Light Intensity Distribution Research Articles

Current-injected photovoltaic array for concentrated space solar power station

In this article, the power generation of a concentrated space solar power station (SSPS) is enhanced by current-injected total-cross-tied (TCT-CI) photovoltaic (PV) array. First, a mathematical model of the TCT-CI–connected PV array is established. Second, PV arrays with several common topologies and TCT-CI topology are simulated and analyzed using MATLAB/Simulink. At last, comparative experiments are conducted for TCT and TCT-CI–connected PV arrays under the condition of non-uniform light intensity distribution. The results of the above indicate the following: 1) TCT-CI–connected PV arrays reduce the difficulty of MPPT in concentrated SSPS, 2) TCT-CI–connected PV arrays increase the power generated in concentrated SSPS, and 3) TCT-CI–connected PV arrays are applicable for concentrated SSPS.

Impact of spatial distribution of light intensity on disinfection kinetics of Mycobacterium smegmatis and E. coli using TiO2-based photocatalyst

Impact of spatial distribution of light intensity on disinfection kinetics of Mycobacterium smegmatis and E. coli using TiO2-based photocatalyst

Monochromatic LED-based spectrally tunable light source for chromatic confocal sensors

Prior art emission spectra of light sources utilized in chromatic confocal sensors share two disadvantages: the uneven spectral power distribution (SPD) and the fixed distribution characteristic. Consequently, the detected peak signal intensity is regulated by the SPD properties of the light source and the spectrum transmittance characteristics of the dispersive lens. To achieve this, 18 types of monochromatic light-emitting diodes (LEDs) with different peak wavelengths were selected to create a wide-spectrum light source with a tunable SPD. The SPD characteristics of the light source can be modified by adjusting the luminous intensity of each LED. The tungsten halogen lamp, the “white” LED, and the designed light source were selected as the light sources for the chromatic confocal measurement system, respectively. Comparing the peak signals obtained under various light sources. The experimental results show that, in the range of 400 to 700 nm, the peak signal intensity extreme value ratio measured with the designed light source is 1.81:1, and the normalized light intensity standard deviation is 0.118. The corresponding light intensity extreme value ratio of halogen tungsten lamp and white LED is 23.3:1, 300:1, and the normalized light intensity standard deviation is 0.302, 0.228. With the help of the designed light source, a group of wave crest signals with uniform light intensity distribution can be obtained. This can reduce the influence of the SPD characteristics of the light source itself and the transmissivity characteristics of the dispersive objective lens on the measured signal, and ensure the accuracy of spectral detection.

Tight Focus Vector Light Field of Hybrid Double Circularly Polarized Beams

Based on the Richard-Wolf diffraction theory, we demonstrate the tightly focused optical field distribution with two beams circularly polarized light. We deduced the expression of the double-beam superimposed vortex light intensity of left-handed circularly polarized light and right-handed circularly polarized light under the focusing condition of a high numerical aperture objective lens. Based on the different vortex topological charge values, amplitudes and initial phases of the dual beams, we numerically simulated the light intensity distribution of the superimposed hybrid focused light field. It is found that a variety of peculiar vortex spots can be obtained through the tight focus stacking of the double beams. These complex hybrid focused light fields with different polarizations can be used in fields such as optical field micro-manipulation or nonlinear fluorescence microscopy imaging.

Optical Texture Super‐Lattices Produced by Talbot Effect at Superimposed Gratings

AbstractFresnel diffraction on periodic gratings results in a two‐dimensional periodic distribution of light intensity, also known as the Talbot effect. Here this approach is extended to the family of superimposed structures with translational symmetry, which consist of superposed spatial harmonics. The Talbot effect is demonstrated to be valid for superimposed gratings. The considered superimposed gratings provide a wide range of textures of optical super‐lattices. These texture super‐lattices represent a Talbot carpets with a complex motif, which can be varied by choosing structure parameters. These results provide a new functionality for structuring optical lattices and can find potential applications in a wide range of light–matter interactions.

