Search Results (36)

Co-infections pose significant challenges not only clinically, but also in terms of simultaneous diagnoses. The development of sensitive, multiplexed analytical platforms is critical for accurately detecting viral co-infections, particularly in complex biological environments. In this study, we present a mass spectrometry (MS)-based detection strategy employing a target-triggered hybridization chain reaction (HCR) to amplify signals and in situ photocleavable mass tags (PMTs) for the simultaneous detection of multiple targets. Hairpin DNAs modified with PMTs and immobilized loop structures on magnetic particles (Loop@MPs) were engineered for each target, and their hybridization and amplification efficiency was validated using native polyacrylamide gel electrophoresis (PAGE) and laser desorption/ionization MS (LDI-MS), with silica@gold core–shell hybrid (SiAu) nanoparticles being employed as an internal standard to ensure quantitative reliability. The system exhibited excellent sensitivity, with a detection limit of 415.12 amol for the hepatitis B virus (HBV) target and a dynamic range spanning from 1 fmol to 100 pmol. Quantitative analysis in fetal bovine serum confirmed high accuracy and precision, even under low-abundance conditions. Moreover, the system successfully and simultaneously detected multiple targets, i.e., HBV, human immunodeficiency virus (HIV), and hepatitis C virus (HCV), mixed in various ratios, demonstrating clear PMT signals for each. These findings establish our approach as a robust and reliable platform for ultrasensitive multiplexed detection, with strong potential for clinical and biomedical research. Full article

This study systematically investigates the temporal characteristics of a high-pressure CO₂ master oscillator power amplifier (MOPA) system under tunable spectral lines. Based on a continuously tunable CO₂ oscillator–amplifier system, we experimentally measured the variation in the laser pulse width before and after amplification at different spectral lines, with the oscillator and amplifier operating at pressures of 7 atm and 3 atm, respectively. The results indicate that, for most spectral lines, the laser pulse width remained nearly unchanged after amplification. However, at certain spectral lines, a distinct phenomenon was observed: pulse broadening for strong lines and pulse narrowing for weak lines. To explain this phenomenon, theoretical calculations were conducted based on a high-pressure CO₂ six-temperature model, and the experimental results were analyzed from the perspective of small-signal gain dynamics. This study reveals that variations in the laser pulse width primarily originated from differences in the gain build-up time across different spectral lines, which in turn influenced the amplification of both the pulse pedestal and the main pulse. For strong spectral lines, the amplifier gain built up rapidly, leading to more uniform amplification of the entire laser pulse and resulting in pulse broadening. Conversely, for weak spectral lines, the amplifier gain built up more slowly, with amplification primarily concentrated in the main pulse, causing a reduction in the pulse width. This finding has significant implications for optimizing narrow-pulse CO₂ lasers and provides crucial insights into the temporal characteristics of applications, such as laser isotope separation and extreme ultraviolet (EUV) light source generation. Full article

This review explores two main topics: the state-of-the-art and emerging capabilities of high-peak-power, ultrafast (picosecond and femtosecond) long-wave infrared (LWIR) laser technology based on CO₂ gas laser amplifiers, and the current and advanced scientific applications of this laser class. The discussion is grounded in expertise gained at the Accelerator Test Facility (ATF) of Brookhaven National Laboratory (BNL), a leading center for ultrafast, high-power CO₂ laser development and a National User Facility with a strong track record in high-intensity physics experiments. We begin by reviewing the status of 9–10 μm CO₂ laser technology and its applications, before exploring potential breakthroughs, including the realization of 100 terawatt femtosecond pulses. These advancements will drive ongoing research in electron and ion acceleration in plasma, along with applications in secondary radiation sources and atmospheric energy transport. Throughout the review, we highlight how wavelength scaling of physical effects enhances the capabilities of ultra-intense lasers in the LWIR spectrum, expanding the frontiers of both fundamental and applied science. Full article

Direct laser acceleration with radially polarized lasers is an intriguing variant of laser-based particle acceleration that has the potential of offering GeV/cm-level energy while avoiding the instabilities and complex beam dynamics associated with plasma wakefield accelerators. A major limiting factor is the difficulty of generating high-power radially polarized beams. In this paper, we propose the use of CO₂-based long-wave infrared (LWIR) lasers as a driver for direct laser acceleration, as the polarization insensitivity of the gain medium allows a radially polarized beam to be amplified. Additionally, the larger waist sizes, Rayleigh lengths, and pulse lengths associated with the long wavelength could improve the injection efficiency of the electron beam. By comparing acceleration simulations using a near-infrared laser and an LWIR laser, we show that the injection efficiency is indeed improved by up to an order of magnitude with the longer wavelength. Furthermore, we show that even sub-TW peak powers with an LWIR laser can provide MeV-level energy gains. Thus, radially polarized LWIR lasers show significant promise as a driver of a direct laser-driven demonstration accelerator. Full article

