In the space optical communication system, the laser transmission in the atmosphere is easily affected by the turbulence effect, and the single-mode fiber with a minimal mode field radius is frequently used at the receiving end for space optical coupling, resulting in a reduction in fiber coupling efficiency and a decrease in communication system performance. To improve the fiber coupling efficiency of the receiving end, the stochastic parallel gradient descent (SPGD) algorithm and the few-mode fiber coupling demultiplexing system are combined to compensate for the wavefront phase distortion caused by the dynamic turbulence. The numerical simulation of the space optical communication with the transmission distance of 5 km is achieved. The simulation results demonstrate that the coupling efficiency of two-mode fiber is 0.5 dB-1.5 dB greater than that of single-mode fiber without SPGD algorithm correction under various turbulence intensity and wind speed circumstances. The relative standard deviation is lowered by 0.03-0.4. After the SPGD algorithm correction, the coupling efficiency of two-mode fiber is improved by 0.4 dB-2.2 dB compared with that of single-mode fiber. The relative standard deviation is reduced by 0.1-0.2 under moderate and strong turbulence conditions. Consequently, using few-mode fiber for coupling in space optical communications has a better coupling effect than using single-mode fiber, which improves the communication system’s stability.

A simulated oceanic weak turbulence channel in Log-normal distribution and an equal-gain combining receiver were adopted in this paper. Various link parameters were taken into account, including avalanche photodiode (APD) shot noise, channel fading, geometrical loss, Log-normal turbulence, and aperture-averaging factor. On this basis, expressions for the average bit error rate and the upper bound of the average channel capacity of the multiple-input multiple-output (MIMO) underwater wireless optical communication (UWOC) system were theoretically derived. Simultaneously, the influences of the aforementioned parameters on the average bit error rate and average channel capacity of the system were discussed quantitatively. Simulation results show that quadrature amplitude modulation with a proper modulation index, more antennas configured, larger receiving aperture, and higher transmitting power all contribute to better system performance.

Total suspended solids (TSS) in water plays a key role in aquatic ecosystems, due to its influences on light propagation in waters and the biological functions of waters. With the bio-optical data collected during 2009—2014 from Taihu Lake, Chaohu Lake, Poyang Lake, Pearl River Estuary, and Daya Bay, this work analyzed the remote sensing response bands for variations of TSS concentrations and constructed a remote sensing-based quantitative estimation model for TSS concentrations in coastal and inland waters. The visible infrared imaging radiometer suite (VIIRS) satellite remote sensing data were employed to obtain the temporal and spatial distribution characteristics of the TSS concentrations. The results show that the model of the band ratio [Rrs(865)/kd(555)] contributed by different components of water can explain 81% of the TSS concentration changes. In the model, the Rrs(865) is the remote sensing reflectance at 865 nm and the kd(555) is the attenuation coefficient of the waters at 555 nm. Compared with other empirical models that have been reported, this model has significantly improved estimation accuracy. The verification results show that the model can be applied to coastal and inland waters. When applied to pre-processed VIIRS satellite remote sensing data, it can reveal the spatial and seasonal variations of TSS concentrations of in waters from Taihu Lake and the Pearl River Estuary.

In this paper, we investigate the identification methods and characteristics of the atmospheric boundary layer structure (ABL) in coastal areas under the influence of typhoon peripheral circulation and local sea-land breeze circulation (SLBC) based on the field observation data and the reanalysis data of meteorological elements in Maoming. We use the meteorological element sounding data and the micro-pulse lidar (MPL) observation data to analyze the applicability of the retrieving method of the atmospheric boundary layer height (BLH). Then, we propose a new MPL-based BLH recognition method, which can greatly improve the BLH results with the complex boundary layer structure. Furthermore, we analyze the ABL structure and the characteristics of the temporal and spatial changes in the atmospheric BLH under the influence of large-scale and local SLBC. In coastal areas, the influence of local SLBC is more significant without the control of large-scale weather systems and thus the ABL will have a multi-layered complex structure. In addition, the BLH shows the daily variation of wave crests and troughs. Generally, BLH starts to grow at the time of land-sea breeze transition in the daytime, and the maximum is generally about 2 km at the top of the aerosol layer at noon. Then, BLH decline is usually accompanied by the sea-land breeze transition at night, and the minimum generally appears at the stable boundary layer top below the residual layer, as low as about 500 m. Under the control of typhoon peripheral circulation, the local convection caused by the local SLBC will be suppressed. The air rising and sinking of the ABL alternation will weaken or even disappear. The vertical distribution of aerosols in the ABL is relatively uniform, and BLH and aerosol top basically coincide at about 2 km. The BLH changes little, without obvious diurnal variation.

