Search Results (200)

In this study, a novel direct laser beam turning (DLBT) approach is proposed for the precision machining of AISI 308L austenitic stainless steel, which eliminates the need for cutting tools and thereby eradicates tool wear and vibration-induced surface irregularities. A nanosecond-pulsed Nd:YAG fiber laser (λ = 1064 nm, spot size = 0.05 mm) was used, and Ø1.6 mm × 20 mm cylindrical rods were processed under ambient conditions without auxiliary cooling. The experimental framework systematically evaluated the influence of scanning speed, pulse frequency, and the number of laser passes on dimensional accuracy and material removal efficiency. The results indicate that a maximum diameter reduction of 0.271 mm was achieved at a scanning speed of 3200 mm/s and 50 kHz, whereas 0.195 mm was attained at 6400 mm/s and 200 kHz. A robust second-order polynomial correlation (R² = 0.99) was established between diameter reduction and the number of passes, revealing the high predictability of the process. Crucially, when the scanning speed was doubled, the effective fluence was halved, considerably influencing the ablation characteristics. Despite the low fluence, evidence of material evaporation at elevated frequencies due to the incubation effect underscores the complex photothermal dynamics governing the process. This work constitutes the first comprehensive quantification of pass-dependent diameter modulation in DLBT and introduces a transformative, noncontact micromachining strategy for hard-to-machine alloys. The demonstrated precision, repeatability, and thermal control position DLBT as a promising candidate for next-generation manufacturing of high-performance miniaturized components. Full article

We report a passively Q-switched self-Raman laser using a dual-end composite c-cut Nd:YVO₄ crystal, which generates switchable visible emissions at 533 nm, 560 nm, and 589 nm. A Cr⁴⁺:YAG/YAG composite crystal served the role of a saturable absorber to achieve passive Q-switching. An angle-tuned BBO crystal was used to achieve the frequency mixing between the first-tokes wave and the fundamental wave. At an incident pump power of 9.5 W, the maximum average output powers were 425 mW for the 589 nm yellow laser, 193 mW for the 560 nm lime laser, and 605 mW for the 533 nm green laser, with corresponding pulse widths of approximately 3.8, 3.6, and 35.1 ns, respectively. This result shows that a passive Q-switching operation with self-Raman crystals presents a promising approach for compact multi-wavelength pulse laser sources. Full article

4H-silicon carbide (4H-SiC) is a cornerstone for next-generation optoelectronic and power devices owing to its unparalleled thermal, electrical, and optical properties. However, its chemical inertness and low dopant diffusivity for most dopants have historically impeded effective doping. This study unveils a transformative laser-assisted boron doping technique for n-type 4H-SiC, employing a pulsed Nd:YAG laser (λ = 1064 nm) with a liquid-phase boron precursor. By leveraging a heat-transfer model to optimize laser process parameters, we achieved dopant incorporation while preserving the crystalline integrity of the substrate. A novel optical characterization framework was developed to probe laser-induced alterations in the optical constants—refraction index ($\mathrm{n}$) and attenuation index ($\mathrm{k}$)—across the MIDIR spectrum (λ = 3–5 µm). The optical properties pre- and post-laser doping were measured using Fourier-transform infrared spectrometry, and the corresponding complex refraction indices were extracted by solving a coupled system of nonlinear equations derived from single- and multi-layer absorption models. These models accounted for the angular dependence in the incident beam, enabling a more accurate determination of $\mathrm{n}$ and $\mathrm{k}$ values than conventional normal-incidence methods. Our findings indicate the formation of a boron-acceptor energy level at 0.29 eV above the 4H-SiC valence band, which corresponds to λ = 4.3 µm. This impurity level modulated the optical response of 4H-SiC, revealing a reduction in the refraction index from 2.857 (as-received) to 2.485 (doped) at λ = 4.3 µm. Structural characterization using Raman spectroscopy confirmed the retention of crystalline integrity post-doping, while secondary ion mass spectrometry exhibited a peak boron concentration of 1.29 × 10¹⁹ cm⁻³ and a junction depth of 450 nm. The laser-fabricated p–n junction diode demonstrated a reverse-breakdown voltage of 1668 V. These results validate the efficacy of laser doping in enabling MIDIR tunability through optical modulation and functional device fabrication in 4H-SiC. The absorption models and doping methodology together offer a comprehensive platform for paving the way for transformative advances in optoelectronics and infrared materials engineering. Full article

