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Investigating the nonlinear optical properties of poly eosin-Y phthalate solution under irradiation with low power visible CW laser light
摘要： In this work, the study of the nonlinear optical properties of poly eosin-Y phthalate solution using the diffraction ring patterns and the Z-scan methods are presented. The diffraction ring patterns were observed when a low power laser beam of wavelength of 473 nm passed through the poly eosin-Y phthalate solution. It was found that the number of rings and diameter of the outer-most ring in each pattern depends on the incident intensity of the laser beam and type of the beam wave front. The Fresnel-Kirchhoff diffraction integral theory was used to simulate the diffraction ring patterns and found good agreement with experimental results. Both diffraction ring patterns and closed aperture Z-scan techniques were used to calculate the nonlinear refractive index, while open aperture Z-scan was used to calculate the nonlinear absorption coefficient of the poly eosin-Y phthalate solution. The possibility of using the sample as an optical limiter is tested.
关键词： Nonlinear refractive index,Self-phase modulation,Optical limiting,Diffraction ring pattern,Z-scan technique,Thermal nonlinearity
更新于2025-09-12 10:27:22
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[IEEE 2019 IEEE 21st International Workshop on Multimedia Signal Processing (MMSP) - Kuala Lumpur, Malaysia (2019.9.27-2019.9.29)] 2019 IEEE 21st International Workshop on Multimedia Signal Processing (MMSP) - 3D Facial Expression Recognition Based on Multi-View and Prior Knowledge Fusion
摘要： This paper presents a novel multi-view convolutional neural network (CNN) model for 3D facial expression recognition (FER). In contrast to existing deep learning-based 3D FER approaches that mainly learn the expressions from frontal facial attribute images, the proposed model incorporates multi-view and facial prior information of the observed 3D face into the learning process. This information is jointly trained in an end-to-end manner to predict the emotion of the input 3D face model. The experiments on public 3D facial expression datasets show that training the CNN with additional information from different views and facial prior knowledge would result in learning more discriminative features as against from a single view. Our model outperforms the state-of-the-art 3D FER methods in term of recognition accuracy indicating its effectiveness. Moreover, the improvement of the proposed model is displayed more clearly in the discrimination of low- intensity facial expressions.
关键词： facial expression recognition (FER),convolutional neural network,3D face scan
更新于2025-09-12 10:27:22
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Investigation on Ti6Al4V laser metal deposition using Taguchi based grey approach
摘要： An optimization of laser metal deposition process considering tensile strength, clad hardness, clad grain size and clad porosity as performance characteristics were investigated. The influence of laser power and laser scan speed on the thermal gradient and cooling rate with regard Ti6Al4V powder coating on Ti6Al4V substrate was focused. Taguchi’s experimental design approach is employed for planning the experiments and analyzing the dependency of input variables on desired performance measures such as micro hardness, tensile strength, porosity and grain size. The laser scan speed is found as the dominant factor on the clad hardness while laser power has the influencing effect on grain size of the substrate. GRA is opted for determining the multi performance machining characteristics of laser metal deposition process. The experimental outcomes reveal that the proposed method of multi objective optimization considerably enhances the multi performance machining characteristics.
关键词： Laser metal deposition,Ti6Al4V,Grain size,Thermal gradient,Grey relational approach,Laser scan speed
更新于2025-09-12 10:27:22
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Facile preparation of high fluorescent carbon quantum dots from orange waste peels for nonlinear optical applications
摘要： A facile and eco‐friendly hydrothermal method was used to prepare carbon quantum dots (CQDs) using orange waste peels. The synthesized CQDs were well dispersed and the average diameter was 2.9 ± 0.5 nm. Functional group identification of the CQDs was confirmed by Fourier transform infrared spectrum analysis. Fluorescence properties of the synthesized CQDs exhibited blue emission. The fluorescence quantum yield of the CQDs was around 11.37% at an excitation wavelength of 330 nm. The higher order nonlinear optical properties were examined using a Z‐scan technique and a continuous wave laser that was operated at a wavelength of 532 nm. Results demonstrated that the synthesis of CQDs can be considered as promising for optical switching devices, bio‐scanning, and bio‐imaging for optoelectronic applications.
