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A method for the statistical evaluation of the fluorescence intensity of single blinking quantum dots using a confocal fluorescence microscope
摘要： The evaluation of the fluorescence intensity of single quantum dots (QDs) using a confocal fluorescence microscope can provide an alternative approach for estimating the effects of environmental changes or surface modifications on the fluorescence intensity of single QDs. In the case of blinking QDs, irregular blinking would significantly influence the intensity evaluation results that are based on the analysis of one or a few single QDs. In this regard, statistical intensity evaluations based on a large number of single QDs would be helpful to estimate an approximate intensity value of single QDs with reduced effects of blinking on the evaluation results. Herein, we developed a convenient method to statistically evaluate the fluorescence intensity of a large number of single blinking QDs using Gaussian distribution. Based on the intensity analysis of thousands of single QDs, the fluorescence intensity of the single QDs evaluated using a confocal fluorescence microscope was approximately 4090 with little data fluctuation induced by blinking.
关键词： confocal fluorescence microscope,statistical evaluation,fluorescence intensity,single blinking quantum dots,Gaussian distribution
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Characterization of Encapsulant Degradation in Accelerated UV Stressed Mini-Modules with UV-cut and UV-pass EVA
摘要： Automated cell segmentation for microscopy cell images has recently become an initial step for further image analysis in cell biology. However, microscopy cell images are easily degraded by noise during the readout procedure via optical-electronic imaging systems. Such noise degradations result in low signal-to-noise ratio (SNR) and poor image quality for cell identification. In order to improve SNR for subsequent segmentation and image-based quantitative analysis, the commonly used state-of-art restoration techniques are applied but few of them are suitable for corrupted microscopy cell images. In this paper, we propose a multistaged method based on a novel integration of trend surface analysis, quantile–quantile plot, bootstrapping, and the Gaussian spatial kernel for the restoration of noisy microscopy cell images. We show this multistaged approach achieves higher performance compared with other state-of-art restoration techniques in terms of peak signal-to-noise ratio and structure similarity in synthetic noise experiments. This paper also reports an experiment on real noisy microscopy data which demonstrated the advantages of the proposed restoration method for improving segmentation performance.
关键词： microscopy cell imaging,Bootstrapping,trend surface analysis,quantile–quantile plot (Q–Q) plot,Gaussian noise,image restoration
更新于2025-09-23 15:19:57
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Self-focusing of multi-Gaussian laser beams in nonlinear optical media as a Keplera??s central force problem
摘要： In this paper self-focusing of multi-Gaussian laser beam in nonlinear optical media has been investigated theoretically. Saturation of the optical nonlinearity has been incorporated through cubic-quintic model. Moment theory approach in W.K.B approximation has been invoked to find the numerical solution of nonlinear wave equation for the field of incident laser beam. Particularly the dynamical evolutions of the beam width of the laser beam with distance of propagation have been investigated in detail. It has been shown that the self-focusing of the laser beam resembles to Kepler’s central force problem.
关键词： Potential well,Self focusing,Kepler’s central force problem,Multi Gaussian
更新于2025-09-23 15:19:57
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Variational method of energy level calculation in pyramidal quantum dots
摘要： We suggest a variational method for finding the ground state energy in pyramidal quantum dots. The method is based on using a Gaussian trial wavefunction. We developed an analytical expression for the expectation value of the carrier energy in quantum dots with a constant confining potential (within a single-band model). The problem of finding the ground state energy was reduced to the minimization of an analytical function of three trial function parameters. The proposed variational approach is much faster than the direct approach when solving the three-dimensional Schr?dinger equation, does not demand any special software, and produces quite accurate values of the carrier ground state energy (an error does not exceed 2% of the potential well depth). Generalization of the method to multi-band models, spatially inhomogeneous potentials, effective mass discontinuity, and excited states is discussed. Applicability of the method to different quantum dot systems is considered.
关键词： Gaussian trial wavefunction,single-band model,Schr?dinger equation,variational method,energy level calculation,pyramidal quantum dots
更新于2025-09-23 15:19:57
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Analysis of the beam waist on spatial emission characteristics from an electron driven by intense linearly polarized laser pulses
摘要： This paper establishes a low-energy single-electron acceleration model based on the Lorentz equation and an energy equation, simulates the trajectories of electrons in laser pulses with different beam waist radii with the help of MATLAB software and analyzes the influence of linearly polarized laser intensity on the dynamic law of high-energy electrons. With the beam waist radius increasing, we find that the longitude drifting distance and the maximum transverse quivering amplitude are growing differently at each part at first (when the beam waist radius <4λ0) and then decreasing differently as well. Furthermore, when the beam waist radius is small enough, the ramifications are found first; increasing the radius of the beam will make the radiated power go up by orders of magnitude and the ramification of the location and number found in the asymmetric bifoliate radiation pattern change throughout.