Articular cartilage is an avascular and aneural connective tissue that is frequently damaged due to trauma or degenerative joint diseases, often resulting in arthritis. Its limited intrinsic capacity for self-renewal poses a significant challenge to effective repair. Hence, the development of regenerative strategies is essential to enhance the poor intrinsic healing of cartilage tissue. Photobiomodulation (PBM) has gained increasing attention as a noninvasive, drug-free, and safe approach. PBM exerts photobiological effects that promote cellular responses and reduce inflammatory conditions, all of which are beneficial for cartilage repair. Nonetheless, the efficacy of PBM varies depending on treatment parameters and treated targets. This review first summarizes PBM parameter-dependent outcomes in cartilage regeneration studies. Reported data indicate frequent use of red lasers (600–660 nm, 0–10 J/cm²), GaAIAs lasers (800–880 nm, 10–50 J/cm²), and Nd:YAG lasers (1064 nm, up to 200 J/cm²) in in vitro, in vivo, and clinical studies. Moreover, PBM in conjunction with cartilage tissue engineering (CTE) has shown synergistic effects, enhancing scaffold-based repair outcomes. This review additionally explores PBM applications within CTE frameworks. The summarized findings aim to inform researchers and physicians by outlining optimized PBM strategies and highlighting PBM’s strong potential in promoting cartilage regeneration, both independently and in combination with CTE. Full article

Lasers are widely employed in the treatment of melanocytic lesions. This scoping review evaluates 77 studies on the efficacy and safety of laser treatments for café-au-lait macules (CALMs), nevus of Ota (NOA), Becker’s nevus (BN), lichen planus pigmentosus (LPP), and other pigmented lesions. The Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG), particularly the 1064 nm, is the most frequently utilized laser, demonstrating strong efficacy for NOA and other dermal pigmentary disorders. Medium-wavelength lasers, including the Q-switched ruby and Alexandrite lasers, also show promise, though results vary based on lesion depth, skin type, and treatment protocols. Recurrence and adverse effects, including post-inflammatory hyperpigmentation (PIH) and hypopigmentation, are common, particularly in patients with darker skin tones. Future studies should standardize and optimize laser parameters across lesion types and skin tones, improve long-term efficacy, and prioritize inclusion of patients with diverse Fitzpatrick skin types to evaluate differential outcomes and promote equitable treatment efficacy. Full article

In this study, a thin film of silicon carbide (SiC) was deposited on a porous silicon (P-Si) substrate using pulsed laser deposition (PLD). The photo–electrochemical etching method with an Nd: YAG laser at 1064 nm wavelength and 900 mJ pulse energy and at a vacuum of 10⁻² mbar P-Si was utilized to create a sufficiently high amount of surface area for SiC film deposition to achieve efficient SiC film growth on the P-Si substrate. X-ray diffraction (XRD) analysis was performed on the crystalline structure of SiC and showed high-intensity peaks at the (111) and (220) planes, indicating that the substrate–film interaction is substantial. Surface roughness particle topography was examined via atomic force microscopy (AFM), and a mean diameter equal to 72.83 nm was found. Field emission scanning electron microscopy (FESEM) was used to analyze surface morphology, and the pictures show spherical nanoparticles and a mud-sponge-like shape demonstrating significant nanoscale features. Photoluminescence and UV-Vis spectroscopy were utilized to investigate the optical properties, and two emission peaks were observed for the SiC and P-Si substrates, at 590 nm and 780 nm. The SiC/P-Si heterojunction photodetector exhibited rectification behavior in its dark I–V characteristics, indicating high junction quality. The spectral responsivity of the SiC/P-Si observed a peak responsivity of 0.0096 A/W at 365 nm with detectivity of 24.5 A/W Jones, and external quantum efficiency reached 340%. The response time indicates a rise time of 0.48 s and a fall time of 0.26 s. Repeatability was assured by the tight clustering of the data points, indicating the good reproducibility and stability of the SiC/P-Si deposition process. Linearity at low light levels verifies efficient photocarrier generation and separation, whereas a reverse saturation current at high intensities points to the maximum carrier generation capability of the device. Moreover, Raman spectroscopy and energy dispersive spectroscopy (EDS) analysis confirmed the structural quality and elemental composition of the SiC/P-Si film, further attesting to the uniformity and quality of the material produced. This hybrid material’s improved optoelectronic properties, achieved by combining the stability of SiC with the quantum confinement effects of P-Si, make it useful in advanced optoelectronic applications such as UV-Vis photodetectors. Full article

