The thermal and electrical characteristics of a photovoltaic cell are obtained according to the Newton heat transfer between photovoltaic cell and environment, and dependence of band-gap width. This research experimental results show that the temperature of the photovoltaic cell is higher than the ambient temperature, and it first decreases and then increases, which is linearly increasing with the radiation intensity. The short-circuit current increases with the increase of radiation intensity while the open-circuit voltage increases first and then decreases with the increase of radiation intensity. Maximum efficiency can be obtained by optimizing the output voltage of the photovoltaic cells and solar radiation intensity. A spectrum splitting photovoltaic-thermal coupled system is constructed to improve the utilization rate of solar energy by inputting part of the radiant energy under the AM 1.5G standard condition into the thermal collection system.

For the high-speed railway LTE-R (long term evolution for mobile communications-railway) handover process, the handover algorithm based on the A3 event decision is prone to frequent ping-pong handovers and has low handover success rate. An optimized handover algorithm based on improved fuzzy prediction is proposed in this work. In this algorithm, the reference signal received power (RSRP) in the handover process is collected, and the collected RSRP value is optimized by the improved GM (1,1) grey prediction algorithm. After the three cycle prediction and weighted average, the measured parameter values are sent to the decision formula for judgment. Simulation results of the algorithm in MATLAB show that the proposed algorithm reduces the parameter fluctuation in the process of handover, thus reducing the number of ping-pang handovers and improving the success rate.

This paper presents a time-domain matched filter for synchronous detection of linear frequency modulation (LFM) signals to consider the influence of poor anti-interference ability and distortion of visible light location source in space transmission and the signal to noise ratio (SNR). The SNR of a received signal decreases significantly with the increase in transmission distance. The matched filter is characterized by a combination of oversampling and a cross-correlation orthogonal algorithm. The application of the proposed filter to the visible light location of the LFM signal effectively improves the signal transmission distance. The logic design and integration of the LFM time-domain matched filter are completed using a field programmable gate array. In the synchronous detection experiment of long-distance visible light communication, the accuracy of synchronous detection of the matched filter is more than 99% at a communication distance of 6 m, which lays a foundation for the application of the LFM signal in the visible light location in the future.

To reduce the data acquisition quantity and improve the accuracy of zero difference symmetric demodulation, a method for extracting interference signals in a time-division multiplexing system with a weak fiber Bragg grating (WFBG) based on Michelson interference is proposed. Continuous wavelet transform is applied to the intensity signal to find the extreme value of the transform coefficient. The adjacent minimum and maximum values are used to define the laser interference region. According to the laser pulses with different width, the wavelet scale factor is adjusted to find the interference region. The interference signal is obtained based on the maximum intensity and the average intensity in the interference region, respectively, and the phase signal of the interference signal is demodulated by the zero difference symmetry algorithm. The WFBG sensor is put into a vibrating liquid column. The same weak sinusoidal signal is measured repeatedly, and the measured signals are fitted by the sinusoidal curve. The fitting results show that extracting the short pulse interference region by the continuous wavelet transform and calculating the interference signal by the average value method are helpful to improve the zero difference symmetric demodulation accuracy of the sensing system.

Aiming at the asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) systems with direct current (DC) offset, a diversity combining receiver using single fast Fourier transform (FFT) is proposed. In a visible light communication (VLC) system, the background light source will inevitably cause a DC offset at the receiving end. Through the symmetric recovery operation, the odd and even signals of the ACO-OFDM system can be reconstructed in the time domain to estimate the DC offset of the system. The results show that the proposed diversity combining receiver has lower complexity, is insensitive to DC components, and has the same diversity gain as that of the conventional diversity combining receiver.

A heating method based on double-beam carbon dioxide (CO2) laser is proposed, and the fabrication system of a long-period fiber grating with a microtapered structure is designed and built. The system achieves uniform heating and fiber softening by accurately controlling the CO2 laser power, heating time, and spot size. The microtapered long-period fiber gratings (MT-LPFGs) with high-precision (extinction ratio >30 dB and insertion loss -1 by the bending experiment. The filter has advantages of high precision, simple preparation, and no spectral degradation, so it has an important application in broadband filtering.

