This PDF file contains the front matter associated with SPIE Proceedings Volume 13248, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

With the advantages of safety, non-contact operation, high precision and real-time feedback, laser cleaning technology plays an important role in the field of intelligent manufacturing. In this study, a nanosecond pulsed laser with a wavelength of 1064 nm, a repetition frequency of 20 kHz, a pulse width of 70 ns, an average power of 3000 W, and a spot size of 40 mm*0.5 mm was used as the laser cleaning light source. Additionally, a laser cleaning prototype was constructed with a three-dimensional gantry displacement platform. With a scanning speed of 160 mm/s, a spot interval of 25 mm, and a laser energy density of 750 mJ/cm² , the oxide film on the surface of marine steel was completely removed, achieving a good cleaning effect and a cleaning efficiency of up to 20 m² /h. The entire cleaning process was achieved without dust emission. Our high-repetition-frequency, high-power nanosecond laser cleaning prototype is highly effective in removing rust from marine corrosion class B steel.

Semi-enclosed parts have a wide range of applications in precision manufacturing, aerospace, and reverse design. Understanding and characterizing the 3D topography and roughness of the internal surfaces of semi-enclosed parts is critical to ensure part performance, assembly quality, sealing effectiveness, friction characteristics, vibration behavior, and wear durability. However, some semi-enclosed parts are small and have complex internal structures, and conventional measurement methods are not effective in accurately measuring the 3D topography and roughness of the internal surfaces of semi-enclosed parts. Therefore, we propose a microdevice-based interferometry system, which adds micrometer-scale devices such as microsteering devices to the interferometric structure, for measuring 3D topography and roughness of the inner surface of semi-closed parts. Experiments have demonstrated that our proposed measurement system has excellent measurement accuracy down to the nanometer level. By providing accurate surface 3D topography and roughness data, this technique opens up new possibilities for future engineering design and manufacturing and is expected to advance the development of advanced manufacturing technologies.

The 1.5-μm waveband lasers have advantages such as good human eye safety, strong atmospheric penetration ability, high signal-to-noise ratio, and strong anti-interference ability, making them very suitable for long-distance LiDAR applications. In response to the application requirements of various coherent and incoherent LiDAR systems, high-power semiconductor lasers in the 1.5-μm waveband using AlGaInAs multiple quantum well (MQW) materials and ridge waveguide structures have been developed. Based on different epitaxial and resonant cavity structures, distributed feedback (DFB) and FabryPerot(F-P) types of lasers are designed for CW/QCW and pulsed operations, with the pulse width varying from 1 ns to hundreds of ns, and the peak power scaling from hundreds of mW to tens of watts for a single emitter. The output of the laser can be collimated in a TO package or coupled into a single-mode or multi-mode optical fiber. In this work, the laser chip design, device packaging, laser temperature control and current driver, temporal waveforms, and corresponding applications are discussed, and the current technological progress and bottleneck issues are analyzed.

Directly inscribing fiber Bragg gratings (FBGs) in ytterbium-doped fiber (YDF) using fs-laser can reduce the melting point in fiber lasers, which is significant for developing efficient fiber laser systems. In this paper, the photoluminescence at 1 µm band excited by the fs-laser in YDF was first reported to assist the FBG inscription, to the best of our knowledge. Moreover, we demonstrate that when the fs-laser scans across the fiber, the unique inner-cladding structure of YDF has a non-negligible effect on the focus position and intensity, thereby presenting a challenge to achieve high reproducibility when inscribing FBGs. The refractive index modulation characteristics of fs-laser incident from different angles are also analyzed.