Design and Theoretical Investigation of an on Chip Two-Dimensional Newton’s Ring-like Plasmonic Sensor for Differentiating the Chirality of Circularly Polarized Lights

In this paper, an on chip two-dimensional Newton’s ring-like plasmonic sensor is designed for differentiating the chirality of circularly polarized lights (CPLS). The structure of the plasmonic sensor consists of a circular arc slit and an array of periodic rectangular nano-grooves that are etched into a silver film. When the sensor is illuminated by CPLS with a given chirality, the surface plasmon polariton waves generated by the slit and nano-groove array will selectively interfere with each other in the near field, which results in two different transmitted light intensity distributions in the far field. The generated far-field light intensity distributions are utilized as criteria to qualitatively differentiate the concrete chirality of the incident CPLS. The finite difference time domain method is utilized to theoretically investigate the function of the designed plasmonic sensor. The simulated results indicated that the proposed sensor has the ability to visually display the chirality information in the far field, and can provide a tool to conveniently and qualitatively differentiate the chirality of CPLS in the far field.

Experimental damage thresholds of a laser suppression imaging system using a cubic phase plate

The development of laser systems leads to an increasing threat to photoelectric imaging sensors. A cubic phase plate wavefront coding imaging system is proposed to reduce the risk of damage owing to intense laser radiation. Based on the wavefront coding imaging model, the diffracted spot profile and the light intensity distribution on the observation plane are simulated. An experimental device is set up to measure the laser-induced damage thresholds and investigate the morphology of laser-induced damage patterns of the conventional and the wavefront encoding imaging system. Simulations and experimental results manifest the superior laser suppression performance of the proposed method, which can help diminish the undesirable effects of laser irradiation on an imaging sensor.

Talbot effect of ring laser array realized by Gyrator canonical transformation

We propose a ring laser array structure and study the Talbot effect. By comparing with the one-dimensional laser array, the near-field distribution of the identical intensity of the ring laser array without edge effect is obtained, which can be more conducive to improving the capability of the external cavity phase locking of lasers. In this paper, Talbot effect and self imaging condition of ring laser array in polar coordinates are calculated by using Gyrator canonical transformation. The sub-image distribution at the fractional Talbot distance is further analyzed. The optical profile and phase distribution of the ring laser array at the fractional Talbot distance are simulated, which are mutually verified with the theoretical calculation results. At a quarter of the Talbot distance, the number of sub-images is twice that of the emitters. The light intensities of the sub-images are identical, and thedifference in phase between adjacent sub-images is <inline-formula><tex-math id="M1">\begin{document}${\pi }/{2}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20222412_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20222412_M1.png"/></alternatives></inline-formula>. At half of the Talbot distance, the number of sub-images is the same as that of the emitters, while the spatial position of sub-image is shifted by half a cycle along the angular direction. Moreover, the sub-images with twice the number of the emitters are present in three quarters of the Talbot distance. The light intensities of the sub-images are identical and the difference in phase between adjacent sub-images is <inline-formula><tex-math id="M2">\begin{document}$- {\pi }/{2}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20222412_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20222412_M2.png"/></alternatives></inline-formula>. Further, the Talbot images with the same spatial and phase distribution as the emitters are generated along the angular direction at the Talbot distance. The optical profile and phase distribution of one dimensional laser array at the fractional Talbot distance are also simulated by FDTD Solutions for comparison. It is found that the edge effect of one-dimensional laser array leads to the uneven distribution of near-field light intensity, in which the intensity of light spot on the edge of array is significantly lower than that in the center of array. While the Talbot sub-images of ring laser array with identical light intensity are obtained. Therefore, We consider that the ring laser array can effectively eliminate the edge effect. The results are helpful in studying the external cavity phase locking of ring laser arrays and its applications in the field of high brightness coherent laser and quantum measurement.

