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Second and third order nonlinear optical studies of a novel thiophene substituted chalcone derivative
摘要： A noncentrosymmetric chalcone derivative (E)-1-(thiophen-2-yl)-3-(3, 4, 5-trimethoxyphenyl) prop-2-en-1-one (TTMP) was synthesized using Claisen Schmidt condensation approach and single crystals were grown using slow evaporation method. The grown TTMP crystals crystallises in orthorhombic structure with Pna21 space group. The intermolecular interactions of the TTMP crystals were envisioned by Hirshfeld surface analysis (HSA). Further, the structural conformations of the crystal were carried out by using 1H NMR, FTIR and FT-Raman spectral analysis. The UV-Vis-NIR spectrum of the sample clearly shows the prime transparency in the entire visible and near infrared region. Thermal studies (TG/DTA/DSC) of the TTMP sample shows excellent thermal stability and phase transition and also noticed that crystal was most stable up to 152.65 0C. The second harmonic generation efficiency was obtained for the crystals using Nd:YAG laser and is to be 1.93 times that of urea . The third order nonlinear absorption coefficient (β), nonlinear refractive index (n2), third-order nonlinear susceptibilities (χ (3)), second order hyper polarizability (γh) and optical limiting thresholds were determined by Z-scan technique using the Diode-Pumped Solid State (DPSS) Continuous Wave (CW) laser. The results suggest that the TTMP molecules are promising materials for optoelectronic device applications.
关键词： Hirshfeld surfaces,Optical limiting,SHG,Z-scan,Single crystal,Chalcones
更新于2025-09-09 09:28:46
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[IEEE 2018 International Conference on Communication and Signal Processing (ICCSP) - Chennai, India (2018.4.3-2018.4.5)] 2018 International Conference on Communication and Signal Processing (ICCSP) - Estimation of Peaks and Canopy Height Using LiDAR Data
摘要： 3D city modelling plays a major role in today’s smart city development. LiDAR facilitates acquisition and processing of point cloud data. The proposed plan in this paper will estimate the height of a building. LiDAR data processing is done by the software, LAS tools. In this paper the study focuses on LiDAR scan of urban scenes (buildings). Canopy Height Model (CHM) of a building is obtained which is useful in finding the height of a building, shape of the building and peak location. This can be a contribution to smart city modeling and urban development. Canopy height model for LiDAR data is obtained through classifiers and filters available in LAStools. Also this paper presents about Digital Terrain Model (DTM) and Digital Surface Model (DSM) for LiDAR point cloud data. Further the obtained CHM can be used for the application of finding the number of buildings in an area which are above a threshold height.
关键词： LAStools,DSM,Point cloud data,DTM,LiDAR scan,Canopy height model
更新于2025-09-09 09:28:46
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Effect of Aluminium doping on photoluminescence and third-order nonlinear optical properties of nanostructured CdS thin films for photonic device applications
摘要： The work presented here reports the influence of Aluminium (Al) doping on CdS thin films for the structural, morphological, optical and third-order nonlinear optical (NLO) properties. Thin films of Pure CdS and Al-doped CdS (Cd1-xAlxS) with x= 0, 0.01, 0.05 and 0.1 are prepared on the glass substrate at 350oC using the spray pyrolysis technique. The observed X-Ray Diffraction (XRD) patterns of CdS films are found to a polycrystalline hexagonal structure and are not much affected by Al doping. Also the films have been examined by Field Emission Scanning Electron Microscopy (FESEM) images. The transmittance of the CdS films is observed to be 50 to 60% in the visible region and that decreased at higher doping concentrations and with higher Al doping the direct optical band gap is decreased from 2.52 to 2.38 eV. To understand the defect states characteristics, the corresponding room-temperaturephotoluminescence (RTPL) spectra have also been taken and found the nonlinear behavior in a band to band-edge emission in the prepared samples upon Al incorporation. The sign and the magnitude of the third-order NLO properties were determined using the Z-scan technique with a continuous wave laser as the excitation source. It is observed that the material exhibit strong two-photon absorption (2PA) with the nonlinear absorption (NLA) coefficient (β) in the range of 10-4 cmW-1 and nonlinear refractive index (NRI) n2 ~10-9 cm2W-1. The third-order NLO susceptibility has found to be enhanced from 3.12 x10-5 esu to 6.36 x10-5 esu upon Al incorporation. Optical limiting characteristics of the prepared films are studied at the experimental wavelength. The results suggest that the Cd1-xAlxS is a promising material for nonlinear optical devices at 532 nm and optical power limiting applications.
