To enhance the absorption of light using a wavelength of 1550 nm using a photodetector device in a communication system, we propose a composite micro-nanoscale structure including a silicon grid, nanoscale silver balls, and a buffer layer. The light absorption of the composite micro-nano array can be improved by means of the local field enhancement effect of surface plasmon resonance on metal and the trapping effect and coupling effect of silicon gate. The finite difference time domain method is used to calculate the light field distribution of the simulated light passing through the silicon grid composite micro-structure array filled with silver nanospheres and alumina. Then, the effect of the silicon column array duty ratio, the silicon column side length, the silicon column height and the filler on the absorption performance are analyzed. The simulation results show that when the silicon gate line or interval, silicon column length is 800?1000 nm, the diameter of the silicon column gap filling nanometer arguably is half of gap width and covered with clearance and covered in alumina, at the bottom of the composite structure of the absorption rate with high silica column array cycle and the column of different can reach 0.2288?0.5753, the near-infrared wavelength of 1550 nm have significantly enhanced absorption effects.

Coherent detection mixer is an essential component of spatial coherent light communication system. Its main function is to mix signal and local oscillator lights to obtain an intermediate frequency signal and then enlarge the optical signal so that the sensitivity of the detector reaches the quantum noise limit. The mixing efficiency is vital for the intensity of the intermediate frequency signal. Therefore, we assume that the local oscillator light has an ideal Gaussian distribution and calculate the influence of different amplitude distributions of the signal light on the mixing efficiency. By designing a set of beam-shaping mirrors, the amplitude distribution of the signal light is changed to a Gaussian distribution, coherent mixing of Gaussian light and Gaussian light is achieved. Experiment results show that the coherent detection mixer with shaping elements can achieve the similar amplitude distribution of the signal light and the local oscillator light, and the mixing efficiency is improved by 17 percentage points compared with the uniformly distributed signal light.

To minimize demodulation error and system instability due to the Guassian white noise and power frequency noise, we presented a fiber Bragg grating (FBG) peak-detection algorithm based on difference of Gaussian (DoG). This algorithm enabled the detection of the peak wavelength of FBG reflection spectrum with strong noise. The mean error and standard deviation are 4 pm and 4.2 pm, respectively, which are much lower than those of other traditional algorithms. Experimental results show that the DoG algorithm can provide good stability and low demodulation error. In addition, it can substantially resist the noise in the FBG reflection spectrum, thereby improving the accuracy of the FBG demodulation system.

Aiming at the problem of inconsistent delay of the uplink and downlink in a railway time synchronization network, a compensation scheme based on the enhanced algorithm for real-time calculation of data package queuing delay (ERTCQD) is proposed in this work. First, based on the transmission link delay, the clock model of a railway time synchronization network is obtained. Second, considering that the calculation parameters of clock frequency difference in the real-time calculation algorithm of data package queuing delay are difficult to obtain and the clock frequency difference will lead to linear shift of delay with time, the calculation method is improved by calculating the linear clock frequency difference, and the queuing delay is estimated by solving the queuing delay minimum data package. Finally, the queuing delay is introduced into the clock model, and a new clock offset estimation method is obtained, which can improve the time accuracy degradation caused by delay asymmetry. The results show that: the ERTCQD algorithm has higher accuracy, and the average error is 0.22 ms. The compensation effect of this scheme is good. Compared with results before compensation, the clock offset error is reduced by 73.2%, and the link delay asymmetry is reduced by 94.2%. The proposed scheme significantly improves the timing accuracy and provides a new reference for solving the delay asymmetry of the railway time synchronization network.

A load balancing-routing wavelength assignment (LBRWA) algorithm based on user traffic distribution for satellite optical networks (OSNs) is proposed. The ant colony algorithm is employed to find the optical path so that the OSNs can achieve effective load balancing. The LBRWA optimization model in the OSNs based on global user traffic distribution is established. It searches for the next-hop link according to the link duration and wavelength idle rate and introduces random disturbance to avoid local optimum. The statistical average optical path cost corrected by the user traffic intensity is employed to update the link status; the traffic is directed to the satellite nodes in the non-hot spot area to find the load balancing optimal optical path for user requests. Numerical simulation results show that compared with traditional elastic load balancing(ELB) algorithm based on link-state, LBRWA algorithm reduces the congestion rate by 20.49%. In addition, LBRWA has better performance in terms of resource utilization, traffic distribution index, and max normalized inter-satellite link load, thereby effectively realizing load balancing in OSNs.