The spatial homogeneity and temporal stability of a fountain clock’s quantized axial magnetic field are essential factors that govern frequency stability and uncertainty. In this study, the quantized axial magnetic field system of a transportable rubidium fountain atomic clock is constructed and optimally designed considering several aspects, such as external magnetic field shielding, magnetic field coil design, and coil current source stability. A five-layer permalloy magnetic shield is used to shield the external magnetic field to eliminate the influence of the ambient magnetic field on the quantized axial magnetic field. The appropriate current is obtained through simulation using four groups of symmetrical compensation coils. The fluctuation of magnetic field less than 1 nT is obtained in a 30-cm free flight trajectory of the cold atoms cloud. The temporal stability of the quantized axial magnetic field is optimized by improving the C-field supply current method, and the fluctuation of the field over time is less than 0.1 nT. After optimization, the long-term frequency stability of the fountain clock reaches 2.9×10-16, and the uncertainty of the second-order Zeeman frequency shift caused by the inhomogeneity of the magnetic field spatial distribution is less than 3.4×10-19. Additionally, the uncertainty of the second-order Zeeman frequency shift caused by the fluctuation of the magnetic field with time is approximately 5.1×10-17.

In a position measurement system based on a phase grating, the grating undergoes asymmetric deformation during processing and post-processing, resulting in a position measurement error. Therefore, this paper established a theoretical diffraction field model of an asymmetric grating and analyzed the influence of grating asymmetry on position measurement accuracy. On this basis, it proposed a weight optimization method with multi-diffraction orders according to the different sensitivity of the diffraction orders to the grating asymmetry. The method is expected to correct the measurement error introduced by the asymmetrical grating deformation. The experimental results show that when the center groove depth of the grating is 1/4 of the incident wavelength, the influence of top tilt asymmetry and bottom tilt asymmetry on the measurement accuracy can be neglected. When the duty cycle is 0.5, the effect of sidewall asymmetry can also be neglected. The position error introduced by asymmetry can be kept within 0.05 nm by the weight optimization method with multi-diffraction orders.

Aiming at the nonuniformity of the received optical power and low positioning precision in the indoor visible light positioning, a received signal strength indicator (RSSI) visible light positioning method is proposed based on adaptive flower pollination quantitative light source optimization scheme combined with improved radial basis function (RBF) based neural network. The adaptive flower pollination algorithm optimizes the light intensity of the transmitter processing the received uniform optical signal using an improved RBF-based neural network RSSI positioning method, resulting in accurate and effective positioning. The kernel principal component analysis K-means+ + (KPCA-K-means+ + )clustering model is used to preprocess the received RSSI sample value. The optimal cluster number and cluster center are obtained as the number and central value of the hidden layer neurons. The genetic algorithm and least mean square (GA-LMS) model is used to optimize the parameters of the RBF neural network. According to simulation results, the received optical power ranges from -28.6 dBm to -25.1 dBm in an indoor space of 9 m×12 m×3.5 m. Moreover, the positioning error is less than 0.1 m. Therefore, the proposed improved visible light positioning method has higher positioning accuracy and stronger practicability advantages.