Aiming at the interference problem introduced by satellite multipath signals, a blind source separation model of satellite multipath interference signals is established. The joint approximate diagonalization of eigenmatrix (JADE) algorithm based on dimensionality reduction Householder transformation is used to perform the joint approximate diagonalization of the fourth-order cumulants of received mixed signals, so as to extract multipath signals. Experimental results show that the algorithm can well separate the multipath signals with spectrum completely overlapped and the interference signals with spectrum partially overlapped. In terms of extracting multipath signals, the performance of this algorithm is superior to fast independent component analysis (FastICA) algorithm . In terms of running time, the average time of FastICA algorithm running 1000 times is about 6 times that of the Cardoso Givens-JADE(CG-JADE) algorithm, and the average running time of this algorithm is 0.0024 s less than that of GG-JADE algorithm, which proves its effectiveness and rapidity.

In this paper, a theoretical scheme to realize nonreciprocity in a three-cavity optomechanical system was proposed. Three optical cavity fields propelled by strong driving light fields were individually integrated to a mechanical oscillator through radiation pressure, and two were driven by weak probe light fields when they were coupled with an optical fiber. Through the Heisenberg-Langevin equation, the steady-state solution of the three-cavity optomechanical system was presented. The specific expression of the transmission amplitudes is obtained using the input-output theory. The results reveal that the nonreciprocity in the three-cavity optomechanical system is because of the quantum interference between the optomechanical interaction and the coupling interaction of two optical cavity fields. The phase difference not only determines whether the nonreciprocity can occur in the system but also determines the direction of the nonreciprocity. Furthermore, it is also discovered that with an increase in the effective optical coupling strength, the transmission amplitude curves change in different forms. Under a certain effective optomechanical coupling strength, the system achieves the perfect nonreciprocity. Our research results can provide reference for the application of quantum information processing based on a cavity optomechanical system.

Optical measurement methods based on full-field phase calculation can obtain three-dimensional (3D) shape of object surfaces. Full-field fringe projection profilometry and phase measuring deflectometry are used to measure the shape of diffuse surfaces and specular surface objects, respectively. There are many composite surface objects composed of diffuse surfaces and specular surfaces in industrial production and daily life. Rapid measurement of the surface shape of these objects is the key to ensuring their quality. Therefore, a composite surface 3D shape measurement method based on phase measurement deflectometry and fringe projection profilometry is proposed in this work, and a corresponding simulation system is established. The influence of different structural parameters on the 3D measurement results is analyzed by simulation, and the parameters of the measurement system are optimized to obtain the optimal parameter configuration. Simulation and experimental results show that the optimized measurement system can accurately and efficiently obtain the 3D shape data of composite surface objects.

This study introduces a new methane measurement method based on the degenerate four-wave mixing effect by coating a methane gas-sensitive film on the inside of two specific cladding pores in a photonic crystal fiber. The method accurately detects methane gas in real time by establishing a direct relationship between the movement of the Stokes and anti-Stokes spectra in optical fiber and the change in methane concentration. The experimental results show that the sensor sensitivity is closely related to the gas-sensitive film thickness and the pump wavelength. At the same pump wavelength, the sensing sensitivity increases as the thickness of the gas sensing film increases. Under an unchanged thickness of the gas-sensitive film, the closer the pump wavelength is to zero dispersion wavelength, the higher the sensing sensitivity. The gas sensing sensitivity corresponding to the Stokes and anti-Stokes spectra can reach -4.87 nm/% and 2.83 nm/%, respectively, after the structural parameter optimization. The related measurement principle is also applicable to the accurate measurement of other gases and the composition analysis of mixed gases.