Traditional signal-decomposition methods require manual setting of the basis function, which cause uncertainty and other problems. Accordingly, a self-driven Fourier decomposition method (FDM) can be used for signal processing and a feature extraction and recognition method based on FDM energy entropy is proposed in this paper. First, FDM decomposition is performed on the vibration signal to obtain several Fourier intrinsic band functions. The signal is then reconstructed based on the autocorrelation principle, and the signal FDM energy entropy feature is extracted. Finally, the fused feature vectors are sent to a support vector machine for training, and damaging vibrations are identified. Experimental results show that the proposed method can correctly identify different types of vibration signals with high accuracy. This method will enable improved recognition of damaging vibrations in optical fiber prewarning systems, thus aiding the development of pipeline protection technology.

This paper studies the application of interference caused by mode coupling in a tapered multicore fiber to temperature sensing. A weakly coupled multicore fiber becomes a strongly coupled multicore fiber after being tapered and has characteristics of supermode interference. A weakly coupled seven-core fiber is fused into a single-mode fiber after being pulled back and forth by a hydrogen flame at a uniform speed. When the diameter of the optical fiber decreases and distance between cores is reduced to a certain extent, supermode interference occurs, thus temperature sensor with simple structure, high sensitivity, and strong specificity is fabricated. It is determined that the smaller the fiber diameter and the longer the taper length, the stronger the mode coupling. A tapered multicore fiber with a cone length of 1.8 μm and a cone diameter of 31.36 μm was selected. The sensitivity of the designed temperature sensor reaches 840 pm/°C, which is 52.7 times higher than the previously reported value.

A design method is proposed for achieving ultra-wide field of view and high-resolution imaging in an optical system including a zoom lens with a large aperture. By analyzing the principle of the optical system and comparing the mode of zoom compensation, an all-motion mode of compensation is adopted to enable zoom motion in the entire system. The primary aberration theory and the ZEMAX software program are applied to determine the initial structure parameters. The optimized design includes 14 components for the refraction lens aperture and large field of view zoom system. The parameters include a system working band of 400?700 nm, focal length range of 6.54?17.00 mm, changing time ratio of 2.6, full field of view angle ranges of 60°?178°, and F-number of 2.8. The modulation transfer function value in the Nyquist frequency, at 55.6 lp/mm, is greater than 0.40; therefore, the imaging quality of the proposed system very good and meets the design requirements.

The vibration reconstruction method based on laser self-mixing interference needs to estimate the optical feedback level factor and the line-width enhancement factor. In order to improve the precision and robustness of vibration measurement, a vibration reconstruction algorithm based on the frequency modulation characteristics of self-mixed interferometer is proposed. The all-fiber Mach-Zehnder interferometer is used to obtain the frequency-modulated signal of self-mixing interferometer, and the instantaneous frequency of the laser is calculated. This method does not need to estimate the optical feedback level factor and the line-width enhancement factor, greatly simplifies the measurement optical path and the solution model, and reduces the complexity of the vibration information extraction while ensuring the measurement accuracy. Numerical simulation shows that the proposed algorithm has good linearity in the measuring range from 2 μm to 100 μm amplitude with moderate optical feedback level. Experimental results show that the standard deviation of repeated measurements is less than 15 nm and the non-linear error is 0.78% in the range of 1.6 μm to 8.3 μm amplitude.

In the dual-wavelength interferometer, the traditional equivalent wavelength method only uses the difference information between two single wavelength wrapped phases, and ignores their size as well as positive and negative information. The effective wavelength method based on the least common multiple directly uses the wrapped phase information of multiple single wavelengths, and thus not only it can achieve a larger unambiguous measurement range than the traditional equivalent wavelength method, but also it has no error amplification effect. However, the existing least common multiple effective wavelength phase unwrapping algorithm is mainly based on the look-up table method, which is slow and not suitable for a practical measurement. In this paper, a new algorithm is proposed, which can greatly improve the calculation speed of the least common effective wavelength method, so that it can be applied in dual-wavelength or multi-wavelength interferometers.