We proposed a novel flip-optical orthogonal frequency division multiplexing (OFDM) scheme based on fast Hartley transform (FHT), namely Flip-FHT. FHT, as a real trigonometric transform, was used to process the Fourier transform. Therefore, Hermitian symmetry was not required for the input signal. At the same time, unlike the traditional fast Fourier transform (FFT)-based asymmetric clipped optical OFDM (ACO-OFDM), in which only odd subcarriers carried information symbols, the proposed scheme flipped the negative part of the real bipolar signal so that even subcarriers could also carry information symbols. Therefore, this scheme is suitable for intensity modulation/direct detection (IM/DD) optical wireless communication (OWC) systems. The spectral efficiency of the Flip-FHT system is 2 times that of the ACO-OFDM system, and the computational complexity at the receiver is 50% that of the ACO-OFDM system. Simulation results show that compared with the ACO-OFDM system under 4-quadrature amplitude modulation (4QAM) and 16QAM, the Flip-FHT system featuring binary phase-shift keying (BPSK) and 4-pulse amplitude modulation (4PAM) achieves the same performance with a simpler system and a smaller constellation size.

The accurate location of optical fiber composite overhead ground wire (OPGW) connection towers and fiber breakpoints is of great significance to the operation and maintenance of power communication networks. At present, during OPGW fault location, the optical time-domain reflectometer (OTDR) is generally used to measure breakpoint distances and attenuation information. Since the OTDR measurement result is fiber length, which does not correspond to the physical distance recorded in the tower schedule. In addition, the OTDR is limited by the spatial resolution when measuring long distances, making the fiber connection points and fiber breakpoints do not correspond to the towers. In response, this paper proposed a method that used the Brillouin frequency shift hopping in multiple fiber cores and the characteristics of the Brillouin frequency shifts of the downleads to achieve precise location of the OPGW connection towers. Precise OPGW fault location was achieved by comparing the Brillouin frequency shifts of the broken fiber cores and the intact fiber core. Moreover, the method proposed in this paper has been initially applied in actual OPGW line operation and maintenance. As a result, precise location of the OPGW connection towers and the faulty fiber cores have been achieved. This study provides a new technical support method for the refined operation and maintenance of the OPGW.

The multi-pulse position modulation combined with quadrature phase shift keying (MPPM-QPSK) has obvious advantages in receiver sensitivity. Equalization algorithms can effectively cope with the influence of limited signal bandwidth and inter-symbol interference in digital coherent optical communication systems and improve the signal transmission quality. To tackle the problem that only the QPSK part of MPPM-QPSK can be optimized by the constant modulus algorithm, this paper improves the inner-ring reference modulus of the two modulus equalization algorithm and proposes a two modulus equalization algorithm with the inner-ring modulus not 0. The algorithm is applied to the MPPM-QPSK coherent optical communication system of 10 Gbit/s single-carrier Gaussian shaping and Nyquist shaping, and some parameters are optimized, such as the inner-ring modulus, the number of taps and the step length. The experimental results show that the receiver sensitivity of the system is optimized by about 0.1 dB compared with that of the system using the traditional two modulus algorithm. When the number of pulses is set at m=2, 4, 8, 16, the receiver sensitivity of this system is improved by 0.9 dB, 0.6 dB, 0.5 dB and 0.4 dB, respectively, in comparison with the system without equalization algorithm.

This paper proposed a generator of signals with a quadruple frequency and a triangular waveform tunable in symmetry based on the dual-parallel Mach-Zehnder modulator and balanced photodetector. In the scheme, modulation nonlinearity and multiparameter manipulation are used to generate the target signals. An approximate characterization of the photocurrent expression using the first three terms of the Fourier expansion of microwave signals following the objective function can be achieved via the adjustments of the modulation index β and time delay τ. As a result, signals with a periodic triangular waveform and a frequency four times the RF modulation frequency are obtained. In the simulation verification, 20 GHz signals with a triangular waveform are output at an RF modulation frequency of 5 GHz. Based on the fitting error, the error of the obtained time-domain waveform can be evaluated. The designed generator is capable of outputting signals with a symmetry factor between 20% and 80% while ensuring the fitting error within 8%.

Aiming at the problem of distortion of the decryption results in the existing optical encryption methods for color images, a new single-channel encryption method for color images that combines chaotic operation and Fresnel diffraction holography is proposed. The first encryption operation uses Fresnel diffraction to convert the RGB channel components of the color image into a real-valued computed hologram; the second encryption operation uses the modified Logistic chaotic system to replace and diffuse the pixels of the computed hologram. The results show that in addition to the traditional chaotic system keys, the Fresnel diffraction distance, the reference light wavelength, and the cosine of the incident angle direction as the key keys all increase the key space (about 10 249) and have a small key volume. The fidelity of the decrypted image is high, and the evaluation indicators such as the correlation of adjacent pixels, information entropy, pixel number change rate, and normalized change intensity are all close to the ideal value. The histogram of the ciphertext image is flat, and the grayscale distribution is uniform, which completely hides the grayscale and color information of the original color image.