Tomographic incoherent holography for microscale X-ray source

At present, in the experiment on inertial confinement fusion (ICF), no single imaging diagnosis of the black cavity plasma or the implosion target region can distinguish the emission intensity information in the depth direction, that is, the images acquired by the detector are intensity integral along the detection direction. In this paper, a tomographic imaging method using incoherent holography for microscale X-ray source is introduced. The incoherent holographic imaging technology has an imaging mechanism that encodes and compresses the three-dimensional space information of the light source into a two-dimensional hologram. In the theoretical part, we examine the imaging mechanism of incoherent holographic tomography. Then the compress sensing model which is appropriate for this incoherent tomography is investigated. Combined with the hologram reconstruction algorithm based on compress sensing, the two-dimensional distributions of light intensity at different object distances along the detection direction can be recovered from the two-dimensional hologram. In order to verify the feasibility of this imaging scheme, we simulate the incoherent holographic imaging process of a light source with an axial length of 16 mm, and obtain the tomography light intensity distribution result with a spacing of 4 mm by reconstructing the corresponding incoherent hologram through using the backpropagation algorithms, Wiener filtering algorithm, and compress sensing algorithm. All reconstruction methods mentioned above can recover the corresponding letter light source at a certain object distance, indicating the potential of incoherent holographic technology for three-dimensional imaging. For the backpropagation reconstruction image, there is a large amount of series noise at the edge of the light source signal, which affects signal recognition in practical applications. Although the Wiener filtering algorithm can recognize the image signal to some extent, the low contrast of the reconstructed image results in the distribution of target source strength mixed with background noise. Compared with the algorithm based on the Wiener filtering and backpropagation, compress sensing theory provides a more professional technique for the ill-condition problem. Results from compress sensing reconstruction show that the crosstalk noise is significantly reduced, and the intensity distribution on the objective plane of the light source is basically concentrated in the signal area. The peak-signal-to-noise ratio of reconstructed image is continuously optimized as the number of iterations increases. Besides, the axial and horizontal resolution caused by the innermost ring radius of Fresnel zone plate are also analyzed, indicating that a shorter innermost ring radius can improve the horizontal resolution, bur reduce the axial resolution.

Calculation of Light Intensity Distribution in Imaging Space of Imaging System with Arbitrary Aperture Diaphragm

Calculation of Light Intensity Distribution in Imaging Space of Imaging System with Arbitrary Aperture Diaphragm

Surface light modulation by sea ice and phytoplankton survival in a convective flow model

Plankton dynamics depend in a complex manner on a variety of physical phenomena, according to both experimental and numerical data. In particular, experimental field studies have highlighted the relation between phytoplankton survival and turbulent upwelling and downwelling from thermal convection. Recent numerical works have also shown the importance of accounting for advective transport by persistent structures in simulation models. In nutrient-rich polar marine environments phytoplankton blooms are critically limited by light availability under ice-covered waters. Such heterogeneity of the light intensity distribution, in association with a large-scale coherent fluid flow, can give rise to nontrivial growth dynamics. In this work we extend a previous advection-reaction-diffusion model of phytoplankton light-limited vertical dynamics in the presence of convective transport. Specifically, we consider horizontally heterogeneous light conditions through the use of two regions with different production regimes, modelling the absence (presence) of light under (in between) obstacles. Such a model is intended as an idealized representation of nonuniformly ice-covered polar waters. By means of numerical simulations, we find that the main role of advective transport is to hinder phytoplankton growth, but also that such effect depends on the positions of the obstacles with respect to the upwelling and downwelling flow regions. Furthermore, we show that the sinking speed due to the density difference between phytoplankton organisms and water, while small, plays an important role, which depends on how it adds to the flow. These results indicate that advective transport can have a crucial impact on the survival conditions of sinking phytoplankton species in polar environments.

Gain Modeling and Numerical Simulation of Fiber Amplifier

As optical communication technology has been developing fast these years, its application in S-band has been valued by people, especially in the field of WDM/DWDM. The energy structure-e in Tm3+exist the transition which can meet the S-band and S+-band. Although the energy structure of ions are very complex, the fiber amplifier is an important device for the S+-band optical amplification. And its research will be very significant for further broadening the optical communication bandwidth. Fiber amplifiers have become a new hot spot for optical fiber communication devices. This paper mainly do analysis, simulation and comparison about the semiconductor laser mufti-core pigtail outputting light field intensity, as well as the outputting light field intensity distribution of LD mufti-core pigtail single-lens and dual-lens coupled. This paper analyzes fiber amplifier performance based on the rate equation, transfer equation and simulations.

Plasmonic lithography fast imaging model based on the decomposition machine learning method.