When detecting microcracks based on the photoacoustic nonlinear frequency-mixing method, the characteristics of nonlinear acoustic signals are affected by the crack contact state, which is affected by its initial width, wall morphology, modulation intensity, and other factors. This results in a change in the detection process of the nonlinear mechanism of the interaction between acoustic waves and microcracks. Therefore, in this paper, a two-dimensional physical model is established to analysis the nonlinear frequency-mixing process of crack detection, and the penalty method is used for the enforcement of contact constraints. The experimental result of the model are compared and analyzed with existing experimental results to verify the applicability of the model. The acoustic signal characteristics are investigated under different contact states, and the nonlinear mechanism is affected by the change of the crack contact state, which provides a theoretical reference for studying the photoacoustic nonlinear detection of microcracks.

To solve the problem of weak local boundary states and narrow bandwidth in the model that produces the photon quantum Hall effect, in this paper, a triangular compound lattice photonic crystal is constructed, and the energy band degeneracy of the reduced Brillouin zone is used to obtain the odd parity p orbital and the even-parity d orbital. First, the position of the two orbitals is reversed by the unit cell scaling to change the topological phase. Then, the main factors affecting the band gap of topologically trivial structure and non-trivial structure are analyzed. Finally, the radii and scaling distances of dielectric cylinders of the two structures are optimized. The optimal parameters for achieving the maximum common band gap of the two structures are obtained. The maximum achievable relative bandwidth is 24.59%. Based on the optimal structure parameters, the boundary structure is constructed, and the boundary states dispersion curve is calculated. The results showed that the boundary states have strong spin direction locking and boundary electromagnetic field local effects when the effective bandwidth is 0.0435.

A fiber laser with a rated power of 1 kW is used to perform a laser direct metal deposition experiment on an airport oil pipeline network material to explore the effects of laser scanning speed on microstructures, hardness, corrosion resistance, and wear resistance of the deposition layers. The experimental results of microstructure and hardness show that as the laser scanning speed increased, the deposition layer thickness and the warpage deformation angle of the substrate decreased, and the peak hardness of path 2 gradually increased. The experimental results of corrosion resistance and wear resistance show that the above performance of the deposition layers had an asynchronous response with the scanning speed. At the laser scanning speed of 10 mm/s, the deposition layer showed very high corrosion resistance, and its self-corrosion current density was 27.76% of the substrate. At the laser scanning speed of 12 mm/s, the deposition layer displayed high wear resistance, and its wear rates were 52% and 42% of the deposition layer prepared at scanning speeds of 6 mm/s and 10 mm/s, respectively.

Aiming at the problem of easy wear and failure of the mold, a series of Fe50/TiC composite coatings with different TiC mass fractions were prepared on the surface of Cr12 mold steel using coaxial laser cladding technology. The microstructure, porosity, microhardness, and wear resistance of the cladding layers were investigated using scanning electron microscopy (SEM), microhardness tester, and tribological tester to explore the effect of TiC content on the cladding layer. Results show that as the TiC content increases, the microhardness and the wear resistance of the composite cladding layer increase, but the porosity also exhibits an increasing trend. At the same time, the higher the TiC content, the more undissolved TiC particles in the cladding layer for nucleation, and the more the microstructure nucleating and growing based on pariticles. When the mass fraction of TiC was 35%, the porosity of the cladding layer decreased and grown dendrite TiC was observed owing to dissolution nucleation. The average microhardness (46.3 HRC) of the cladding layer was approximately 2.4 times that of the substrate, and the wear volume was approximately 13% of the substrate. Fe50-TiC cladding layer fabricated using Fe50-35% TiC exhibits better comprehensive properties.

To improve the thermal fatigue performance of brake disks, we prepared an Fe-based coating on the cast steel material for the brake disks using laser cladding technique, and then analyzed the crack growth rate and microstructure evolution of the cladding layer and matrix material during thermal fatigue using optical microscope and scanning electron microscope. Results show that the microstructure of the laser cladding layer exhibited severe segregation. In the thermal cycle process, the supersaturated M7C3 became the rapid propagation channel of thermal fatigue cracks, thereby resulting in brittle fracture and poor thermal fatigue performance. Through heat treatment at 850 ℃ for 5 h, the element distribution was homogenized and dendrite segregation and internal stress were eliminated. Moreover, M7C3 transformed into M23C6 with relatively stable high temperature performance, which remarkably optimizes the thermal fatigue performance of the cladding layer. No macrocracks were observed on heat-treated cladding sample after 2000 thermal fatigue tests, and its thermal fatigue properties were considerably better than those of the matrix materials.

