- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Solving method without integration of some differential equation systems for coherent dynamics of quantum media excited by laser radiation
摘要： A pragmatic mechanism to obtain exact analytical solutions of equations describing the coherent dynamics of quantum multilevel systems by laser radiation is implemented. The technique shows interesting features and significant connections between different mathematical structures for constructing exact solutions for a large family of quantum systems, and is based on discrete orthogonal polynomials which are used to express the Fourier spectra of the probability amplitudes of an excited quantum system.
关键词： Discrete orthogonal polynomials,Dynamical systems in quantum mechanics,Exact solutions,Discrete Fourier transform
更新于2025-09-12 10:27:22
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Real-time characterization of spectral instabilities in a mode-locked fibre laser exhibiting soliton-similariton dynamics
摘要： the study of dissipative solitons in mode-locked lasers reveals a rich landscape of interaction dynamics resulting from the interplay of nonlinearity, dispersion and dissipation. Here, we characterize a range of instabilities in a dissipative soliton fibre laser in a regime where both conventional soliton and similariton propagation play significant roles in the intracavity pulse shaping. Specifically, we use the Dispersive fourier transform technique to perform real-time spectral measurements of buildup dynamics from noise to the generation of stable single pulses, phase evolution dynamics of bound state “similariton molecules”, and several examples of intermittent instability and explosion dynamics. These results show that the instabilities previously seen in other classes of passively mode-locked fibre lasers are also observed in the presence of strong nonlinear attraction of similariton evolution in an optical fibre amplifier.
关键词： explosion dynamics,Dispersive fourier transform,similariton molecules,intermittent instability,dispersion,nonlinearity,mode-locked lasers,dissipative solitons,dissipation
更新于2025-09-12 10:27:22
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[IEEE 2019 2nd International Conference on Electrical Materials and Power Equipment (ICEMPE) - Guangzhou, China (2019.4.7-2019.4.10)] 2019 2nd International Conference on Electrical Materials and Power Equipment (ICEMPE) - Elemental Analysis of Aged Composite Insulators Based on Laser Induced Breakdown Spectroscopy
摘要： This paper aims at proposing a novel 2D non-linear phase decomposition of images, which performs the image processing tasks better than the traditional Fourier transformation (linear phase decomposition), but further, it has additional mathematical properties allowing more effective image analysis, including adaptive decomposition components and positive instantaneous phase derivatives. 1D unwinding Blaschke decomposition has recently been proposed and studied. Through factorization it expresses arbitrary 1D signal into an infinite linear combination of Blaschke products. It offers fast converging positive frequency decomposition in the form of rational approximation. However, in the multi-dimensional cases, the usual factorization mechanism does not work. As a consequence, there is no genuine unwinding decomposition for multi-dimensions. In this paper, a 2D partial unwinding decomposition based on algebraic transforms reducing multi-dimensions to the 1D case is proposed and analyzed. The result shows that the fast convergence offers efficient image reconstruction. The tensor type decomposing terms are mutually orthogonal, giving rise to 2D positive frequency decomposition. The comparison results show that the proposed method outperforms the standard greedy algorithm and the most commonly used methods in the Fourier category. An application in watermarking is presented to demonstrate its potential in applications.
关键词： hardy space,Fourier transform,adaptive Fourier decomposition,greedy algorithm,Nevanlinna factorization,unwinding Blaschke decomposition
更新于2025-09-11 14:15:04
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Wavelet Transform Subspace-based Optimization Method for Inverse Scattering
摘要： Inspired by the new fast Fourier transform subspace-based optimization method (NFFT-SOM), wavelet transform subspace-based optimization method (WT-SOM) that represents minor part of induced current by wavelet bases is proposed in this paper to solve the inverse scattering problem. This paper provides a guideline for choosing the appropriate bases for the minor part of induced current in the inverse problem, and it is shown that Daubechies 20 (D20) wavelet bases and Fourier bases are better choices than Daubechies 4 (D4) wavelet bases and Haar wavelet bases. Compared to NFFT-SOM, it is shown that WT-SOM can be used to improve the resolution of a specific region of a scatterer. By using only part of the detail coefficients, the convergence rate of the algorithm can be greatly accelerated compared to using all the detail coefficients. For a piecewise constant scatterer, additive total variation (TV) regularization is used together with WT-SOM. We prove that TV-regularized WT-SOM has exactly the same performance when the contrast is represented by no matter natural pixels bases, Fourier bases, or wavelet bases.
