Interface engineering stands out as an effective method for enhancing the performance of photodetectors. This study presents ultraviolet(UV) photodetectors featuring a Gr (2D) /GaN (3D) van der Waals heterojunction, skillfully regulated through interface engineering control. The GaN film efficiently absorbs photons, generating electron-hole pairs promptly separated by the built-in electric field. Photogenerated holes traverse to the Gr side through the tunneling effect, while photogenerated electrons move towards the GaN side. At elevated built-in field levels, high-speed photogenerated carriers undergo impact ionization, leading to a multiplication of the photocurrent. The outcomes highlight the significant influence of lead sulfide quantum dots (PbS QDs) on the light absorption efficiency and photoelectric conversion efficiency of the device. Consequently, the device achieves a remarkable responsivity value of 395.2 A/W and a substantial detectivity value of 4.425×1015 Jones under 5 μW/cm2 light at -2 V. This research contributes to the application of interface engineering technology in Gr-based UV photodetectors, opening possibilities for the preparation of high-performance UV detectors.

As the core communication technology in the 6G era, terahertz technology can effectively address the challenge of increasingly diminishing frequency band resources. It caters to the rapidly growing demand for traffic and connections while enabling large transmission bandwidth. Machine learning algorithms, such as deep neural networks, convolutional neural networks, and short-term memory networks, play a pivotal role in mitigating strong nonlinear effects within 6G transmission systems and are crucial tools for realizing 6G terahertz wireless communication. This review delves into diverse deep learning paradigms implemented in the photonic millimeter wave and terahertz wireless transmission systems. It highlights the notable strides made in leveraging photonic technology for generating ultra-high-speed terahertz wave wireless signals on domestic and international fronts. The paper provides a comparative analysis of different technical approaches. Additionally, the review offers a comprehensive view of traditional and emerging artificial intelligence technologies applied to terahertz communication systems. Finally, it outlines future development directions for terahertz communication technology, focusing on achieving high-speed and high-capacity performance.

Deep learning methods used in the field of gas detection mostly focus on learning a single task, such as the qualitative classification of gas or the quantitative regression of gas concentration. However, training a model in this way ignores the correlation of information between related tasks, reducing the accuracy and efficiency of training. This paper proposes a multi-task learning (MTL) model that combines a one-dimensional convolutional neural network (1DCNN) and a long short-term memory (LSTM) network to realize qualitative identification of mixed gas species in parallel with a quantitative regression prediction of gas concentrations. Using a thulium-doped fiber, a two-stage amplified thulium-doped ring-cavity fiber laser was constructed, and the absorption spectral data of mixed gases, comprising CO2 and NH3, were detected based on the active intracavity absorption spectroscopy method. The experimental data were put into the MTL model to train until the model performance was optimized. The trained model achieves a gas classification accuracy rate of 100%, while the coefficient of determination of NH3 and CO2 are 99.86% and 99.62%, respectively. These values are superior to the equivalent values obtained using conventional single-task models and gas inversion algorithms such as the backpropagation neural network and support vector machine. By combining the deep learning algorithm with the active intracavity spectroscopy method, a superior absorption spectroscopy-based gas inversion technology is developed.

In this study, we report the application of mid-infrared absorption spectroscopy for simultaneous gas sensing of NO and NO2 using a flexible hollow core fiber (HCF) and two quantum cascade lasers (QCLs). The utilization of QCLs with intermittent continuous wave (iCW) operations and a flexible hollow-core optical fiber can miniaturize sensor systems. The optimal absorption lines for NO and NO2 detection were selected at approximately 1929.03 cm-1 and 1599.91 cm-1, respectively. Both laser beams were simultaneously coupled into a 100 cm flexible HCF with an inner diameter of 530 μm. Initially, direct absorption spectroscopy was performed as an intuitive demonstration of the iCW operation of QCLs with a time-division multiplexing (TDM) strategy for dual-species detection. Following this, we applied wavelength modulation spectroscopy using the first harmonic normalized second harmonic (2f/1f) method to eliminate the influence of any nonabsorption intensity variation, thereby enabling us to thoroughly investigate the performance of the gas sensor. The precision of NO and NO2 detection was estimated by measuring the concentrations of 50×10-6 NO and 15×10-6 NO2. Results indicated a precision of 5.2% for NO and 4.1% for NO2. Furthermore, we achieved minimum detection limits of 39×10-9 NO with a 60 s integration time and 9.2×10-9 NO2 with a 50 s integration time.