The microstructure and stress of the laser cladding layer have a significant impact on crack control of the cladding layer. The microstructure and stress of the cladding layer are closely related to preheating temperature during the cladding process. The microstructure and stress distribution of the cladding layer under different preheating temperatures are analyzed . The results show that the higher the preheating temperature, the stronger is the element interaction between the cladding layer and matrix. At a preheating temperature of 100 ℃, the peak value of the transverse residual stress decreases. The peak value of the residual stress parallel to the scanning direction decreases from 594 MPa at room temperature to 442 MPa, and that perpendicular to the scanning direction decreases from 579 MPa at room temperature to 383 MPa. Besides, when the preheating temperature is 200 ℃, the stress reduction effect significantly reduced. When the preheating temperature is 300 ℃, the microstructure stress effect is greater than that of room temperature, resulting in a significant increase in residual stress level.

Because rails wear down after long-term use, laser cladding technology is used to repair damaged surfaces. Using U75V rail as base material, we optimize the process parameters of multilayer and multipass laser cladding. The results show that optimal process parameters is laser power of 900 W, cladding speed of 600 mm/min, feeding speed of 7.58 g/min, overlapping ratio of 58.8%, Z-axis lifting amount of 0.6 mm and preheating temperature of 200 ℃. There are many equiaxed grains in multilayer and multipass cladding areas, but acicular martensite is present in heat-affected areas. Hardness of the cladding zone is not much different from that of a base material: 480 HV in the cladding zone and a maximum of 430 HV for the base material. Under the effects of martensite, the hardness of the heat-affected zone is about twice that of the base material. Wear resistance of the cladding layer is slightly lower than that of a base metal.

Targeting the gas-powder coupled transmission process of coaxial powder feeding laser cladding, an equivalent model is proposed to consider the influence of the complex collision behavior between the powder and nozzle wall and the powder on the exit angle and speed of the powder. In addition, the gas-powder transmission model outside the nozzle is established. Key variables, e.g., transient position of the powder, trajectory of motion, and average density of the continuous distribution of the powder, were simulated, and the influence of the surface state of the workpiece and flow rate of compressed gas on the above variables was studied. The results demonstrate that the simulation results are in good agreement with experimental results from the overall shape of the powder beam, gathering position, and track line density. The rebound of powder when the molten pool is not formed is more significant in the center of the powder beam (about 10 mm from the workpiece), the powder density in this area increased by approximately one times at the maximum, and as the height from the workpiece increased, the effect of increasing the powder density gradually weakened. The compressed gas flow rate increased to 2.5 m/s, the powder density on the central axis of the powder beam increased to approximately 5.2 kg/m3, the compressed gas flow rate continued to increase to 5.0 m/s, and powder density on the centerline was reduced by approximately 8%.

A Y-cavity dual-wavelength laser based on Nd∶?GdVO4 and Nd∶?YVO4 crystals is designed, and the dual-wavelength laser signal with a wide tunable frequency separation range is experimentally realized. By independently adjusting the heat sink temperatures of the two crystals and controlling the temperature difference from -50 °C to 30 °C, the measured dual-wavelength frequency separation increases from 270.13 GHz to 379.75 GHz. Furthermore, the dual-wavelength power balance is realized by adjusting the pump powers of the two crystals. Finally, the dual-wavelength laser signal is obtained, which has a tunable frequency separation range of 266.05?379.75 GHz and an output power of 230 mW.

Aiming at the stability of output wavelength and power of chaotic semiconductor lasers, a high stability control system for chaotic semiconductor lasers is designed. The deep negative feedback circuit is used to realize high stability and high precision constant current control. The high stability control of laser temperature is realized by using fuzzy adaptive proportional-integral-differentiation algorithm and H bridge drive circuit. The results show that the output current range of the designed dual-channel current source is 0.00?40.00 mA and 0.00?100.00 mA, and the stability at room temperature of 25.0 ℃ is better than 0.002% and 0.004%, respectively. The adjustment accuracy can reach 0.01 mA. When the driving current is 20.00 mA, the output optical power drift of the chaotic semiconductor laser works continuously for 120 min is only 0.0066 dBm and 0.0072 dBm, respectively. The temperature control range of the temperature control circuit is 18.0?40.0 ℃, and the central wavelength shift of the laser working at 25.0 ℃ for 120 min is only 0.007 nm. The control system can work stably at the ambient temperature of 10.0?40.0 ℃.