To satisfy the high-precision and high-efficiency measurement requirements of aero-engine blades, a fast three-dimensional measurement method based on the HSI (hue, saturation, intensity) color model is proposed herein. First, the HSI model is analyzed to design a structured light-based three-dimensional measurement system, and a look-up table (LUT) based color correction method is employed to correct the color crosstalk and calibrate the mapping relationship between hue and depth. The proposed approach uses only one color pattern to obtain the hue of a package. A color-coded color bar image is used on the discontinuous surface to recognize the fringe level and then complete the hue unwrapping. The feasibility of the proposed method is verified by simulation. Finally, the three-dimensional measurement of the rotor blades of a high-pressure aero-engine compressor is performed, and the efficiency of the proposed method is compared with that of the conventional method of obtaining the wrapped phase and unwrapping. Experimental results show that the proposed method satisfies the measurement requirements of aero-engine blades and can improve measurement efficiency.

Direct phase measuring deflectometry (DPMD) solves the measurement problem of discontinuous mirror objects. It uses a new mathematical model to directly establish the relationship between phase and depth. In the DPMD system, a liquid crystal display (LCD) is used to display a high-contrast fringe pattern, and a camera captures the deformed fringe image reflected by the mirror surface to be tested. However, the refractive effect of the LCD transparent layer causes errors in the DPMD measurement results. Therefore, we propose a method for compensating the refraction effect of the display in the DPMD system. By establishing a single layer refraction model, the thickness and refractive index of the transparent layer are first calibrated using the light equations, and then the refraction angle is calibrated using the system’s geometric relationship. Finally, the offset is calculated based on the calibrated parameters to compensate the system's depth data. The measurement results of a specular step and a concave mirror show that the measurement accuracy is enhanced by 30%. Therefore, this method effectively increases the measurement accuracy of the DPMD.

To explore the process parameters of the laser directly-induced coloring for a stainless steel surface, we used a nanosecond laser to induce the coloring of the stainless steel surface, and various colors such as dark blue, black, gray, pink, green, purple, gold, yellow, brown, and maroon were obtained. While the maroon color has not been reported in other researches of laser-induced stainless steel surface coloring. The three elements in the Lab color space under the aforementioned laser-induced coloring process parameters were measured. The results show that the color difference ΔE of the samples is less than 7, the color of the color block surface is stable, uniform, and undamaged, and the obtained laser-induced process parameters are repeatable. This research topic has great application value in industries such as automobiles and electronics.

In the experiment of this work, high purity hafnium (Hf) sample are irradiated with the a 1.064 μm Nd∶YAG pulse laser to generate plasmas in a vacuum chamber, and the soft X ray time integral spectra of Hf plasma in the wavelength range of 1.0 ~ 8.5 nm under different power densities are measured. First, the atomic spectrum data of unresolved transition arrays (UTA) atomic spectrum data is calculated based on Cowan program, and the data are broadened to Gaussian line shape, which is in good agreement with the experimental spectra. Then, the ion abundances of Hf plasma from Nd∶YAG laser with electron temperature ranging from 0 to 500 eV are calculated based on the collision radiation balance model (CRM). The results show that the abundance of high valence Hf ions increases with the increase of electron temperature, which is consistent with the experimental spectral analysis. Comparing experimental and theoretical calculations, it is found that the indistinguishable transition arrays of 4f n-4f n-15g of Hf XXI-Hf XXV and 4d n-4d n-15p of Hf XXVII-Hf XXXV are located in the water window band. Finally, based on MED103, the spatiotemporal evolution of the plasma under the experimental conditions is simulated, and the temporal and spatial distributions of electron density and electron temperature are obtained. Through the analysis and comparison of electron temperature and electron density distribution under different laser power density, the experimental spectrum and CRM calculations results are further verified.

Via-hole processing was carried out in the 2 mm thick nickel-base superalloy GH4037 by the millisecond pulse laser precision drilling system. In order to solve the problem that the overflow of the set number of via-hole machining laser pulses in the traditional control variable method might cause many adverse effects, the mathematical model of the threshold number of laser pulses was established by the penetration detection technology. The influence of the defocusing amount, the beam expanding ratio and the pulse repetition frequency of the laser on the inlet and outlet aperture, the taper and the drilling efficiency was studied by the improved control variable method based on the mathematical model. The results indicated that when the defocusing amount was -2 mm to 0 mm, the beam expanding ratio was 2 to 4, the repetition frequency was 45 Hz to 85 Hz, and the auxiliary gas was oxygen, the drilling efficiency could be improved by 89.09% compared with the traditional control variable method.