Bending of flexible screens often leads to issues such as device damage and adhesive layer delamination. Therefore, it is essential to understand the strain distribution in the protective layer during the bending process. This study presents a method for measuring the strain in a flexible screen during bending, utilizing digital image correlation. The method enables synchronized full-field strain measurements in the protective layer while simultaneously capturing speckle pattern images applied to the screen surface. Subsequently, we calculate the bending plane equation based on matching point coordinates, revealing the relationship between bending angle and strain. Experimental results validate the effectiveness of this approach in providing comprehensive strain data for the protective layer at various bending angles. Consequently, this method quantifies the strain occurring on the screen and provides insights into stress distribution during the bending process.

On the composite thin-film composed of platinum metal and amorphous silicon, periodic structures with oxidation periodicity induced by s-polarized laser, far from the central axis, and tilted outer structures are observed under oblique incidence conditions. First, the generated stripe structures exhibit a leaf vein-like pattern, neither parallel nor perpendicular to the polarization direction of the laser. Second, the structural orientation generated during dynamic scanning is single and dependent on the scanning direction. Finally, the period of the structure decreases with increasing incident angle. These phenomena differ from typical laser ablation periodic structures. This discovery provides more possibilities for regulating laser-induced self-organization.

The increasing demand for advanced applications of ultrafast lasers creates an urgent need to develop techniques for the on-demand manipulation of ultrashort pulses. In dissipative systems, multi-pulse structures, which suffer from composite-balance problems involving the gain/loss and dispersion/nonlinearity, yield versatile ultrafast soliton dynamics. Recent research indicates that various pulse characteristics, including the number of pulses, temporal separation, and relative phase, can be artificially manipulated, which leads to the concept of upgrading the on-demand manipulation of multi-pulse structures. Here, we first introduce the multi-pulse soliton dynamics and real-time spectral monitoring methods. Then, we review the approaches for artificially manipulating multi-pulse structures based on gain control, polarization control, dispersion control, and optomechanical effect. We also discuss their performances and corresponding application perspectives.

Femtosecond laser direct-writing technology is being increasingly employed in the fabrication of integrated optoelectronic and optical sensor devices. This technology is popular due to its precision, efficiency, brief pulse duration, substantial peak power, and versatility in material processing. In recent years, the advancements in femtosecond laser direct writing, specifically in the context of optical waveguide amplifiers and lasers have garnered increasing research attention. This article mainly introduces the latest research progress of femtosecond laser direct writing optical waveguide amplifiers and lasers, including waveguide transmission and insertion losses, optical amplification gain characteristics, and waveguide laser output characteristics of Type-I, Type-II, ridge, and variable cross-section optical waveguide amplifiers and lasers. Finally, the paper concludes with a synthesis and analysis of the current technological progress, along with a prospective outlook on the future research, applications, and development trends within this domain.

