Four lowest Ω substates (X2Π3/2,g, X2Π1/2,g, A2Π3/2,u and A2Π1/2,u) of the I+2 cation are studied by high-precision ab?initio calculations, and the calculated results are compared with the experimental high-resolution spectra of literatures. Firstly, the potential energy curves of the four Ω substates are calculated using the multi-reference configuration interaction (MRCI) method, and the rovibrational levels of these electronic states are derived by solving the radial Schrodinger rovibrational equation. Then, molecular constants are obtained by fitting energy levels to a spectroscopic model, and based on the fitted spectroscopic constants and calculated transition dipole moment matrix elements, line strengths of vibronic bands in the A2Π3/2,u- X2Π3/2,g system for 45 bands with υ'=11-19 and υ''=1-5 have been derived, and the Einstein A coefficients are employed to compute radiative lifetimes of the υ'=11-19 vibrational levels of the A2Π3/2,u state. Finally, based on the calculated predissociation lifetimes of the higher vibrational levels, the predissociation mechanism of the A2Π1/2,u state is discussed.

To improve the detection accuracy of laser-induced breakdown spectroscopy (LIBS) for heavy metal elements in water, LIBS technique is combined with single variable calibration curve (SVCC-LIBS) method and partial least squares regression (PLS-LIBS) method respectively to quantitative analyze Cr, Mn, and Ca in mixed aqueous solutions. The influence of coexisting elements on the detection accuracy of analytical elements is studied by PLS-LIBS. The results show that the detection accuracy of analytical elements is greatly influenced by coexisting elements, and the total relative errors of the prediction of the analyzed element concentrations are significantly reduced when the analytical line intensities of analytical elements and coexisting elements are taken as the input variables of PLS model. The total relative errors of concentration prediction of Cr, Mn, and Ca elements obtained by SVCC-LIBS method are 14.3%, 8.46%, and 6.35% respectively, while the relative errors of PLS-LIBS method are improved to 2.30%, 0.74%, and 0.03%, respectively. The linearity R2 of the concentration prediction correlation curve for Mn element is improved from 0.985 for SVCC-LIBS method to 0.999 for PLS-LIBS method. The research results indicate that the PLS-LIBS method can effectively improve the detection accuracy of trace metal elements in mixed aqueous solutions.

Rosa rugosa Thunb., Rosa sp. and Rosa chinensis Jacq. all belong to the genus Rosa L. The three kinds of flowers are similar in appearance and easily confused. The genus Rosa L. has important ornamental value and medicinal value, so it is of great significance to quickly identify the genus Rosa L. Laser induced breakdown spectroscopy (LIBS) is used for in?situ detection of the main elements in the three flowers in this work. In addition, CN can also be recognized in the spectrum of the genus Rosa L, sothe CN in the spectrum is simulated by using LIFBASE, and the vibration temperature and rotation temperature of CN are calculated. Then the parameters obtained can be regarded as experimental parameters. By comparing and analyzing the laser induced breakdown spectra of the three different kinds of flowers, the characteristic spectral lines with significant difference in intensity are selected as variables to predict flower genus, and combined with the general regression neural network (GRNN), the prediction accuracy could reach 93.3%.

The characteristic analysis of the seawater hydrate enrichment area can be used as an important basis for deep-sea combustible ice exploration. In order to analyze the dissolved gases in seawater in real time, the off-axis integrating cavity output spectroscopy (ICOS) is used to detect the dissolved gases obtained by membrane separation technology. A precise spectrum analysis instrument suitable for deep-sea navigation observations is built, and theoretical analysis and experimental verification are carried out. The experimental results show that the detection range of CH4 concentration (volume ratio) is 1.073×10-8-1×10-3, the detection range of CO2 concentration (volume ratio) is 3.39×10-6-1×10-2, the measurement accuracy of CH4 isotope abundance is 1.2‰, and the measurement accuracy of CO2 isotope abundance is 1.74‰. It is shown that the system has good sensitivity and stability, and can realize continuous navigation observation in the deep sea.

