A new tapered semiconductor laser with an integrated multimode interference coupler is presented in this paper. The seed source of the new laser is a multimode interference coupler semiconductor laser, which overcomes the limitations imposed by the relationship between single mode output and gain medium volume in the ridged waveguide region. The simulation results show that the multi-mode interference coupler can effectively provide a spatial single-mode seed light source for the tapered output waveguide, and the tapered output waveguide of the tapered semiconductor laser can also effectively reduce the optical power density of the output laser, which verifies the feasibility of the design scheme and provides a new idea for the design of high beam quality and high power tapered semiconductor laser.

Nano-light-emitting diodes (LEDs) are ideal for ultra-high resolution displays due to their small size and high pixel density. However, traditional photolithography techniques fall short in meeting the requirements for nanoscale LED fabrication. Besides, as the size decreases and the specific surface area increases, non-radiative recombination generated by sidewalls defects becomes a significant issue, affecting the efficiency of nano-LEDs. To address this challenge, a nano-LED array with a single nanorod size of 800 nm was fabricated in this work by using nanosphere lithography and etching technology. Meanwhile, localized surface plasmons (LSPs) coupling technology was employed to enhance the PL efficiency of these nano-LEDs. By comparing with bare nano-LEDs, the PL intensity was boosted by about 43% and 129% when Ag and Ag@SiO2 nanoparticles were added separately. The existence of LSPs coupling process has been further confirmed through time-resolved photoluminescence measurement and finite element simulation analysis of different samples. The results provide compelling evidence for the LSPs coupling technology in enhancing the efficiency of nanoscale LEDs.

Quantum cascade lasers (QCLs) in the mid-infrared (MIR) hold significant potential for widespread applications in both military and civilian contexts. However, the utility of present single-chip QCLs is hampered by issues such as low output power and subpar beam quality. This study addresses these limitations by employing spectral beam combining (SBC) based on a diffraction grating, with an aim to enhance both power and beam quality of MIR QCLs. Coaxial power synthesis of three single-chip QCLs (around 4.75 μm) is achieved experimentally, importantly, the beam quality did not decrease after combining, essentially maintaining the same quality as before combining. It is proposed that there are four main factors affecting the combining efficiency, namely operating optical power (or driving current) of the chips, individual differences in QCL chips, diffraction grating, and reflectivity of feedback mirror, and their effects on the combining efficiency are discussed separately. This study confirms that SBC is an effective way to obtain high-power and high-beam quality MIR QCL sources, and lays a research foundation for more beam spectral combining.

This research investigates the use of excitation-emission matrix fluorescence (EEMF) in conjunction with chemometric models to rapidly identify and quantify adulteration in olive oil, a critical concern where sample availability is limited. Adulteration is simulated by blending soybean, peanut, and linseed oils into olive oil, creating diverse adulterated samples. Principal component analysis (PCA) was applied to the EEMF spectral data as an initial exploratory measure to cluster and differentiate adulterated samples. Spatial clustering enabled vivid visualization of the variations and trends in the spectra. The novel application of parallel factor analysis (PARAFAC) for data decomposition in this paper focuses on unraveling correlations between the decomposed components and the actual adulterated components, which offers a novel perspective for accurately quantifying adulteration levels. Additionally, a comparative analysis was conducted between the PCA and PARAFAC methodologies. Our study not only unveils a new avenue for the quantitative analysis of adulterants in olive oil through spectral detection but also highlights the potential for applying these insights in practical, real-world scenarios, thereby enhancing detection capabilities for various edible oil samples. This promises to improve the detection of adulteration across a range of edible oil samples, offering significant contributions to food safety and quality assurance.

This study delves into the feasibility of using amorphous silicon photocells as photosensitive units for retinal prostheses. Firstly, theoretical simulations coupled with experimental results demonstrated its strong light absorption and quantum efficiency within the 300–800 nm range. Subsequently, measurements on its visual sensitivity properties were conducted. The findings revealed that under photopic vision conditions, the photocells could provide the stimulating current required for the human retinal nerve cells. Finally, the visual spectral sensitivity curve of the amorphous silicon photocells was assessed, and the results indicated that the spectral sensitivity curve of the amorphous silicon photocells closely mirrors the visual function curve of the human eye under photopic conditions, demonstrating a response to light across various wavelengths.