Laser powder bed fusion (LPBF) is an ideal technique for the comprehensive fabrication of intricate components using cobalt-based superalloys. Despite the outstanding performance of ECY768, a novel cobalt-based superalloy, there exists a research gap concerning the LPBF processing of this alloy. This study delves into the metallurgical defects, microstructure, and fundamental mechanical properties of the ECY768 cobalt-based superalloy when subjected to LPBF. The findings reveal that the predominant metallurgical defects in ECY768 alloy processed by LPBF are gas pores, lack-of-fusion, and hot cracks. Adjusting processing parameters, such as laser energy density, facilitates the production of ECY768 specimens devoid of cracks and exhibiting high density (porosity <0.5%). The LPBF-processed ECY768 alloy exhibits a mixed grain structure comprising predominantly columnar grains with some equiaxed grains. A〈0 0 1〉preferred orientation, nearly parallel to the build direction, is evident. Within the solidification grains, a cellular dendritic microstructure is observable. Sub-grain boundaries concentrate both a dislocation network and two types of nano-scale carbides-ball-shaped MC-type carbides and band-shaped M23C6-type carbides. Under optimized processing parameters, the yield strength of ECY768 specimens reaches 1002 MPa (parallel to build direction) and 1268 MPa (perpendicular to build direction), surpassing that of other main cobalt-based superalloys formed by casting or LPBF. Simultaneously, the elongation of ECY768 specimens is 10.5% (parallel to build direction) and 13.3% (perpendicular to build direction), aligning closely with the performance of other main cobalt-based superalloys produced through casting or LPBF. The exceptional mechanical properties of LPBF-processed ECY768 alloy are attributed to satisfactory relative density, a refined cellular dendritic microstructure, substantial nanocarbide precipitation, and their interaction with the dislocation network.

Supercapacitors have advantages such as high power density, extended lifetime, and fast charging rate, which make them good energy-storage devices. Laser-induced graphene (LIG) is a widely used electrode material for double-layer electric capacitors; however, double-layer LIG electric capacitors typically exhibit low electrochemical performance, and the addition of active materials improves the supercapacitor performance. To control the incorporation of active substances, we propose a method for preparing LIG-Fe3O4 composite-based micro-supercapacitor by laser direct writing polyimide (PI) films coated with Fe(NO3)3. The laser treated area will simultaneously undergo PI film ablation and Fe (NO3)3 decomposition, resulting in LIG-Fe3O4 composite electrode composed of Fe3O4 and LIG.The performance of the prepared LIG-Fe3O4 composite-based micro-supercapacitor has been improved by 7.58 times compared to LIG-based micro-supercapacitor. The proposed method establishes a new route for preparing high-performance LIG-based micro-supercapacitor.

Photoluminescence of plasmon nanomaterials is now a fundamental property of plasmons. Over the past two decades, this phenomenon has been observed in various plasmon materials with diverse structures. This study briefly discusses experimental research progress in plasmon photoluminescence, focusing on the representative types of proposed plasmon photoluminescence and briefly analyzing their photophysical processes. Furthermore, this study explores the cutting-edge applications of photoluminescence using plasmon materials in recent years in sensing, biological imaging, and other fields. Finally, it summarizes the research progress and problems faced in the photoluminescence of plasmon materials, the prospects of this photophysical process, and future research directions.

Using nonlinear optical crystals for laser frequency conversion is a key method for extending laser wavelengths. These crystals, particularly borates, are crucial in all solid-state laser systems, especially for ultraviolet laser output, due to their diverse structures and superior optical properties. The K3B6O10Br crystal, notable for its short ultraviolet cutoff edge (182 nm), significant nonlinear optical coefficient (d22 of 0.83 pm/V), and moderate birefringence index (0.046@1064 nm), shows promise in second and third harmonic laser output. This article provides an overview of the growth and fundamental characteristics of the K3B6O10Br crystal. Recent advancements in visible/ultraviolet lasers and optical parametric chirped pulse amplification, achieved through crystal frequency doubling and sum frequency techniques, are summarized. Additionally, the potential future developments and applications of the K3B6O10Br crystal are explored in this study.

Exceptional points are singularities in non-Hermitian systems, generated when two or more eigenvalues and their corresponding eigenvectors merge simultaneously. Metasurfaces are two-dimensional artificial electromagnetic materials constructed at subwavelength scales, which provide a versatile platform for studying this non-Hermitian phenomenon by introducing dissipation and amplification within their unit cells. This paper provides an overview of the latest research progress in exceptional points sensing. It begins by introducing the basic theory of non-Hermitian systems and exceptional points, then focuses on the research achievements in exceptional points sensing on metasurfaces in terahertz band. Lastest, we summarize the disadvantages of exceptional points sensing, and its future development trends are also discussed.

