Search Results (63)

Diode-pumped alkali vapor lasers (DPALs) offer high quantum efficiency, low thermal loading, excellent beam quality, and emission wavelengths matched to important application scenarios. Extending DPALs toward pulsed regimes is of particular interest for applications such as lidar, free-space optical communication, and precision material processing, where high peak power and flexible temporal control are required. This review surveys the key technologies underlying DPAL systems and summarizes the progress in pulsed-generation approaches. The pulsed techniques reported to date are systematically reviewed, including pump modulation, intracavity modulation, cavity dumping, and mode-locking, together with a comparison of their performance. The current status indicates that pulsed DPALs remain at an early stage, with limitations in parameter space exploration and performance scaling. Future developments are expected along several directions, including further exploration of mode-locked DPALs, burst-mode pulse generation for structured temporal output, power scaling through MOPA architectures, and spectral extension via nonlinear frequency conversion. These directions collectively define the pathway toward high-performance pulsed DPAL systems. Full article

The 6.45 μm mid-infrared laser is highly promising for medical applications due to its efficient tissue ablation with minimal collateral damage. In this work, we demonstrate a stable and compact 10W-level, all-solid-state nanosecond laser source at 6.45 μm based on a Ho:YAG MOPA pumped ring-cavity ZnGeP2 optical parametric oscillator (ZGP OPO). The influence of spot size, phase-matching scheme, and crystal length on the output performance was systematically investigated. Using a 30 mm long Type I ZGP crystal, the system achieved optimal performance: a record-high average output power of 14.6 W at 6.45 μm with an optical-to-optical conversion efficiency of 17.57%, a peak power of 51.7 kW, and excellent power stability (1.45% fluctuation over 120 min at 11.7 W). To our knowledge, this represents the highest reported output power and conversion efficiency for an OPO in this spectral region, surpassing previous sources by an order of magnitude in average power and showing nearly double efficiency. This work provides a stable and reliable laser source tool for application research for techniques such as laser ablation. Full article

Laser slicing of 4H-SiC wafers offers high efficiency and minimal material loss. While nanosecond lasers are the preferred light source, simultaneously achieving high output power, excellent beam quality (M² < 1.3), and broad operational tunability remains an outstanding challenge. This study developed a highly efficient nanosecond laser source using hybrid fiber and solid-state multi-stage amplification architecture. With excellent beam quality (M² < 1.3), it achieves the highest output power, widest continuously tunable pulse width range, and broadest repetition rate range currently reported for 4H-SiC laser slicing. This advancement is poised to advance the continued development of 4H-SiC slicing technology. Full article

Background: Streptococcus pneumoniae (Spn) is a leading bacterial pathogen responsible for severe invasive diseases, including meningitis, sepsis, and pneumonia. Current pneumococcal vaccines, which are all based on capsular polysaccharide antigens, provide limited protection and are further compromised by post-vaccination serotype replacement. Pneumococcal surface protein A (PspA), a highly conserved virulence factor expressed across diverse serotypes, has emerged as a promising candidate antigen for novel protein-based vaccines. However, progress in this field has been hindered by the absence of standardized in vitro functional antibody assays. Methods: This study established a robust functional antibody detection method for PspA-based protein vaccines by modifying the conventional multiplex opsonophagocytic killing assay (MOPA), originally designed for polysaccharide-based vaccines. Using polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA) typing, a target strain panel was selected and developed to include representative strains from PspA Family 1-Clade 2 and Family 2-Clades 3 and 4. The MOPA protocol was optimized by extending the phagocytic reaction time to enhance sensitivity. Specificity was confirmed through recombinant PspA competitive inhibition assays. Results: The assay demonstrated high linearity (R² ≥ 0.98) between opsonophagocytic index (OI) and serum dilution, along with acceptable repeatability (CV ≤ 30%) and intermediate precision (CV ≤ 50%). Both preclinical and clinical serum samples exhibited potent bactericidal activity against diverse PspA families, independent of capsule type. Conclusions: This study provided a standardized framework to support the development and regulatory assessment of protein-based pneumococcal vaccines. Full article