Cellulose Nanocrystals (CNCs) are nanoscale, rigid rod-shaped cellulose fibers, measuring 100-500 nm in length, 2-20 nm in diameter, and with aspect ratios ranging from 5-100. At concentrations below a critical threshold (Critical Concentration I), CNC suspensions maintain isotropic characteristics. Upon surpassing another threshold (Critical Concentration II), the suspension transitions to an anisotropic phase, spontaneously forming chiral nematic structures. These chiral configurations are preserved even after drying the CNC suspensions. CNC photonic films exhibit the optical attributes of chiral nematic liquid crystals, including selective reflection and polarization, which manifest as pronounced structural colors and circular birefringence. This research demonstrates the structure color of CNCs through the conformal assembly with micro-nanostructures. By assembling CNCs at a 0.1 wt% concentration with triangular micro-nanostructures of varied sizes, the resulting structures displayed enhanced polarization characteristics. The conformal assembly technique introduced in this study is pivotal for advancing CNC-based photonic devices, opening new avenues in the realm of optoelectronic and environmentally friendly nanomaterials. These developments hold considerable potential for applications in optical filters, sensors, visual identifiers, and color display technologies.

The decay of surface plasmons in metal nanostructures followed by the generation of hot electrons has attracted widespread attention from researchers due to its potential for injecting into silicon to generate photocurrent and achieve infrared photodetection. However, the extremely low photoconversion efficiency of hot electrons limits their large-scale practical application. Despite extensive research on hot electron devices based on various gold/silicon nanoholes (Au/Si NHs), understanding of hot electron photoconversion in individual Au/Si NHs remains inadequate. In this study, we systematically investigated the hot electron response of individual Au/Si NHs. Many randomly distributed independent Au/Si NHs were fabricated using nanosphere lithography and metal-assisted chemical etching (MACE). By employing photocurrent mapping (PCM), the response of Au NHs to hot electrons was directly correlated. The results revealed that the photocurrent response at Au/Si NHs was significantly higher than that on planar Au films. The photocurrent increased continuously with the increasing depth of Au/Si NH embedding, and the circular spots corresponding to the positions of Au NHs in the PCM gradually enlarged, with the position of maximum photocurrent response shifting from the center to the edge of the holes. Additionally, we compared the photocurrent of multiple Au NHs on different samples and positions at different wavelengths, all showing good consistency and uniformity. Our study on the hot electron response of individual Au NH contributes to optimizing the structure of hot electron photodetectors and improving the photoconversion capability of metal/semiconductor devices.

When two two-dimensional semiconductors stack and form the type-II band alignment van der Waals heterojunction, sub-bandgap photoelectric detection can be realized, thus overcoming the intrinsic bandgap limit on the working wavelength of traditional semiconductor detectors. Therefore, photodetectors based on 2D heterostructures have great potentials and advantages in infrared photoelectric detection. High-performance infrared photodetectors based on two-dimensional transition metal chalcogenide heterojunction have been widely reported. However, the current design of two-dimensional heterojunction photodetectors primarily focused on the diode, which has low carrier utilization efficiency and with no extra gain, rendering poor photo responsivities. In addition, the acquisition of monolayer MoTe₂ is difficult, and there are few researches based on monolayer MoTe₂ heterojunction devices. This work aims at a comparative analysis of photoconductive and diode MoS₂/MoTe₂ heterojunction infrared photodetectors. By assessing the photo response of the photodetectors in both operational modes to the same infrared wavelength, our findings reveal that the photoresponsivity of the two-dimensional heterojunction detector in photoconductive mode reaches 10⁴ nA/W, which is 100 times higher than the diode under the identical conditions. In the photoconductive mode, the inherent photogating effect within the heterojunction engages electrons in the MoS₂ layer in multiple photoconductive processes before recombining with holes in the MoTe₂ layer, significantly enhancing optical gain and consequently improving responsiveness. The superior detection performance of the two-dimensional heterojunction photodetector in photoconductive mode presents a novel approach to addressing the performance limitations of infrared detectors.

Black phosphorus is a novel two-dimensional semiconductor with a special structure and excellent properties. It belongs to the natural P-type narrow bandgap semiconductor, which has a direct bandgap from bulk to monolayer, and can fill the gap between zero bandgap graphene and wide bandgap transition metal chalcogenides. This article mainly conducts a comparative study on the electrical properties of three-layer and thick layer black phosphorus field-effect transistors, exploring the advantages of their application in infrared photoelectric detection. The results show that the device made of three-layer black phosphorus has a smaller dark current and a faster response speed of 8 ms, making it more sensitive in detecting near-infrared light; The carrier mobility of multilayer black phosphorus devices is higher, reaching 68.4 cm² V^-1 s ^-1 when subjected to a bias voltage of 1 V. At the same time, the photoresponsivity is also higher, reaching up to 0.5 mA/W, and the photoelectric conversion ability is stronger.