Plasmonic lithography can make the evanescent wave at the mask be resonantly amplified by exciting surface plasmon polaritons (SPPs) and participate in imaging, which breaks through the diffraction limit in conventional lithography. It provides a reliable technical way for the study of low-cost, large-area and efficient nanolithography technology. This paper introduces the characteristics of plasmonic lithography, the similarities and the differences with traditional DUV projection lithography. By comparing and analyzing the already existed fast imaging model of mask diffraction near-field (DNF) of DUV/EUV lithography, this paper introduces the decomposition machine learning method of mask diffraction near-field into the fast imaging of plasmonic lithography. A fast imaging model of plasmonic lithography for arbitrary two-dimensional pattern is proposed for the first time. This model enables fast imaging of the input binary 0&1 matrix of the mask directly to the light intensity distribution of photoresist image (PRI). The illumination method employs the normal incidence with x polarization, the normal incidence with y polarization and the quadrupole illumination with TM polarization respectively. The error and the operating efficiency between this fast imaging model and the rigorous electromagnetic model is compared. The test results show that compared with the rigorous electromagnetic computation model, the fast imaging model can greatly improve the calculation efficiency and maintain high accuracy at the same time, which provides great conditions for the development of computational lithography such as SMO/OPC for plasmonic lithography technology.

Generation of chemical deposits on fused silica optics and their modulation on the light intensity distribution.

Deposited substances generated from hydrofluoric acid based (HF-based) etching are found to be the precursors that deteriorate the resistance of fused silica optics to laser damage. In this paper, the surface of polished fused silica was treated with a buffer oxide etchant (BOE, 5-10%wt. HF + 10%wt. N H 4 F+80-85% w t.H 2 O). The optic surface area affected by the etching-induced deposits (N H 4)S i F 6 was found to increase significantly with the amount of material removal and sensitivity to the post-cleaning procedure. Three shapes of deposited particles are simultaneously identified on the treated samples. The 3D finite-difference time-domain (FDTD) was used to simulate the light field distribution near the deposited particles, which demonstrates that fused silica is subject to more light modulation when a particle is exposed on the front surface laser than on the rear surface laser. In addition, dense particles barely increase the light intensification factor (LIF) while markedly increase the light focused probability inside fused silica. Moreover, a multiple linear regression (MLR) analysis for the LIF builds a fitting plane model of the LIF and the particle height as well as the horizontal size, revealing that the LIF increases with the size of the deposited particle, especially its height. The laser damage testing results indicate that a deposited layer of ∼76n m in height had little influence on the laser-induced damage threshold (LIDT) of the optics and larger deposited particles with up to 9µm thickness may deteriorate the LIDT to 41.62% that of the reference sample. Both the simulation and experimental results demonstrate that deposited particles with a height of more than 0.1µm should be inhibited to achieve fused silica with superior laser damage performance.

A remotely controlled automated field measurement system for light extinction in coastal waters

The Secchi disk depth (SD) is an important parameter in aquatic ecosystem monitoring. As algal growth depends on solar irradiation, the SD - a measure of light extinction - gives an indirect indication of the chlorophyll concentration. However, most SD measurements are manually based and too sparse to resolve water quality variations during algal blooms.A remotely controlled automatic system for field measurement of light extinction has been developed and installed in three marine fish culture zones in Hong Kong. The visual images of the disk at different prescribed depths and the surrounding water are taken. Based on the contrast theory and image analysis, the recorded light intensity distributions can be analyzed to give the SD and the light extinction coefficient. The method has been extensively verified by field data over a wide range of water quality and hydro-meteorological conditions. The proposed system enables high frequency SD measurements on demand for environmental management and emergency response.

An Optical Encoder Chip with Area Compensation

A photodiode area-compensation method based on light intensity distribution characteristics is introduced to solve the problem of the hybrid optical encoder’s inconsistent absolute code output signals. This method performs area compensation of different degrees according to the irradiance received by the photodiodes at different positions, thus achieving the consistency of output signals and reducing the bit error rate of absolute code signals. Based on the 0.35 μmm CMOS process, a four-channel photodiode array chip for a reflective hybrid optical encoder was designed. Moreover, the absolute code photodiode arrays were designed with area compensation. The test results show that the square wave duty cycle error of the output signals is less than 2% when the LED light source works normally. When the LED working current changes by ±2.85 mA, the output signal’s square wave duty cycle error is less than 3.1%. In each case, the square wave duty cycle error of the output signals is small, so it can be seen that the area compensation method based on light intensity distribution can achieve good consistency of the output signal. The chip has been taped and packaged, and the chip area is 21.45 mm2.