This study proposes a diaphragm type Fabry-Perot (F-P) cavity liquid level sensor based on frequency-modulation continuous-wave laser interferometry. According to the frequency modulated continuous wave interferometry technology liquid level measurement system theory, the liquid level sensor is made, the liquid level measurement system is built, and its linearity, sensitivity, resolution and other tests are carried out. The experimental results show that the linearity of the liquid level measurement is 0.99998, the sensitivity of the liquid level measurement is 465 nm/mm, and the measurement resolution is 33.998 nm, the corresponding level value is 0.0731 mm, and has good stability, repeatability and hysteresis. Therefore, the designed frequency-modulated continuous wave optical fiber liquid level sensor can achieve high precision and stable liquid level measurement.

Photonic integrated circuits (PIC) and photonic chips have the advantages of low power consumption, high speed, and large bandwidth, and they are the inevitable trend of the next generation optical information processing system. And on-chip light source is the key technology of PIC. An optical-pumping laser based on optical microring resonator is proposed, and the pumping light and laser light are output to different waveguides through the all-optical control. Combining the four-level two-electron energy level model and the time-domain finite difference method electromagnetic field simulation, the time-domain characteristics of laser output, particle state density and steady-state electromagnetic field mode distributions are analyzed. After 94 ps, the steady-state particle number density inversion distribution is reached, and pumping light of 1064 nm and laser light of 1550 nm are output to Through port of the upper channel and the Add port of the lower channel, respectively.

Based on the coaxial powder-feeding laser cladding technology, two-dimensional abrupt gradient materials were fabricated with 316L stainless and nickel 718 superalloy powders. An electron probe microanalyzer was used to detect the elemental change laws of the whole sample at the macro-level. A scanning electron microscope and an energy dispersive X-ray spectroscope were used to analyze the interfacial microstructure and detect the elements change law at the micro-level. The results show that the element content suddenly changes in macroscopic analysis, while there is a transition interval of about 500 μm in microscopic analysis. The microhardness significantly varies while the microstructure gradually varies at the interface. An obvious segregation in nickel 718 leads to the Laves phase and carbonitride; the microstructures are mainly cellular crystals with a few carbonitride on the side of 316L stainless steel.

As one of the most important algorithms for white-light interferometry, the spacial frequency-domain algorithm (FDA) is widely applied in the field of micro-nano structure surface topography measurement. However, traditional FDA measurement result involves phase error accumulation effect caused by sample slope and the surface fluctuation, and the phase error is closely related with the offset of zero optical path difference (OPD) positon in the interference signal. This paper explains the reason of phase error accumulation effect existing in traditional FDA, and proposes an envelope-signal-assisted analysis (ESAA) method based on traditional FDA to exhibit the phase error accumulation. The ESAA method firstly perform a symmetric adjustment for the offset of zero OPD position existing in the original interference signal. Then, the FDA is applied for the adjusted symmetric interference signal which can restrict the phase error accumulation effect as more as possible. To demonsrate the validity of proposed method, both simulation and experimental analysis are elaborated and discussed.

Herein, a Monte Carlo ray-tracing method is proposed to investigate the influence of the roughening of the sapphire substrate sidewall caused by laser hidden cutting technology on the light extraction efficiency (LEE) of GaN-based flip chip light-emitting diodes (LEDs). Monte Carlo ray tracing method is used to analyze the influence of the sidewall invisible cutting on the LEE of each light-emitting surface of the LED flip chip and optimize the number and position of the sapphire sidewall invisible cutting of the LED flip chip. Simulation results show that as the number of invisible cutting layers on the sapphire sidewall and equivalent roughness of the sapphire sidewall increase, the LEE of the light-emitting surface on the top of the LED flip chip gradually decreases and the total LEE of the sidewall and LED flip chip gradually increase. The Monte Carlo ray-tracing method is used to simulate the effect of uniform and combined laser dotting on the LEE of the LED flip chip. Experimental results show that when the number of invisible cutting layers is fixed, the sidewalls and total LEE of uniform laser dots are higher than those of combined laser dots.