Currently, widely used glucose sensors rely on enzyme catalysts, which suffer from issues such as enzyme inactivation, high production costs, and insufficient stability. To address these challenges, this study fabricated TiO₂ films on Ti sheets using radio frequency magnetron sputtering and subsequently modified Au nanoparticles (NPs) and CuO films via direct current magnetron sputtering. Then, Au and CuO co-modified TiO₂ (CuO-Au@TiO₂) photoelectrode with a Z-type band structure was prepared, enabling enzyme-free glucose detection via photoelectrochemical (PEC) sensing technology. The optimized photoelectrode exhibited high sensitivity for glucose detection, with values of 7300 μA μM^-1 cm-² (0–1 mM) and 500 μA μM^-1 cm^-2 (1–10 mM) under AM 1.5G illumination at a bias of 0.2 V (vs. Ag/AgCl). The detection limit was determined to be 58.14 μM (Signal/Noise = 3), with excellent stability, repeatability, and selectivity. Spectral and PEC performance analyses revealed that the outstanding sensing performance of the CuO-Au@TiO₂ photoelectrode can be attributed to: (1) unique Z-Type band structure promoting carrier separation; (2) the local surface plasmon resonance (LSPR) effect induced by Au NPs enhancing light absorption; (3) CuO can undergo a specific enzyme-like catalytic reaction with glucose molecules under alkaline conditions. This research offers a novel, convenient, and accurate monitoring approach for diabetes management and prevention.

To solve the quantitative measuring problem of shape and position changes in micronano-scale, a method based onspeckle correlation and polarization is proposed. This method divides 650nm laser into S and P plane polarized light beams, which are focused on micro targets, incident and reflect near the normal line of surfaces. After passingthrough a polarizer, the reflected beams is directly recorded by a digital imaging chip as a two-dimensional specklepattern with polarization characteristics. This speckle pattern is the convolution of the reflection lights caused by therandom fluctuation of the target object's surface, be knew as complex interference pattern. Therefore, it can beregarded as a stationary two-dimensional random signal, and the correlation is used to calculate parameters of spatial domain. According to the principle of superposition, when there are multiple micro targets, the total correlation peak can be regarded as the superposition of the sub cross-correlation factors from multiple microtargets. That is, when the shape and position changes from multiple micro targets are consistent, the total cross- correlation peak is high and steep. Otherwise, it will divide into multiple sub cross-correlation peaks. Todistinguish the shape and position changes of targets corresponding to the deviation of different sub cross- correlation peaks, two polarization beams S and P, are currently used to correspond to two detection channels. This experiment used Sony IMX179 CMOS to achieve 0.08~1.41μm/pixel in-plane displacement sensitivity. Thermal expansion of the metal wires are used to achieve the shape and position changes, and the results met expectations.

In this work, we introduce a novel microfluidic refractive index (RI) sensor based on concave reflection grating. COMSOL Multiphysics is employed to perform simulation calculations. We analyzed the reflection spectra withdifferent grating structural parameters and incidence angles, to evaluate its sensing performance. Additionally, sensitivity, full-width half maximum (FWHM) and figure of merit (FOM) were considered as performance parametersto evaluate the proposed optical sensor. The results demonstrate that the microfluidic channels increase the spatial overlap between the strong electric field and the analyte, ensuring the high sensitivity for refractive index sensing; thegroove structure of the periodic concave reflection gratings enhances the grating's ability to confine the optical field, improving the FOM of the sensing. With the optimum structural parameters, the sensor demonstrates a high sensitivityof 1015 nm/RIU and a high FOM of 780.88. The sensor shows the advantages of high FOM while maintaining a highsensitivity, promising excellent prospects for practical applications.

