Sea surface temperature (SST) is an important marine hydrologic parameter, and its accurate prediction is critical in marine-related fields. Deep learning has been widely and increasingly used for SST prediction in recent years because of its strong analytical ability. However, the volatility and randomness of SST time series still constitute a challenge for accurate prediction. In this study, variational mode decomposition (VMD) is first introduced as a denoising module to reduce the influence of SST sequence noise on the prediction results. Then, to solve the lag phenomenon of depth models in SST prediction, the method of transfer learning is adopted to combine the concepts of long-short term memory (LSTM) and broad learning system (BLS). LSTM is used as the feature mapping node of BLS to improve the prediction accuracy. As a result, an SST prediction model based on VMD, LSTM, and BLS is proposed. The SST of the East China Sea is selected as an example for verification. By comparing with benchmark models, support vector regression (SVR), LSTM, gate recurrent unit (GRU), and existing deep models, it is shown that the proposed model is relatively stable and efficient in SST prediction, which provides a new idea for the development of SST prediction.

A continuous zoom optical system for underwater that has the characteristics of a large field of view, high resolution, and high zoom ratio at the same time is designed to satisfy the needs of deep-sea exploration and achieve higher quality optical imaging in the deep sea. According to the operating deep sea environment, the image quality degradation caused by the extrusion deformation of the optical window caused by deep water pressure was considered, an integrated optomechanical analysis of the optical window was carried out, and the surface shape change results were substituted into the optical system in the form of a Zernike polynomial for optimization. After studying the characteristics of underwater optical aberration and the design method of zoom system, the optical system adopts the mechanical negative group compensation zoom method and image square telecentric design scheme. The system's working distance is 5 m, the F-number of the whole zoom is constant 3.0, and the system can achieve the full field of view of 5.7°-90°, 10 times continuous zoom. The zoom system uses three aspheric surfaces with a total length of 260 mm. At 208 lp/mm, the maximum distortion of each zoom position of the system is <3% and the modulation transfer function values of the entire field of view in the whole zoom area are >0.3. The zoom system features a compact structure, good imaging quality, and a smooth zoom curve, which can accommodate real application demands.

With the completion and use of BDS-3, this paper proposes two improved methods for retrieving tide surface height from global navigation satellite system reflectometry (GNSS-R) based on the BDS-3/GPS multi-frequency signal to noise ratio data, namely, method of eliminating gross errors based on the relationship between the highest peak and the second peak and the method of optimal frequency band. The effectiveness of the method is verified by the observation data of 333-337 consecutive 5 days of accumulated days (DOY) in 2020 at the MAYG station on Mayotte near the Indian Ocean. The results show that the method of removing gross errors based on the relationship between the highest peak and the second peak can improve the accuracy of tide level inversion. The GPS frequency band is increased by 9.16% and the BDS frequency band is increased by 17.34%, but it will reduce the number of inversion results. The optimal frequency band correction method can improve the accuracy while increasing the number of inversion results. The inversion accuracy of the corrected GPS S1C and S2W frequency bands is increased by 26.54% and 22.89%, respectively. In BDS S1X, S2I, S6I, and S7I, the 5-day tide level inversion root-mean-square error decreased by 61.36%, 34.23%, 47.68%, and 55.38% respectively. The accuracy improvement is higher than the former.

To enhance the high-temperature performance of the fiber Bragg grating array (FBGA), an on-line writing high-temperature resistant FBGA is proposed. FBGA is coated with polyimide and is written on the drawing tower by single laser pulse with phase mask technology. After continuous processes of repeated coating, drying and final imidization, the final coating diameter, central wavelength, and reflectivity are 145-150 μm, (1551.35±0.1) nm, and 0.06%, respectively. The transmission loss of polyimide-coated FBGA (PI-FBGA) is 1.601 dB/km at 1550 nm. Additionally, the thermal stability and reliability of polyimide-coated FBG were studied. The findings reveal that the on-line writing high-temperature resistant PI-FBGA has excellent thermal stability and reliability and can be used for a long term below 300 ℃ and for a short time between 300 ℃ and 400 ℃. The high-temperature resistant PI-FBGA has vast application potential in petrochemical, environmental monitoring, aerospace, and other fields.

An acoustic sensitization method based on a fiber-wrapped thin-walled cylinder is studied. The sound pressure sensitivity calibration experiment system is established based on a 3×3 coupler. The directional characteristics of a thin-walled cylinder are experimentally investigated. The influence of the cylinder radius and wall thickness on the acoustic sensitization of fiber is studied experimentally, and the sound pressure sensitivity reaches 1.338 rad/Pa (-117.47 dB re rad/Pa). Then, the fiber-wrapped thin-walled cylinder is applied to a quasi-distributed acoustic sensing system for testing. For a 20.06-km sensing distance, the error between the 1-kHz sinusoidal applied waveform and experimental recovered waveform is below 4.1%. The signal-to-noise ratio (SNR) is 21.03 dB higher than that of unsensitized fiber coil sensing, showing the effect of the acoustic sensitization sensing of the thin-walled cylinder. The results provide an experimental basis for further developing high-sensitivity quasi-distributed acoustic sensing.

To solve the problem of low applicability and high complexity of the estimators based on the moments, this paper proposes an improved moment estimation algorithm based on fitting to improve the efficiency of Ricean-factor estimation. First, this improved model approximates the original function with a rational function, then inverts the approximate formula, and finally obtains two closed formulas pertaining to the Ricean factor. Simulation results show that the estimated efficiency increases at least 2.5 times when samples are 50000 or 1000. Further, under the condition of ensuring the estimation accuracy, the improved algorithm has less time complexity, leading to advantages in wireless communication scenarios wherein terminal resources are limited.

Optical orthogonal frequency division multiplexing (O-OFDM) technology is widely used in visible light communication (VLC) to improve the data transmission rate. However, O-OFDM systems have high peak-to-average power ratios (PAPRs), which limit their system performance. First, this study uses unipolar optical orthogonal frequency division multiplexing (UO-OFDM) without Hermitian symmetry to solve the problems of low spectral efficiency and high computational complexity of the conventional asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) system. Second, the conventional partial transmission sequence (PTS) technique is applied to the UO-OFDM system to decrease its PAPR, and a genetic algorithm (GA) is used to optimize the PTS technique for solving high computational complexity and low efficiency in searching for the optimal phase rotation factor of the conventional PTS technique. The simulation results show that GA-PTS significantly reduces the time required to search for the optimal phase rotation factor compared to the conventional PTS technique, with a slight difference in the PAPR suppression performance. Compared to the time used by the ACO-OFDM system based on the GA-PTS algorithm, the time used by the UO-OFDM system based on the GA-PTS algorithm is reduced. With an increase in the maximum generation, the reduced time becomes more significant.