A systematic research on the gain-switched thulium-doped fiber laser is carried out in this paper. Based on the rate equation and the propagation equation, numerical models of a gain-switched thulium-doped fiber laser oscillator and an amplifier are constructed, and the solution is obtained by the finite difference time domain method. The characteristics of 2 μm laser output under different pump light and laser structure parameters are explored theoretically and experimentally. Through numerical simulation and experimental optimization, the nanosecond laser output at 2 μm band with high conversion efficiency, narrow linewidth, and single polarization is obtained. The seed source oscillator obtains the highest power of 796 mW, pulse width of 67.9 ns, and slope efficiency of 54.4%. A 2 μm pulsed laser with the highest power of 9.13 W and pulse width of 50.5 ns has been obtained after the first-stage amplifier. Simulation results of the numerical simulation model agree well with the experimental results. The model can provide a reference for the experimental research and engineering design of this type of laser.

A novel discontinuous Galerkin time domain (DGTD) method based on compressive sensing (CS) is proposed to accelerate the analysis of electromagnetic characteristics of cavity devices. In the method, a nodal basis function and a leapfrog scheme are used for the spatial and time discretization of Maxwell equations. Meanwhile, all elements in the computation domain are updated individually by applying the conventional method at the initial stage for electromagnetic field updating. When the electromagnetic wave covers the whole domain, all elements are updated as a whole and a global solution is conducted. First, the underdetermined equations are established by randomly extracting rows from the global mass matrix. Second, the results after a few previous time steps are taken as the prior knowledge to construct a sparse transform. Finally, the underdetermined equations are solved by the recovery algorithms to realize the fast analysis of electromagnetic characteristics of cavity devices.

Effects of nanosecond pulsed fiber laser surface remelting on the microstructure, mechanical properties, and wear-resistance of 316L stainless steel were investigated. Three-dimensional laser scanning confocal microscopy, optical microscopy, and scanning electron microscopy were used to characterize the surface morphologies, microstructures, tensile fracture morphologies, and wear morphologies of the stainless steel before and after remelting. The results show that the remelting layer can be divided into a planar crystal zone, a dendrite growth zone, and an isometric zone from the bottom to the surface. Laser remelting can increase the tensile strength of 316L stainless steel from 580 MPa to 710 MPa, significantly increasing the microhardness and wear resistance of the stainless steel.

Aiming at the technical challenge that it is difficult to realize the on-site detection of the particle size of the underground injection water for the water-drive oilfield development, we present a design concept of an optical system based on the optical scattering principle for the on-site injection water particle size detection. Using a laser beam with a wavelength of 640 nm and a 4× collimated beam expander system, we obtain an 8 mm illumination aperture. Using pupil matching and aberration balance, we achieve the optimal design of a compact optical system with a diameter of 42 mm, which meets the particle size detection requirements in the 1--100 μm range and has the ability to realize the real time underground on-site detection. The focal length of the optical system is 50 mm, the field of view is 17°, the aperture is 8 mm, and the spot radius within the field of view is less than 6 μm, which can effectively avoid the interference of non-scattered light on the energy of the photosensitive ring. The detection of standard particle samples via prototype shows that the test accuracy is less than 5%, which meets the design requirements and thus verifies the feasibility and rationality of the designed system.

An optoelectronic oscillator with time delay varying feedback is an important means for generating laser chaos signals in a high speed optical chaos security communication system. Three typical routes to laser chaos (cataclysm, periodic and quasi periodic oscillations, and ‘breather’ oscillations) and their characteristics are investigated in detail through analyzing the Hopf bifurcation behaviors. The simulation shows that with the increase of time delay, the complex degree of the output signal increases, and when the time delay is large enough, there occur periodic pulse phenomena within a limited time range. In addition, there exists a critical point caused possibly by the filer, at which the phase diagram changes suddenly, but the complex degree of the output signal does not change obviously.