In this paper an Optical Time Domain Reflectometer (OTDR) sensing method based on Orthogonal Frequency Division Multiplexing (OFDM) technology is proposed. In this system, the probe signal consist of multiple Simplex coded sequences which modulated onto different orthogonal sub-carriers. The signal-to-noise ratio (SNR) of the system can be improved by the coding gain of the Simplex codes. Meanwhile, different pulsed sequences can be sent into the fiber simultaneously, which solves the time-consuming problem of the traditional coded OTDR. In the Simplex coding OTDR distributed sensing system based on OFDM technology built by this method, compared with a 50 ns single pulse, the SNR of the fiber end of the 31-bit coding curve is improved by 4.42 dB, and the measurement time is reduced by 96.77% compared to traditional Simplex coding OTDR system.

Van der Waals (vdW) heterostructures based on transition metal dichalcogenides (TMDs) generally possess a type-II band alignment that facilitates the formation of interlayer excitons (IEs) between constituent monolayers. Due to the spatially indirect property of interlayer excitons, the oscillator strength of it is of two orders of magnitude smaller than that of the intralayer excitons, resulting in a relatively low photoluminescence (PL) efficiency. Here, we achieve the PL enhancement of interlayer excitons across the entire heterostructure area at room temperature through introducing silicon nanodisk array. The significant enhancement mainly arises from the localized resonant electric field, which highly aligns with the out of plane (OP) interlayer excitons. Moreover, the silicon nanodisk array is demonstrated to greatly modify the far field emission properties of interlayer excitons to the surface normal direction, which further improves the PL intensity. The work contributes a novel method to control the emission of interlayer excitons in TMDs heterostructures to build efficient excitonic devices.

Wide-bandgap (WBG) perovskite solar cells (PSCs) hold significant promise for various applications. However, issues such as substantial open-circuit voltage (V_OC) deficit and halide phase separation have hindered their rapid development. Herein, additive engineering was utilized by introducing the multifunctional additive 2- (trifluoromethanesulfonyl)aminoethyl methacrylate (TFSMA) into the WBG perovskite absorber layer, leading to a significant enhanced V_OC and operational stability in corresponding PSCs. Sulfonic acid groups of TFSMA interact with the uncoordinated lead ions (Pb²⁺) and halide vacancies, thereby suppressing non-radiative recombination. Additionally, the highly electronegative fluorine ions (F^- ) effectively inhibit phase separation, enhancing film stability under rigorous conditions. Ultimately, the 1.77 eV WBG PSC achieved a conversion efficiency of 18.28% with V_OC of 1.304 V. Moreover, the encapsulated PSC maintained 93% of its initial efficiency after continuous operation for 200 hours under 1 sun illumination.

Semiconductor optical amplifiers (SOAs) offer advantages such as high-speed direct modulation, wide wavelength coverage, and high integration, making them suitable for high-speed optical communication networks to enhance transmission efficiency and capacity. In long-distance high-speed optical communication systems, the use of polarization-insensitive SOAs (PISOAs) can improve signal stability, enhance transmission quality, reduce system complexity, and lower maintenance costs associated with polarization. However, existing SOAs suffer from high polarization sensitivity. To mitigate this issue, this study designs, simulates, and develops a 1.5 μm band SOA. The active region is composed of quaternary compound AlGaInAs, creating a strained quantum well due to compositional differences in the barrier and well materials, enabling the realization of PISOA. At an input power of 0 dBm, the device achieves a gain of 32.89 dB. At an input power of 10 dBm, the saturated output power is 228.7 mW with a gain of 13.59 dB, and the 3 dB gain bandwidth reaches 125 nm. At an input power of -20 dBm, the polarization sensitivity is less than 1.82 dB.