A laser-based selective wax ablation method using a 532 nm Nd:YAG laser was developed to improve the foliar uptake efficiency of agrochemicals in citrus leaves. In contrast to conventional applications that suffer major losses, our approach exposes up to 80% of the underlying epidermis (within the irradiated footprint) with no visible tissue damage, thereby substantially enhancing substance penetration. Efficacy was confirmed using two indicators: (1) A fluorescent glucose analog (2-NBDG) exhibited a radial expansion velocity reaching 0.0105 mm/min in treated areas, enabling rapid phloem transport across an 8 cm distance within just three minutes—an 11,280% improvement over untreated controls. (2) Laser-induced breakdown spectroscopy (LIBS) demonstrated a threefold increase in zinc (Zn) uptake (and over fivefold compared to untreated leaves) when using a Zn-based foliar fertilizer. To assess processing efficiency, we quantified the ablation footprint by combining single-pulse laser shots in a 1 cm-diameter region and found that 23.4% of the total area was fully exposed. This selective, non-invasive approach enables precise targeting, potentially reducing fertilizer and pesticide usage while improving crop health. Beyond citrus, it is readily adaptable to other crops, with integration into orchard or greenhouse spraying systems as a promising path for scale-up. Such versatility highlights the technique’s potential to optimize efficacy, cut input costs, and diminish environmental impact in modern precision agriculture. Full article

We reported on a nanosecond regenerative amplified laser with a repetition rate of 1 kHz by employing laser diodes (LDs) with distinct wavelengths as both the seed laser and the pump source and utilizing Nd:YAG as the gain medium. The single-pulse energy was 1.58 mJ and the pulse duration was adjustable, ranging from 1 to 5 ns. Combining two oppositely oriented BBO crystals for second harmonic generation (SHG) and an LBO crystal for third harmonic generation (THG), a 355 nm laser with a single-pulse energy of 257 μJ was attained, corresponding to a THG efficiency of 16.2%. Full article

Vortex lasers have shown significant advantages in fields such as quantum communication and optical detection due to their unique optical field structure. In this manuscript, we present a watt-level nanosecond Laguerre–Gaussian vortex beam from an end-pumped bonded Nd:YAG/V:YAG laser, which was pumped by a ring-shaped beam shaped by an axicon focusing system. By solving the transfer matrix of the resonator and designing a corresponding pump beam shaping system, mode matching between the LG₀₁ beam and the annular pump beam was effectively achieved. The conditions for exciting the LG₀₁ mode were theoretically calculated, and experimental results verified that the pump power required to excite the LG₀₁ vortex beam is approximately twice that for exciting the fundamental Gaussian mode. Stable output of nanosecond lasers in the LG₀₁ mode was achieved, with an output power of 1.943 W, a highest repetition rate of 291.3 kHz, a pulse width of 3.3 ns, and beam quality factors of ${\mathrm{M}}_{\mathrm{x}}^2=2.17$ in the horizontal direction and ${\mathrm{M}}_{\mathrm{y}}^2=2.21$ in the vertical direction. The results have significant value for applications such as visible light communication and high-resolution laser imaging. Full article