Photoacoustic spectroscopy (PAS) technology is very useful in online detection of dissolved gases in transformer oil to ensure the safety of transformers. However, in the outdoor environment, the measured background signal of the instrument is easily affected by the ambient temperature and humidity, and the correction of these factors must be considered to improve the stability and reliability of the online measurement of PAS instrument. The background correction factor is generally obtained by regressionof different humidity and temperature measured in the laboratory, but the environment often changes during measurement procedure, so a robust regression algorithm is needed to obtain accurate correction factor. The temperature and humidity correction method based on the support vector regression is studied in this work. Acetylene is selected as the research object. Humidity air with different concentrations is generated by using humidity generator in laboratory,and the temperature of the PAS cell is measured by temperature sensor, and then the background signal correction factor of acetylene is regressed from the measured data. Furthermore, the method is verified by acetylene air mixture with acetylene volume fraction of 0, 5×10-6 and 2×10-5. The results show that the proposed method and the least squares regression method have the same trend for acetylene mixture with volume fraction of 5×10-6 and 2×10-5. Whereas the least squares regression has tendency in residuals, and the proposed method has better repeatability and stability for temperature and humidity correction than the least square method.

To meet the current demand of climate change for solar spectral radiation observation, a wavelength scanning solar spectral irradiance meter is developed in order to accurately monitor the solar spectral irradiance. The solar spectrum irradiance meter is mainly composed of a spectrum measurement unit and a wavelength scanning unit. As the precise positioning mechanism of dispersion spectrum, the wavelength scanning unit is the key to ensure the measurement accuracy of the instrument. Therefore, a wavelength precision scanning positioning device based on a small AC servo motor is designed. In the device, the rotation of the motor is controlled by a timer, the linear CCD is driven by STM32 to work, then the closed-loop control is realized with the precisionless than 2 pixels based on the deviation between the centroid position detected by the CCD and the preset position. Finally, the repeatability of the linear CCD centroid position detection and the stability of the scanning positioning device are tested. It is shown that the standard deviation of CCD centroid position detection is 0.0693, the maximum deviation does not exceed 0.3 pixels width, and the closed-loop accuracy of the system is less than 2 pixels width during operation, which meets the repeatability and stability requirements of wavelength scanning.

An optimized partial least squares (PLS) quantitative prediction model is designed for the nondestructive determination of apple acidity by visible and near infrared spectroscopy (Vis-NIRS). Firstly, Savitzky-Golay smoothing combined with wavelet transform is used to preprocess the spectral data. Then the successive projections algorithm (SPA) is used to generate a modeling set, and a modeling candidate set is also generated at the same time by the competitive adaptive reweighted sampling (CARS) and SPA. Furthermore, the wavelength variable is successively selected from the modeling candidate set to the modeling set, and a prediction model is established finally according to the modeling set until the change of the determination coefficient tendsto be stable, thus achieving a best-fit model. The experimental results show that when apple acidity is predicted, the determination coefficient and the relative percent deviation of the optimized PLS model reaches 0.9776 and 6.6812 respectively, and thenumber of selected wavelength variables is reduced from 129 to 36, which is obviously superior to that of SPA and CARS. The designed model not only ensures the model accuracy, but also reduces its complexity, which provides an important reference for theestablishment of online nondestructive determination model of apple acidity.

Based on the free electron gas model, the plasmon frequency of a monolayer-atom system is solved by using the linear response theory and the Green function method, and the analytic expression for the plasmon dispersion, which can be applied to high electron density and short wavelength cases, is obtained. The results show that the thickness of the atomic layer can reduce the plasmon frequency. The thicker the atom layer is, the smaller the plasmon frequency will be, and this reduction is more obvious when the wave vector is larger. When the thickness of the monolayer-atom system tends to zero, the plasmon dispersion of the monolayer-atom system tends to that of a pure two dimensional system. In addition, in the first-order approximation of the plasmonfrequency in monolayer-atom system, it is found that the relative correction of the plasmon frequency in the case of long-wave approximation is linearly related to the wave vector and the thickness of the atomic layer.