A novel plasmonic sensor based on a D-shaped photonic crystal fiber (PCF) is designed to detect low refractive index changes, and its performance is numerically analyzed using the finite element method (FEM). Unlike the traditional D-shaped PCF, this paper proposes that etching a C-shaped groove channel at the cross-section of the D-shaped fiber and coating the Au layer to excite the plasmons. The design of the C-shaped groove channel can enhance the energy leakage of the fiber core and the coupling strength of both the fiber core and the plasmonic modes. A TiO2 dielectric layer is added on top of the Au layer to enhance the protection of the metal layer and improve the sensitivity of the sensor. The operating wavelength range of the PCF surface plasmon resonance (PCF-SPR) sensor is extended to the infrared region. The maximum sensitivity obtained from the simulation results is 24236 nm/RIU. The sensor can effectively monitor small changes in a low refractive index and has potential value for biomedical and organic detection and related applications.

A algorithm of combination of proportional-integral-derivative (PID) and active disturbance rejection control (ADRC) is proposed to solve the problem of the airborne laser communication platform in a work environment caused by the transformation of its motion posture, instability of the work environment, and susceptibility to external factors such as interference of atmospheric turbulence with the tracking system. The PID control algorithm is added to the linear active disturbance rejection link to perform simulation and experimental testing of the system. The results show that the improved ADRC is superior to the traditional ADRC in terms of tracking accuracy, anti-disturbance capability, and robustness. The tracking accuracy values of the improved and traditional ADRC are approximately 6.8 and 8 μrad, respectively. Thus, the tracking accuracy of the improved ADRC is approximately 15% higher than that of the traditional ADRC. Introducing the control algorithm of the improved ADRC into the fast steering mirror system also has a good tracking effect.

In this study, covariance matching technology is combined with a Sage-Husa adaptive Kalman filter to compensate for the lag in the miss distance obtained from a photoelectric tracking platform during airborne laser communication. First, a Sage-Husa adaptive Kalman algorithm is used to compensate for the off-target lagging, and the idea of forgetting filtering is introduced to reduce the influence of past measurement data on the present study. Subsequently, a criterion based on covariance matching technology is applied and if valid, the noise covariance matrix is updated and the forgetting factor is increased to accelerate the balancing of the estimated and theoretical values of the covariance matrix, thereby guaranteeing the real-time performance of the system. Based on the experimental results, the equivalent target sinusoidal motion in the simulation reduces the prediction error by 31.1% compared with the ordinary Kalman motion. Moreover, the tracking accuracy and real-time performance are increased by 18.5% and 18%, respectively, which meets the requirements for system control during off-target delay compensation and increases the stability of the system.

An ultrasensitive long period fiber grating (LPFG) sensor is proposed and investigated for the measurement of methane volume fraction by applying the selective adsorption property of cryptophane-E to methane. The cladding diameter is reduced to make the low order cladding mode LP06 work near dispersion turning point (DTP). The TiO2 thin film with optimized thickness is coated on the surface to ensure coupled cladding mode LP06 within the mode transition (MT) region, which can result in higher refractive index (RI) sensitivity of LPFG. The methane gas changes the RI of the cryptophane-E that is coated on the surface of the LPFG sensor, and then the methane volume fraction can be measured by monitoring the shift of the resonance wavelength. A high sensitivity of 249.6 nm/% can be achieved when the methane volume fraction changes from 0% to 3.5% owing to the contribution of DTP and MT. A back-propagation (BP) neural network is designed for the nonlinearity response of the sensor at different volume fraction. The result shows that a maximum predicted error of 0.008% is recorded in the methane volume fraction change range. The excellent performance shows that the proposed sensor has potential application value in the field of coal mine safety monitoring.

We investigate off-axis phase-matched terahertz (THz) radiation in laser plasma pumped by few-cycle laser pulses. We find that the THz amplitude and angular distributions in the far field are sensitively dependent on the pump pulse's focal carrier-envelope phase (CEP). Ring-like profiles of THz radiation are obtained at CEP values of 0.5 π and 1.5 π, due to the inversely symmetric local THz waveforms emitted before and after laser focus. Off-axis phase-matched THz radiation offers a tool to accurately measure the CEP of few-cycle pulses at the center of a medium.

We experimentally demonstrate an 80-channel wavelength division multiplexing (WDM) transmission system over a 400 km fiber link. Raman amplification results in a non-flat WDM signal spectrum. Therefore, bit allocation optimization is used to enable different channels to carry different order quadrature amplitude modulation signals according to their optical signal-noise-ratios. A neural network equalizer based on a convolutional neural network (CNN), long short-term memory (LSTM) network, and fully connected (FC) layer structure is adopted in Rx digital signal processing, in which CNN is used for characteristic extraction, LSTM is used for equalization and demodulation, and FC layers are used for output. After transmission, the bit error rate of all channels is below the 25% soft-decision forward error correction threshold, and the line rate reaches 53.76 Tbit/s.

A pre-distortion fringe deflection approach based on reverse ray tracing was proposed to address the blurred edges and low contrast of the fringe pattern captured by the camera while measuring a convex sphere with a small radius of curvature (ROC) using phase measuring deflectometry. In this approach, the pre-distortion fringe pattern was obtained by employing the reverse ray tracing model based on the nominal ROC of the spherical element to be tested. N-step phase shift algorithm and iterative optimization algorithm were applied to obtain the coordinates and height of each point on the element surface and subsequently combine with the differential geometry approach to compute the mean ROC of each point of the element. For a convex surface with an ROC value of 8 mm, the measurement accuracy in numerical simulations was approximately 11 μm. Finally, the mean ROC obtained for the points on the convex sphere with a ROC value of 8.26 mm was 8.28 mm, and the diameter of the measurement area increased from the original 4 mm to 5 mm. The findings reveal that compared with the traditional deflection approach, this approach can not only overcome the issue of blurred edge and low contrast of the fringe pattern when measuring convex spheres with small ROC but also improves the measurement accuracy and effective measurement area.

Aiming at the problem that the mapping relation between cavity misalignment parameters and cavity loss is unclear, and the relative cavity offset is not clear during the cavity tuning process, this study proposes a cavity loss optimization method based on cavity misalignment parameter scanning. In this method, the scanning optimization of the tilt adjustment of the cavity mirror was carried out. Similarly, the optimized cavity state of the relative misalignment between the initial cavity and test cavity was determined based on the ring-down time of the optical cavity. The experimental results reveal that there is an improvement in the measurement repeatability accuracy of the six experimental measurement results of the same high reflectivity sample, from 1.26×10-4 to 9.83×10-6. Furthermore, the measurement repeatability peak-to-valley value increases from 3.25×10-4 to 2.7×10-5 compared with the traditional method. Thus, the results verify that the proposed method can obtain a cavity tuning state with less relative cavity misalignment, which improves the optical cavity ring-down measurement system with low-initial cavity reflectivity.