This paper presents the technical design of the pathfinder Barcelona Raman LIDAR (pBRL) for the northern site of the Cherenkov Telescope Array Observatory (CTAO-N) located at the Roque de los Muchachos Observatory (ORM). The pBRL is developed for continuous atmospheric characterization, essential for correcting high-energy gamma-ray observations captured by Imaging Atmospheric Cherenkov Telescopes (IACTs). The LIDAR consists of a steerable telescope with a 1.8 m parabolic mirror and a pulsed Nd:YAG laser with frequency doubling and tripling. It emits at wavelengths of 355 nm and 532 nm to measure aerosol scattering and extinction through two elastic and Raman channels. Built upon a former Cherenkov Light Ultraviolet Experiment (CLUE) telescope, the pBRL’s design includes a Newtonian mirror configuration, a coaxial laser beam, a near-range system, a liquid light guide and a custom-made polychromator. During a one-year test at the ORM, the stability of the LIDAR and semi-remote-controlled operations were tested. This pathfinder leads the way to designing a final version of a CTAO Raman LIDAR which will provide real-time atmospheric monitoring and, as such, ensure the necessary accuracy of scientific data collected by the CTAO-N telescope array. Full article

This paper presents a time-shared pumping technology for semiconductor lasers based on polarization-combined technology, which enables a compact passively Q-switched Nd³⁺:YAG/Cr⁴⁺:YAG laser to generate tunable pulse sequence output. Two 808 nm laser diodes (LDs) with high polarization were integrated into a casing system measuring 61.5 mm × 32 mm × 12.5 mm through the implementation of fast and slow axis collimation, polarization-combined, and beam-shaping techniques. The study introduces a temporal modulation function to the electrical driving signals, allowing for synchronous and delayed control of the two laser pump sources. By adjusting the pumping delays (200 μs, 240 μs, 280 μs, and 320 μs), two types of pulse sequences combined by “1 + 1” and “2 + 2” at 1064 nm were successfully generated. Experimental results demonstrated that the energy and intensity of each sub-pulse within the burst-mode remain stable throughout the entire sequence, with adjustable sub-pulse interval. Furthermore, the laser system exhibited good beam quality with near-diffraction-limited output characteristics (M² < 1.5). In general, the tunable pulse sequence laser source offers significant potential for applications in high-precision laser processing, laser ranging and precision measurement, demonstrating its broad application potential. Full article

Objective: Colorectal pulmonary metastasis is the most common resected metastatic disease of the lung. Pulmonary metastasectomy (PM) for colorectal oligometastases is a well-established intervention with curative intent. Local recurrence at the resection site in the lung is a problem, with an impact on survival. The use of a 1320 nm neodymium:yttrium aluminum garnet (Nd:YAG) laser causes the vaporization and coagulation at the resection line and thereby increases safety margins around the nodule. We aimed to evaluate the local recurrence rate after laser-assisted pulmonary metastasectomy (LPM) for colorectal metastases. Methods: We conducted a retrospective analysis of 49 patients treated with laser-assisted pulmonary metastasectomy for 139 metastatic nodules from colorectal cancer from 2010 to 2018. All nodules were resected using Nd:YAG 1320 nm laser, aiming for a safety margin of five mm. The minimum follow-up time after PM was 24 months. Results: Local intrapulmonary recurrence developed at 7 of the 139 (5.0%) resection sites in 5 of the 49 patients (10.2%). Microscopically incomplete resection was a significant risk factor for recurrence (p = 0.023). Larger nodule size (>12 mm) negatively impacted local recurrence (p = 0.024). Nodules larger or equal to 12 mm in size also lowered the patients’ probability of survival by 67.29% (HR: 0.3271, 95% CI: 0.1265–0.846, p = 0.018). Conclusions: The rate of local recurrence at the resection site after LPM for colorectal metastases is low. Complete resection is a positive predictor of survival without local recurrence. Microscopic complete resection with the addition of vaporization and coagulation at the resection margin seems to be sufficient to prevent local recurrence. However, larger nodules may require larger safety margins. Full article