The near-infrared light source possesses strong penetration, non-destructive testing capabilities, and a high signal-to-noise ratio for biological tissues. It finds extensive applications in component detection, security monitoring, biomedicine, national defense, and the military industry. However, the lack of highly efficient and portable near-infrared light sources has become a key obstacle to the development of intelligent detection technology. In comparison with traditional near-infrared light sources, phosphor-converted near-infrared LED light sources (NIR pc-LEDs) offer advantages such as portability and high efficiency. This study focuses on synthesizing Li3Na3Ga2F12∶Cr3+ broadband phosphors through a simple and environmentally friendly hydrothermal synthesis method. By controlling factors like holding temperature and holding time, an optimal synthesis scheme for fluorescent materials is determined. The influence of fluoride particle size, morphology evolution, and Cr3+ doping concentration on the luminescence properties of Li3Na3Ga2F12∶Cr3+ is also investigated. The synthesized Li3Na3Ga2F12∶Cr3+ material exhibits broadband emission ranging from 630 nm to 980 nm with a full width at half maximum (FWHM) of 110 nm and a peak value at 766 nm. Its internal quantum efficiency reaches an impressive 74%. Through successful packaging with commercial blue LED, a NIR wideband LED source is achieved. The output power of NIR light at 50 mA driving current is 10.32 mW, and the photoelectric conversion efficiency reaches 5.1%. Finally, the feasibility of using the NIR broadband LED light source in imaging fields such as medical and food detection is verified by NIR imaging of veins under chicken breast and night vision imaging demonstrations.

High-energy radiation detection and imaging technology has important applications in high-energy physics research, medical imaging, industrial detection, and other fields. Lead-free metal halides have many advantages, such as low toxicity, good stability, high light yield, and large stokes shift; they exhibit excellent potential in indirect X-ray detection. The latest research progress of lead-free metal halide scintillators and imaging devices is reviewed herein. First, the material composition and luminescence mechanism are introduced. The key parameters of scintillator performance are listed. The synthesis methods of single crystal, powder, and nanocrystal are summarized. Some recent novel ideas about improving the resolution of imaging devices are also described. We focus on the new-type scintillator imaging devices, including composite film, ceramic, glass, and structured scintillators. Finally, we have summarized the challenges and potential problems of scintillator imaging detectors and provided some suggestions.

Glass with heavy doping of noble metal nanoparticles is expected to exhibit high optical nonlinearity. In this study, the effects of glass composition, structure, and heat treatment on the formation of silver nanoparticles (Ag NPs) in phosphate-bismuthate (PB) glass are investigated. By optimizing the chemical composition and preparation parameters, strong localized surface plasmon resonance is achieved in the PB glass with a silver mass fraction of more than 13%, which is 20 and 6 times higher than that in bismuthate and phosphate glasses reported previously, respectively. The high solubility of the phosphate component and the self-reduction effect of the bismuthate component jointly contributed to the stability and high content of Ag NPs in the PB glass. Z-scan measurements show that such heavy doping PB glass has a reverse saturable absorption coefficient of -14×10-12 m·W-1 and a saturable absorption coefficient of 4.94×10-12 m·W-1 at 800 nm. Furthermore, the heavy doping PB glass exhibits excellent thermal stability, making it promising for the fabrication of nonlinear optical fibers. In addition, with a heavily silver-doped PB glass rod as the core and a commercial silicate glass tube as the cladding, a composite glass fiber with high Ag-NP doping is successfully fabricated using a "molten-core" fiber drawing method.

Upconversion photoluminescence, an anti-Stokes process in which the emitted photon energy exceeds the excitation photon energy, can effectively achieve energy renormalization and conversion, with great application prospects in fields such as biological imaging, solar cells, photocatalysis, and optical refrigeration. As a strategically important new material in the post-Moore era, two-dimensional materials are crucial in realizing efficient room-temperature excitonic upconversion because of their large dipole moments, narrow linewidths, low disorder, and high exciton binding energies, which have recently attracted extensive research interest. This study first introduces the luminescence mechanisms used to achieve photon upconversion, including phonon-assisted upconversion, two-photon absorption, and Auger recombination. Then, research on upconversion based on two-dimensional material systems, such as hexagonal boron nitride, monolayer transition metal dichalcogenides, and two-dimensional perovskites, is summarized. Modulation and enhancement approaches for upconversion in two-dimensional materials that target low upconversion efficiency are also discussed. Finally, application prospects of excitonic upconversion effects in two-dimensional material systems are envisioned.