Three-dimensional (3D) shape non-contract measurement with fringe projection profilometry is a primary method for measuring the size of complex objects in many areas. However, for an object whose surface has both high reflectivity and low reflectivity areas, rapid and accurate 3D measurements have been the research object of many scholars, and is considered an urgent problem that needs to be solved in the industry. In this study, the phase errors of different fringe projection intensity amplitudes at different signal-to-noise ratios are first obtained using both theoretical and simulation analysis. Further, a new method, which can achieve the high dynamic range shape measurements without requiring calibration of the measured surface reflectivity and the optimal projection fringe intensity amplitude in advance, is proposed. Specifically, two appropriate different fringe intensity amplitudes are projected, and the measurement results are combined. The feasibility and effectiveness of this method are verified experimentally. Finally, the 3D shape measurement experiment is carried out on the surface of the measured object with large reflectivity difference. According to the experimental results, this method can not only effectively measure a surface with a large range of reflectivity variations, but can also improve the measurement efficiency and provide a theoretical and experimental basis for the effectiveness of the recently proposed high-speed measurement method (double-shot-in-single-illumination).

Multi-parameter synchronous measurement of optical fiber is the key to accelerate the rapid development of optical fiber towards the direction of low loss, low nonlinearity, and so on. In this paper, a multi-parameter synchronous measurement method of single-mode fiber based on bidirectional Rayleigh scattering is proposed, which can realize synchronous and accurate measurement of fiber multi-parameter. Based on the principle of Rayleigh backscattering, the optical fiber multi-parameter measurement synchronous measurement system is established, and the distribution of parameters such as mode field diameter, effective mode field area, core diameter, relative refractive index difference, cut-off wavelength, and attenuation coefficient of 1 km optical fiber are successfully tested, and the measured values are 9.24 μm, 66.22 μm2, 8.28 μm, 0.323%,1.258 μm, and 0.196 dB/km, respectively, and are compared with traditional measurement methods. Experimental results show that the proposed method is basically consistent with the traditional measurement method, and the multi-parameter distribution measurement is achieved and the measurement results are stable.

The imaging quality of light stripe is one of the important factors determining the 3D measurement accuracy of line structured light. In order to solve the problems of poor consideration of the image's whole and details and lack of comprehensive evaluation criteria in the present imaging quality evaluation methods of light stripe, an imaging quality comprehensive evaluation method by multi-parameters of line structured light stripe is proposed. First, the characteristics of light stripe image set acquired with a gradual change in exposure time are analyzed from three aspects: one-dimensional image entropy, local contrast, and light stripe's definition. Then the imaging quality of light stripe images are reversely evaluated by the extraction accuracy of the image set's light stripe centers, and the change rule of multi-feature parameters with the light stripe center extraction accuracy is analyzed. Finally, the imaging quality is comprehensively evaluated by multi-feature parameters of line structured light stripe image set, and the multi-parameter comprehensive quantitative evaluation model is constructed. The experimental results show those the evaluation result of the proposed method is more accurate and effective than those of the existing methods, and the high-precision rack measurement results obtained from the evaluated high-quality light stripe images have the highest accuracy, whose Rssa value is only 0.022.

The payload of laser ranging interferometer based on the two-satellite formation can on-orbit show numerous vital technologies in the space-based gravitational wave detection mission. In this mission, to realize the picometer-level precision in the inter-satellite displacement measurement, it is required to achieve the optical carrier phase measurement with an accuracy of better than 10-6 cycle/Hz1/2 in the mHz frequency range. The sample jitter of the phase meter's analog-to-digital converter is the bottleneck limiting the precision of the phase measurement. By applying the techniques of pilot tone and clock side-band modulation, the sampling jitter noise could be suppressed in the data post-processing algorithm. The clock side-band modulation method towards time-delay interferometry in the three-satellite formation is extended to the two-satellite formation-based dual optical carrier phase measuring system. The systematic approach is proposed to suppress the sampling jitter noise in the optical carrier phase measurement considering the inter-satellite Doppler frequency shift. The technique could be applied in the next-generation earth gravitational detection mission to on-orbit demonstrate the phase meter technology towards space-based gravitational wave detection. Furthermore, it could be used in the high-precision inter-satellite laser time and frequency transfer mission, supporting the future global navigation satellite system.

A femtosecond laser micromachining experiment was carried out on a quartz sheet to cut and separate devices with complex shapes from a quartz single crystal wafer. The relationship between the ablation aperture square and laser parameters was studied experimentally at high repetition frequencies of 50 kHz, 100 kHz, and 200 kHz. The etching thresholds of pure quartz at the corresponding repetition frequencies were 3.73 J/cm2, 3.45 J/cm2, and 3.2 J/cm2, respectively. The effects of femtosecond laser pulse energy, scanning speed, and other processing parameters on the cutting quality of microgrooves were studied. The laser pulse energy could change the surface morphology of the machined microgroove significantly. In addition, the machining effect was the best when the scanning speed was approximately 3.5 mm/s. Finally, using optimized process parameters, the resonant tuning fork devices with complex shapes were cut out on a 0.45 mm thick quartz wafer, which generally meets the expected quality requirements.

A theoretical investigation of the influence of pump parameters of quasi-continuous-wave laser-diode (LD) pumped Yb∶KYW/Cr4+∶YAG laser on pulse characteristics based on passively Q-switched rate equations is presented. Through numerical calculation, the relationship between the characteristics of Q-switched pulse delay, pulse width, sub-pulse sequence, and pump rate is analyzed to obtain the optimal pump-light duty cycle and effectively reduce the thermal effect caused by continuous-wave pump. Furthermore, the high-repetition-rate LD pump source is used in the experiment, and the accurate locking and control of output characteristics such as repetition rate, pulse delay, and the number of pulse trains of the passively Q-switched laser are realized by adjusting the pump parameters. When the duty cycles of 15.6-W pump power are 6.5%, 8%, and 9.65%, stable outputs of single pulse, double pulse, and triple pulse, respectively, are obtained, and the coupling resonance of pump pulse and laser pulse is improved. The experimental results are in agreement with the theoretical calculation.