This paper presents an energy flow uniformity measurement system and method based on CCD camera and dual Lambertian target. The system has two Lambertian targets, one of which is fixed and water-cooled. An heat flow detector at the center opening of the target is used to obtain the regional gray value. The other is a movable Lambertian target, which is used to capture spot images without a detector. The proposed method can directly obtain the pixel gray value of the detector area, making the measurement process simple and accurate. In this paper, the measurement principle and the entire process of extracting the energy flow density distribution of the gray images of the focus spot are described in detail. The platform is built and the spot energy flow distribution of multiple small heliostats is measured, verifying the correctness and feasibility of the proposed method. It can be seen from repeatable experiments and error analysis that the peak energy flow density error detected using the proposed method is less than 2.4%. The proposed method can be used for the energy flow distribution detection on the surface of the heat-absorbing tube at the opening plane of the secondary condenser in a linear Fresnel concentrator system.

In this study, a solar blind ultraviolet optical system with a fast focal ratio and long focal length is presented. Its F number is 2.0, and its focal length is 100 mm. The ratio of the total length to its focal length is approximately 1.5. The proposed system comprises all spherical lenses without using aspherical or diffractive optical elements, which is convenient for manufacturing and testing. The positive lenses are made of calcium fluoride, and the negative lenses are made of fused quartz, which are used to effectively correct the color aberration. The maximum lateral color aberration is less than one pixel in size. Design results show that the proposed system exhibits excellent imaging performance, high resolution, and is compatible with the characteristics of fast focal ratio and long focal length, which satisfies the design requirements. Furthermore, the tolerance analysis demonstrates that the proposed system can be realized in the practical engineering.

This paper describes a theoretical study of the lowest-order transverse electric (TE1) mode of a terahertz parallel-plate metal waveguide, and an approximate expression for the effective refractive index of the TE1 mode of the terahertz parallel-plate metal waveguide is derived under the condition of real metal parameters. First, the TE1 mode is numerically simulated based on the finite element method, and the simulation results are compared with the values obtain from the approximate expressions to verify the feasibility of the theoretical derivation. The error analysis shows that the deduced approximate expression has high accuracy in the entire terahertz band and exhibits the characteristics of a wide range of applicable frequencies. Simulation results show that this approximate expression has a high degree of applicability to the analysis of the TE1 mode and will promote the research and application of parallel-plate metal waveguides.

Aiming at the large error problem of distance vector-hop (DV-Hop) algorithm in multilateral positioning, the cause of positioning error is analyzed in detail, and an improved artificial bee colony optimization DV-Hop localization algorithm is proposed in this work. The algorithm introduces a mathematical optimization model, uses an improved area-limited artificial bee colony algorithm to optimize the model, and optimizes the execution process of multilateral positioning. Experimental results demonstrate that the modified artificial bee colony algorithm can reduce the error and the amount of calculation in the multilateral positioning stage, and the positioning effect is good.

Herein, a series of blue organic electroluminescence devices are fabricated with 4,4',4″-tris(N-carbazolyl)triphenyl-amine (TCTA), N,N'-dicarbazolyl-3,5-benzene (mCP), and 1,3,5-tri(m-pyridin-3-ylphenyl)benzene (TmPyPB) as the host materials. Owing to the different lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO) energy levels of the host materials, a structure in the light-emitting layer (EML) with different energy level gradients is formed by changing the host materials and the number of EMLs. The effects of different EML structures on the performances of blue phosphorescent organic light-emitting diode are investigated. Among them, the double light-emitting layer device A3 with the host materials of TCTA and mCP obtains the best performance, and the maximum current density, the maximum current efficiency, and maximum luminance are 134.94 mA/cm 2, 40.28 cd/A, and 12070 cd/m 2, respectively. Among all devices, device A3 also exhibits the characteristics of low turn-on voltage (3.25 V) and low efficiency roll-off.