The oscillating tailing shape and spectrum of the decelerated finite-energy Airy pulse are influenced by various parameters. This study examined the impacts of peak power, width, initial chirp, truncation coefficient, and distribution factor of the Airy pulse on the generation of rogue waves in a supercontinuum (SC) as well as the SC coherence and stability. The findings reveal that altering these parameters can regulate the rogue waves and affect the SC coherence and stability. Moreover, a multiobjective particle-swarm optimization algorithm is used to simultaneously optimize the five pulse parameters. By using the average peak power of 500 analog output solitons (i.e., twice of that required for generating the rogue waves) and considering the number and distribution of rogue waves among the solitons as optimization objectives, this study identifies optimal parameters for the Airy pulse. These parameters either promote or suppress the generation of rogue waves, enabling controlled manipulation of rogue wave generation within the SC.

Artificially constructed planar metasurfaces play a crucial role in photonics and emerging optoelectronic technologies due to their unique electromagnetic characteristics, ultrathin profiles, and seamless integration capabilities. Light-emitting metasurfaces based on near-field resonance modes exhibit unique advantages in scattering radiative photons, directing and enhancing light emission, expanding their applications in advanced photonics. This review provides an insightful overview of the basic principles of manipulating and controlling the emission behavior of ensembled quantum emitters, and provides a detailed introduction to the latest research and application progress of light-emitting metasurfaces within the visible light spectrum, including applications in fields such as miniature solid-state lighting devices, virtual reality and augmented reality high-definition displays, visible light communication, high-energy X-ray detection, chiral light-sources, and low threshold micro/nano lasers, etc. Finally, future development directions of light-emitting metasurfaces are prospected.

In recent years, neuromorphic computing, inspired by the structure and function of biological nervous systems, has gained substantial attention. Memristors, which are capable of modulating conductivity via electric charge or magnetic flux, mimic synaptic interactions in the human brain, making them promising candidates for neuromorphic computing. This study proposes a method using femtosecond laser-processed graphene oxide memristors. Adjusting the scanning voltage at both device ends achieves polarity-controlled resistance switching. The device exhibits unipolar resistance switching at low voltages and stability over 150 cycles with a power consumption of only 0.75 nW. At higher voltages, bipolar switching occurs with increased conductivity over the test cycles. This study explores switching mechanisms under two voltage conditions, thus providing a comprehensive understanding of these mechanisms. This innovative approach using femtosecond laser-processed graphene oxide memristors shows promise for neuromorphic computing, offering efficient performance, stability, and adaptability across voltage scenarios.

Plasmonic tunnel junctions are metal-insulator-metal structures with a nanoscale dielectric gap that can simultaneously support surface plasmons and electron tunneling. The extremely strong confinements and interactions of electrons, plasmons, and photons in the junctions provide a novel platform, merging electronics and photonics for studying and manipulating electrons and photons at the nanoscale. In this review, the recent progress in the field of plasmonic tunnel junctions is overviewed as concerns their applications in plasmon/light generation and plasmon/light-electron conversion.