Pore defects adversely affect the mechanical properties of laser-additive manufacturing alloys. To elucidate the effect of pore defects on the tensile properties of Al-Mg-Sc-Zr alloy formed by selective laser melting (SLM), this study characterizes the internal pore defects of the alloy in three dimensions using X-ray computed tomography and obtains the tensile properties of the alloy through room-temperature tensile tests. Based on the pore data and tensile-test results of the Al-Mg-Sc-Zr alloy, a representative volume element (RVE) model that reflects the constitutive and pore characteristics of the material is established. Assuming an unchanging matrix of the Al-Mg-Sc-Zr alloy formed by SLM, the tensile properties of the alloy are evaluated for different porosities and pore sizes in the RVE model. The calculations show that the tensile strength and elastic modulus of the alloy decrease obviously when the porosity increases. And, when the pore size increases, the tensile strength of the alloy decreases significantly, but the elastic modulus does not change significantly. When the pore size exceeds 100 μm, obvious stress concentration appears around the pores.

Gallium nitride (GaN) has widespread applications in the semiconductor industry because of its desirable optoelectronic properties. The fabrication of surface structures on GaN thin films can effectively modify their optical and electrical properties, providing additional degrees of freedom for controlling GaN-based devices. Compared with lithography-based techniques, laser processing is maskless and much more efficient. This paper shows how surface micro-nano structures can be produced on GaN thin films using 355 nm nanosecond laser irradiation. The effects of the laser pulse energy, number of pulses, and polarization direction were studied. It was found that distinct micro-nano structures were formed under different irradiation conditions, and their geometries and elemental compositions were analyzed. The results indicate that different types of surface micro-nano structures can be produced on GaN thin films in a controllable manner using 355 nm nanosecond laser irradiation. The results of our study provide valuable guidance for the surface modification of GaN-based optoelectronic devices.

The specimens with straight channels and the product with complex channels were manufactured by laser powder bed fusion. The results showed that when the diameter of the channel was less than 2 mm, the remaining powder inside the channels could not be removed completely due to the shrinkage of the flow channels after fabricated. In addition, the forming quality of the top surface of the circular channels became worse, with the increase of the diameter while the forming quality and dimensional accuracy for ridge shape channels still kept better with the increase of the size of the section, since the inclination angle of the inner surface was a fixed value. Meanwhile, the semi-melted powder particles adhered to the upper region of the flow channels caused by the deep penetration of the laser into the powder in the non-forming region could be removed by abrasive flow machining, high pressure airflow or water. The test results of the laser powder bed melting product with complex flow channels indicated that there were no defects such as crack or remaining powder by X-ray and computed tomography test. And the pressure test suggested that the product with complex flow channels was not damaged or leaked when the pressure reached 2 MPa for 5 min. Finally, the processes “design-form-test” were successfully established for the products with complex flow channels.

To address the problem of limited wavelength output by a traditional fiber laser for its gain medium of rare-earth-ion-doped fiber owing to the size-dependent wavelength of quantum dots, an all-normal dispersion mode-locked fiber laser with PbSe quantum dot as the gain medium is demonstrated and studied through numerical simulation. A stable dissipative soliton of 1.7 μm is obtained by calculation. The buildup dynamics, evolution in the cavity, and output characteristics in a steady state of generating dissipative solitons using a PbSe quantum dot fiber laser are investigated systematically. Influences with respect to the length and doping concentration of the gain fiber and the length of the passive fiber are explored. The optimal gain fiber length and doping concentration obtained under a pump power of 0.1 W are 0.3 m and 12×1021 m-3 respectively, corresponding to a pulse duration of 7.59 ps and a spectral width of 13.77 nm. However, the steady-state disappears beyond a passive fiber length range of 2-7 m. Furthermore, when the passive fiber is 0.1 m, a multi-wavelength output is generated by the laser, with 22 peaks, a spectral range of 1678-1724 nm, and an envelope width of 22.33 nm. In the time domain, a dual soliton is emitted with a width of 0.92 ps and a pulse interval of 4 ps. This work provides theoretical guidance for establishing and optimizing an ultrafast quantum dot fiber laser and a new option for fiber lasers of special wavelengths.

An HR-2 hydrogen embrittlement resistant stainless steel was subjected to selective laser melting process testing performed at different levels of volume energy density. The microstructure and properties of the formed parts were characterized. The results revealed that, for a certain range of volume energy density values, the density, microhardness, tensile strength, and elongation of the parts increased with increasing volume energy density. At the maximum energy density of 113.3 J/mm3, the maximum density of the formed part, corresponding tensile strength, yield strength, elongation after fracture, and reduction in area were 99.9%, 765.5 MPa, 634 MPa, 44.0%, and 61%, respectively. These values satisfy the performance requirements of HR-2 forging specified in the GJB 5724 standard. The printed structure of HR-2 is composed of columnar crystals, with equiaxed grains inthe XY plane and columnar grains in the YZ plane. In the XY plane, the grain size increases first and then decreases with the increase of bulk energy density. This is the combined effect of poor fusion pores caused by insufficient heat input, the increase of undercooling caused by the decrease of scanning speed, and the increase of the proportion of remelting zone caused by the decrease of scanning spacing on grain size.

In this study, the instability phenomenon of an infrared trigger device that has operated for a long period of time is examined on the basis of working principle of the device and by means of experimental monitoring and analysis. The threshold current, Ith(T), of the infrared laser, which is the source of the infrared laser triggering device, increases after the infrared trigger device works for a long time owing to heat accumulation. In contrast, the output current, Iout(T), of the constant current source decreases with the increase in temperature. When Iout(T)<Ith(T), the infrared laser cannot emit the laser normally, and the output power becomes unstable; this leads to the instability of the infrared trigger. Upon increasing the output current of the constant current source to 1.44 times the maximum threshold current, that is, beyond 640 mA to make Iout(T)>Ith(T), the infrared laser can be guaranteed to be in a stable luminous state within the range of temperature change, and the infrared trigger device is therefore in a stable working state. After a long period of power-on operation experiment, the infrared trigger worked stably and did not trigger the signal by mistake, indicating that its instability problem is effectively addressed. The findings of this study have important engineering application value in improving the stability of infrared trigger devices.