Aiming at the problem of scene degradation in haze and sandy weather, a degraded scene restoration algorithm based on convex optimization of Gaussian model and double constraints of light curtains is proposed. First, according to the correlation between depth of field and scene brightness and saturation, Gaussian model and convex optimization are used to estimate depth of field. Second, the relationship between atmospheric light curtain and scene is deeply analyzed, and the atmospheric light curtain of degraded scene is obtained by combining minimum channel smoothing and depth-of-field attenuation constraints. Then, the atmospheric light value is obtained through the improvement of the bright channel a priori and the local atmospheric light. Finally, the degraded scene is restored based on the restoration model, and the color of the sand and dust scene is corrected to realize the scene restoration. The experimental results show that the restored scene of the proposed algorithm has suitable brightness, natural color and rich detail information. It can also obtain an ideal score in the quantitative index, which can effectively solve the problems of color cast and detail loss in degraded scenes.

Phase-measuring profilometry is one of the most effective methods of obtaining the three-dimensional topography information of the object surface. However, in terms of objects with large changes in surface reflectivity, it is difficult for traditional fringe projection technology to achieve high-precision topography measurement in both high reflectivity and low reflectivity regions. To solve this problem, we propose a recursive adaptive fringe projection method. This method can analyze the pixels with saturated and insufficient brightness in the collected image and adjust the brightness of the projected pattern adaptively according to the coordinate mapping relationship. Then, the projection brightness of all the pixels would be recursively driven to approach the best projection brightness so as to avoid saturation and improve the signal-to-noise ratio. The experimental results show that the proposed method can accurately adjust the projection brightness. Only a small amount of recursion is required to correct 99.3% of pixels with unreasonable projection brightness. In addition to improving the three-dimensional display effect of the high dynamic range surface, this method has also enhanced the measurement accuracy of the three-dimensional topography.

Affected by factors such as distance and observation conditions, ground-based facilities have limited ability to observe high-orbit space targets, but space-based observation facilities can effectively break through the observation limitations of ground-based facilities, thereby improving the efficiency and accuracy of observation of high-orbit space targets. Based on this, combined with the current status of space-based measurement technology, the method for determining the orbit of high-orbit space targets based on space-based optical angle measurement, including the initial orbit determination method and the orbit improvement method, is studied. In view of the influence of the observation type on the orbit determination result, the orbit improvement method that directly uses the space-based observation angle and the orbit improvement method based on the space-based observation direction vector are deduced. The two improved methods are compared with simulated data and measured data. The research results show that the orbit accuracy obtained from the space-based observation direction vector calculation is relatively high, which can provide a useful reference for the construction of space situation awareness system.

Angles-Only initial orbit determination (IOD) is the key to space object cataloguing for optical observation systems. For space objects in Low Earth Orbit (LEO), the observed arcs obtained by ground-based optical observation systems are too short and without range information. Therefore, the IOD results of them have large errors and are unusable in further studies. For this reason, this paper studies the non-cooperative common-view observation technology of LEO space objects and relevant initial orbit determination. Based on statistics, a new method of space object positioning by non-cooperative common-view observation technique is proposed. With optical observations from the space object and debris observation network of the Chinese Academy of Sciences, the experiment is conducted to validate the proposed method. The results show that the root mean square (RMS) error of the proposed method is less than 100 m for the satellite Ajisai and that is less than 200 m for the space debris CZ-2C R/B, which means this method is better than the traditional trigonometric parallax method. The positioning results are then used to IOD, and the obtained semi-major axis errors are around 1 km.