关键词： Z‐scan analysis,fluorescence quantum yield,CQDs,HR‐TEM,hydrothermal method
更新于2025-09-11 14:15:04
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[IEEE 2018 IEEE International Workshop on Metrology for the Sea; Learning to Measure Sea Health Parameters (MetroSea) - Bari, Italy (2018.10.8-2018.10.10)] 2018 IEEE International Workshop on Metrology for the Sea; Learning to Measure Sea Health Parameters (MetroSea) - Preliminary assessment of Photogrammetric Approach for detailed dimensional and colorimetric reconstruction of Corals in underwater environment
摘要： The use of 3D scan technologies to provide 3D color models of some bio-constructor organisms without removing them from the sea represents a valuable contribution for the preservation of current marine flora and fauna. The necessity to perform accurate measurements of volume, surface area and other morphometric characteristics is to increase the knowledge about the habitat-forming species. In this way, it is possible to describe the modification they made to the seabed topography, to monitor their shape modification according to local environmental conditions and evaluate 3D structure and color of some species sensitive to climate changes. The necessity of working in an environment characterized by different light conditions and particulate concentrations, the need of having high-performance sealing and, last but not least, the portability guarantee have limited the range of possible measurement techniques among those available for 3D shape reconstruction. Within this context, the idea underlying this research activity is to adopt photogrammetric technique for underwater surveys. In particular, a comprehensive and detailed analysis of a small object in and outside-water is performed in lab-scale tests by means of two different camera lenses, to pinpoint the effectiveness and the weakness of the solution identified. Another contribution of this paper is the uses of a color correction algorithm in order to correct the scene illumination, improving the 3D reconstruction of the detected objects. It is shown the capability of the algorithm to solve the color mismatch problem in multi-view color images. Results show the 3D models with details very well reconstructed both in and outside-water. The image pre-processing step drastically improve the matching points recognition and the reconstruction of the whole object independently to environmental illumination changes.
关键词： underwater 3D reconstruction,detailed scan,image processing,photogrammetry,color correction
更新于2025-09-11 14:15:04
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Pyrene Based NLOphoric D‐π‐A‐π‐D Coumarin‐Chalcone and Their Red Emitting OBO Difluoride Complex: Synthesis, Solvatochromism, Z‐scan, and Detailed TD‐DFT Studies
摘要： NLOphoric D-π-A-π-D coumarin chalcone 5 and their BF2 complex 6 were designed, synthesized and characterized through Mass,13C-NMR, and 1H-NMR analysis. Their Photophysical properties are extensively studied in solvents of different polarity. On BF2 complexation of coumarin chalcone shows highly red shift in absorption and emission spectra compared to uncomplexed coumarin chalcone. Positive solvatochromism observed which is well supported by linear and multilinear regression analysis. For BF2 complexed coumarin-chalcone 6 the solvent dipolarity (CSdP) is the main factor responsible for slightly red shift in absorption spectra, and also for the highly red-shift in emission spectra. Frontier molecular orbital, molecular electrostatic potential and Generalized Mulliken-Hush analysis revealed intramolecular charge transfer in these compounds. Nonlinear optical (NLO) properties for compounds 5 and 6 were studied by solvatochromic and computational method. The linear polarizability (α), first-order hyperpolarizability (β) and second-order hyperpolarizability (γ) of compounds were studied by the time dependent density functional theory using three different functionals namely B3LYP, BHHLYP and CAM(cid:0) B3LYP with the 6–31 G (d) basis set. BF2 complexed compound 6, show higher values for αe + αv as well as βe+βv compared to compound 5. Third order nonlinear optical susceptibility (χ(3)) of these compounds obtained by Z-scan analysis. Third-order (χ(3)) non-linear optical properties of BF2 complexed coumarin-chalcone 6 were observed to be several times higher than those of the uncomplexed coumarin-chalcone 5 these justify the design approach.