The influence mechanism of the laser remelting path on the residual stress and surface quality of the cladding layer was studied by combining numerical simulation and experiment to further improve the surface quality of the remanufactured alloy layer and its comprehensive mechanical properties. First, the laser cladding and remelting models were established using the Simufact Welding software platform, and the variation laws of the temperature field and stress field during the remelting process were simulated and studied under three different scanning paths, respectively. Subsequently, the laser remelting process experiment was performed, and the residual stress and surface morphology of the remanufactured alloy layer were detected and analyzed using an X-ray residual stress detector and a Keyence ultra-depth-of-field microscope. The simulation results show that the temperature gradient of each point on the workpiece's surface during the remelting process is significantly lower than that during the cladding process. The workpiece's maximum residual stress before remelting is 269.59 MPa. The residual stress of the workpiece is significantly reduced after laser remelting, and the residual stress value of the workpiece under the L1-type-remelting path is the smallest, which is only about half of the stress value before remelting. Furthermore, the residual stress test results and the numerical deviation of the simulation calculation are both within 10%, which proves the simulation calculation's accuracy. Laser remelting can effectively reduce the surface roughness of the cladding layer, according to three dimensional extraction of the surface morphology of the alloy layer.

In this study, the Monte Carlo method is used to examine the effects on the sputtering characteristic parameters of sputtering yields, damage density distributions, and longitudinal energy damage distributions with different sputtering parameters and material models. Based on the particle tracking and physical statistical results of SRIM-2013 software, the effects of the initial energy of the ion beam, incident angle, ion type, and material type on surface sputtering and energy deposition are analyzed, and the relationship among surface damage distribution, sputtering parameters, and sputtering yield are studied. The results show that a beam-source inclination of 85° can promote the density concentration and peak density group of cascading particles to a surface of 2.8×108 atom/cm2 and 3×10-10 m, respectively, thereby reducing the average energy loss by 45.6% and increasing the Ar+ sputtering yield by a factor of 4.7. The substantial energy loss caused by phonons and ionization inhibits the increase in sputtering yield, and the two energy losses account for 69% and 30% of the total loss, respectively, at an incidence angle of 0°.

Based on the open trapezoidal three-energy level atomic model and density matrix equation theory, the variation of population with time during double-color and double-resonant enhanced multiphoton ionization is numerically simulated under different parameters. When the frequency detuning of two lasers is zero, the populations of the ground as well as first- and second-excited states exhibit damping Rabi oscillation with time. The oscillation frequency of the population distributed in the first-excited state is twice that in the ground and second-excited states. Large population inversion occurs between the second-excited and ground states and exhibits the possibility for the output of coherent light with short wavelengths. Furthermore, the oscillation frequency and population inversion increase with Rabi frequency. Population inversion is evident as the two lasers become synchronous.

A fiber bundle monitoring system appropriate for test conditions is devised and implemented to assure the stability of the state transfer of electrical and electronic equipment in radiated immunity tests. Components such as the objective lens, fiber bundles, conversion lens, and charge coupled devices compose the majority of the system. The monitoring system's objective lens is designed and optimized using Zemax in conjunction with fiber bundle specifications. The design results show that the optical modulation transfer function value of each field of view of the objective lens is greater than 0.8 at the spatial frequency of 36 lp/mm, image area fits the fiber bundle size, and telecentric optical system in image space meets the criteria. The technical indicators of the processed objective lens are in line with the theoretical design, according to the performance test. The imaging experiment is conducted using the fiber bundle monitoring system, and the depixelation processing is achieved using the Gaussian filtering technique that improves the monitoring system's video transmission quality, and the system's anti-electromagnetic interference ability is demonstrated by the radiation immunity test.

This study proposed a design method for a double spherical reflection compensation detection system to detect the surface accuracy of a large aperture high-order aspheric surface. A spherical surface tangent to the edge as the best-compared sphere was selected. The aspheric gradient and normal aberration of the high-order aspherical mirror was also fitted with an outer diameter of about 860 mm and a middle hole of about 200 mm. The formula of the compensation detection system was derived using the three-stage aberration theory, and was utilized to calculate the initial parameters, analyze the compensation effect, and improve and optimize the final structure. The wavefront root mean square of the system was less than 1/90λ by optical software simulation, and 98% tolerance analysis results revealed that the wavefront is less than 1/40λ, which meets the actual detection requirements. This method can solve the problem of inability to detect high-order aspherical mirrors to be inspected.

This study aims to accurately detect the surface shape of large-aperture high-order aspheric mirrors. A compensation detection system is designed, and lightweight analysis of a semi-annular concave high-order aspheric mirror with inner and outer diameters of 572 mm and 800 mm, respectively, is performed. Based on the theory of three-order aberration, the aspheric mirror is compensated for and detected using the double-lens structure and single-reflecting surface, and a compensation detection system with a root-mean-square (RMS) value of 0.0037λ (λ=632.8 nm) is developed. Triangular holes are used to lighten the high-order aspheric mirror. After achieving light weight, the weight of the lens body becomes less than 30 kg, and the weight reduction rate is 32.7%. A finite element analysis of the high-order aspheric mirror and the support structure under its gravity, combined with the mechanical support structure, is conducted. The RMS values obtained when the optical axis is parallel and perpendicular to the direction of gravity are 0.012λ and 0.013λ, respectively. The maximum stresses on the mirror body and mechanical support structure are 1.308×105 Pa and 1.381×105 Pa, respectively. The stresses on the aspheric mirror and support structure are lower than the ultimate stress of the respective material.

A monotonic compositionally graded hole reservoir layer (MCG-HRL) and a symmetric compositionally graded hole blocking layer (SCG-HBL) structures are proposed to optimize the electro-optical conversion efficiency and output power of the deep ultraviolet laser diode (DUV-LD). Crosslight software is used to simulate the DUV-LD with infrastructure, rectangular HRL (R-HRL), MCG-HRL, and MCG-HRL structures. The simulation results indicate that the MCG-HRL and SCG-HBL effectively contribute to the increased hole concentration in the quantum wells (QWs), reduce hole leakage in the n-type region, increase radiation recombination rate in the QWs, reduce threshold voltage and resistance, and increase electro-optical conversion efficiency and output power of the DUV-LD.

Aiming at the shortage of a single-photodiode (PD) receiver and geometric algorithms, we set up a real visible light positioning (VLP) scene of a multi-PD receiver and then use the fingerprint positioning technology based on the received signal strength, which commonly uses machine learning algorithms (MLAs). The positioning performance of four typical MLAs is studied. The results show that in two-dimensional positioning, the probabilities that the positioning error is less than 2 cm are 96.67%, 48.57%, 67.14%, and 15.24% for the K-nearest neighbor (KNN), extreme learning machine (ELM), random forest (RF), and adaptive boosting (AdaBoost), respectively, and in three-dimensional positioning, the probabilities that the positioning error is less than 2 cm for the KNN, ELM, RF, and AdaBoost are 74.52%, 38.81%, 59.76%, and 6.43%, respectively. Therefore, the positioning performance of the KNN is better in both the cases. On this basis, the influence of factors such as the number of light-emitting diodes (LEDs), number of PDs, and emission power of LEDs on the positioning accuracy is compared in detail. The results show that the increase in both the number of LEDs and PDs effectively reduces the positioning error. When the emission power of LEDs is 5 W, the positioning error convergence is achieved. The results provide a new theoretical support and practical application value for the design of VLP systems in the low LED distribution density scenes.