Particle streak velocimetry based on defocused imaging is proposed to measure three-dimensional (3D) velocity by recognizing defocusing parameter σ of straight and curve trajectories, called defocused particle streak velocimetry(DPSV). Assuming that σ varies linearly along the trajectory, it can be recognized by the surface fitting of the gray value distribution of particle images, and thereby the depth information of particles is estimated. Based on the linear fitting of straight trajectory, the arc fitting is proposed for the processing of images with curve trajectories, which are commonly captured in turbulent flow by PSV. The relevant image processing algorithm is developed and its correctness in the parameter recognition is validated by synthetic images. The results show that the relative error is about 9.4% in the presence of the noise from the experimental device in this paper. The linear relationship between σ and particle depth z is verified by experiments using an LED light and a diaphragm of 5 μm. Finally, the DPSV technique is applied to a jet flow field and its 3D velocity distribution is presented.

In this paper, we propose a unidirectional wave guide based on valley Hall effect, which is composed of two kinds of photonic crystals with different topological properties. These two kinds of photonic crystals are composed of Al70Ga30As and Si dielectric cylinders, which can realize the unidirectional passage of light in the communication band. The simulation results show that the proposed structure can not only realize the large angle turn of the optical path, but also has good tolerance to defects, which provides a reference for the design of new optical waveguides with efficient optical transmission characteristics.

An erbium-doped fiber laser system based on divided-pulse amplification and fiber nonlinear compression is demonstrated in this paper. The separation and combining of eight replicas are realized by polarization multiplexing with three length-multiplied YVO4 crystals. The combining efficiency of the main-amplifier with different pulse widths is first investigated. Then, the amplified pulses are coupled into a single-mode polarization-maintaining fiber to be further compressed. The nonlinear compression process is optimized by controlling the pump power of the main-amplifier and the fiber length in the compressor, and the pulses with 55 fs temporal duration, 510 mW output power and 80.4 MHz repetition rate are generated. Furthermore, the frequency-doubled laser at 783.4 nm with 146 mW average power and 75 fs temporal duration is achieved using a 0.3-mm-length MgO…PPLN crystal, and the corresponding conversion efficiency is 31%.

Aiming at the characteristic of the internal space limitation of the optical system of large aperture telescope, in order to realize the correction of the misalignment, a method for solving the misalignment based on the eigen coefficient is proposed. Firstly, based on the principle of wavefront curvature sensor, the light spot patterns are collected by alternately measuring the front and back defocused surfaces. Then, the wavefront is reconstructed by the eigenfunction method without partition detection, the eigen coefficients are used to characterize the system wave aberration,and the sensitivity matrix model is established according to the misalignments. Finally, the misalignments can be solved according to the eigen coefficients of the misalignment state and the ideal state. Compared with other technical approaches, this method has the characteristics of no need to add optical components, no partition detection, and simple operation. The experimental results by the telescope with the primary mirror diameter of 1.8 m show that when the eccentric distance range of the secondary mirror is from -0.9 mm to 0.9 mm and the tilt angle range is from -0.2° to 0.2°, the errors of the calculated values obtained by the eigen coefficient sensitivity matrix method are less than 10%, which has certain significance for the application of large aperture telescopes.

It is very important to develop high performance electro-optic modulator to construct on-chip photonic circuits. A novel surface isoplasmon waveguide electro-optic modulator based on graphene mixing is designed, which consists of bias-silicon nanowires, double graphene layers, and silver nanowires placed between the two graphene layers. A two-dimensional finite-difference time-domain algorithm is used to calculate and analyze the influence of structural parameters on the modulation performance of the device. The simulation results show that the designed modulator can achieve excellent modulation performance at the operating wavelength of 1550 nm, and its 3 dB modulation bandwidth is as high as 250 GHz. The modulation depth and power consumption are higher than 0.15 dB/μm and lower than 11.5 fJ/bit, respectively. This modulator can provide design ideas for the development of a new generation of high-performance integrated electro-optic modulators.