Thermal action is a crucial process in laser processing. The classical Fourier heat conduction theory, which assumes an infinite speed of heat propagation, is commonly applied to describe steady-state and mild transient thermal processes. However, under the influence of ultra-short pulse lasers, such as those with picosecond and femtosecond durations, the heat propagation speed within the material is finite and deviates from Fourier’s law. This article addresses the unique characteristics of heat conduction in materials subjected to ultra-short pulse laser exposure by integrating Fourier’s law with the Gaussian distribution of the actual pulse laser output power density and the material’s optical absorption properties. It introduces a time variable to establish a time-dependent heat conduction equation. This equation is numerically analyzed using a difference algorithm. Based on this, simulation and experimental studies on the processing of dental hard tissues with a 1064 nm ps laser were conducted. The results show that the experimental processing depths were slightly larger than the simulation results, which may be due to damage to the dental hard tissues and the thermomechanical effects during processing. The results offer a technical reference for adjusting laser parameters in the ultra-short pulse laser processing technique.

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Surface enhanced fluorescence (SEF) based on noble metal nanoparticles is an effective means to achieve high sensitivity in fluorescence detection. Currently, the physical mechanism behind enhanced fluorescence is not fully understood. This paper measures the fluorescence signals of Dihydroporphyrin f methyl ether (CPD4) under both single-photon and two-photon excitation based on submicrometer silver particles with rough morphologies, achieving enhancement factors of 34 and 45 times, respectively. On this basis, by combining the radiative field characteristics produced by the silver particles, a stimulated radiation model of molecules is established to elucidate the changes in the molecular photophysical process when influenced by silver particles. Moreover, the fluorescence lifetime of the molecules was measured, showing that the presence of silver particles induces an increase in the molecular radiative decay rate, causing the fluorescence lifetime to decay from 3.8 ns to 3 ns. The results indicate that the fluorescence enhancement primarily originates from the submicrometer silver particles’ enhancement effect on the excitation light. Additionally, the fluorescence signal emitted by the molecules couples with the silver particles, causing the local surface plasmon resonances generated by the silver particles to also emit light signals of the same frequency. Under the combined effect, the fluorescence of the molecules is significantly enhanced. The findings provide a theoretical foundation for understanding the fluorescence enhancement mechanism of silver particles, adjusting the enhancement effect, and developing enhanced fluorescence detection devices based on submicrometer silver particles, holding significant practical importance.

Recent research has indicated that metal nanoparticles, known for their unique optical properties, can enhance the spectral response of photovoltaic modules. Since most nanoparticles demonstrate enhancement effects within a specific wavelength range, broadening the spectral response of photoelectric devices is critical for their application in imaging, energy harvesting, and optical communication. In this study, we applied flower-like silver particles to achieve this broadband enhancement. The optical absorption of photovoltaic modules, featuring an amorphous Si p-i-n structure, was improved across a broad wavelength range of 400~2000 nm by integrating these flower-like silver particles, resulting in an approximately tenfold increase in peak spectral responsivity. The theoretical investigation further elaborates that the enhancement originates from the near-field effects of silver particles due to the interaction of different parts of the flower-like silver particles. Through these studies, we demonstrate that utilizing the flower-like silver particles with roughness surface can achieve the spectral response of the photoelectric device enhanced in broadband range, which can improve the utilization efficiency of optical energy for the applications of sensing, imaging, optical communication, and energy harvesting.