A new method based on a telecentric lens and curved screen is proposed to measure a discontinuous mirror's three-dimensional (3D) shape. This technique increases the imaging range of mirrors having large curvature and improves the measurement accuracy of 3D data. First, a display screen shows sinusoidal fringe patterns, and a camera records the sinusoidal fringe images reflected through the plane reference mirror and the measured mirror. Second, the corresponding phase distribution is obtained using the four-step phase shift method and the optimal three fringe selection method. The phase change modulated by the object surface of the measured mirror is obtained by comparison to the plane reference mirror. Furthermore, according to the established mathematical model, the relationship between phase and depth is deduced, and the system parameters are calibrated. Finally, measurements are taken to verify the accuracy and effectiveness of the proposed method using an artificial mirror step with large curvature and a discontinuous mirror.

Recently, perfect vortex beams have been proposed and studied. Therefore, in this paper, we combine perfect vortex beams and polarization singularities to generate perfect polarization singularity light fields by superimposing two orthogonal circularly polarized perfect Laguerre-Gaussian beams with different topological charges. The results show that the radius of the perfect singular field is much smaller than that of the conventional singular field. We also study the superposition of orthogonal circularly polarized perfect Laguerre-Gaussian and conventional Laguerre-Gaussian beams for different cases. Consequently, we obtain that the polarization states of the superimposed light fields are different, and the phenomenon of “quasi-high-order polarization singularities” appears. Moreover, the simulation of perfect singularities has broadened the theoretical study of singular optics.

To improve the reliability of the integrated navigation system and the accuracy of pose estimation, a novel visual inertial integrated navigation system assisted by polarized light is proposed and constructed by introducing a polarization orientation sensor into the process of simultaneous localization and mapping. The data from the polarization orientation sensor, monocular vision camera, and micro-inertial measurement unit are collected. The target equation is established using the least square optimization method after multi-sensor data has been time-stamped aligned and preprocessed, and the best motion estimation is then produced by solving nonlinear equations. In the suggested system, the observability of azimuth is achieved based on the polarization distribution of the sky, and multi-sensor data are fused. Based on the above-integrated navigation system, an outdoor vehicle-mounted experiment is carried out. The experimental findings indicate that, in the long-distance operation of 2 km, the location inaccuracy of the polarized light-assisted visual-inertial navigation system is 16.7% lower and the heading angle accuracy is 23.4% greater than the estimated value of the original visual-inertial system. The polarization orientation sensor can reduce the drift of inertial devices, enhance the position accuracy and attitude angle accuracy of the navigation system, and meet the needs of the position and pose estimation accuracy and reliability under the interference of satellite signals.

Fast axis ajustable photoelastic modulator (FaaPEM) not only has the advantages of high modulation frequency, large aperture, and good seismic performance, but also makes up for the shortcomings of traditional elastic optical modulator, such as phase delay and fast axis azimuth. It plays an important role in polarization modulation and polarization measurement. FaaPEM is a resonant optomechanical device composed of two piezoelectric drivers and elastic optical crystals. In the high voltage resonant state, due to its own temperature rise, the resonant frequency of elastic optical crystals does not match the frequency of driving voltage, which greatly affects the modulation efficiency of incident light. In order to ensure the optimal modulation capability and stability of FaaPEM at work, this paper carries out the research on the stable closed-loop control of FaaPEM, proposes a closed-loop drive control method based on modulation signal tracking and phase regulation, and tests the stability of FaaPEM. The test results show that the stability of the system reaches 4.18% under half wave state and 3.43% under quarter wave state after loading feedback control.

In this study, a multicast routing protocol for hyperentangled relay quantum networks is proposed to solve the problem of path selection, the establishment of multicast communication in quantum networks, and improve the communication performance of quantum multicast networks. The networks use a diamond structure to ensure the fidelity of quantum clones in multicast communication. The single-photon polarization-space mode quantum state was cloned using a quantum cloning machine, and an optimization algorithm based on the Steiner tree was used to generate a multicast tree by considering the number of hyperentanglement resources, hops, and fidelity of the cloned state. A multicast quantum channel between remote users was established based on simultaneous hyperentanglement swapping after selecting the routing. Theoretical analysis and simulation results show that in multicast communication of an increase in destination nodes, the routing protocol based on a hyperentangled relay can obtain a multicast tree with high fidelity. When the number of relay nodes increases, the delay in establishing a quantum channel using simultaneous hyperentangled swapping is lower than that of traditional sequential entangled swapping, and the transmission rate of a quantum state is faster. Therefore, the routing protocol of quantum multicast networks based on hyperentangled relays has the advantages of high fidelity and low-multicast communication delay.

The three-qubit Toffoli gate is equivalent to the combination of two two-qubit controlled NOT gates and three two-qubit controlled phase-shift gates. The controlled NOT and phase-shift gates respectively comprise a combination of nuclear-magnetic-resonance pulse sequences and a free development operator of two nuclear spins with time. According to the order in which the controlled NOT and phase-shift gates act on the nuclear spin system, the nuclear-magnetic-resonance-based physical realization of a quantum Toffoli gate is achieved. The time-dependent Schr?dinger equation is numerically solved by the Suzuki formula to confirm the correctness and feasibility of the realization of the quantum Toffoli gate based on nuclear magnetic resonance.

Combining with the development of current technology, this paper proposes an improved greedy dynamic programming algorithm based on the fusion of greedy algorithm and dynamic programming algorithm for the problems of large number of station observation tasks, difficult problem modeling, and high solution complexity. First, this algorithm divides the scheduling problem into several subproblems, iteratively solves them with the objective function of maximizing the observation income according to constraints and generates an approximate optimal observation plan. Experimental results show that this algorithm has certain feasibility and practicability in solving observation task scheduling problems, and lays a solid foundation for the next step of establishing an automated station operation system.

A fiber tapering technique is used to optimize a central symmetry multicore fiber that has a large core spacing. The tapered fiber has the characteristics of a strong evanescent field and high sensing sensitivity; however, it is difficult to use as a bending sensor because of its poor flexibility. This paper proposes a flexible structure design so that the optimized tapered fiber can be used as a bending sensor. The transmission spectrum of the optimized multicore optical fiber sensor is analyzed using supermode coupling theory. In addition, the bending sensing characteristics of the sensor are experimentally studied. The experimental results indicate that there is a good linear relationship between the interference fringes and bending curvature. The sensitivity of the optimized tapered fiber sensor is 2.90 nm/m-1.