关键词： photoluminescence,spray pyrolysis,Al-doped CdS thin films,Z-scan,structural,nonlinear optical properties
更新于2025-09-09 09:28:46
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The third-order nonlinear optical properties of gold nanoparticles-methylene blue conjugation
摘要： Third-order nonlinear properties of a thiazine dye (methylene blue (MB)) and a plasmonic nanoparticle (gold nanoparticles (GNPs)) have been studied by Z-scan method with a 50 mW continues wave (CW) diode pumped solid state laser (DPSSL) operating at 532 nm. The nonlinear parameters (nonlinear refractive (NLR) index (n2) and nonlinear absorption (NLA) coefficient (β)) are determined. The mechanism of the observed NLA and nonlinear refraction is attributed respectively to reverse saturable absorption (RSA) and thermal nonlinear effects. The magnitude of the measured NLR index (n2) and NLA coefficient (β) are founded to be the order of 10?8 cm2/W and 10?4 cm/W respectively. The effect of MB and GNPs on each other has been studied. Z-scan experiments for GNPs-MB conjugation shows noticeable increase in nonlinear parameters.
关键词： Z-scan method,Metal nanoparticles,Nonlinear optics,Organic dye,Nonlinear refractive index,Nonlinear absorption coefficient
更新于2025-09-09 09:28:46
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Prevalence and type of artefact with spectral domain optical coherence tomography macular ganglion cell imaging in glaucoma surveillance
摘要： Purpose The ganglion cell analysis (GCA) of the CIRRUSTM HD-OCT (Carl Zeiss, Meditec; Dublin, CA) provides measurement of the macular ganglion cell-inner plexiform layer (GCIPL) thickness. This study determined the frequency of scan artefacts and errors in GCIPL imaging in individuals undergoing HD-OCT surveillance for glaucoma. Method A total of 1439 eyes from 721 subjects enrolled in a prospective study assessing predictors of glaucoma progression underwent macular GCIPL imaging with the CIRRUS HD-OCT at recruitment. The prevalence of acquisition errors, segmentation errors, and co-morbid macular pathology was determined. Results A total of 87 (6.0%) of the 1439 scans had either acquisition errors, segmentation artefacts, or other macular pathology. The most common co-morbid macular pathology was epiretinal membrane in 2.2% of eyes. Conclusion The macular GCIPL scan was artefact free in 94% of eyes. However, epiretinal membrane and high myopia can cause scan artefact and should be considered when interpreting the results.
关键词： glaucoma,optical coherence tomography,ganglion cell analysis,scan artefacts,macular pathology
更新于2025-09-09 09:28:46
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Reverse saturable absorption behaviour of Disodium 8-Hydroxy-5,7-Dinitro-2-Naphthalenesulfonate Hydrate for nonlinear optical applications
摘要： Nonlinear optical properties, vibrational features, optical and electronic properties of organic dye Disodium 8-Hydroxy-5,7-Dinitro-2-Naphthalenesulfonate Hydrate have been studied. Spectral and electronic properties were studied by FT-IR, FT-Raman and UV-visible spectroscopic technique combined with density functional theory (DFT) and time dependent density functional theory (TD-DFT) methods respectively. The intramolecular charge transfer interactions leading to nonlinear optical response have been analyzed by natural bond orbital analysis. The kinetic stability, chemical reactivity and electrophilicity index were studied by frontier molecular orbital analysis. The first- and second hyperpolarizabilities were calculated at DFT level using B3LYP and CAM-B3LYP hybrid functional. The third-order nonlinear optical performance of the compound have been investigated experimentally by open and closed aperture Z-scan techniques. Z-scan measurements were performed using Q-switched Nd: YAG laser with 5 ns pulses at 532 nm with different dye concentrations and intensities. The Z-scan results confirm the sign of nonlinear absorption and refraction is positive. The optical limiting threshold and laser damage threshold were measured. The obtained results promote the title compound can be considered as a promising candidate for developing future optoelectronic and photonic devices.