Limited by the imaging mechanism, the spatial resolution and temporal resolution of ghost imaging are mutually restricted. If the spatial resolution is higher, more modulation patterns are required, so the longer acquisition time is consumed. Aiming at this bottleneck, a method using multiple low spatial resolution patterns to simultaneously modulate high spatial resolution object is applied, a single-pixel detector is employed to collect the corresponding backscattered signal, and the iterative algorithms and compressed sensing algorithms are employed to construct the high spatial resolution image of the imaging object. The effectiveness of the proposed method is verified by numerical simulations. Itis shown that the high spatial resolution ghost imaging technology implemented here can greatly reduce the number of modulated patterns as well as the online sampling time. Therefore, it is believed that the method has important application value in biomedicine and other fields which require high spatial resolution and less sampling time.

The traditional photon tomography method cannot be suitable for the objects containing heavy metal shielding. So in this study, based on the visual characteristics of photon tomography, pixel prediction based on unsupervised learning is carried out for the tomographic projection, and an encoder based on the surrounding information of metal shielding is constructed to generate the structure of the sheilded area. At the same time, on the basis of the generative adversarial network (GAN), the encoder is used as the generative network, and the discriminator is built for the training of the encoder. The results show that the reconstruction method based on pixel prediction can reconstruct the photonic tomography information in the area covered by heavy metal shielding, and the reconstruction results can accurately reflect the internal details of real objects, which indicates that the reconstruction method based on pixel prediction can effectively reduce the influence of metal structure in the object on the tomography results.

The matching of time domain stretcher and compressor is the key to obtain high contrast femtosecond pulse in chirped-pulse amplification (CPA) laser system. Compared with the conventional Martinez type stretcher and ffner type stretcher, the stretcher based on concentric structure can eliminate the effect of higher-order dispersion induced by aberration due to the fact that the object is completely coincident with the image, and can further realize better pulse compression with double grating compressor. The concentric stretcher, which consists of a transmission grating pair and a concave mirror, has the advantage of compact structure. Replacing the original Martinez stretcher with the concentric stretcher, under the condition of 1 kHz repetition rate and11.4 W pump power, the stretched chirped pulse is amplified by the ring-cavity Ti: Sapphire regenerative amplifier and then compressed by the grating pair compressor. The compression result with pulse duration of 47.5 fs is obtained, which is close to the Fourier transform limit of spectral bandwidth of 22.1 nm. The results show that the concentric stretcher based on transmission grating can achieve better compression result for femtosecond pulse.

The process of ultrafast laser regenerative amplification has complex dynamic behavior that requires to build a model for solution and iterative calculation. Based on the improved Frantz-Nodvik equation, the output properties of the Yb:KGW regenerative amplifier are calculated, the influences of pumping intensity, crystal length and pumping duration on the output performance of the amplifier are investigated, and the output behaviors of the regenerative amplifier with different repetition rates are also analyzed. Based on the theoretical analysis, a regenerative amplifier is constructed and the laser amplification results with pulse energy of 1 mJ at repetition rate of 1 kHz are realized, which are in good agreement with the theoretical analysis results. The improved Frantz-Nodvik equation gives an insight into the design of laser amplification which is scalable to high pulse energy with high stability at high repetition rate.

In order to reduce the hole leakage of deep ultraviolet laser diode (DUV-LD) in the n-type region effectively and optimize its performance, a novel M-shaped hole blocking layer (HBL) structure is proposed. By using Crosslight software，the rectangular, N-shaped and M-shaped HBL structures are simulated and compared. It is found that the M-shaped HBL structure can more effectively reduce the hole leakage in the n-type region, increase the radiation recombination rate in the quantum well, reduce the threshold voltage and threshold current of the laser diode, and improve the electro-optic conversion efficiency and output power of the laser diode. It is shown that the M-shaped HBL structure can effectively reduce the hole leakage of DUV-LD in the n-type region and optimize its performance.