An interferometric microfiber magnetic field sensor composed of a microfiber interferometer and a TbDyFe magnetostrictive rod is proposed. The microfiber interferometer was formed by tapering a single-mode fiber and placed in lateral contact with a TbDyFe magnetostrictive rod. Under the action of a magnetic field, the axial strain of the magnetostrictive rod and the microfiber interferometer causes a wavelength shift of the interference spectrum, which forms a wavelength coding fiber magnetic field sensor. The experimental results show that for the microfiber interferometers with the same strain characteristics, the smaller the diameter of the magnetostrictive rod is, the higher the magnetic field sensitivity is. The sensitivity of the fiber magnetic field sensor composed of TbDyFe magnetostrictive rod with a diameter of 2 mm can reach up to 0.178 nm/mT. The sensor has the advantages of simple structure, easy fabrication, low cost, and fast response. It can realize highly sensitive detection of weak magnetic field.

In this study, an immunosensor based on a graphene oxide (GO)-functionalized microfiber is developed and used for the analysis of rabies virus (RV) immunodetection. For this, first, a standard single-mode fiber was discharged through an optical fiber fusion splicer to form a double-tapered fiber, after which the double-tapered fiber was fused and tapered to produce a high-sensitivity microfiber. Subsequently, the microfiber surface was modified with GO, and RV antigens were immobilized on the surface of the sensor for the immunoassay of RV antibodies. The experimental results indicate that the detection range of the biosensor for RV antibodies is 200 fg/mL-1 ng/mL, its detection of limit (LOD) is approximately 225.56 fg/mL, and its detection sensitivity and dissociation coefficient are approximately 1.099 nm/log (mg·mL-1) and 2.92×10-11 M, respectively. When the sensor is used in control experiments and clinical immunoassays for other antibody solution samples and RV-positive serum, it yields weak responses to the former and significant responses to the latter, indicating its high specificity to RV antibodies. The proposed immunosensor based on the GO-modified microfiber demonstrates the advantages of facile fabrication, micro-nano size, high sensitivity, and low cost.

With the development of satellite optical communication technology, networking through optical links can meet the access, transmission, and distribution needs of the explosive growth of internet services in the future. First, the satellite internet architecture based on optical communication and constellation types are introduced. Then the key technologies of the next generation of satellite optical network are analyzed, including photoelectric hybrid switching, satellite optical network wavelength routing, wavelength demand analysis, and traffic grooming technology. Finally, the technical development directions of satellite optical network are discussed.

Diffractive optical components were widely used in many fields such as optical sensing, optical communication, computational optics, laser beam shaping, biomedicine, and optical data storage. This paper first summarizes the development of diffractive optical elements based on scalar diffraction theory in various stages. The development of diffractive optical elements can be divided into four stages: Fresnel zone plate, hologram and kinoform, binary optical element, and diffractive optical element. The design principles, structural characteristics, processing difficulties, diffraction efficiency, and application possibilities in reality are analyzed for each stage of diffraction elements followed by an overview of diffractive optical elements based on vector diffraction theory. Finally, a summary of current applications of diffractive optical elements in conventional and new imaging and non-imaging systems is presented. The current problems in the development of diffractive optical elements are sorted out and the future development trend is predicted according to the corresponding problems, which will be a guide for the future research of diffractive optical elements.

2 μm band laser has a wide range of applications, not only in the fields of lidar, laser ranging, and medical surgery, but also as a pump source for mid and long wavelength infrared lasers. Using laser diodes to directly pump thulium-doped crystals to obtain lasers in the 2 μm band is a direct and efficient technical means, which has attracted wide attention. This paper introduces the research progress of Tm∶YAG, Tm∶YAP, and Tm∶YLF pulsed lasers, and makes a summary and prospect.

The excellent device performance of lead-based perovskite is attributed to its remarkable optical and electronic properties. This series of solar-cell absorber materials has greatly improved the energy conversion efficiency from approximately 3.8% initially to more than 25%. Despite the rapid development of lead-based perovskites, the toxicity of lead atoms and their instability under heat, light, and humidity hinder the practical application of this type of perovskite photovoltaic technology. Therefore, it is very important to develop lead-free, non-toxic, and eco-friendly halide perovskites to replace lead-based materials in practical applications. The research on lead-free halide perovskites is one of the current study frontiers. This review summarizes the application of lead-free double perovskite Cs2AgBiBr6 in perovskite solar cells, introduces the structure and material preparation methods of Cs2AgBiBr6, discusses the device performance of perovskite solar cells, analyzes relevant strategies to improve the performance of this type of photovoltaic device, and discusses the challenges and development directions of lead-free perovskites.

In the near-infrared region, the noise of optical and electronic components affects the signal-to-noise ratio of the second-harmonic signal when wavelength modulation spectroscopy is used to detect gas concentration. Therefore, to suppress the noise, a compound denoising algorithm based on empirical mode decomposition, detrended fluctuation analysis, and the wavelet adaptive threshold is proposed. The algorithm, in view of the existing traditional empirical mode decomposition noise reduction algorithm, is useful for the signal loss problem. Therefore, detrend fluctuation analysis is used to optimize the information intrinsic mode function screening, and it filters out information for the intrinsic mode function for signal reconstruction. Then, the wavelet adaptive threshold algorithm is used to improve the noise reduction accuracy. The proposed algorithm is compared with the classical denoising method and evaluated. The correlation number between the proposed denoising method and the original second-harmonic signal after denoising is 99.9018%, and the root mean square error is 0.0087%. By denoising the second-harmonic signals obtained in the experiment, the results show that the proposed algorithm has a noticeable denoising effect and can retain useful information points.

To improve the accuracy of the quantitative analysis of heavy metals in pig feed by laser-induced breakdown spectroscopy (LIBS), the Cu element in common pig feed in the market is taken as the research object, and a quantitative analysis model of the Cu element in pig feed is established by the partial least square (PLS) method, combining spatial confinement to improve LIBS signal intensity and quantitative model accuracy. The diameter and height of the spatial confinement cavity used in the experiment are 4.5 and 2 mm, respectively. Nine smooth, standard normal variable transformation, multiplicative scatter correction, and other methods are used to perform spectral preprocessing on the LIBS spectra of 60 groups of pig feed samples and build a PLS prediction model. The results show that, based on the cylindrical cavity confinement, using nine smooth combined with multiplicative scatter correction preprocessing has the best effect. Without spatial confinement, the correlation coefficient of the prediction set (R) is 0.8684, the root mean square error of prediction set (RMSEP) is 49.3, and the average relative error of the prediction set (ARE) is 43.95%. With spatial confinement, the R is 0.9881, the RMSEP is 14.4, and the ARE is 12.51%. The research results show that the addition of spatial confinement to LIBS technology can significantly improve the spectral signal intensity of the Cu element in pig feed and the accuracy of the PLS model. It provides better support for the precise safety inspection of pig feed.