关键词： relativistic motion,beam waist radius,radiation pattern,spatial distribution of emission,linearly polarized femtosecond Gaussian laser pulse,ramification
更新于2025-09-23 15:19:57
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Laser Beam Shaping Applications || Laser Beam Shaping in Array-Type Laser Printing Systems
摘要： In a variety of applications, including longitudinal solid-state laser pumping,1–4 fiber coupling for fiber lasers, and line printers,5–12 laser diode arrays have proven to be very effective light sources when combined with the appropriate beam shaping optics. As laser arrays can be designed in numerous ways, such as with phase-coupled single-mode emitters, uncoupled single-mode emitters, or uncoupled multimode emitters, the output properties of both the individual beams and the ensemble of beams vary dramatically. Inherently, many beam properties, including the output power level, beam profiles and beam propagation properties, beam coherence effects, and the overall device layout, are dependent upon the emitter structure. The optical systems that have been designed to work with these highly nontraditional light sources, which are anamorphic in both physical layout and beam properties, are themselves nontraditional, and typically employ a variety of modern micro-optical components. Within that context, a variety of unique systems13–15 have been developed for high-power, high-throughput printing applications, where the laser light is transformed into a linear arrangement of individually modulated beams and imaged onto a light-sensitive media. These systems typically combine the design and analysis techniques from classical imaging optics, illumination optics, and Gaussian beam optics into integral wholes. Certainly, many of the design concepts that have evolved to support the laser thermal printing application are applicable to other endeavors, of which laser projection is an example.
关键词： beam shaping,laser thermal printing,Gaussian beam optics,micro-optical components,laser diode arrays
更新于2025-09-23 15:19:57
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Performance of Free Space Optical Communication Base on Orbital Angular Momentum with Pointing Errors
摘要： Due to the misalignment of the receiver, the spiral spectrum appears to be extended when the Laguerre-Gaussian beam is applied to atmospheric laser communication. This paper investigates the spiral spectrum spread of the Laguerre-Gaussian beam in the case of receiver misalignment. The analytical expression of Laguerre-Gaussian spiral spectrum under the influence of alignment error is studied by mathematical derivation and simulation. The results show that the detection probability of the original orbital angular momentum (OAM) state varies with the lateral displacement distance and the inclination angle. The bit error rate and channel capacity of each channel were studied to verify the effects of misalignment in multiple OAM communication systems.
关键词： Orbital Angular Momentum,Laguerre-Gaussian beam,Pointing Errors,Free Space Optical Communication,Spiral Spectrum
更新于2025-09-23 15:19:57
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Role of magnetic field on self focusing of super-Gaussian laser beam under relativistic effect
摘要： Considering an external magnetic field along the direction of propagation of laser, the self focusing of a super-Gaussian laser beam is studied when it propagates through the plasma at relativistic intensities. We consider the cyclotron motion of the electrons and use the tensor form of the plasma dielectric constant obtained based on the direction of the external magnetic field. For completeness, relativistic mass effect is incorporated in both the plasma frequency and electron cyclotron frequency. Using appropriate conditions, an equation for the beam width parameter is derived and solved. The equilibrium beam radius for a self trapped laser beam is also derived. Self focusing is better when cyclotron effects are taken into account. At higher intensity and higher spot size of the laser beam, self focusing becomes better.
关键词： Super-Gaussian laser,Moment theory,Beam width parameter,Self focusing,Relativistic nonlinearity
更新于2025-09-23 15:19:57
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A V-Folded Digital Laser for On-Demand Vortex Beams by Astigmatic Transformation of Hermitea??Gaussian Modes <sup>*</sup>
摘要： A V-folded digital laser using a spatial light modulator (SLM) for intra-cavity loss shaping is exploited to generate Hermite–Gaussian modes with on-demand mode order. With a ??/2 astigmatic mode converter, vortex beams carrying on-demand orbital angular momentum (OAM) with a tunable range from ?11(cid:126) to 12(cid:126) are obtained. The mode order of the HG mode, hence the OAM of the vortex beam, is digitally switched by changing the phase pattern imposed on the SLM without requiring any mechanic alignment of the cavity. This work has great potential applications in various OAM-tunable vortex beams.
关键词： spatial light modulator,vortex beams,orbital angular momentum,Hermite–Gaussian modes,digital laser
更新于2025-09-23 15:19:57
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Laser Spot Center Location Method for Chinese Spaceborne GF-7 Footprint Camera
摘要： The Gaofen-7 (GF-7) satellite is equipped with two area array sensor footprint cameras to capture the laser altimeter spot. In order to establish a direct correspondence between the laser data and the stereo image data, a new method is proposed to fit the center of the spot using the brightness difference between the spot image and the footprint image. First, the geometric registration between the spot image and the footprint image is completed based on feature matching or template matching. Then, the brightness values between the two images are extracted from the corresponding image position to form a measurement, and the least squares adjustment method is used to calculate the parameters of the brightness conversion model between the spot image and the footprint image. Finally, according to the registration relationship, the center of the identified spots is respectively positioned in the footprint images, so that the laser spots are accurately identified in the along-track stereo footprint images. The experimental results show that the spot error of this method is less than 0.7 pixel, which has higher reliability and stability, and can be used for a GF-7 satellite footprint camera.
关键词： gaussian fitting,footprint camera,satellite laser altimeter,spot center extraction,GF-7 satellite
更新于2025-09-23 15:19:57