In this work, we have designed a novel surface structure for enhancing the optical absorption of the two-dimensional indium arsenide (InAs) photodetectors, with a combination of local light-field enhancement and coupled back reflection effect to break through the performance bottleneck of thin-film photodetectors. Through a finite element-based coupled opto-electronic simulation, our-proposed device has elevated light absorption and marked light field localization within the visible to near-infrared spectrum. Notably, it achieves a maximum absorption of 70.8% at wavelength of 780nm, which is 5.53 times that of the comparison sample. Moreover, the introduction of the metal grating structure has endowed our design with excellent photoelectrical response performance, namely a responsivity of 177.65 A·W^-1 , a specific detectivity of 1.367×10¹⁰ Jones, and a response time of 1.5 ns under a bias voltage of 0.01V. This work provides an effective strategy for enhancing the performance of two-dimensional photoconductive detectors and offers beneficial guidance for designing high-performance optoelectronic devices

Silicon thin film solar cells have the advantages of simple preparation process, large area preparation and low cost, but its photoelectric conversion efficiency is low, with the decline of the preparation cost of crystalline silicon cells industry, silicon thin film solar cells have been weakened. Based on the unique physical and chemical properties of gold nanoscale double-cone particles and the excitation characteristics of plasmon, the reflectance spectra are simulated by finitedifference time-domain method. The results show that in the wavelength range of 300nm-900nm, the optical reflectance of the solar cell can be effectively reduced by 61.25% compared with the flat structure, and the absorption rate of the solar cell can be significantly improved. The effect of particle size on the electrical characteristics of the solar cell was studied. Under the optimal conditions, the short-circuit current density (J_sc) and maximum power (P_max) of the solar cell with the gold nano double-cone particles are 9.37mA/cm² and 8.65mW/cm² , respectively, which are 37.81% and 41.57% higher than that of the flat panel cell. The photoelectric conversion efficiency η of the battery was enhanced, which was 44.2% higher than that of the flat panel battery. Combined with electric field enhancement effect, the mechanism of the enhancement of light absorption of the solar cell was explored, and the effectiveness of the plasmon effect of the gold nanopyramid structure in improving the performance of the solar cell was verified.

Flexible photonic devices based on metasurfaces exhibit characteristics such as ultra-thinness and light weight, enabling versatile applications across various surfaces, particularly in smart wearable devices, visible light communication, and conformal optics, etc. Among existing methods, direct flip transfer and stamp-assisted transfer are the two most prevalent processes. However, metasurfaces produced by these methods are typically embedded within a flexible substrate, constraining the dielectric environment of the metasurface. Moreover, conventional approaches often utilize materials like metal or amorphous silicon for nanoantennas, leading to unnecessary optical losses. In contrast, monocrystalline silicon offers a larger scattering cross-section and lower absorption loss, promising superior performance for photonic devices. Herein, we propose a method for fabricating reconfigurable, flexible centimeter-scale monocrystalline silicon metasurfaces. The process involves a polymer membrane containing monocrystalline silicon metasurface, followed by transferring the polymer onto a stretchable substrate (PDMS) utilizing water tension. The monocrystalline silicon nanoparticle arrays are affixed to the PDMS substrate via van der Waals force, with the surrounding area directly exposed to air. Further, photonic devices with upper and lower refractive index matching can be achieved by pouring PDMS. By adjusting the mechanical stretching of the photonic device, dynamic control of the light field can be realized.

Driven by the continuous advancement in solid-state lighting, medical imaging, display anti-counterfeiting technologies, and wireless optical communication, there is a growing demand for efficient energy down-conversion devices. Limited by low light absorption and emission efficiency, existing energy down-conversion devices suffer from low effective input energy, resulting in low conversion efficiency. However, using metasurfaces enhances the interaction between light and matter, significantly improving the out-coupling efficiency of energy down-conversion devices. This report's experiments discovered a notable phenomenon of edge, significant photoluminescence enhancement (PLE) at the edges of crystal silicon (c-Si) nanoparticle array (NPA) coated with a 530 nm thick film of dye molecules when illuminated with ultraviolet (UV)-extended light. This phenomenon disappears when the thickness of the dye film is reduced to 100 nm. Analysis reveals that the effective refractive index of the polymer layer encapsulating the particle array is higher than that of the substrate and air, forming the waveguide layer due to refractive index matching. The dye molecules induce Mie multipole resonances in the particles upon spontaneous emission, coupling with the periodic array's waveguide modes to form quasi-guided modes, resulting in strong scattering into free space. Furthermore, when the sample is excited with a laser close to the particle array, significant scattering is observed at the edges, with the PL intensity of the edge linearly decreasing as the laser moves away, further confirming the source of PL intensity of the edge as originating from the planar waveguide modes.