The structures of photoacoustic cavities are among the most important factors affecting the sensitivity of photoacoustic spectrum detection systems. Considering the emerging trend towards the miniaturization and portability of photoacoustic spectrum detection systems, this study considers a cylindrical photoacoustic resonator as its research subject. With a fixed total length of the photoacoustic cavity, finite element analysis of the photoacoustic resonator model is conducted to investigate the influence of the structural layout of the resonator and buffer chamber on the performance of the photoacoustic cavity. The results reveal that when the length of the resonator is constant, the maximum sound pressure signal intensity can be obtained when the two buffer chambers are symmetrically distributed. When the buffer chambers are symmetrical, and the total length of the photoacoustic chamber remains unchanged, the resonator quality factor Q increases with an increase in the length of the buffer chamber. The characteristic frequency first increases and subsequently decreases with the increase in the buffer chamber length and reaches a maximum of 2110 Hz at Lbuff=70 mm. In the resonant state, the sound pressure signal reaches a maximum value of 5.61×10-6 Pa at Lbuff=40 mm.

The rapid and accurate coupling interference analysis and concentration detection of the multiple pollutants in complex water bodies are significantly important for the in-situ real-time monitoring of field water quality. To address the problems of characteristic coupling and the interference of spectral peaks in the synchronous detection of chemical oxygen demand (COD) and turbidity using ultraviolet spectroscopy, which significantly affect the detection accuracy, a decoupling method for predicting water pollutant concentration was developed in this study based on the continuous projection algorithm combined with support vector regression. The continuous projection algorithm was used to screen the characteristic wavelengths of the ultraviolet absorption spectra of water quality samples and eliminate irrelevant redundant numbers, to improve the iteration rate and accuracy of the model. Based on the concept of the multi-classification support vector machine, the support vector regression algorithm was improved via multi-regression fitting, and the ultraviolet coupling analysis of COD and turbidity, as well as the simultaneous prediction of concentration, was realized. The test results for actual water samples reveal that the maximum relative errors are reduced to less than 4%, and the improvement rate of the root mean square error of predictions before the coupling analysis reaches 76%. Thus, the proposed method offers a better detection accuracy, as compared with similar methods. Notably, this work is expected to serve as a reference for the application of ultraviolet spectroscopy in water-quality multi-coupling parameter detection.

Soil organic matter (SOM) plays an important role in ameliorating environmental problems such as land salinization, desertification, and grassland degradation in arid areas. To explore the feasibility of the fractional differential method in hyperspectral SOM inversion, 73 soil samples from Weigan River to Kuqa River oasis were considered as research objects. By measuring the SOM content and spectral reflectance, the mathematical transformation of a fractional differential of order 0-2 was performed using a 0.2-order differential as the step size. Further, the correlation between the fractional processing spectrum and SOM content was analyzed. Support vector machine regression, partial least squares regression, and random forest (RF) methods were used to quantitatively invert the SOM content. The results reveal that the prediction accuracy of the SOM inversion model established by the 1.2 RF derivative is the highest, with Coefficient of determination of 0.93, Root mean squared error of 1.62, and Relative percent difference of 3.65. These results can provide a basis for accurate inversion of SOM in this study area, and they also have a certain reference significance for inversion of SOM in other areas.

Laser-induced breakdown spectroscopy (LIBS) inside liquids is accompanied by the emission and expansion of plasma, propagation of intense shockwaves, and growth of cavitation bubbles. A comprehensive time-resolved observation of these processes is essential to reveal the underlying physiochemical mechanism and improve the analytical performance of LIBS in liquids. In this work, by using a laser-beam-transmission probe (LBTP), a continuous wave He-Ne laser coupled with a photodiode are utilized to simultaneously record the transmission signals from the shockwave and bubble as well as the emission signals from the laser pulse and plasma during an individual LIBS event. Under the excitation of different laser pulse energies, the negative peak of the LBTP signal is proportional to the peak area of LIBS spectra with a relatively high correlation coefficient (R2>0.99). On the basis of this approach, for aqueous alkali metal solutions with different concentrations, the regression model of LBTP signal to the relative deviation of spectral characteristic peak area is established by using partial least square regression (PLSR), and the LIBS spectral normalization is realized.

The tungsten trioxide sol is prepared using the tungsten powder-hydrogen peroxide-polytungstic acid method, doped using chloroplatinic acid, and spin-coated into a platinum-doped nanotungsten trioxide film exhibiting hydrogen-induced discoloration. The film properties are analyzed using X-ray diffraction, field-emission scanning electron microscopy, and energy-dispersive spectroscopy. The film is amorphous and exhibits a flat, bump- and crack-free surface over which platinum metal and loose porous-structured tungsten trioxide particles are evenly distributed. A transmission optical-fiber hydrogen sensor system is fabricated using the prepared film. When hydrogen molecules are present, the film chemically reacts through platinum catalysis, thereby changing the film refractive index. The hydrogen concentration is determined by measuring the transmitted light intensity. The hydrogen-sensitive film spin-coated for 60 s using a homogenizer rotating at 3100 r/min and subsequently annealed at 400 ℃ for 60 min exhibits a hydrogen-passing response time of approximately 62 s at a H2 concentration of 5%. The average change rate of the signal response amplitude is 91.54% before and after hydrogen sensing, and the film exhibits good repeatability and stability.

Multisource magnetron sputtering technology was used to prepare Ga and Al co-doped zinc oxide (GAZO)/Ag/GAZO transparent conductive thin films on a glass substrate. Comparative experiments showed that sputtering Ag with oxygen can increase the optical transmittance of the thin films in the 600-800 nm spectral region. After further optimization, at an oxygen flow of 1.0 sccm, Ag films with a thickness of 12 nm obtained continuous structure, which improved the photoelectric properties of the GAZO/Ag/GAZO thin films. Subsequent annealing at 150 ℃ for 1 h under ambient pressure further improved the photoelectric and structural properties of GAZO/Ag/GAZO thin films. After annealing, the sheet resistance of the thin films is 8.99 Ω/sq, the average transmittance in the 380-780 nm visible region is 98.17%, and the figure of merit is as high as 2260 Ω-1. The prepared GAZO/Ag/GAZO transparent conductive thin films show excellent photoelectric properties and are expected to replace indium tin oxide films in the field of optoelectronic devices.