Fabrication of nanostructure on Au nano-film by nanosecond laser coupled with cantilevered scanning near-field optical microscopy probe

Diffraction limit has been the constraint of the nanostructure fabrication. Because the scanning near-field optical microscopy (SNOM) can work in the evanescent near-field region, its application in nano-processing has received extensive attention from researchers globally. In this paper, we combined nanosecond laser with cantilevered SNOM probe. Utilizing the high precision of the confinement and enhancement effect of probe tip and the high instantaneous energy of the laser, we realized nanostructure fabrication and in situ detection on Au nano-film. Feature sizes down to 47 nm full width at half maximum were fabricated. We investigated the laser propagation through the SNOM tip aperture and the light field intensity distribution on the surface of substrate theoretically. The calculation results demonstrate that the laser is highly restricted within the SNOM aperture and enhanced on the exit plane at the rim of aperture. After the transmission, the light field intensity distribution on the surface of the Au nano-film was enhanced due to the localized surface plasmon resonance. The thermal distribution on the surface of Au nano-film indicates that the peak of the temperature distribution appeared at the surface right underneath the center of the aperture. It is proved that the simulation results are consistent with the experimental results.

Scalar vortex solitons and vector dipole solitons in whispering gallery mode optical microresonators

Governed by the coupled variable-coefficient Lugiato-Lefever equation, the soliton characteristics of whispering gallery mode microresonators in a coupled system are studied. Based on analytical solutions of the relevant models in the absence of pump, the dynamic evolution of vortex solitons is discussed in the periodic system, and the periodic phase change of vortex solitons and the stability of dipole solitons are discussed under the condition of the external excitation. In addition, the influence of the topological charge on the energy distribution of two-component and total light intensity for dipole solitons is investigated. The vortex solitons show great anti-interference performance after the addition of the external excitation, and dipole solitons can maintain the stability with periodical behaviors during a long evolution process. With the addition of the topological charge, the branch of dipole solitons for the single component and the number of spiral layers for vortex solitons increase.

Research on achromatic Risley prism in normal tracing angle measurement system

The normal tracing angle measurement system based on Risley prisms can eliminate the influence of aberrations other than the dispersion of Risley prisms on the angle measurement accuracy. Although the traditional dispersion optimization method based on the extreme point can make the beam directions of different wavelengths more consistent after passing through the Risley prisms, the light intensity distribution that deviates from the extreme point wavelength causes the spot centroid to deviate from the target position, thus introducing the angle measurement error. In this paper, we propose a highly symmetry-glued achromatic Risley prisms optimization method for the needs of a normal tracing angle measurement system. Our method not only realizes the beam direction as closely as possible after the deflection of the Risley prisms but also compensates for the centroid error caused by the beam deviating from the central wavelength. ZEMAX simulation shows that, in the normal tracing angle measurement system, within the angle measurement range of ±700 ″ and the light source wavelength range of 600 to 700 nm, the angle measurement error introduced by the dispersion of the optimized Risley prisms is not >0.01 ″ .

Mechanism of nanostructure processing on Au and Ag nano-film by a nanosecond laser illuminating cantilevered scanning near-field optical microscopy tip.

Nanostructure processing by a laser illuminating cantilevered scanning near-field optical microscopy (SNOM) tip is a novel technology that has received extensive attention from researchers. In this paper, theoretical investigations of the mechanism for nanostructure fabrication on Au and Ag nano-film by this technology are realized by the finite element method. The light field intensity and temperature distribution on Au and Ag surfaces at the near-field of the SNOM tip apex after illumination is simulated. The results reveal that the laser is restricted and enhanced within the SNOM tip aperture during illumination. Locally excited surface plasmon polaritons, which induce near-field enhancement on the Au and Ag nano-film at the vicinity of the aperture, are significant for nanostructure fabrication. The impacts of several parameters such as aperture width w, gap between the apex and substrate g, and the initial electric field intensity |E0| of the laser on the temperature of the Au and Ag substrate surfaces during fabrication are deeply studied. It reveals that the surface temperature depends on both the enhancement of the light field intensity and the transmitted laser. The enhancement is dominant in affecting temperature when the gap is small, while the transmittance becomes the main factor influencing the surface temperature with the increase of the gap.