In recent years, graphene/silicon heterojunction photodetectors have attracted wide attention in the world, and promoted the research and development of related devices. However, the ultra-low light absorption of graphene, coupled with the limitation of the silicon band gap, result in a constrained absorption capacity for infrared light within this category of photodetectors. Although the device performance can be improved by introducing some optical structures such as surface plasmons, optical waveguides, optical microcavities, quantum dots, the preparation process is complex, resulting in high cost and low yield. In this paper, we propose a novel infrared photodetector structure based on graphene/silicon ternary heterojunction modified with black phosphorus. Black phosphorus is used to absorb near-infrared light, generate photogenerated charge carriers, which then injected into graphene to change the Fermi level of graphene, thus changing the Schottky barrier between graphene and silicon, so that the carriers are easier to cross the Schottky barrier and be collected by silicon to generate photocurrent and realize near-infrared photoelectric detection. The experimental results show that compared with the graphene/silicon photodetectors without black phosphorus, in the wavelength range from 1500 nm to 1800 nm, the device responsiveness exceeds 0.1 mA/W, and reaches a maximum value of 0.18 mA/W at 1730 nm.

This study proposes a microwave photonics instantaneous frequency measurement (IFM) system assisted by machine learning , employing a Polarization-division multiplexing dual-parallel Mach-Zehnder modulator (PDM-DPMZM) as the primary modulation device. The system utilizes the periodic attenuation of dispersion-compensating fibers (DCF) to establish an intensity ratio function (ACF), enabling large-range and high-precision frequency measurement. Additionally, the Stacking ensemble learning method from machine learning is employed to train and test stimulation data obtained from the measurement system, further enhancing the accuracy of frequency measurement. The simulation results indicate that the proposed IFM system achieves an error within 20MHz, removing a small amount of abnormal data, within the frequency range of 4.5GHz to 20GHz. This study provides a novel approach and methodology for the design and optimization of microwave photonics IFM systems, offering practical application value.

A non-volatile 2×2 optical waveguide switch structure is proposed based on silica wafer integrated with chalcogenide Ge₂Sb₂Se₄Te₁ (GSST) quaternary phase change film and silicon strip waveguide. By applying external electrical pulses on indium tin oxide (ITO) electrodes which are deposited on GSST film, the phase change film can be heated and non-volatile switched back and forth between the two phase states for turning on or off the optical transmission paths. Such an electrically controlled waveguide switch structure is established and simulated by using COMSOL Multiphysics software. The response time of the optical switch is determined by the phase transition time of the amorphous and crystal states of GSST. The results show that it requires about 0.5μs from crystal state to amorphous state with a pulse voltage of 16V, and the energy consumption is 11.36nJ. The amorphous state will remain non-volatile until the next specific pulse arrives. The response time is about 1.3μs from amorphous state to crystal state with a pulse voltage of 5V, and the energy consumption is 2.41nJ. The heat dissipation times are both under 3.0μs. The working wavelength is set at C-band of optical communication with central wavelength of 1550 nm. This type of non-volatile optical waveguide switch presents fast responses, low energy consumption and smart characteristics, which provides an optional possible implementation approach for the construction of large-scale and high-capacity on-chip optical switching networks.