关键词： NLOphoric,Z-Scan,positive solvatochromism,pyrene-chalcones,TD-DFT,solvatochromic NLO
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Video-Rate Phase Retrievals from Dispersion Scan Traces using Artificial Neural Networks
摘要： The full characterization of ultrashort pulses is crucial for all their applications. Lately, the dispersion scan (d-scan) technique has been developed, which stands out by its simplicity [1, 2]. Therefore, it is a promising candidate for a low-maintenance pulse characterization technique. The reconstruction of the spectral phase from a d-scan measurement relies on optimization algorithms [3, 4]. Considering the fact that the spectral phase of the pulses is directly imprinted on the d-scan trace, the phase reconstruction can also be regarded as an image recognition task. During the last few years, artificial neural networks have shown excellent performance in different fields, e.g. image recognition [5]. Here we present the retrieval of spectral phases from d-scan traces using deep neural networks (DNN) that is more than 3000 times faster than conventional optimization algorithms (16 ms) [6]. Our DNN is an optimized variant of the DenseNet-BC architecture that has already shown great performance in image recognition tasks [7]. Training our shallow variant of the DenseNet takes only 12 h using a low cost GPU (NVIDIA GeForce GTX 1080 Ti). After training with up to 1.5 × 106 different, randomly generated traces, we can employ the network for reconstruction of the spectral phases from a d-scan traces. Fig. 1(a) and (b) show a randomly generated d-scan trace and its corresponding reconstruction, respectively. The spectral intensity (black curve), the original spectral phase (blue curve) and the retrieved phase (red dashed curve) are depicted in Fig. 1(c). Additionally, Fig. 1(d) compares the original and the reconstructed temporal pulse shapes (same color code). The consistency between the original and the retrieved phases and their corresponding temporal shapes shows the excellent performance of the DNN. Furthermore, to prove the fidelity of phase reconstruction from experimentally measured traces, we retrieved the spectral phase from a Ti:sapphire based amplifier system [8]. Compared to a differential evolution optimization algorithm, we observe identical full width at half maximum pulse durations, as well as nearly identical temporal pulse shapes. We believe that DNNs combined with single-shot d-scan setups [9] enable video-rate measurements with an inherent error estimation due to the redundancy in the data.
关键词： deep neural networks,spectral phase retrieval,dispersion scan,ultrashort pulses
更新于2025-09-11 14:15:04
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Benzothiazole pyrazole containing emissive azo dyes decorated with ESIPT core: Linear and non linear optical properties, Z scan, optical limiting, laser damage threshold with comparative DFT studies
摘要： Positional isomers of "benzothiazoles-pyrazole based azo dyes containing separate with ESIPT core" are analyzed for their "linear and non-linear optical (NLO)" properties. Dyes are emissive in ACN having Stokes shift in the range of 75 nm. Spectroscopic properties are further utilized to calculate band gap by CV. Band gap obtained by DFT and cyclic voltammetry (CV) are in good agreement with each other. Vertical excitation in six different functionals is compared with experimental absorption maxima. Non-linear absorptive coef?cient (b), nonlinear refractive index (?2), third-order non-linear optical suscep- tibility (c3) and optical limiting (OL) in acetone, ethanol and DMSO are obtained using Z-scan technique and results are appreciable than previously reported dyes. Satisfactory laser damage threshold (LDT) values are in the range of 7.9e9.7 (cid:1) 1013 W/m2. TGA study indicates that these compounds are useful in several high-temperature processes in the construction of electronic and optical devices. The geometry of the dyes are optimized at "B3LYP/6-311 t G (d,p) level". "Molecular Electrostatic Potential" (MEP), "Frontier Molecular Orbitals" (FMO) are presented using "Density Functional Theory (DFT)" to gain structural insights. Relatively new electrophilicity descriptor- "Hyperhardness" for both the molecules are calculated which suggests the stability of molecules. Global hybrid (GH) functional (B3LYP, BHandHLYP) and range separated hybrid (RSH) (CAM-B3LYP, uB97, uB97X, and uB97XD) functional are used to calculate linear and NLO properties. uB97 is a more suitable functional observed for determining bo and g. Direct relation in-between "dipole moment" (m) and "linear polarizability" (a) is also presented. These dyes can emerge as attractive NLOphores in optoelectronic applications.