Most studies on the application of CsPbBr3 perovskite quantum dots mainly focus on LED with green light emission, while few reports are applied to WLED. Therefore, the current stability of white LED devices based on CsPbBr3 perovskite quantum dots is studied. First, CsPbBr3 perovskite quantum dots are prepared by thermal injection method and their absorption and emission spectra are tested. The absorption and emission peaks are 502 nm and 512 nm, respectively. Then the CsPbBr3 perovskite quantum dots are mixed with ultraviolet-curable adhesive to form a CsPbBr3 perovskite quantum dot colloid, and red phosphors are superimposed to make two white light-emitting diodes (WLEDs) with different packaging structures, WLED Ⅰ and WLED Ⅱ. Under a current of 10 mA, WLED Ⅰ has a color rendering index of 92.1, a correlated color temperature of 4323 K, and a lumen efficiency of 33.04 lm/W. All three indicators are higher than WLED Ⅱ. Finally, WLED Ⅰ and WLED Ⅱ are tested for current stability. The performances of the two WLED devices are tested under the conditions of slowly increasing the drive current from 10 mA to 150 mA, switching time of 720 min and driving current of 15 mA. The results show that WLED Ⅰ shows a more stable trend of change.

Through aging experiments, an organic light-emitting diode (OLED) luminance decay model based on a restoration model is proposed to study the lifetime of OLED-on-silicon microdisplays. The luminance decay model is a fusion of the traditional stretched exponential decay and OLED brightness restoration models. The brightness degradation data is used to fit the undetermined parameters in the attenuation model to obtain the qualitative and quantitative relationship between the initial brightness and duty cycle and the life of the OLED to realize the high-precision brightness attenuation prediction of the OLED. Comparing with the measured, it can be concluded that the prediction error of the proposed model is small, and the fitting accuracy is as high as 99.22%. Under the same initial brightness drive, the life prediction accuracy of OLED can be improved by 79.1%. The lifetime performance of OLED-on-silicon microdisplay driven by pulse-width modulation (PWM) is superior to that of traditional current/voltage driven types. At a duty ratio of 12.5%--87.5%, the lifetime of OLED-on-silicon microdisplays can be increased by 1.6--20.9 times.

Marine mineral particles are one of the important factors influencing underwater photon transmission. In order to study the influence of marine mineral particles on the channel performance of underwater quantum communication, the relationship model among marine mineral particle group density, transmission distance and link attenuation is established and the simulation is conducted. In addition, as for depolarization channels, the relationship among mineral particle density, transmission distance, channel capacity and channel bit error rate is established and the simulation is conducted. The simulation results show that when the transmission distance is 50 m, the link attenuation increases from 0.098 dB to 2.92 dB and the link efficiency decreases from 6.2×10-6 to 2.7×10-7 with the increase of mineral particle group density. When the mineral particle group density is 1.0×104 m-3, the channel capacity decreases gradually from 0.97 to 0.6 with the increase of transmission distance, but the bit error rate increases exponentially. Thus it can be drawn that the influence caused by the extinction effect cannot be ignored in the transmission process. In the practical communication process, the parameters of the transmission equipment should be adjusted in time according to the environmental conditions in order to ensure the communication quality.

The accuracy of envelope alignment of imaging motion compensation in inverse synthetic aperture lidar (ISAL) directly affects the accuracy of phase error estimation. When the velocity and acceleration of the target are large, the range envelope is severely skewed and the phase error is tremendous, making it impossible to focus the image well. To address the above problem, a global motion error compensation joint estimation algorithm based on Nelder-Mead simplex method and particle swarm optimization is proposed in this paper, which is on the basis of high precision imaging model. The algorithm first estimates the target velocity using the simplex method to realize the envelope alignment. Then, the target velocity obtained in the envelope alignment process is used as the constraints for the initialization of the phase error estimation. The particle swarm optimization algorithm is used to search the global optimal solution for each motion parameters. Finally, the estimation of high-precision motion parameters and compensation of high-order phase error are achieved. Meanwhile, the well-focused two-dimensional images are obtained. The experimental results show that the parameter estimation error of the algorithm is mainly distributed within ±0.2%, and the parameter estimation accuracy and noise immunity are superior to the traditional ISAL imaging algorithm.