In order to obtain excellent slow light performance, we propose a photonic crystal waveguide (PCW) with extrinsic defect rods introduced into the center row of a complete square lattice rotated 45° counterclockwise and the second row adjacent to it. And successive cavities are introduced as electromagnetic energy reservoirs and light speed reducers for slow light transmission in the PCW concerning applications for optical communication, optical computation, and optical signal processing. Then, the plane wave expansion method is used to study the slow light transmission characteristics of the proposed structure, and the influence of the structure parameters on the slow light performance is analyzed. Finally, the bandwidth is obtained at 23.37 nm when the normalized delay bandwidth product (NDBP) reaches 0.40. The design method of the proposed structure provides an important theoretical basis for further improving the storage capacity with high bandwidth and high NDBP slow light.

In this study,we consider two processing methods of graphene thin layers in plasmonic nano-optical waveguides analyzed by the finite element calculation. More specifically,we employ surface current and thin layer methods. We obtain the field distributions and effective mode indices of the fundamental modes in planar and curved graphene waveguides for different frequencies and geometric parameters. The simulation results show that both methods can efficiently tackle the problems in question. In particular, the difference between the surface current methods and the theoretical calculation results is less than 1%, and this method saves computing resources. Our results can be used to simplify the processing of graphene layers in finite element calculations and improve calculation efficiency.

To calibrate liquid crystal spatial light modulators, a method for measuring their phase modulation characteristics is proposed based on the principle of polarization display. First, the modulation characteristics of the liquid crystal spatial light modulator to the polarization state of the incident polarized light are analyzed. Then, a theoretical relationship is established between the long axis direction of the elliptically polarized light after passing through the azimuthally polarization axis finder and the phase modulation amount of the liquid crystal spatial light modulator. By building an optical system, the phase characteristics of the liquid crystal modulator are measured. The results show that the maximum phase modulation of the spatial light modulator used is 2.45π rad, and the phase modulation curve within the gray scale range of 15 to 210 approximately meets the linear distribution. Finally, the phase modulation curve is linearly corrected by applying inverse interpolation, and a look-up table of the input gray scale and the driving gray scale is generated. The correlation coefficient between the corrected phase modulation curve and the ideal linear modulation curve reached 0.9993.

Compared with ordinary light sources, Gaussian beams have good directivity and have a wide range of applications. COMSOL multiphysics simulation software is used to study the propagation characteristics of Gaussian beams incident at Brewster angle. The simulation results show that under s polarization, the refracted beam is a Gaussian beam, and the direction of the reflected beam is perpendicular to the refracted beam; under p polarization, the refracted beam is a Gaussian beam, and the reflected beam does not exist, but the electric field modulus at the reflection interface shows a double-lobe profile with significantly reduced central intensity and very weak bimodal reflection. Under the different refractive index, the larger the refractive index of the refractive medium, the narrower the intensity concentration range of the refracted beam, the lower the energy, and the smaller the electric field modulus difference between the refracted beam and the incident beam.

A laser-assisted pulsed discharge method for generating plasma in water is proposed. Combining with the classical Drude model, a two-dimensional fluid mathematical model of the plasma generated by laser injected into the water pulsed discharge system is established, and the corresponding mathematical equations are given. The COMSOL Multiphysics software is used to simulate the interaction process between charged particles and laser vertically injected into the plasma channel, The local electron density when the laser with a certain energy is applied to the water dielectric pulse discharge system is studied. The preliminary simulation results show that the peak value of electron density increases from 1.65 × 1021 m-3 to 8.29 × 1021 m-3 when a laser with 50 mJ energy and 0.1 mm spot diameter is added into the plasma channel. This process plays a significant role in improving the ionization rate of plasma, which indicates that the technical scheme of laser assisted pulse discharge in water to generate plasma is feasible.

In order to study the influence of rainfall on the transmission quality and quantum communication performance of the satellite-to-ground quantum links, this paper analyzes the relationship between rainfall intensity, extinction coefficient of raindrops and attenuation coefficient of the satellite-to-ground links based on the M-P raindrop spectra and the Mie scattering theory, establishes the model of relationship between the capacity and average fidelity of information channels under the rainfall background, and obtains the teleportation fidelity under rainfall environment on the basis of the two-particle entangled state probabilistic teleportation scheme. The theoretical analysis and simulation results show that the increase of rainfall intensity results in the increase of extinction coefficient, which further leads to the decrease of capacity and average fidelity of information channels. At the same time, rainfall causes the channel entanglement degree to be weakened, thereby reducing the fidelity of teleportation. Therefore, rainfall has a significant impact on the performance of the quantum satellite-to-ground links, and the various parameters in the satellite-to-ground quantum links must be appropriately adjusted according to rainfall intensity in order to ensure the communication quality.