Amidst the escalating issue of drug abuse, an urgent need for effective illicit drug detection methods has arisen. This paper introduces a novel optical approach utilizing the Goos–Hänchen Shift (GHS) to explore the possibility of on-site rapid detection of illicit drugs. Delving into the mechanisms, light absorption and attenuation in biological samples are considered through absorption and attenuation coefficients, establishing connections between complex refractive indices, complex dielectric constants, and GHS. A self-assembled GHS detection system measured GHS values across various samples: ultrapure water, serum, methamphetamine, serum–methamphetamine, heroin, and serum–heroin. These experiments unveiled substantial GHS variations among the samples. Refractive indices for serum, serum–methamphetamine, and serum–heroin samples were computed using GHS values and sample extinction coefficients, highlighting GHS’s remarkable sensitivity to refractive index variations as a high-sensitivity refractive index sensing technology. The correlation between the dielectric constant and GHS was explored, yielding refractive indices for pure solutes—serum, methamphetamine, and heroin—of 1.66300, 1.51300, and 1.62300, respectively. Notably, the dielectric constants for these solutes were 2.76557, 2.28917, and 2.63413, emphasizing the dielectric constant’s discriminative potential in identifying illicit drugs. In conclusion, these findings suggest that GHS holds promise for distinguishing various illicit drug types, charting an innovative path for illicit drug detection.

介绍了受激拉曼散射(SRS)对强激光系统的危害,主要包括强激光在空气中长距离传输时产生的受激转动拉曼散射(SRRS)与大口径KDP(磷酸二氢钾,KH2P04)晶体中的横向受激拉曼散射(TSRS).研究表明,SRS不仅会损耗激光能量降低光束质量,TSRS还可能会损坏KDP晶体.针对SRS对强激光系统的危害,文章介绍了国内外关于SRS的主要抑制方案,而且重点介绍了通过控制偏振方向降低SRS增益的新思想.

Antimonide semiconductor laser is a new type of laser with unique advantages in the 2 μm band. However, employing FP cavities causes multiple transverse modes to degrade beam quality despite achieving higher power output. In this paper, an antimonide semiconductor laser operating in 2 μm band is realized by utilizing fiber coupling and combining. Fiber combining results in higher output power, while the uniform patterns in both near-field and far-field are obtained, and the beam quality is improved. The experimental results illustrate that the output power reaches 1.2 W after 7-channel beam combination, and the near-field distribution is approximately Gaussian, while the far-field distribution is a flat-top.

首先综述了气体波导激光器、空芯光纤气体激光器和固态波导激光器的发展史,然后分别介绍两类激光器的工作原理,最后根据两类激光器的发展现状对未来的研究进行了展望和分析.

A symmetric grating is proposed to obtain higher output power in spectral beam combination by increasing the number of lasers and spectral utilization. The grating allows laser beams to be incident from both sides of the grating normal to achieve coaxial beam combining, so the number of beams and the combined output power are doubled compared with the traditional grating under the same spectral line-width. The grating is designed with the central wavelength of 4.65 μm, and the calculation results show that this grating is very advantageous for spectral beam combining, especially for the light waves in the range 4.55–4.71 μm, where their diffraction efficiencies are high (over 80%) and correspond to a wide and linear range of incidence angles. Meanwhile, based on the symmetric gratings we further propose a circular grating to achieve the same frequency spectral beam combining. This beam combining design will not increase the laser spectral line width while enhancing the laser power, reducing the requirements for the unit laser spectral line width, which is very meaningful in some application fields and will further enrich the research of spectral beam combining.

提出了一种在光学参量振荡器中基于级联光学差频在周期极化铌酸锂晶体中产生高效太赫兹(THz)波的方法.通过优化谐振腔参数,各阶级联Stokes光子在谐振腔内往返振荡,而各阶anti-Stokes光子只能在谐振腔内穿过一次.结合优化差频技术,各阶Stokes光子在谐振腔内每循环一次,级联光的能量向高阶Stokes光子转移一次,经多次重复转移,绝大部分泵浦光子被转移到高阶Stokes光,达到在增强级联Stokes过程的同时抑制级联anti-Stokes过程的效果.在工作温度为100 K,泵浦光强度为10 MW/cm2、信号光强度为0.01 MW/cm2时,THz波的能量转换效率达到21.2％.该转换效率超过了 Manley-Rowe关系限制,为产生高效率的脉冲、准连续、连续THz波提供了优化方案.