This manuscript focuses on studying the radiation response of the Commercial-off-the-shelf (COTS) AD524CDZ operational amplifier. Total Ionizing Dose (TID) effects were tested using low-dose ⁶⁰Co irradiation. Single-Event Effect (SEE) sensitivity was studied on this operational amplifier using a 105 MeV proton beam. Additionally, further study of the SEE response was carried out using a Two-photon absorption laser to scan some sensitive sectors of the die. For this laser experiment, different gain setups and laser energies were employed to determine how the Single Event Transient (SET) response of the device was affected based on the test configuration. The results from the TID experiments revealed that the studied device remained functional after 100 krads (Si). Proton experiments revealed the studied device exhibited a high SET response with a maximum DC offset SET of about 1.5 V. Laser experiments demonstrated that there was a clear SET reduction when using 10× and 1000× gain setups. Full article

A glass composition using TeO₂-K₂TeO₃-Nb₂O₅-BaF₂ co-doped with Er₂O₃/Ho₂O₃ and Er₂O₃/Yb₂O₃ was successfully fabricated. Its thermal stability and physical parameters were studied, and luminescence spectroscopy of the fabricated glasses was conducted. The optical band gap, E_opt, decreased from 2.689 to 2.663 eV following the substitution of Ho₂O₃ with Yb₂O₃. The values of the refractive index, third-order nonlinear optical susceptibility (χ⁽³⁾), and nonlinear refractive index (n₂) of the fabricated glasses were estimated. Furthermore, the Judd–Ofelt intensity parameters ${\Omega }_t (t=2,4,6)$, radiative properties such as transition probabilities (A_ed), magnetic dipole-type transition probabilities (A_md), branching ratios (β), and radiative lifetime (τ) of the fabricated glasses were evaluated. The emission cross-section and FWHM of the ⁴I_13/2→⁴I_15/2 transition around 1.54 μm of the glass were reported, and the emission intensity of the visible signal was studied under 980 nm laser excitation. The material might be a useful candidate for solid lasers and nonlinear amplifier devices, especially in the communications bands. Full article

This study used the DNA of Bacillus amyloliquefaciens Ba168 as a template to amplify the flagellin BP8-2 gene and ligate it into the fusion expression vector pCAMBIA1300-35S-EGFP after digestion for the construction of the expression vector pCAMBIA1300-EGFP-BP8-2. Next, using Nicotiana benthamiana as receptor material, transient expression was carried out under the mediation of Agrobacterium tumefaciens C58C1. Finally, the transient expression and subcellular localisation of flagellin BP8-2 protein were analysed using the imaging of co-transformed GFP under laser confocal microscopy. The results showed that flagellin BP8-2 was localised in the cell membrane and nucleus, and the RT-PCR results showed that the BP8-2 gene could be stably expressed in tobacco leaf cells. Furthermore, there was stronger antiviral activity against tobacco mosaic virus (TMV) infection in Nicotiana glutinosa than in BP8-2 and ningnanmycin, with an inhibitory effect of 75.91%, protective effect of 77.45%, and curative effect of 68.15%. TMV movement and coat protein expression were suppressed, and there was a high expression of PR-1a, PAL, and NPR1 in BP8-2-treated tobacco leaf. These results suggest that flagellin BP8-2 inhibits TMV by inducing resistance. Moreover, BP8-2 has low toxicity and is easily biodegradable and eco-friendly. These results further enrich our understanding of the antiviral mechanisms of proteins and provide alternatives for controlling viral diseases in agriculture. Full article

In order to address the ‘capacity crisis’ caused by the narrow bandwidth of the current C band and the demand for wide-spectrum sensing sources and tunable fiber lasers, a broadband luminescence covering the C + L bands using Er³⁺/Yb³⁺ co-doped fluorotellurite glass fiber is investigated in this paper. The optimal doping concentrations in the glass host were determined based on the intensity, lifetime, and full width at half maximum (FWHM) of the fluorescence centered at 1.5 µm, which were found to be 1.5 mol% Er₂O₃ and 3 mol% Yb₂O₃. We also systematically investigated this in terms of optical absorption spectra, absorption and emission cross-sections, gain coefficients, Judd–Ofelt parameters, and up-conversion fluorescence. The energy transfer (ET) mechanism between the high concentrations of Er³⁺ and Yb³⁺ was summarized. In addition, a step-indexed fiber was prepared based on these fluorotellurite glasses, and a wide bandwidth of ~112.5 nm (covering the C + L bands from 1505.1 to 1617.6 nm) at 3 dB for the amplified spontaneous emission (ASE) spectra has been observed at a fiber length of 0.57 m, which is the widest bandwidth among all the reports based on tellurite glass. Therefore, this kind of Er³⁺/Yb³⁺ co-doped fluorotellurite glass fiber has great potential for developing broadband C + L band amplifiers, ultra-wide fiber sources for sensing, and tunable fiber lasers. Full article