As an important part of quantum cryptography, quantum blind signature has attracted more and more attentions in recent years. A protocol of quantum blind signature based on two-qubit and three-qubit maximally entangled states is proposed. By using the special characteristics of quantum entanglement, the blindness of a message is realized, and the recovery of this message is conducted by the help of the quantum coherence principle. In the proposed protocol, the operation on qubits via quantum logic gates is used for the realization of the quantum state expression of two-bit classical information. Finally the proposed protocal is confirmed to satisfy the properties of undeniability, unforgeability and blindness. Based on the quantum key distribution and one-time pad technology, the absolute security of the proposed protocol is guaranteed. Moreover, the proposed protocol is more efficient than other existing protocols.

In this paper, the influences of the environmental memory effect, Dzyaloshinskii-Moriya interaction, and non-uniform magnetic field on the quantum entanglement of Heisenberg XXZ spin chain are investigated by using the non-Markov quantum state diffusion method. It is found that the smaller the value of the environmental memory effect is, the longer the environmental memory time is, the stronger the non-Markov nature in the environment is, and the longer the survival time of quantum entanglement is. In addition, it is also found that the quantum entanglement of the system can be controlled by adjusting the Dzyaloshinskii-Moriya interaction and uniformity of magnetic field, so that the system maintains good entanglement characteristics.

At present, the continuous-variable quantum key distribution (CV-QKD) protocol based on discrete modulation has received more attention. In this paper, we propose a three-state CV-QKD protocol based on post-selection. The security key rate of the proposed protocol is calculated under collective attack and reverse reconciliation and compared with that of the four-state protocol. The simulation results show that the proposed three-state protocol can outperform the four-state protocol in security rate if the transmission distance is not too long, indicating that the three-state protocol is more feasible for a short-range application, such as metropolitan area networks.

In recent years, as a novel strategy based on the excitation mechanism of photon-matter interaction, laser-controlled optimization of noble metal nanocomposite configuration can not only effectively construct multifunctional nanomaterials with clean surface, but also obtain metastable phase composite configuration which is difficult to achieve by conventional synthesis methods. Therefore, it has significant advantages in many frontier applications. In a simple liquid phase environment, this strategy mainly generates high-temperature and high-pressure metal plasma by focusing a high-power pulsed laser beam to ablate target materials, and then instantaneously cools and nucleates under the thermodynamic non-equilibrium state, thereby constructing various unique nanostructures. In addition, making full use of the high photon energy of the short wavelength laser beam, this strategy can also excite the substrate material to produce hot electrons, which can be used as a unique reducing agent to realize the reduction of metal ions in the surrounding solution, and finally grows multi-morphology metal nanostructures on the precursor. By adjusting the laser liquid phase irradiation parameters, the surface atom microscopic morphology of the optimized noble metal nanocomposite configuration can be effectively adjusted to make it have excellent light excitation performance, and then it is widely used in surface enhanced Raman scattering, photocatalysis, near infrared strong absorption, and other application areas. In this paper, the controllable synthesis mechanism of the laser-induced liquid-phase strategy is summarized based on laser-induced optimization of metal matrix nanocomposites, and the potential applications and future development trend of laser-controlled optimization of noble metal composite configurations are prospected.

Improving the performance of the photoelectric-detectors, as a kind of the important optoelectronic devices, is a key research topic. In recent years, using nanostructure has resolved the bottleneck in the development of traditional infrared photoelectric-detectors. Metal nanoparticle, patterned-graphene with nanostructure, and resonators have been extensively used to stimulate the surface plasmon, promoting the interaction between light and matter to obtain a relatively high-performance photodetector. Herein, graphene photodetectors based on surface plasmons are mainly introduced, which have been developed from the aspects of patterned-graphene nanostructure, metal nanoparticle, quantum dots, and periodic nanostructure.

The power of diode-pumped alkali laser (DPAL) with high power has reached 10 kW and shows great potential because of its high optical-optical conversion efficiency, light weight, small size and so on. Alkali vapor lasers are under extensive investigation and development during the past decade because of their potential for scaling to high power and maintaining good beam quality. First, the basic principles and research development of DPAL are introduced. Then, a historical review of the alkali laser research and development, and the most important achievements and future perspectives in this field, are presented. Besides, the obstacles in research are analyzed. The solutions are summarized and their deficiencies are presented. Finally, the future development of alkali vapor laser is discussed.

