemental images with high resolution and bilinear interpolation algorithm to increase the number of pixels in slice image which improves the resolution obviously. To show the feasibility of the proposed method, we carried out our experiment and presented the results. We also compared it with other merit functions. The results show that merit function SMD2 to determine the depth of objects is more accurate and suitable for real-time application.
TL;DR: In this paper, the authors describe the method of measuring surface topography with application of BRDF (bidirectional reflectance distribution function), ellipsometry and spectrophotometry.
Abstract: The presented work describes the method of measuring surface topography with application of BRDF (bidirectional reflectance distribution function), ellipsometry and spectrophotometry. This non-contact method enables measurement and analysis of large area surfaces, such as plasters and facades. A standard method of topography analysis does not describe sufficiently all of the interesting features. The visual aspect of the surface evaluation is very important from the functional and utilitarian point of view. The proposed methods of surface analysis enable not only the quantitative evaluation but also indirectly the qualitative properties (visual aspects).
TL;DR: In this article, a material with a refractive index of 2.41 was obtained and in a wide spectral range it was possible to reduce the reflection from the silicon surface below 5%.
Abstract: Titanium dioxide thin films have been deposited on silicon wafers substrates by an atomic layer deposition (ALD) method. There optical parameters were investigated by spectroscopic ellipsometry and UV/VIS spectroscopy. A material with a refractive index of 2.41 was obtained. Additionally, in a wide spectral range it was possible to reduce the reflection from the silicon surface below 5%. The Raman spectroscopy method was used for structural characterization of anatase TiO2 thin films. Their uniformity and chemical composition are confirmed by a scanning electron microscope (SEM) energy dispersive spectrometer (EDS).
TL;DR: In this article, a series-connected one-dimensional photonic crystal nanofiber cavity sensor (1-D PC-NCS) and 1-D PLSN bandgap filter (1DPC-NBF) were proposed to obtain a single air mode with an extinction ratio of 58.64 dB.
Abstract: We propose a design of series-connected one-dimensional photonic crystal nanofiber cavity sensor (1-D PC-NCS) and one-dimensional photonic crystal nanofiber bandgap filter (1-D PC-NBF). The proposed structure can get a single air mode for refractive index sensing with its extinction ratio of 58.64 dB. It filters out the high order mode and reduces the interaction between signals. By 3D FDTD, the calculated sensitivity is 848.18 nm/RIU (RIU – refractive index unit). Compared with general silicon on-chip nanobeam cavity, the sensitivity is increased by eight times. The additional 1-D PC-NBF will not change the sensitivity and the position of the resonance wavelength. Therefore, the new design we propose addresses the issue of crosstalk, and can be applied to ultra -high sensitivity index-based gas sensing and biosensing without the need for complicated coupling systems.
TL;DR: A method for image analysis using asynchronous delay-tap sampling (ADTS) technique and convolutional neural networks (CNNs), allowing simultaneous monitoring of many phenomena occurring in the physical layer of the optical network.
Abstract: The article presents a method for image analysis using asynchronous delay-tap sampling (ADTS) technique and convolutional neural networks (CNNs), allowing simultaneous monitoring of many phenomena occurring in the physical layer of the optical network. The ADTS method makes it possible to visualize the course of the optical signal in the form of characteristics (so-called phase portraits), which change their shape under the influence of phenomena (including chromatic dispersion, amplified spontaneous emission noise and other). Using the VPIphotonics software, a simulation model of the ADTS technique was built. After the simulation tests, 10000 images were obtained, which after proper preparation were subjected to further analysis using CNN algorithms. The main goal of the study was to train a CNN to recognize the selected impairment (distortion); then to test its accuracy and estimate the impairment for the selected set of test images. The input data consisted of processed binary images in the form of two-dimensional matrices, with the position of the pixel. This article focuses on the analysis of images containing simultaneously the phenomena of chromatic dispersion and optical signal to noise ratio.