Spintronic terahertz (THz) emitters offer distinct advantages such as high efficiency, ultrabroadband capability, low cost, and easy integration. These emitters find applications not only in THz time-domain spectrometers driven by high-repetition-rate laser oscillators but also in the generation of intense THz electromagnetic pulses powered by high-energy femtosecond laser amplifiers. They have proven valuable in THz spectroscopy imaging and the exploration of strong-field THz physics. However, previous research on spintronic THz radiation mechanisms and device development relies primarily on far-field THz time-domain spectroscopy. The results of this approach present average THz emission information for the laser-pumped spot areas, which does not provide any insights into ultrafast spin currents and THz emission properties for the materials at micro- and nano-scales. In this study, we employ ultrafast THz scattering scanning near-field optical microscopy, driven by a femtosecond fiber laser oscillator, to investigate the spintronic terahertz emission properties of the ferromagnetic heterojunction material W/CoFeB/Pt at nanoscale. The utilization of this technology enables the detection of high signal-to-noise ratio spintronic THz emission at transverse scales as small as hundreds nanometers. This novel approach explores the generation, detection, and manipulation of ultrafast spin currents at THz frequencies with nano-spatial resolution. This study may inspire innovative ideas for the advancement of ultrafast THz spin optoelectronics.

The use of liquids as terahertz (THz) wave emitters and detectors has been historically avoided due to the high absorption of polar liquids in the THz range, especially liquid water. This hinders the development of THz liquid photonics. Compared with other matter states, liquids exhibit numerous unique properties. In particular, liquids have a material density comparable to that of solids, meaning that the number of molecules interacting with laser pulses is three times higher than that of gas. In contrast to solids, liquid fluidity allows each laser pulse to interact with a fresh target area. Therefore, the material damage threshold is not an issue even with high repetition rate laser pulses. This makes liquids very promising candidates for studying high-energy-density plasma and ultrafast dynamics of ionized particles in laser-matter interaction. THz liquid photonics is an emerging topic, offering an alternative for researchers to obtain THz emission from liquid material. This interdisciplinary and transformative topic will enable new science and advance numerous THz wave sensing and spectroscopy technologies that significantly impact THz technology, including next-generation liquid source, device, and system development.

We construct a propagation model of Gaussian beam in non-Hermitian system and explore the cross-polarization effects near the exceptional points in parity-time symmetric (PT-symmetric) structure. The results show that when the light beam is incident near the exceptional points, the cross-polarization component shows a double-peak intensity distribution similar to the first-order Hermite-Gaussian model. Conversely, the original polarization component shows a double-peak intensity distribution similar to the single circularly polarized components, which are perpendicular to the cross-polarization component. By adjusting the incident polarization angle, a significant rotation of the cross-polarization component near the exceptional point is revealed. Moreover, the direction of rotation of the cross-polarization component is reversed when the system crosses the exceptional points, providing a novel idea to precisely explore the position of the exceptional points. Finally, the strong cross-polarization effects near the exceptional points provide a theoretical guide for enhancing the photonic spin Hall effect.

Reducing the average number of copies consumed in quantum state discrimination under a given error rate is referred to as minimum-consumption quantum state discrimination. Minimum-consumption quantum state discrimination allows the saved resources to be utilized for subsequent quantum tasks, and it holds significant practical value in tasks such as quantum cryptography. In this paper, we investigate minimum-consumption quantum state discrimination of two-qubit quantum states. The theoretical results indicate that even when two-qubit quantum states only possess classical correlations and no quantum entanglement, entangled measurements still far outperform the effects of performing local measurements on the two qubits individually. Experimental results confirm that when the error rate requirement is low enough, the average number of copies consumed by entangled measurement device is only one-twelfth of that consumed by local measurements, while still meeting the error rate requirement. Our research results highlight the role of entangled measurements in minimum-consuption quantum state discrimination, demonstrating the importance of entanglement in quantum measurements.

Frequency-modulated continuous-wave (FMCW) light detection and ranging (LiDAR) has the advantages of noncontact measurements, resistance to ambient light interference, high resolution, and the ability to simultaneously determine speed and distance information. In recent years, it has been widely used in various fields, including aerospace, precision manufacturing, and autonomous driving. The ranging performance of FMCW LiDAR significantly depends on the sweep linearity of its light source, which is typically influenced by several factors, such as uneven stress stretching, temperature variations, and circuit noise. These factors decrease the ranging resolution and accuracy. The influence of light source nonlinearity in FMCW LiDAR is analyzed theoretically, and research progress in different types of nonlinearity correction techniques is presented. The characteristics, advantages, and disadvantages of each method are summarized to provide a reference for future research.