This paper studies the superposition characteristics of singularity beams, theoretically analyzes the phase distribution and polarization distribution after superposition of singularity beams, and experimentally verifies the correctness of the theoretical derivation. The polarization state of superimposed same-order non-coherent vortex beams is analyzed, and it is found that the superimposed beam maintains the original orbital angular momentum and the polarization state of the beam changes periodically with the azimuth. The change period is determined by the vortex topological charges. The variation of the polarization state of the light field after superposition of the cylindrical vector beams with different polarization topological charges is analyzed. The superposition characteristics of the cylindrical vector vortex beams with both phase singularities and polarization singularities are investigated, and it is found that the polarization state of the superposed beam varies periodically with the azimuth, where the change period is determined by the vortex topological charges. The polarization state of each point of the light field is determined by the vortex topological charge, polarization topological charge, and initial phase angle.

In this paper, a mathematical model of intensity distribution in multi-beam interference field is established, and the four-beam interference light field based on the joint modulation of azimuth angle, incident angle and polarization angle is simulated by Matlab. The influence of changes in beam azimuth angle, incident angle and polarization state on multi-beam interference is analyzed, and the reason for the formation of the isolation band phenomenon in the asymmetric incident light field is explained. Based on the interference of four-beam and the combination of polarization states of s-s-s-s waves, the azimuth angle of one beam is rotated 180° and the incident angle is changed. A method for fabricating high aspect ratio elliptical array is obtained. Experimental results show that the polarization vector of the beam is determined by the azimuth angle, the incident angle and the polarization angle. Due to the introduction of two degrees of freedom of azimuth and incidence angle, the diversity of interference patterns is increased by asymmetric incidence, which makes the multi-beam interference not only limited to the preparation of periodic circular aperture array and circular dot array, but also provides theoretical reference for the preparation of multi period and trans-scale patterns.

To investigate the relationship of the soil organic matter (SOM) content to the electrical conductivity (EC), pH, and Fe content, we collected 110 samples at the Ebinur Lake Reserve in August 2017 and measured the soil reflectance spectra, SOM content, EC, Fe content, and pH. We performed three kinds of pre-treatments, including Savitzky-Golay (SG) smoothing, multiplicative scatter correction (MSC), and first-order differentiation (FD), on the original spectrum and then performed a principal-component analysis of the spectral data. The eigenvalues of the first five principal components were selected as the spectral variables. Strategy I used the original spectrum, performed SG-MSC and SG-MSC-FD on it, and employed the original spectrum as a control group. Strategy II used the soil covariates (EC, Fe, pH) as the input variables. Strategy III combined strategy I and strategy II. Predictions of the SOM content were obtained for all three strategies using partial least squares regression. The results show that predictions based on the pre-processed spectral data (for the verification set, the coefficient of determination was R2=0.66-0.82) were better than those based on the soil covariates as the prediction variables (for the verification set, the coefficient of determination was R2=0.40) and that combining the soil covariates and spectral data significantly improved the spectral-prediction accuracy for SOM (for the best verification set, R2=0.88). Pre-processing the spectral data effectively enhanced the potential spectral information and improved the predictive accuracy of the model. In summary, the combination of visible-near-infrared spectral information and soil covariates effectively improves the predictive performance of SOM models.

To improve the accuracy of all-sky cloud detection of ground-based infrared cloud-measuring system, the corresponding relation between downwelling infrared radiation and optical depth of clouds was simulated by Santa Barbara DISTORT Atmospheric Radiative Transfer (SBDART) model. The simulation result shows that it is feasible to invert optical depth by fitting its curve. On this basis, a new method under a combination of infrared and laser technologies was proposed. First, more accurate atmospheric profiles and precipitable water vapor applicable to specific regions and seasons were established. Simultaneously, the aerosol and cloud base height were inverted by laser extinction profiles. Second, the atmospheric parameters obtained above were substituted into SBDART to simulate the cloud optical depth inversion curve at zenith. Finally, the optical depth distribution of the all-sky clouds could be inverted by the curve. The experimental results reveal that the distribution of the all-sky optical depth obtained from the inversion curve of single- and two-layer clouds is consistent with the distribution of the all-sky radiation. Moreover, the optical depth of clouds at different heights in the all-sky is clearly distinguished.