A 1570 nm single-wavelength fiber laser based on fiber Bragg grating (FBG) with direct emission was demonstrated in this work. A Sagnac broadband reflector composed of fiber coupler and a output coupler composed of a partial reflection FBG were used to build a straight cavity fiber laser. By optimizing the reflectivity of the FBG and output direction, the highest resonant efficiency of 24.42% was realized with the maximum output power of 2.834 W and the side mode suppression ratio of 65 dB. By increasingthe cavity length to increase the number of resonant longitudinal modes, the stable beat-free laser emission of 1570 nm single wavelength fiber laser was obtained based on the average effect among the longitudinal modes. And then, the passively mode-locked output of 2 μm-band fiber laser was realized by utilizing the 1570 nm fiber laser as the pump source of thulium-doped fiber.

The properties of the macroscopic quantum superposition state prepared by modulating the opto-mechanical coupling in an atom-cavity ultrastrong coupled opto-mechanical system are studied, considering the effects of the initial state of atom-cavity and theatom-cavity coupling strength. Firstly, the evolution operator of the system is calculated by the method of Wei-Norm, and the analytic form of the evolution wave function of the whole system is given for any atom-cavity initial state. The results show that, assuming that the atom-cavity system is measured, the oscillator will be in a macroscopic quantum superposition state under certain conditions. Then the analytical expression of Wigner function of the macroscopic quantum superposition state of the mechanical oscillator is given, and the possible factors affecting the quantum properties of the macroscopic quantum state are calculated and analyzed. Finally, the influence of different initial states of atom cavity on the strength of macroscopic quantum coherence is discussed, and the initial state parameters with the strongest macroscopic quantum coherence are given. The influence of atom cavity coupling strength on the quantum coherence of macroscopic quantum superposition state is also discussed. It is found that the stronger the coupling strength is, the stronger the quantum coherence of macroscopic quantum superposition state will be.

In order to explore the exciton effect of two-dimensional layered transition metal sulfide, especially the up-conversion fluorescence process, the layered WS2 sample was taken as an example to study. Using 532 nm continuous laser and micro-Raman technology, the physical origin and basic properties of X0 and X- exciton of WS2 crystal were investigated. The continuous laser of 633 nm was used to realize single photon up-conversion fluorescence enhancement, which confirmed the physical mechanism of double resonance, that is, the incident light resonates with the X- exciton state, then exciton transitions to the high-energy X0 exciton state with the aid of optical phonons A1g and E12g, and finally produces spontaneous up-conversion fluorescence. In addition, the influencing factors of X0 were further analyzed including exposure time, temperature and excitation power. The fitting results showed that the up-conversion fluorescence efficiency could be improved by appropriately increasing the exposure time, decreasing the ambient temperature and increasing the excitation power.

Reduced graphene oxide-CuInS2 quantum dots (rGO/CuInS2-QDs) hybrids with different weight ratios of rGO and CuInS2-QDs are controllably synthesized by solvothermal method. Then graphene based hybrid polymer solar cells are fabricated by blending the rGO/CuInS2-QDs hybrid with poly(2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylene vinylene) (MEH-PPV) as photoactive layer, and the effects of the weight ratio (x) of rGO to CuInS2-QDs in rGO/CuInS2-QDs hybrid acceptor material and the weight ratio (w) of MEH-PPV donor material to rGO/CuInS2-QDs hybrid acceptor material in photoactive blend on device performance are studied. The results show that when the content of rGO/CuInS2?(x=0.25) hybrid acceptor material increases from 10% (w=9) to 17% (w=5), the electron collection efficiency (ηc) of the device increases from 0.61 to 0.78, which improves the photoelectric conversion efficiency of the device.

As one of the effective means of atmosphere detection, lidar is developing towards miniaturization and lightweight. In view of the function specificity of lidar, the detection and acquisition system is integrated and optimized based on field programmable gate array (FPGA). The handshake protocol and the synchronous finite state machine are used to complete the construction and transmission of data link between modules. FIFO is used as the data memoryof ADC, FIFO data is burst into DDR orderly through AXI bus protocol and Xilinx MIG IP, and the transmission of the collected data is completed through Gigabit Ethernet. The data acquisition card of lidar based on FPGA integrates the gain control function of photomultiplier tube and echo signal acquisition function, and supports the compatible hardware and logic design. Therefore, it has many advantages such as high integration, convenient gain adjustment and high precision, fast and convenient acquisition, and fast adaptation.