Surface-enhanced infrared absorption spectroscopy technology substantially boosts the interaction between light and molecules by confining the infrared light around the detection molecules, enabling susceptible detection of weak molecular vibration signals. Recent advancements in polariton in two-dimensional materials offer an effective strategy for enhancing surface-enhanced infrared spectroscopy because of their unique properties, such as highly confined electric field and low intrinsic loss. This study reviews the ongoing research progress of infrared spectroscopy technology enhanced by polaritons in two-dimensional materials. We begin by outlining the fundamental characteristics of polaritons in various materials and discussing the coupling mechanisms between polaritons and molecular modes. Building on this, we summarize the key research interests in polariton-enhanced infrared spectroscopy technology, including plasmon-enhanced, phonon polariton-enhanced, and near-field enhancement infrared spectroscopy technology. In conclusion, we provide a prospective outlook on the future development directions of polariton-enhanced infrared spectroscopy technology.

Light-induced thermoelastic spectroscopy (LITES) technology is a novel trace gas detection technology that has developed rapidly in recent years. The technology employs miniature, cost-effective, and wavelength-insensitive quartz tuning fork as substitutes for high-cost, narrow-bandwidth photodetectors in the field of optoelectronic transduction. The target gas concentration is achieved by detecting the variation in optical intensity resulting from the interaction between laser radiation and the target gas. LITES technology has the advantages of high detection sensitivity, short response time, and independence of excitation wavelength. In this paper, the research of trace gas detection system based on LITES technology is carried out with hydrogen sulfide (H2S) gas in sewers as the measurement target. A near-infrared distributed feedback laser with an output wavelength of 1.582 μm is employed as the excitation light source. The wavelength modulation spectroscopy and second harmonic detection techniques are utilized for trace gas concentration measurements. The impact of laser wavelength modulation depth on the signal amplitude generated by the LITES system is analyzed, and then the effect of operating pressure on the performance of the LITES system is also studied in detail. In addition, to further improve the detection sensitivity of the device, a Herriott multipass cell with an effective optical path length of 14.5 m is assembled between the laser and the quartz tuning fork. The sensor reached a minimum detection limit of ~4.87×10-7 of H2S with an integration time of 300 ms. By extending the integration time to 52 s, the minimum limit can be reduced to ~7.78×10-8. Using optimized parameters, on-site measurements of H2S in the sewer are conducted. The results indicate that the system is fully capable of meeting the application requirements in the fields of sewer odor monitoring and analysis.

The echelle spectrometer is a major spectroscopic instrument with its high spectral resolution in a wide range of applications. The spectral reduction technique is the core of the data processing of the echelle spectrometer, which realizes the rapid reduction of two-dimensional images to one-dimensional spectra by establishing the correspondence between wavelength and imaging position. The performance of the echelle spectrometer is directly determined by the accuracy of spectral reduction, which is the most important point and greatest difficulty in instrument development. In view of this, the development of the spectral reduction technique is reviewed, and its evolution is classified into three stages: ray tracing, modeling, and calibration methods. The core ideas and principles of spectral reduction algorithms in each stage are discussed in detail. Finally, the development history is summarized, the development trend is predicted, and the outlook of the development direction for the echelle spectrometer spectral reduction technology is discussed.

X-ray scintillators are widely used in medical diagnosis, safety inspection, industrial non-destructive detection, and other fields. In the past decade, zero-dimensional (0D) organic-inorganic hybrid metal halides have gradually attracted attention and shown great potential in X-ray imaging due to their excellent physical properties and luminescent properties such as non-deliquescence, high stability, no self-absorption, and high luminescent quantum efficiency. This article will overview the basic detection principles and key detection performance parameters of X-ray scintillators, introduce the research progresses of the most representative 0D manganese-based, tin-based, antimony-based, and copper-based halide scintillators in the field of X-ray imaging, and look forward to the future development direction of these 0D hybrid materials.