This paper proposes a laser self-mixing interference (SMI) detection method that simple structure, easy collimation, and can detect single micro-nano particle. A laser SMI signal model generated by a single particle is established, the characteristics of the interference signal are theoretically analyzed, and a microfluidic particle detection system is built. Self-developed LabVIEW program is used to carry out detection experiment and signal acquisition of polystyrene particles, and the diameter of a single particle is analyzed from both the time-domain and frequency-domain. The results show that the method can effectively detect and distinguish polystyrene microspheres with diameters ranging from 0.5--10 μm.

This study investigates the role of shaping circuits in lidar systems. Two types of pulse-shaping circuits based on the constant-ratio timing and pulse peak detection methods are designed. Performance experiments on the above mentioned pulse-shaping circuits are carried out in a laboratory and under external conditions to investigate the performance of different pulse-shaping circuits in lidar systems. The circuits based on the constant-ratio timing and pulse peak detection methods show sub-ns time discrimination capabilities. The time discrimination capability of the constant-ratio timing circuit is slightly affected by distance and echo pulse; therefore, the detection accuracy needs to be optimized. This study provides a reference for the optimization of the ranging accuracy of lidar systems.

One-dimensional (1D) well-ordered nanostructures of functional oxides open new avenues of applications in wide-range of fields, such as nano-laser, flat panel display, magnetic memory, nano-transistors due to their unique chemical and physical properties. Precise synthesis and assembly of well-ordered 1D oxide nanostructures is therefore essential to the development of next generation nanodevices. Pulsed laser deposition (PLD) is one of the most important methods for producing well-ordered 1D oxide nanostructures. Here we briefly introduce the fundamentals and characteristics of PLD techniques, discuss in detail on the routes and mechanism of preparing 1D well-ordered oxide nanostructures by PLD, and review current research process centering on several typical oxide nanostructures fabricated by PLD. At the end of this review, we briefly point out the existing problems in preparing well-ordered 1D nanostructures by PLD and prospect the application of ultrafast laser in this technology.

Photodynamic therapy based on Cherenkov radiation is a new type of photodynamic therapy without external light excitation. Cherenkov radiation produced by radionuclides can activate photosensitizers nearby to produce reactive oxygen, so as to damage target cells and tissues. It overcomes many limitations of the traditional photodynamic therapy, such as limited tissue penetration and dependence on external light. It is a promising new field and provides a novel direction for tumor treatment. The weak Cherenkov radiation, the attenuation of Cherenkov radiation by tissues, the lack of corresponding photosensitizers, and the poor tumor targeting are the key factors limiting the further clinical applications of Cherenkov radiation. How to enhance the efficacy of photodynamic therapy based on Cherenkov radiation is the future research focus. Increasing the intensity of Cerenkov radiation and combining with nanotechnology to modify the surface of photosensitizers can improve the therapeutic effect. Meanwhile, the mechanism of photodynamic therapy is still controversial and further studies are needed. The research progress of photodynamic therapy based on Cherenkov radiation for tumors is reviewed.

A spaceborne Doppler wind lidar is an efficient active detection device that can be used to obtain the global three-dimensional atmospheric wind field in global scale. It is able to make up for the weakness of passive sensing of meteorological satellites. The review for its requirements and progress indicates important scientific significance. First, this study describes the urgent needs for three-dimensional wind fields in various fields such as accuracy improvement of weather forecast, numerical weather forecast model assimilation, and global climate change research. Then, it reviews the development history of spaceborne wind lidar based on three schemes of coherent detection, direct detection and hybrid detection, and summarizes the challenges of the present spaceborne wind lidar. After that, according to the research progress of Chinese Doppler wind lidar, this paper summarizes the current seven key and unsolved technologies of Chinese spaceborne wind lidar. Finally, it is suggested that the spaceborne hybrid wind lidar with the advantages of both coherent detection and direct detection can well reduce the research and fabrication cost and significantly enhance the detection accuracy of atmospheric vertical wind profiles, and the spaceborne hybrid wind lidar will be the future trend in the field of spaceborne wind lidar.