The existence of amplified spontaneous emission (ASE) is a fundamental principle of laser dyes. ASE indicates the spectral variation of the optical gain of a laser dye. Analyzing the spectral distribution of ASE is important for designing lasers. We demonstrate ASE investigations on planar waveguides made of a (co-)polymer. Similar to organic DFB (distributed feedback) lasers, a line grating allows a partial decoupling of the guided radiation. This decoupled radiation is detected as an indicator of the guided radiation. The diffraction of the radiation is utilized to perform a spectrally selective investigation of the ASE by spatially splitting it. This analysis method reduces the influence of isotropic photoluminescence and allows ASE to be analyzed across its entire spectrum. We were able to observe ASE in F8BT over a range from ${\lambda }_{ASE,min}$ = 530 nm to ${\lambda }_{ASE,max}$ = 570 nm and determine ASE threshold power densities lower than $E_{ASE}<$ 2.57 μJ/cm². The study of the power density of the ASE threshold is performed spectrally selectively. Full article

Laser pulse amplification by a high-pressure CO₂ amplifier in the long-wave infrared (LWIR) spectral range is a feasible technology for strong-field physics research. Crystals such as ZnGeP₂ (ZGP) have high nonlinear coefficients and transmittance in the LWIR region, with spectral widths of generated pulses closely matching the gain spectrum of high-pressure CO₂ amplifiers. Therefore, ZGP optical parametric oscillation (OPO) may allow higher-efficiency energy extraction in amplifiers, improving the output characteristics of LWIR amplification systems. In this study, the gain measurement of ZGP OPO pulses amplified by a high-pressure CO₂ amplifier was carried out for the first time. Single-detector acquisition was utilized to achieve a unified sensor responsivity, and a laser signal-triggered function generator was used to synchronize the seed pulse and amplifier. Six-pass amplification was performed successively, yielding an amplification factor of 4.5 for the peak power and a maximum coefficient of 0.42% cm⁻¹ for the small-signal gain. The gain and loss effect during small-signal amplification were discussed. The potential capability of acquiring ultra-short pulses with ZGP OPO pulses was also explored with the FFT function of MATLAB software. Full article

The properties of a conjugated copolymer (CP), poly[(9,9-Dioctyl-2,7-divinylenefluorenylene)-alt-co-(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene) (PDVF-co-MEH-PV), were investigated in the presence of graphene oxide (GO) and reduced graphene oxide (rGO) using absorption, fluorescence, laser, and time-resolved spectroscopy. CPs are usually dissolved in low-polar solvents. Although GO does not dissolve well, rGO and PDVF-co-MEH-PV dissolve in chloroform due to their oxygen acceptor sites. Hence, we studied rGO/PDVF-co-MEH-PV (CP/rGO), performing all experiments and simulations in chloroform. We performed simulations on PDVF-co-MEH-PV, approximate GO, and rGO using time-dependent density-functional theory calculations to comprehend the molecular dynamics and interactions at the molecular level. The simulation polymer used a tail-truncated oligomer model with up to three monomer units. The simulation and experimental results were in agreement. Further, the PDVF-co-MEH-PV exhibited fluorescence, laser quenching, rGO-mediated laser blinking, and spectral broadening effects when GO and rGO concentrations increased. The experimental and simulation results were compared to provide a plausible mechanism of interaction between PDVF-co-MEH-PV and rGO. We observed that for lower concentrations of rGO, the interaction did not considerably decrease the amplified spontaneous emissions of PDVF-co-MEH-PV. However, the fluorescence of PDVF-co-MEH-PV was considerably quenched at higher concentrations of rGO. These results could be helpful for future applications, such as in sensors, solar cells, and optoelectronic device design. To demonstrate the sensor capability of these composites, a paper-based sensor was designed to detect ethanol and nitrotoluene. An instrumentation setup was proposed that is cheap, reusable, and multifunctional. Full article