随着固体激光技术发展以及啁啾脉冲放大技术加持,激光峰值功率得到极大的提高,促进了激光物质相互作用领域的研究并衍生出若干具有很好前景的应用.激光驱动的台面级离子加速器便是其中重要的应用领域之一.激光加速的质子具有源体积小、脉冲时间短和时间分辨高等特点,可以广泛应用于成像、医疗及科研领域,并能有效降低这些领域的相关成本,促进其高效发展.影响获得优质离子束的条件很多,文中从靶形状及与激光作用后形成的等离子体性质角度对近期该研究方向的一些进展进行了总结及展望.

In order to obtain new resonance modes for frequency selection of the metasurface, one or two slits were introduced into the all-dielectric resonance unit, all-dielectric frequency selective metasurface based on this type resonance unit was designed by using the local characteristics of electromagnetic field by slit. After simulating its transmission characteristics, it was found that when the long side of the slit and the direction of the incident electric field were the same, a stop band could appear at the low frequency, and the electromagnetic field was mainly distributed between the resonance units. When the long side of the slit was perpendicular to the direction of the incident electric field, a stopband and a passband could appear at the high frequency. Meanwhile, with the increase of the resonance frequency,the local characteristics of the electromagnetic field were more obvious and were better limited within the slit. By adjusting the width, number and spacing of slits, the operating frequency of the metasurface could be adjusted in a large frequency range. At the same time, the relative position of the slit and incident electric field could be changed by rotation to realize the reconfiguration of the metasurface. These theoretical results provide important theoretical guidance for the design of more complex resonant units based on slit.

Type-I clathrate compounds Yb x Ba8-x Ga16Ge30 have been synthesized by the high-pressure and high-temperature (HPHT) method rapidly. The effects of the synergy of atom filling and pressure regulation on the microstructure and thermal and electrical properties have been investigated. With the content of Yb atom increasing, the carrier concentration is improved, the electrical resistivity and the absolute Seebeck coefficient are decreased, while the thermal conductivity is reduced significantly. A series of extremely low lattice thermal conductivities are achieved, attributed to the enhancement of multiscale phonon scattering for the "rattling" of the filled guest atoms, the heterogeneous distribution of nano- and microstructures, grain boundaries, abundant lattice distortions, lattice deformations, and dislocations. As a result, a maximum ZT of about 1.07 at 873 K has achieved for the Yb0.5Ba7.5Ga16Ge30 sample.

Si-based clathrate thermoelectric (TE) materials composed of low-cost, nontoxic, lightweight, and earth-abundant elements are typical representatives of cheaper thermoelectric materials. However, synthesis is difficult, and the relatively low ZT values are the barriers hindering the further development of the silicon clathrates. So, it is necessary to explore an alternative synthetic method and improve the ZT values simultaneously. In this work, Si-based clathrate Ba8Cu6Si40 samples have been synthesized by a simple, rapid, and feasible HPHT method with 25 min. We have investigated the changes of the TE properties and microstructures depending on the pressure in detail. The power factor has been increased due to the decreased carrier concentration, meanwhile, the thermal conductivity has been cut down on account of the strengthened full-spectrum-phonons scattering resulting from the multiple and multiscale microstructures by high-pressure processing. Ultimately, a relatively good ZT value 0.31 is achieved at 773 K for the sample synthesized at 4 GPa. To the best of our knowledge, it is higher than all of the results of pure Si-based Ba8Cu6Si40 compounds formed by other methods.

Fluorescence detection of petroleum related samples has excellent application value for unconventional oil exploration and petrochemical detection. In this paper, based on the concentration-resolved fluorescence spectra, the synchronous fluorescence spectra were used in the range of 3.0 x 10(-3) g/L to 5.0 g/L for different kinds of petroleum samples and petrochemical products with n-hexane and isopropanol as extractants. A red shift of the fluorescence spectra with an increase in the concentration was found under both extractants. The solubility of n-hexane on crude oil was stronger while that of isopropanol was better for aromatic compounds. The results show that the effect of different extracting agents on the spectra can be used to acquire more information about aromatics components in petroleum related samples, which should be carefully considered in the process of quantitative and qualitative analysis of crude oil samples by fluorescence spectra. It is also shown that the combined extraction of different extractants could enhance the analytical ability of the fluorescence spectrometry, and the rapid, non-contact measurement is promising for in-field use.