This work presents results on nanosecond laser ablation of a titanium (Ti) plate immersed in a liquid medium using the fundamental wavelength (1064 nm) of a nanosecond Nd:YAG laser system. The laser radiation was focused on the target surface as scanning was accomplished by an XY translation stage. The laser processing of the Ti targets took place in two organic liquids—liquid paraffin and diesel oil. The morphology of the structured surfaces and the structure and phase composition of the samples were studied; their dependences on the processing parameters are discussed. With both liquid media used, crack formation on the surface of the laser-treated Ti target was observed. Formation of a titanium carbide (TiC) phase was found whose properties could be tuned by varying the laser irradiation parameters. Raman measurements were utilized to analyze the carbon structure formed in the resulting coatings. The results of surface electron microscopy reveal that the thickness of the resulting coatings reached 20 µm. Some of the obtained coatings demonstrated about three times higher hardness compared to the native Ti sample. The technique proposed can be used in surface modification of materials in view of improving their mechanical properties. Full article

Zirconia is increasingly favored for dental implants owing to its corrosion resistance, hypoallergenic properties, and superior esthetics, but its biocompatibility remains a challenge. This study explores laser-assisted surface modification to enhance zirconia bioactivity. Zirconia transitions from the monoclinic to the tetragonal phase during sintering, with mixed phases observed in the pre-sintered stage. These transitions are critical for understanding its structural stability and malleability. Grid patterns were imprinted on the green body implant surface using a 1064 nm Nd-YAG laser (Continuum Surelite II, San Jose, CA, USA), with mesh sizes ranging from 7 to 50 µm and depths up to 2 µm, controlled by varying laser fluence, irradiation time, and templates. SEM, AFM, and XRD analyses were used to characterize the surface morphology and crystallography. Protein adsorption studies compared two patterned samples with different surface coverage—the first sample had a patterned area of 0.212 cm² (27%), while the second sample had a patterned area of 0.283 cm² (36%)—to a control sample. Protein adsorption increased by 92% in the first and 169% in the second sample, demonstrating a direct correlation between increased pattern area and bioactivity. Enhanced protein adsorption facilitates cell attachment and growth, which are crucial for improving osseointegration. These results underscore the potential of laser-assisted surface modification to optimize zirconia’s performance as a medical implant material. Full article

The European Society for Laser Dermatology (ELSD) has established recommendations for safe and effective photo epilation; however, short-term common adverse effects occur as a result of laser treatment, such as edema and perifollicular erythema. Post-inflammatory hyperpigmentation also appears in certain skin types. Very few clinical studies have been conducted on the topical application of cosmetic skin care products aimed at decreasing the adverse effects on the skin epidermis following laser-assisted epilation procedures. Stem cells are found in plant and animal organisms and are responsible for the growth and restoration of damaged tissues. Plant stem cells divide throughout the life of the plant, creating new plant parts. Our aim was to develop a new cosmetic cream to decrease the intensity of some of the side effects of laser epilation and thus reduce the administration of topical medication. We developed a formulation with the active substance Olea europaea (Olive) Callus Culture Lysate (OLEA VITAE™ 02), which is derived from plant stem cells of the Mediterranean wild variety of Olea europaea, for application following laser epilation with an Nd:YAG 1064 nm laser. The new skin care cream was tested for its physicochemical and microbiological stability, according to the European Pharmacopoeia. The impacts of this substance on the potential side effects of Nd:YAG 1064 nm application, i.e., trans-epidermal water loss, keratin hydration, melanin, erythema, and skin elasticity, in comparison with the appropriate placebo, were investigated using biophysical measurements and a self-assessment questionnaire. Skin biopsies were also performed to evaluate the influence of the procedure and the application of the products on the epidermis and papillary dermis thickness. According to our findings, the incorporation of the plant stem cell extract of Olea europaea into our cream resulted in a stable cream with an appealing texture. Furthermore, the activity of erythema and hyperpigmentation was decreased when the cream was applied after Nd:YAG 1064 nm laser epilation. Full article