Polar optical phonon modes in wurtzite GaN nanowires with equilateral triangular cross-section are deduced and analyzed by using the dielectric continuum model. It is found that the frequency of exactly confined (EC) modes in the GaN nanowire systems is the characteristic frequency (ωz,L) of longitudinal-optical phonons in free z-direction, which is obviously different from the case of EC modes in wurtzite GaN-based quantum wells due to their different confined dimensions. Then by using the method of nonseparable variables, the Laplace equation of the electrostatic potential of the nanowire structure is solved, the exact analytical phonon states of EC modes are obtained, and the polarization eigenvectors and their orthogonal relations, the free phonon field, as well as the corresponding Frohlich electron-phonon interaction Hamiltonian for the EC phonon modes are also derived. Finally, the numerical calculation on GaN nanowire is performed, the electron-phonon coupling functions are depicted and discussed, the symmetries and coupling strength of the coupling functions are analyzed in detail, and some meaningful conclusions are drawn.

Taking Mg2Si sintered target as target, Mg2Si amorphous thin films were deposited on Si, quartz and Al2O3 substrates by magnetron sputtering method, and then the effects of substrate type, annealing temperature and annealing time on the structure of Mg2Si polycrystalline thin films were investigated. The results show that the optimal annealing temperature and annealing time of Mg2Si films on Si, quartz and Al2O3 substrates are all 350 °C and 1 h. The crystal quality of Mg2Si film on the Al2O3 substrate is the best, followed by that on Si substrate, and that on quartz substrate is the worst. And it is found that this difference is mainly due to the different thermal mismatch between the substrate and the film.

A kind of hollow-core negative curvature fiber (HC-NCF) with polarization filtering and polarization maintaining characteristics is designed, and its characteristics are analyzed. By introducing an inner cladding ring to break the symmetry of the conventional negative curvature fiber, the fundamental mode and the inner cladding glass mode in two orthogonal directions are coupled, which increases the birefringence and loss ratio in the two polarization directions. Then the influence factors of fiber birefringence characteristics and loss are analyzed, including the wall thickness, the inner diameter of the inner cladding tube, and the core diameter. The results show that when the fiber core diameter and the inner diameter of the outer cladding tube ring are 30 μm, the wall thickness of the outer cladding and inner cladding tube ring are 1.116 μm and 1.56 μm, respectively, and the inner diameter of the inner cladding tube ring is 9 μm, the birefringence at 1.55 μm reaches 1.33×10-4, the polarization extinction ratio in the x polarization and y polarization directions ofthe fundamental mode reaches 4723 (36.7 dB), and the bandwidth with polarization extinction ratio greater than 100 is 7 nm. In addition, the minimum loss at 1.55 μm is as low as 0.03 dB/m. It is shown that this kind of polarization maintaining negative curvature fiber can be used in fiber devices that are sensitive to polarization.

Aiming at the disadvantages of optical fiber SPR open-loop system, the premature convergence problem of particle swarm optimization (PSO) with global search is improved, and an improved cooperative particle swarm optimization (ICPSO) algorithm with dynamic information adjustment and controllable speed is proposed. By introducing the optimal information of subgroups into the iterative equation of the flight-state controlling of particle, the particles' diversity is well maintained, and the premature convergence of particles in optimization flight can be effectively avoided for the proposed algorithm. Furthermore, the algorithm is used as the training algorithm of BP neural network, and a more optimized ICPSO-BP neural network is established. Finally, the ICPSO-BP neural network is used to identify and compensate the internal nonlinear model of optical fiber SPR open-loop system, and the compensation models of single-input, double-input and three-input ICPSO-BP neural network are established respectively. The simulation results show that the new algorithm has good performance in speed and accuracy test, thus ensuring the good linearity test effect of SPR, and laying a foundation for the further application of optical fiber SPR sensor.