The imaging spectroscopy technology can obtain the spatial and spectral information of the observed object, and effectively distinguish the material composition of the object surface. It is widely used in the military and civilian fields. In recent years, the imaging spectroscopy devices based on filter arrays have received extensive attention due to their compact structure, fast imaging speed, and large coverage band. As a core component to determine the spectral performance of such devices, the filter array is a research hotspot. In this paper, by summarizing the main progress of spectral filter arrays, the advantages and disadvantages of different spectral filter arrays and their application range are analyzed, and the development trend of spectral filter arrays is prospected.

In this paper, laser-induced breakdown spectroscopy (LIBS) was used to obtain 320 sets of spectral data at different positions on the surfaces of aluminum alloy samples. Then, these spectral data were preprocessed, and 20 characteristic spectral lines of the six main elements in aluminum alloy were selected to form a 320×20 spectral data matrix. Next, the 20 variables that were inputted into the model were reduced to 6 through principal component analysis. Finally, the reduced-dimensional spectral data were inputted into the radial basis function neural network model to establish multivariate calibration models for five main nonaluminum elements (Si, Fe, Cu, Mn, and Mg) in aluminum alloy. The results revealed that the mean goodness of fit of the model was 0.978 and its mean root mean square error was 0.31%. Principal component analysis combined with a radial basis function neural network can effectively reduce parameter fluctuations, correct matrix effects, and improve the accuracy and stability of the model quantitative analysis; in particular, this combination can significantly improve the accuracy of analysis of elements with relatively low content, such as Fe, Si, and Cu.

To achieve the online correction of the misaligned error of large aperture thin film splicing mirrors, an imaging model comprising five pieces of Fresnel lens was established herein. By analyzing the point spread function (PSF) and the modulation transfer function of the optical system in the presence (MTF) of the misaligned error, the relationships between the misaligned error and PSF as well as MTF were obtained. The stochastic parallel gradient descent (SPGD) algorithm was used to correct the misaligned error online. To verify the performance of the proposed algorithm, five performance evaluation functions, including sum of square of far-field light intensity, equivalent radius of far-field light spot, power in barrel, MTF integral, and second-order moment of light intensity, were selected as optimization indexes to correct the misalignment error, and the convergence speed and accuracy of evaluation indexes were compared. The correction results of 100 random errors show that the five indexes can convergence, and the root mean square values of the corrected wavefront are less than 0.13λ and the Strehl ratio is greater than 0.96. The MTF integral and the second-order moment of light intensity converge fastest, and the precision of the equivalent radius of far-field facula index is optimal.

The interfacial stress in sapphire-GaN heterogeneous film system is simulated using the finite element method herein. The distribution of the interfacial stress and its influencing factors in the process of the growth temperature (1373 K) falling to the room temperature (300 K) are studied. The rationality of the proposed model was verified through theoretical calculations. Results show that the interfacial stress in the system is uniformly distributed along the radial direction, and only the interfacial stress at the edge changes suddenly and drastically. When the thickness of GaN film or sapphire substrate is changed without considering the edge effect while the thickness of another is unchanged, the maximum value of interfacial stress appears when the thickness ratio ds/df of sapphire substrate to GaN film is approximately 1.5, and the minimum value appears when the thickness ratio is approximately 4.3. It shows that the interfacial stress of the film system is not determined by the difference of coefficient of thermal expansion or the difference of temperature, but it is greatly influenced by the thickness ratio. Furthermore, it is found that the stress due to lattice mismatch is much greater than that owing to thermal mismatch.

Phase compensation is one of the key technologies for pulse compression and ultrashort laser pulse generation. First, we use the phase function of the Fresnel binary phase shaping scheme can achieve a lens-like function, and can introduce a negative secondary spectral phase (negative dispersion) in the frequency domain. Then, the proposed scheme is used to compensate the dispersion of the chirped pulse, thereby turning it into a transformed-limited pulse, and its pulse width is compressed to the time width of the transformed-limited. The proposed scheme is only related to the quadratic phase and does not depend on the spectral amplitude, so it is applicable to various pulse shapes with symmetrical distribution. Finally, the numerical calculation results of common Gaussian pulse and square-wave pulse are given to verify the correctness of the proposed scheme in theory. The proposed scheme provides a new idea and method for chirped pulse compression, and can be extended to other fields related to dispersion compensation.