关键词： wavelet transform,optimization method,Fourier transform,inverse scattering
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) - Optical Soliton Molecular Complexes in Ultrafast Fiber Lasers
摘要： Optical soliton molecules are under intense research focus, owing in particular to the interesting analogies between their self-assembly and internal dynamics, and those of matter molecules. Two interacting dissipative solitons can form a soliton-pair molecule, which can behave as a robust entity traveling around the cavity for an indefinite time [1]. The internal oscillatory dynamics of soliton molecules can be compared to molecular vibrations, though they are fundamentally different [2,3]. The recent experimental investigations in Refs. [2,3] have been enabled by the dispersive Fourier transform (DFT) technique, which allows recording spectral measurements at multi-MHz frame rates. They showed the existence of various oscillatory dynamics among soliton-pair and soliton-triplet basic molecules. Following the analogy between light and matter molecules, we now consider the experimental possibility of forming a “soliton molecular complex” (SMC), namely, a higher-order pattern obtained by the stable bonding of several soliton molecules, and investigating its complex internal dynamics. Such structure implies two different bond types, a strong one within each soliton molecule, and a weaker one to maintain the overall structure. We here report the first real-time recording and analysis of several internal dynamics of SMCs, which support this new structural concept. We shall describe our results concerning the dynamics of the fundamental SMC, made of two soliton-pair molecules, or (2+2)-SMC. The experimental configuration is based on an erbium-doped fiber ring laser, which is mode-locked by means of nonlinear polarization evolution (NPE), and its output spectrum analyzed in real-time through DFT [4]. The formation of various SMC is controlled by the laser output power and the tuning of NPE through the orientation of intracavity waveplates, in an experimental procedure which utilizes the hysteretic laser behavior in the multi-pulse regime. SMCs with sliding-phase and oscillating-phase dynamics have been characterized by real-time spectral interferometry measurements, thus revealing the dynamics of the major internal degrees of freedom of the complexes, namely the dynamics of the relative temporal and phase separations between the different soliton constituents. Numerical simulations confirm the experimental observations and offer an additional insight into the understanding of the complex dynamics of SMCs. By showing that soliton molecules can form various bonds according to the distance between soliton constituents, which we can manipulate, this work opens the way to the manipulation of large-scale optical- soliton complexes, which can be extended to other photonic platforms, such as microresonators.
关键词： soliton molecular complex,Optical soliton molecules,nonlinear polarization evolution,ultrafast fiber lasers,dispersive Fourier transform
更新于2025-09-11 14:15:04
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Spectroscopic characterization at THz frequencies of glucose-based biomaterials: paramylon, paramylon-ester and cellulose
摘要： The terahertz (THz) spectroscopy of paramylon (β-1,3-glucan) and paramylon-ester extracted from microalgae called as Euglena have been studied by Fourier Transform Infrared Spectrometer (FT-IR) in a frequency range from 0.3 to 9 THz. The absorption spectra of paramylon were analyzed by comparing them with cellulose that has a similar long-chain -(C6H10O5)n-structure with paramylon. The differences in absorption features between paramylon and cellulose may be caused by their different chain structures. The broad absorption spectra of paramylon-ester can be attributed to some sort of disorder of long-chain molecular vibration modes due to the substitution of propionyl chloride and long-chain acid chloride by esterification.
关键词： microalgae,Euglena,paramylon-ester,paramylon,cellulose,terahertz spectroscopy,Fourier Transform Infrared Spectrometer
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) - A Hyperspectral Camera Based on a Birefringent Ultrastable Common-Path Interferometer
摘要： Spectral imaging (or imaging spectroscopy) is a powerful technique that acquires the complete light spectrum at each point in the image of a scene. This can be obtained by a wide variety of methods. A first approach relies on placing band-pass spectral filters in front of a monochrome camera, thus acquiring the hyperspectral image at a limited number of spectral bands. A second class of techniques collects the whole continuous spectrum of each image point; an example is the combination of a dispersive spectrometer with a raster-scanning approach, at the cost of high losses imposed by the entrance slit of the spectrometer. An alternative approach combines imaging with Fourier-transform (FT) spectrometry [1]. This technique can retrieve in parallel the spectra for all pixels in a scene and is hence suited for imaging, but it requires controlling the delay with sub-cycle precision, which is very difficult to achieve with standard Michelson or Mach-Zehnder interferometers. Here we introduce a compact hyperspectral camera based on the FT approach, in which the interferometer is a version of the birefringent TWINS device [2, 3]; this inherently provides excellent robustness, accuracy and reproducibility thanks to its common-path geometry. Figure 1(a) shows the experimental setup. A and B are (cid:302)-BBO birefringent blocks with crossed optical axes; P1 polarizes the input light at 45° with respect to them. Block A is shaped in the form of two wedges, so that its thickness can be changed by translating a wedge with a motorized stage. During propagation, the ordinary and extraordinary light projections accumulate a relative delay ranging from positive to negative values according to the relative thickness of A and B. P2 projects the replicas to the same polarization (45°), enabling interference. The spectral resolution of the interferometer is inversely proportional to the user-adjustable total phase delay. The largest position scan of our interferometer introduces a delay of ±250 fs at (cid:540) = 600 nm, which corresponds to spectral resolution of 3 THz (~4 nm). Finally, a camera lens collects the light from the interferometer and creates an image of the object on an off-the-shelf 10-bits silicon monochrome CMOS camera. To characterize our innovative hyperspectral camera, we imaged the object shown in Fig. 1(b): it is made of four Spectralon color materials (green, blue, red, yellow, G, B, R, Y) acting as diffusive colorimetric standards with calibrated spectral reflectivity, and a white standard (W) with ~98.3% reflectivity in the 0.3-2.5(cid:541)m wavelength range. A 150-W Xenon lamp illuminated the object; on the test object we also sent the beams of a green (L1, (cid:540) = 532 nm) and a red (L2, (cid:540) = 635 nm) diode laser, employed to calibrate the frequency axis of the spectrometer and to provide its spectral resolution. The lens was set at the largest aperture; 400 delay-images were acquired with 25-ms integration time. The visibility of the interferograms is >84% for all pixels, demonstrating that our device fulfils the interferometric coherence required by the FT approach. Reflectance spectra retrieved from the measured interferograms, after white balance by weighting each curve by the W spectrum, are in excellent agreement with the calibrated ones (see spectra in Fig. 1(c)), demonstrating the very high spectral accuracy of our camera in the visible and near-infrared spectral range. The RGB image of panel (b) was generated from the collected hyperspectral image. In addition, we will show that the high sensitivity of the device allows measuring the weak emission from fluorescent samples.