Background: Pneumococcal diseases remain a global threat due to the serotype-specific limitations of polysaccharide vaccines. This study evaluated a recombinant protein-based pneumococcal vaccine (PBPV) combining three PspA variants (PRX1/Family1Clade2, P3296/Family2/Clade3, P5668/Family2/Clade4) and detoxified pneumolysin (PlyLD). PspA targets conserved surface epitopes to block immune evasion and achieve broad coverage, while PlyLD neutralizes pore-forming toxins and enhances adaptive immunity. Methods: We evaluated the safety and immunogenicity of the PBPV in animal models. Acute toxicity studies were conducted by administering a single intramuscular injection to ICR mice, whereas chronic toxicity and immunogenicity studies were performed in cynomolgus monkeys via repeated intramuscular injections, with an equal number of male and female animals in both groups. Immune responses were assessed using ELISA, multiplexed opsonophagocytic killing assays (MOPAs), and neutralizing antibody assays. Results: Acute toxicity studies in ICR mice showed no signs of abnormal toxicity or irritation at one-dose levels. In the chronic toxicity study, cynomolgus monkeys received repeated intramuscular injections once every 3 weeks for a total of four administrations, at doses of one dose/monkey and five doses/monkey, followed by a 4-week recovery period. No significant systemic toxic reactions were observed, and the safe dose was determined to be five doses/monkey. In the immunogenicity study of monkey serum, both low-dose and high-dose groups demonstrated significant increases in antigen-specific IgG titers against each component; opsonophagocytic killing activity against pneumococcal strains from Clades 2, 3, and 4 from PspA Families 1 and 2; and neutralization antibody titers against pneumolysin post-vaccination. Conclusions: The recombinant protein-based pneumococcal vaccine exhibited a favorable safety profile and potent immunogenicity in animal models, indicating promise for broad protection against pneumococcal disease. These findings support the further development of PBPVs as a viable alternative to conventional polysaccharide-based vaccines. Full article

Optimized designs of the ytterbium-doped fiber (YDF) have been effective at mitigating transverse mode instability (TMI) and enabling high-power scaling. In this study, the use of low-NA confined-doped YDFs is explored to achieve high-power nearly-single-mode continuous-wave lasers. Three types of 25/500 µm YDFs are manufactured with ~80% doping ratio and respective NAs of 0.058, 0.053, and 0.048. Experimental results indicate that the corresponding TMI thresholds increase with the descending NA in the YDFs. Based on the YDF with a NA of 0.048, the master oscillation power amplification (MOPA) fiber laser is scaled to 6.79 kW with nearly-single-mode beam quality. Full article

This study examines the influence of key technological parameters—marking speed, raster step (Δx), pulse duration, power density, and effective energy—on the laser marking of copper using Yb-doped fiber and CuBr MOPA lasers. Two experimental setups were used: the fiber laser, with 100 ns and 200 ns pulses, and the CuBr laser with 30 ns pulses. Marking speed ranged from 10 to 80 mm/s, with raster steps from 3 to 20 µm for the fiber laser and 3 to 27 µm for the CuBr laser. The study compares different pulse durations and evaluates the impact of laser wavelength on the marking process. Optimal effective energy ranges were identified: 17.4–43.1 kJ/cm² for the Yb-doped fiber laser and 9.90–43.1 kJ/cm² for the CuBr laser. The originality of this work lies in its direct comparison of Yb-doped fiber and CuBr MOPA lasers for copper marking, alongside the simultaneous optimization of multiple parameters. The study provides novel guidelines for high-contrast copper marking, a material with known laser-processing challenges. The identified optimal energy ranges and process parameters can significantly improve the efficiency and quality of industrial copper marking applications. 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

A high-power and high-repetition KTiOAsO₄ (KTA) optical parametric oscillator (OPO) was established in this study, with the adoption of plane-parallel and ring cavities. The pump was a high-power Nd:YAG master oscillator power amplifier (MOPA) system with a pulse repetition frequency (PRF) of 300 Hz, and the corresponding beam quality factors were M_x² = 3.4 and M_y² = 3.2. In the plane-parallel cavity experiment, powers of 51.1 W (170 mJ) and 15.9 W (53 mJ) in the signal and idler were obtained, respectively. In terms of the average power of 1 μm of a pumped KTA OPO, to our knowledge, this is the highest average power for KTA OPO. The ring cavity was constructed to achieve lasers with both high power and beam quality. The output powers of the ring cavities for the signal and idler were 33.9 W (113 mJ) and 8.7 W (29 mJ), respectively, and the corresponding beam quality factors of the signal were M_x² = 5.3 and M_y² = 7.9. The 300 Hz 100 mJ class 1.54 μm laser with a beam quality factor of less than 10 is an ideal eye-safe light detection and ranging (LiDAR) source. Full article

This Special Issue brings the Indigenous American lacquer community together, building bridges and overcoming the existing geographical and language obstacles. With dual-language (English and Spanish) articles focusing on barniz de Pasto and mopa mopa, Mexican lacquer (or maque) and cumatê, this collection includes contributions covering a number of disciplines. This volume is a ‘go-to’ research resource encompassing scientific and historical reviews, case studies, articles focusing on sociological and anthropological perspectives, and on cross-cultural contact and exchanges between Asia, Europe and the ‘New World’. The approach used to compile this Special Issue goes beyond European and North American perspectives, and includes voices that represent the genesis and context of Indigenous American lacquer objects more faithfully and objectively. Full article