Brillouin dynamic grating (BDG) based on stimulated Brillouin scattering effect has been extensively investigated globally. Compared with fiber Bragg grating (FBG), BDG has many advantages, such as fast reconstruction, read-write separation, and parameter control. It has been realized in polarization-maintaining, single-mode, low-mode, and photonic crystal fibers. Simultaneously, different types of BDG research, such as chirped BDG, phase-shifted BDG, chaotic BDG, and random BDG, are constantly emerging. This paper briefly introduces the generation principle of BDG and gives a detailed overview of different BDG fibers, different types of BDG, and BDG application in distributed fiber sensing and all-optical signal processing. Finally, the development trend of BDG is summarized and prospected.

The photonic integrated circuit (PIC) has led to the development of miniaturized optical devices that can achieve very complex functions on a single chip. Many integrated optical devices, such as beam splitters, resonators, lasers, amplifiers, filters, and modulators, have achieved monolithic integration or hybrid integration. Countries have invested a lot in designing and manufacturing complex PICs research work. The optical gyroscope manufactured by integrated optical technology can effectively reduce the weight and size of the gyroscope, reduce the cost and power consumption, and increase the reliability of the system. The performance index is also gradually improved, and it has good development potential. This article introduces the research status of integrated optical gyroscopes at home and abroad, and briefly analyzes the current research characteristics of improving the performance of integrated optical gyroscopes by using different material platforms and new resonant structure designs.

Laser cladding, an advanced surface modification technique, is widely applied to aerospace, petrochemical, and other fields. Herein, the research progress with respect to cracks in laser cladding coating is reviewed. Furthermore, the classification, formation mechanism, and detection methods of cracks are described. In terms of the optimization of process parameters, cladding design, powder composition, and process methods, the countermeasures to prevent and control cracks are summarized; some suggestions to solve the problem of cladding cracks and future research directions and ideas are suggested.

Laser-induced surface periodic structure (LIPSS) is a universal characteristic of solid materials. The LIPSS on the material surface can change the properties of the material. Many special functions can be achieved using these characteristics. This study summarizes recent representative studies on LIPSS. First, the surface energy distribution and material flow under the action of laser are used as the starting point to theoretically explain the formation principle of LIPSS. Then, the research work on the formation of LIPSS on the surface of thin films and etched materials and the influence of laser parameters on LIPSS are described. Finally, applications of LIPSS in modern industry, such as special crystal preparation, superhydrophilic/hydrophobic materials, and medical materials, are introduced. This study sorts out and summarizes the recent study on LIPSS-related fields from the above three aspects and looks forward to the future development of LIPSS-related technologies.

Vertical cavity surface emitting laser (VCSEL) as an ideal laser light source has a broad development prospect. In the application fields of optical fiber communication, optical interconnection, and laser printing, VCSEL is required to work in a single fundamental mode. Due to the structural characteristics of VCSEL, it is easy to shoot multiple horizontal modes, so the limitation of the lateral mode of VCSEL has become a research hotspot. In this paper, the research reports of VCSEL transverse mode control method are reviewed, and the research progress of photonic crystal, surface relief, anti-waveguide, extended resonator, and high contrast grating structure is classified and analyzed.

Due to its lower concentration limit, wavelength modulation spectroscopy has been widely used for gas concentration detection based on laser absorption spectroscopy. Various background noises and optical fringes can decrease the accuracy of concentration measurement and increase the lower limit of concentration measurement. To reduce the background noise and improve the signal-to-noise ratio of the measurement system, the absorption spectral lines at 2.25 μm were used to measure the NH3 concentration in the experiment and theoretically analyze. In signal processing, wavelet and Gabor transform techniques were used to reduce the noise in harmonic signal. The results show that Gabor and wavelet transforms can effectively remove the influence of various noises while preserving the integrity of the harmonic signal with the optimal control parameters. Wavelet transform has better denoising ability than the Gabor transform for harmonic signals mainly containing white noise and optical fringes, and can improve the signal-to-noise ratio and the smoothness of the signal curve. The lower limit of NH3 concentration after denoising is reduced from 0.36 mg/m3 to 34.45×10-3 mg/m3.