The mode field diameter (MFD) of the silicon-based III-V semiconductor lasers is around 3 μm, while the size of the silicon waveguide is less than 1 μm, and the difference in the size of the two leads to a large mode mismatch, which results in a large coupling loss between the two. In this paper, a novel SOI edge coupler based on cantilever structure is proposed for the coupling problem between silicon-based III-V hybrid integrated lasers and SOI silicon waveguides. The mode characteristics of the silicon-based hybrid integrated laser are investigated. The SOI edge coupler structure for siliconbased hybrid integrated lasers is designed, in which a cantilever-structured silicon waveguide is first fabricated on a SOI wafer, and then four silicon dioxide (SiO₂) layers and three silicon nitride (Si₃N₄) layers are alternately deposited on top of it, and the uppermost layer of Si₃N₄ is etched into the shape of a ridge waveguide. The dimensions of the silicon waveguide taper in the longitudinal direction (light transmission direction) to form a tapered waveguide, and the refractive index of the Si₃N₄ tapers in the longitudinal direction as the longitudinal length of the Si₃N₄ shortens layer by layer from bottom to top. The SOI coupler is simulated and designed by the finite-difference method in time domain (FDTD) and the eigenmode expansion (EME) method, and the mode field overlap between the 3 μm diameter silicon-based hybrid integrated laser and the SOI silicon waveguide is 88.2%, and the gap between the laser and the silicon waveguide can be eliminated from the reflection loss by the filler so that the gap between the two is 0 in the simulation process, to study the positional offset on the coupling efficiency. The simulation results show that the coupler has a 1 dB alignment tolerance of 1.4 μm in the horizontal direction and 0.8 μm in the vertical direction, which is a large alignment tolerance and requires less alignment accuracy in the actual fabrication.

The phase noise in phase-sensitive optical time domain reflectometer (φ-OTDR) system is primarily composed of laser frequency drift, beat frequency noise, electrical noise, and fading noise, which affect phase demodulation and vibration signal analysis. In order to enhance the signal-to-noise ratio (SNR), a phase noise suppression method based on Successive Variational Mode Decomposition (SVMD) and Pearson Correlation Coefficient (PCC) is studied and introduced. The SVMD-PCC method initially decomposes the phase signal adaptively into several intrinsic mode functions (IMFs) with different center frequencies using SVMD. Subsequently, the PCC between each IMF and the original phase signal is computed. IMFs with PCC values below a preset threshold are discarded. Finally, the remaining IMFs with PCC values exceeding the threshold are superimposed to achieve suppression of various phase noises. Compared to the VMD method, the proposed method does not require predefining the number of modes, K, thereby eliminating the need for additional optimization algorithms to determine K. This resolves the issue of performance degradation in VMD caused by inaccurate K. Furthermore, using a piezoelectric transducer (PZT) as the vibration source, experiments were designed for single-frequency vibrations at 10 Hz and 200 Hz, as well as multi-frequency vibrations at 100 Hz and 500 Hz. The results demonstrate that the SVMD-PCC method achieves a superior SNR improvement. Compared to methods such as VMD, EEMD, and EMD, the SNR improvements are 2.22 dB, 4.94 dB, and 5.00 dB, respectively, with a significantly reduced computational complexity. In summary, the SVMD-PCC method effectively suppresses various phase noises, enhances the φ-OTDR’s capability in detecting vibration events, and improves the recovery of vibration signals, thus facilitating precise distributed acoustic sensing applications with strong adaptability.

A Q-switched mode-locked (QML) laser at 2 μm waveband is demonstrated with with a maximum average power of watts. Graphene oxide are prepared by the vertical growth method and employed as a saturable absorber for passively QML operation. The stable QML pulses at 1897 nm are obtained with pulse width of 5.04 ns. The maximum output power of the laser is 1050 mW with a pump power of 20 W for an output coupler of 9%. The repetition frequency and width of QML pulses are 53.19 MHz and 5.04 ns, respectively. The modulation depth reach almost 100%. The Watt level QML all-solid-state Tm, Ho:LLF ceramic laser has broad application prospects in space target detection, environmental detection, and nonlinear optical research.

Contact-free manipulation technology represents a novel approach that offers a fresh possibility for human-machine interaction, aiming to meet the evolving demands of this interface. In this paper, we introduce a contact-free planar display control technique based on imaging. In our research, we employ cameras as sensors and integrate infrared lasers with image processing techniques to detect and localize input signals. By establishing a coordinate mapping relationship between the operational plane and the display plane, we achieved contact-free control over the planar display. Our paper introduces two methods for establishing this coordinate mapping. The first involves constructing mapping functions between the rectified and transformed camera imagery and the display plane, thereby creating a point-to-point correspondence. The second method entails dividing both the camera imagery and the display plane into segments, establishing a one-to-one relationship between regions. We analyze the strengths and limitations of these two approaches. While the former boasts higher theoretical precision, it is more susceptible to equipment factors and exhibits slower response speeds. Conversely, the latter, despite its lower theoretical precision, offers faster response times. Through the setup of an experimental platform, we demonstrate the feasibility of our proposed.