We reported on a single-longitudinal-mode operated distributed Bragg reflector laser diode emitting at 1950 nm with an on-chip integrated power amplifier. Second-order Chromium–Bragg gratings are carefully designed and fabricated at the end of the ridge waveguide. Achieving a stable single-mode operation with a large injecting current range of 800 mA from 15 °C to 40 °C. The maximum side-mode suppression ratio (SMSR) is up to 42 dB. To increase the output power, an on-chip integrated master oscillator power amplifier (MOPA) is also introduced. MOPA-DBR lasers with different matching configurations between the gain peak and Bragg wavelength are fabricated, resulting in various amplification consequences. The best device is realized with 40 nm red-shifted between Bragg wavelength and photoluminescence (PL) peak. A power amplification of 5.6 times is achieved with the maximum output power of 45 mW. Thus, we put up the feasibility and key design parameters of on-chip integrated power amplification DBR lasers towards mid-infrared. Full article

Utilizing long-wavelength laser diodes (LDs) for pumping to achieve high-power fiber laser output is an effective method for attaining high quantum efficiency and excellent thermal management. In this work, we report on a Master Oscillator Power Amplifier (MOPA)-structured long-tapered Yb³⁺-doped fiber laser directly pumped by long-wavelength laser diodes. By shifting the center wavelength of the pump source to 1010 nm, the heat generation within the fiber laser is effectively controlled, thereby increasing the transverse mode instability (TMI) threshold. Additionally, the use of a long-tapered fiber enlarges the mode area and suppresses stimulated Raman scattering (SRS) effects that typically arise from increased fiber length. As a result, an output of 6030 W is achieved with an optical-to-optical (O–O) efficiency of 83.7%, a SRS suppression ratio exceeding 50 dB, and no occurrence of dynamic TMI. This approach provides a valuable reference for optimizing long-wavelength pumping to suppress nonlinear effects and also holds potential for wide-temperature operational applications. Full article

CVBs (cylindrical vector beams) are widely used in optical imaging, optical trapping, material processing, etc. In this study, based on mode-selective couplers and passive mode-locking fiber technology, a cylindrical vector fiber amplifier with an MOPA (master oscillator power amplifier) structure was developed. In the experiment, the pre-amp stage reached 19.87 mW output power and a CVB output with a mode purity greater than 97%. The measured beam quality factor was M² = 2.1. The CVB output power obtained by the first-amp stage was 152.4 mW, and the mode purity was greater than 92%. The measured beam quality factor was M² = 1.99. The internal inhomogeneity and external effects of the isotropic LMA (large-mode-area) fiber led to a decrease in beam quality and mode purity. After amplification, the gain of the fundamental mode was higher and the power was greater, resulting in a greatly reduced mode purity. This CVB fiber amplifier yielded important research value in expanding the applications of high-power fiber lasers. Full article

This article intends to highlight and reconstruct the relationships between humans (harvesters, woodworkers and master artisans) and non-humans (raw materials, tools, places, products, etc.) in the Barniz de Pasto mopa-mopa tradition. These relationships were lost when the focus came to be primarily on the objects, as happens in most popular art forms worldwide. This text is organised in ethnographic overviews: the home workshops of masters of Barniz de Pasto; woodworker workshops; montañas-selvas (Andean rainforest highlands) and mopa-mopa harvesters; until we reach the objects. Unlike a conventional article, it does not end with firm and immutable conclusions. Our reflections from our eleven years (2013–2024) of accompanying men and women artisans and collectors, during the process of including the traditional knowledge and techniques associated with Barniz de Pasto mopa-mopa as Intangible Cultural Heritage (patrimonialización) and its safeguarding, are always open for discussion. Full article

This paper summarises the research carried out so far on barniz de Pasto objects from the Victoria and Albert Museum (V&A) and outlines future areas of development for our collection of Indigenous lacquer from Latin America. The V&A was the first UK public institution to identify objects decorated with barniz de Pasto within its collection. Two of these were acquired in 2015 and 2018; others had entered the collection between 1855 and 1902 but were recognised as barniz de Pasto only after 2018. The acquisition in 2015 of a cabinet marked the start of a research campaign to understand the materiality and context of all the museum’s barniz de Pasto objects. The analytical techniques used included X-radiography, polarised light microscopy and digital microscopy, Raman microscopy, X-ray fluorescence (point and scanning), chromatography (py-GC–MS and LC–DAD–MS), Fourier transform infrared spectroscopy, X-ray diffraction, and X-ray micro-computed tomography. Unexpected discoveries were made along the way, including the characterisation and documentation of mercury white (mercury(I) chloride, or calomel) used as a white pigment, a world first. Gel-based cleaning methods were used to remove a non-original, discoloured, natural varnish covering nearly the entire surface of one of the objects, and the recent overpaint on its lid, revealing original surfaces which had been repaired and drastically repainted in the second half of the twentieth century. Full article