In this study, a novel technique for the quantification of the human chorionic gonadotropin (hCG) hormone using localized surface plasmons and a tapered optical fiber decorated with gold nanoparticles (Au-NPs) is reported. The tapered optical fiber fabrication process involves stretching a single-mode optical fiber using the flame-brushing system. The waist of the tapered optical fiber reaches a diameter of 3 $\mathsf{\mu }$m. Decoration of the taper is achieved through the photodeposition of 100 nm Au-NPs using the drop-casting technique and a radiation source emitting at 1550 nm. The presence of the hCG hormone in the sample solutions is verified by Fourier-transform infrared spectroscopy (FTIR), revealing the presence of bands related to functional groups, such as C=O (1630 cm${}^{-1}$), which are associated with proteins and lipids, components of the hCG hormone. Quantification tests for hormone concentrations were carried out by measuring the optical power response of the tapered optical fiber with Au-NPs under the influence of hCG hormone concentrations, ranging from 1 mIU/mL to 100,000 mIU/mL. In the waist of the tapered optical fiber, the evanescent field is amplified because of localized surface plasmons generated by the nanoparticles and the laser radiation through the optical fiber. Experimental results demonstrated a proportional relationship between measured radiation power and hCG concentration, with the optical power response decreasing from 4.45 mW down to 2.5 mW, as the hCG hormone concentration increased from 1 mIU/mL up to 100,000 mIU/mL. Furthermore, the spectral analysis demonstrated a spectral shift of 14.2 nm with the increment of the hCG hormone concentration. The measurement system exhibits promising potential as a sensor for applications in the biomedical and industrial fields. Full article

Emerging infectious diseases pose a serious threat to human health and affect social stability. In recent years, the epidemic situation of emerging infectious diseases is very serious; among these infectious diseases, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has affected many countries and regions in a short time. The prevention and treatment of these diseases require rapid on-site detection methods. However, the common detection method, RT-PCR, requires expensive instruments, complex operations, and professional operators. Here, we developed a portable low-cost assay for rapid on-site detection of viral nucleic acid using reverse transcription-loop-mediated isothermal amplification (RT-LAMP). The SARS-CoV-2 RNA can be successfully amplified within 15 min in a thermos, and the detection result is read rapidly in a portable low-cost device with a sensitivity of 10⁰ copies/µL. The portable low-cost device consists of a black box, a laser or LED and a filter, costing only a few cents. The rapid on-site detection method can provide strong support for the control of biological threats such as infectious diseases. It is also an emergency detection method for low-resource settings, relieving the huge pressure on health care. Full article

This paper reports the implementation of two critical technologies used in light detection and ranging for space applications: (1) a microchip Q-switched laser breadboard; (2) a breadboard of an indium gallium arsenide avalanche photodiode working at 292 K with high reverse polarization voltages. Microchip Q-switched lasers are small solid-state back-pumped lasers that can generate high-energy short pulses. The implemented breadboard used an erbium and ytterbium co-doped phosphate glass, a Co:Spinel crystal with 98% initial transparency, and an output coupler with 98% reflectivity. For the sensor test, a system for simultaneous operation in vacuum and a wide range of temperatures was developed. Avalanche photodiodes are reverse-polarized photodiodes with high internal gain due to their multiple layer composition, capable of building up high values of photocurrent from small optical signals by exploiting the avalanche breakdown effects. The test avalanche photodetector was assembled to be operated in two modes: linear and Geiger mode. The produced photocurrent was measured by using: (1) a passive quenching circuit; (2) a transimpedance amplifier circuit. These two technologies are important for mobile light detection and ranging applications due to their low mass and high efficiencies. The paper describes the breadboard’s implementation methods and sensor characterization at low and room temperatures with high bias voltages (beyond breakdown voltage). Full article

Er-doped optical fiber (EDF) with ultra-broad gain bandwidth is urgently needed given the rapid advancement of optical communication. However, the weak crystal field of the host silica glass severely restricts the bandwidth of traditional EDF at 1.5 μm. In this study, we theoretically explored the introduction of PbS nanomaterials in the silica network assisted with the non-bridging oxygen. This can significantly increase the crystal field strength of Er³⁺ ions in the local structure, leading to their energy level splitting and expanding the fluorescence bandwidth. Additionally, the PbS/Er co-doped optical fiber (PEDF) with improved fluorescence and gain characteristics was fabricated using modified chemical vapor deposition combined with the atomic layer deposition technique. The presence of PbS nanomaterials in the fiber core region, which had an average size of 4 nm, causes the ⁴I_13/2 energy level of Er³⁺ ions to divide, increasing the fluorescence bandwidth from 32 to 39 nm. Notably, the gain bandwidth of PEDF greater than 20 dB increased by approximately 12 nm compared to that of EDF. The obtained PEDF would play an important role in the optical fiber amplifier and laser applications. Full article