关键词： Fourier-transform spectrometry,common-path interferometer,hyperspectral camera,birefringent
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) - Nonlinear Fourier Transform for Analysis of Coherent Structures in Dissipative Systems
摘要： The conventional Fourier transform is widely used mathematical methods in science and technology. It allows representing the signal/field under study as a set of spectral harmonics, that it many situations simplify understanding of such signal/field. In some linear equations, where spectral harmonics evolve independently of each other, the Fourier transform provides a straightforward description of otherwise complex dynamics. Something similar is available for certain classes of nonlinear equations that are integrable using the inverse scattering transform [1, 2], also known as the nonlinear Fourier transform (NFT). Here we discuss potential of its application in dissipative, non-integrable systems to characterize coherent structures. We present a new approach for describing the evolution of a nonlinear system considering the cubic Ginzburg-Landau Equation (CGLE) as a particularly important example in the context of laser system modeling.
关键词： Coherent Structures,Ginzburg-Landau Equation,Dissipative Systems,Nonlinear Fourier Transform
更新于2025-09-11 14:15:04
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A Self-Adaptive Model for the Prediction of Soil Organic Matter Using Mid-Infrared Photoacoustic Spectroscopy
摘要： Fast quantification of soil organic matter (SOM) is important in crop production and soil fertility evaluation. Fourier-transform infrared (FTIR) spectroscopy has been widely utilized for rapid, cost-effective, and non-destructive SOM determination. However, the lack of accuracy has limited the application of FTIR spectroscopy to quantitative SOM prediction because the models are built from a typical database, resulting in large errors in new independent samples. In this study, using 933 paddy soil samples collected in Lishui, China, a “self-adaptive” model was designed for predicting SOM content, in conjunction with Fourier-transform mid-infrared photoacoustic spectroscopy (FTIR-PAS). The resulting FTIR-PAS spectra afforded abundant soil information, reflected in O–H, N–H, and C–H vibrations (4000–2800 cm?1), C=O and C–H vibrations (2500–1200 cm?1), and the fingerprint region (1200–500 cm?1). The self-adaptive model was established by: (i) identification of soil samples, selected by Euclidean distance, with soil spectra to similar the target (unknown) soil sample and ranking of the Euclidean distance values in ascending order; (ii) selection of the optimal parameters to build a partial least squares (PLS) model based on an optimal calibration sample subset; and (iii) prediction and validation of the unknown soil sample. The predictive capabilities of the self-adaptive model and conventional PLS model were compared; the self-adaptive and conventional PLS models had R2 values of 0.9293 and 0.5796, root mean square errors of prediction of 1.65 and 3.26 g kg?1, and ratios of percentage deviation (RPD) of 3.18 and 1.62, respectively. Therefore, the self-adaptive model showed greater potential for application, having significantly enhanced applicability while improving the accuracy of prediction.
关键词： Fourier-transform mid-infrared photoacoustic spectroscopy,partial least squares,paddy soils,self-adaptive model,soil organic matter
更新于2025-09-11 14:15:04
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[IEEE 2019 International Topical Meeting on Microwave Photonics (MWP) - Ottawa, ON, Canada (2019.10.7-2019.10.10)] 2019 International Topical Meeting on Microwave Photonics (MWP) - Nonuniform Microwave Photonic Delay-Line Filter For Optical Sensor Network Interrogation
摘要： We propose a new design of nonuniform spaced microwave photonic delay-line filter based generic optical fiber sensors interrogation platform. Both the amplitude and phase response of the microwave filter are used to demodulate optical sensors. Therefore, a large sensor network with different types of optical sensors can be interrogated simultaneously. The concept of this new microwave photonics enabled interrogation approach is presented and verified by simulations where four different types of optical sensors are simultaneously interrogated via inverse Fourier transform of filter frequency response.
关键词： time delay,fiber Bragg grating,microwave photonics,finite impulse response,Fourier transform,optical sensors
更新于2025-09-11 14:15:04