关键词： ESIPT,NLO,Z-scan,LDT,DFT,Emissive azo dyes,Benzothiazole-pyrazole
更新于2025-09-11 14:15:04
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[IEEE 2018 IEEE Symposium on Product Compliance Engineering - Asia (ISPCE-CN) - Shenzhen, China (2018.12.5-2018.12.7)] 2018 IEEE Symposium on Product Compliance Engineering - Asia (ISPCE-CN) - Segmentation of Precast Concrete Elements in Outdoor Laser Scan Data via Image Processing
摘要： Image processing technology has many applications, such as medical image processing, face detection and vehicle detection. At present, in the field of civil engineering, there are many difficulties in the intelligent manufacturing process of precast concrete elements (PCEs), such as non-contact measurement of PCEs using 3D laser scanners. In order to solve the data acquisition problem of PCE data in outdoor laser scan data, this paper is the first attempt to map a 3D laser scan data into 2D images, and then use image processing technology to realize the segmentation of outdoor laser scan data which contains the PCE data. We convert the processed objects from laser scan data to images, and computation time is reduced effectively as a result. This segmentation technique includes four steps, data preprocessing, 3D laser scan data mapping into 2D images, image processing for segmentation and laser scan data processing. Finally, the results obtained by experiments prove the effectiveness of this segmentation technique.
关键词： Image processing,Segmentation technique,Outdoor laser scan data,Precast concrete element
更新于2025-09-11 14:15:04
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Growth, Optical, Thermal, Mechanical, Laser Damage Threshold and Electrical Polarizability of Cadmium Chloride Doped l-Alanine (LACC) Single Crystal for Optoelectronic Applications
摘要： L-Alanine doped with cadmium chloride crystal was grown by slow evaporation technique in an optimum condition using de-ionized water as solvent. Single crystal x-ray diffraction analysis was carried out to con?rm the unit cell parameters and cell volume. The presence of amine vibrations and carboxylic acid vibrations af?rm the presence of L-alanine in grown material by Fourier transform infrared (FT-IR) analysis. The ultraviolet visible near-infrared region (UV–Vis-NIR) spectrum revealed that the grown crystal has a lower cut-off wavelength at 246 nm and has high transmission in the entire visible region. Further, energy gap and the refractive index of the crystal were also calculated. Thermo-gravimetric (TG) and differential thermal analysis (DTA) were carried out, and it is estimated that the material is thermally stable up to 233°C and the melting point of the crystal was found to be 298°C. The mechanical strength of the material is estimated for various loads using Vicker’s microhardness and it reveals that material belongs to a soft material category. The electrical polarizability was calculated using known values such as valence electron, molecular weight, energy gap and density of the material. Z-scan technique for nonlinear studies was carried out on a LACC crystal to determine the third order nonlinear absorption (b), nonlinear refractive index (n2) and third order nonlinear susceptibility (v(3)) using continuous wave Nd: YAG laser of 532 nm. Grown crystal shows that the material is very much suitable for second harmonic generation for frequency conversion applications.
关键词： electrical polarizability,LDT,Z-scan technique,X-ray diffraction,FT-IR,microhardness,TG-DTA
更新于2025-09-11 14:15:04