关键词： RSA,Third-order NLO,Optical limiting,Z-Scan,DFT
更新于2025-09-09 09:28:46
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Geometry optimization of a barrel silicon pixelated tracker
摘要： We have studied optimization of the design of a barrel-shaped pixelated tracker for given spatial boundaries. The optimization includes choice of number of layers and layer spacing. Focusing on tracking performance only, momentum resolution is chosen as the (cid:12)gure of merit. The layer spacing is studied based on Gluckstern’s method and a numerical geometry scan of all possible tracker layouts. A formula to give the optimal geometry for curvature measurement is derived in the case of negligible multiple scattering to deal with trajectories of very high momentum particles. The result is validated by a numerical scan method, which could also be implemented with any track (cid:12)tting algorithm involving material e(cid:11)ects, to search for the optimal layer spacing and to determine the total number of layers for the momentum range of interest under the same magnetic (cid:12)eld. The geometry optimization of an inner silicon pixel tracker proposed for BESIII is also studied by using a numerical scan and these results are compared with Geant4-based simulations.
关键词： least squares,numerical scan,BESIII silicon pixel tracker,optimal spacing,kalman (cid:12)lter initialization,tracker geometry optimization
更新于2025-09-09 09:28:46
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Sodium Doping Effect on Optical Permittivity, Band Gap Structure, Nonlinearity and Piezoelectric Properties of PZT Nano-colloids and Nanostructures
摘要： In this research, effects of sodium atoms doping on optical properties of lead zirconate titanate (PZT) nanoparticles (NPs) are studied and compared with undoped particles. Analyses show formations of PZT nanostructures with dimensions below 30 nm. X-ray diffraction patterns show that the particle size increases and the intensity of the preferred direction decreases as the doping sodium atoms are used in the structure. Analyzing absorption spectra of the colloidal solutions shows doped particles are better absorbers at violet-green region of spectra. Also, it has been concluded that PZT NPs only have indirect optical band gap that is narrower for doped particles. Optical permittivity of the ?lms has been compared using a numerical method and shows the prominent effect of doping on real and imaginary parts of permittivity. Also, z-scan experiments have been done to measure thermo-optical and nonlinear absorption coef?cients of the nano-colloids using continue wave Nd-YAG laser illumination. Finally, sodium doping effects on piezoelectric properties of the samples are investigated using a Michelson interferometer.
关键词： z-scan,Piezoelectric,Michelson interferometer,dispersion curve,PZT nanoparticles
更新于2025-09-04 15:30:14
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Image-Forming System Design of Dynamic Targets Based on Reflecting Mirror Splicing
摘要： In this paper, the author designed an area-scan CCD reflecting mirror splicing image-forming system with area-scan CCD ICX415AL as its transducer module and this system can be used for tracking dynamic targets. By analyzing the theory of vignetting generating, the author made mathematic model of vignetting and confirmed the splicing and overlapping pixel number of the optical system. What’s more, the sequential circuit and driving power circuit of ICX415ALwas designed and the correlated noise in video signals was strained with CDS technology. Therefore, the signal-to-noise ratio (SNR) of the system was elevated. With FPGA as its core controlling module, this system postponed the splicing image-forming system to a period during which a line of CCD data are read, thus the need of real-time tracking was completely met.
关键词： dynamic targets,FPGA,area-scan CCD,reflecting mirror
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Substrate-insensitive Phased Array with Improved Circularly-polarized Scan Angle for 5G Mobile Terminals
摘要： This paper introduces a concept of a substrate-insensitive circularly-polarized phased array for 28 GHz mobile terminal applications. Each array element is a metalized cross slot antenna, which covers the bandwidth of 25-31 GHz. The performance of the designed circularly-polarized antenna is insensitive to substrate permittivity and loss tangent. By adjusting the edge effects of the phased array, the array scan angle with circular polarization can be efficiently improved. User hand effect on the array scan angle with circular polarization is investigated. The proposed mobile terminal phased array is fabricated. S parameters, radiation patterns and realized gain of all the array elements are measured. The measured results agree well with the simulations.
关键词： scan angle,mobile antenna,circular polarization,5G application,substrate-insensitive antenna
更新于2025-09-04 15:30:14