Over the past few decades, the development of lidars has great significance for ocean monitoring. The spaceborne single photon lidar shows its advantage in marine remote sensing because of high resolution and precision. In this paper, based on the response characteristics of single photon detectors and the sea surface reflection model, a theoretical model for quantitatively calculating the intensity of sea surface returns was proposed. Inputting the system parameters of the advanced topographic laser altimeter system (ATLAS) carried by ICESat-2 (the Ice, Cloud, and land Elevation Satellite 2), we verified the model with the echo intensity based on the measured point cloud data ATL03 from ICESat-2 and the global wind field data. The results show that this model performs well according to many tracks’ data above the Philippine Sea. When the sea surface wind speed is in the range of 4-10 m/s, the mean error is 0.0037 count/pulse, and the root mean square error is 0.153 count/pulse. The relationship between the echo intensity of the spaceborne single-photon ocean altimeter and the average wind speed above the sea level was analyzed. The conclusion provides an important theoretical basis for the wind speed inversion above the sea level.

A high-sensitivity terahertz microfluidic sensor based on the irregular U-type structure is proposed. The influence of the length, width, and angle of the metal wires in the sensor’s metal structure on the quality factor (Q factor) and the absorptivity of the sensor and that of the microfluidic channel height and the cap thickness on the sensing properties of the sensor are studied with simulation software. Finally, the detection performance of the sensor in glucose solutions at different mass fraction is calculated by simulation. The results show that the best combination of structural parameters for the sensor is L1=84 μm, L2=82 μm, L3=52 μm, W=5 μm, and θ=60°, in which case the Q factor of the sensor can reach 24 and the sensitivity can reach 313 GHz/RIU. In short, this kind of microfluidic sensor with a high Q factor and high sensitivity has great application value in the field of label-free trace detection.

This paper proposes a method for simultaneous measurement of particle size and refractive index based on the orthogonal distribution difference of scattered light intensity of particles. The method uses the perpendicular/parallel components of the scattered light of the particles and the preset refractive index to calculate the particle size distribution through inversion with an improved Chahine algorithm. According to the obtained particle size distribution, the parallel/perpendicular components of the scattered light of the particles are calculated and compared with the measurement results for further calculation of the fitting residual. The possible refractive indexes are traversed and the fitting residual is driven to be infinitely small. The corresponding refractive index equals the refractive index of the particles and the corresponding particle size distribution equals the sample’s particle size distribution. The measurement results of ethylene-propylene copolymer standard particles, silicon carbide, and graphite samples show that the refractive indexes of non-absorbent particles and the imaginary part of the absorptive particles can be accurately measured by this method. An accurate particle size distribution can also be obtained with the preceding refractive indexes.

Temperature is an important factor affecting the stability of the light source. Temperature changes will lead to changes in the parameters of the light source, which in turn influences the visual and non-visual effects of the light source. The relationship between the spectral parameters of the single-channel light source and the heatsink temperature is determined based on three models, and the temperature spectral model of the multi-LED light source is built. In addition, temperature experiments on the four-color (RGBY) LED light source (using D50 and D65 light sources) are conducted. The results show that the light source spectrums at different heatsink temperatures in the temperature spectral model are basically in line with measured spectrums. The maximum relative errors of the parameters of these two do not exceed 6.15%, which verifies the reliability of the model. For the changes in light source parameters (illuminance, correlated color temperature, and circadian action factor) caused by temperature, we use the temperature spectral model and differential evolution algorithm to determine the compensation weight of each channel in the pulse width modulation control system in real time. At the same time, the light source parameter compensation is realized based on the heatsink temperature feedback to the weight. This research can be applied to the dynamic design and the temperature stability control of multi-LED light sources.

X-ray Fourier-transform ghost imaging has the potential to achieve tabletop nanoscale microscopy. However, due to the limited luminous flux in practical applications, the imaging signal-to-noise ratio is low, which leads to poor image quality. In light of the binary characteristics of the X-ray modulating screen, this paper studies the X-ray Fourier-transform ghost imaging using a super-Rayleigh speckle field to solve the above problem. The theoretical derivation of the X-ray speckle field generated by the binary modulation screen is first carried out. Then, with the speckle contrast and the difference of local contrast as objective functions, the non-dominated sorting genetic algorithm with elite strategy is adopted to optimize the design of the binary modulation screen. Numerical simulation results show that the proposed method can obtain high-contrast X-ray super-Rayleigh speckle fields, with which the Fourier-transform ghost imaging can be realized. As a result, the image visibility can be enhanced, and the image quality can be improved especially at a low signal-to-noise ratio.