With the widespread application of Ethernet Passive Optical Network (EPON) technology, higher demands are placed on the output fiber power of devices. In the realm of semiconductor chips, increasing the power of semiconductor lasers stands as an effective approach. This paper proposes a Fabry-Perot (FP) semiconductor laser with lateral mode control based on step-index waveguide. This design aims to meet both power and divergence angle requirements. Through simulation and experimental verification, a series of chips have been successfully fabricated. Under a continuous current of 500 mA at room temperature, the output powers corresponding to ridge waveguide widths of 3 μm, 4 μm, and5μmare 182.06 mW, 198.23 mW, and 202.07 mW, respectively, with divergence angles of 15.31°, 17.00°, and 17.82°. In comparison, semiconductor lasers with ridge waveguide widths of 3 μm, 4 μm, and 5 μm from the same batch exhibit output powers of 136.26 mW, 224.72 mW, and 221.10 mW, respectively, with divergence angles of 40.22°, 43.01°, and42.56°. Although the power of the new laser slightly decreases, it demonstrates significant advantages in improving the divergence angle, which is acceptable. This innovation is poised to further enhance the output power of optical fibers, meeting the demands of practical optical communication networks. Additionally, it holds the potential for wide-ranging applications, characterized by its low cost and high yield rate.

In the scenario of measuring a signal under strong interference using distributed acoustic sensing (DAS) system based on phase-sensitive optical time domain reflectometry (φ-OTDR), the unwrapped DAS exhibits change point distortion due to noise interference. In order to improve the signal-to-noise ratio (SNR), a phase unwrapping noise suppression method based on Bayesian Estimator of Abrupt change, Seasonality, and Trend （BEAST） and Smoothness prior approach （SPA） is proposed and studied. The BEAST-SPA method begins by employing the BEAST algorithm to decompose the time series data into four components: abrupt changes, seasonal signals, trend signals and remainder signals. The points of abrupt changes correspond to the distortion points where change point distortion occurred in the unwrapped signal. Subsequently, the time series data is partitioned into several segments using distortion points. Finally, the SPA algorithm is applied to fit and remove the non-linear trend components in each segment of the time series data. The BEAST-SPA method not only excels in effectively removing non-linear trend components without the need to assume the type of trend, but it is also applicable for distortion recovery in long-term scale signals. In order to validate the feasibility of this method, we conducted multiple experiments using Piezoelectric Transducer (PZT) as active signal source and actions such as desk tapping and stamping as strong interference. Experiments were designed for single-frequency vibration at 300 Hz. The recovered signals closely matched the PZT reference signals, indicating the effectiveness of the BEAST-SPA method in eliminating change point distortions caused by strong interference. In conclusion, the BEAST-SPA method effectively suppresses phase noise, significantly enhances the SNR.

The utilization of generative artificial intelligence models, such as GAN and diffusion model, is increasingly pervasive in the field of image processing. Generative models effectively learn the distribution of photoacoustic data to optimize and enhance image quality, demonstrating superior performance in photoacoustic tomography (PAT). While most image optimization efforts in PAT occur within the image domain, improving the quality of image reconstruction could be better achieved through direct optimization in the data-domain. However, the majority of publicly available datasets are currently based on the image domain, and the high cost and complexity of PAT systems contribute to a shortage of publicly available datasets in the data-domain. To address this issue, this study has established a data-domain sharing database. The dataset consists of photoacoustic signals captured from various samples at different sparse views using a self-designed and constructed system. This work aims to mitigate the deficiencies in data-domain database for PAT, thereby fostering the development of generative artificial intelligence in data-domain of photoacoustic imaging.