Search Results (11)

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

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

In the present research, the AlZnMgCu1.5 alloy was machined via an industrial-type Nd-YAG laser cutting process. The Box–Behnken design of response surface methodology was used to plan the trials. The experiments were carried out by varying the nitrogen pressure (4–10 bar), pulse energy (2.5–5.5 J), cutting speed (10–18 mm/min), and pulse width (1.5–2 ms). ANOVA was conducted to assess the impact of process factors on response characteristics. The ANOVA results suggest that nitrogen pressure has the greatest influence on the input process parameters. A detailed investigation was conducted to examine the effects of various parameters on kerf deviation. The metaheuristic algorithms (i.e., Giant Trevally Optimizer—GTO; and Zebra Optimization Algorithm—ZOA) were implemented to determine the optimum process parameters for producing the best performance measures. A comparative analysis demonstrated that the parametric value provided by the GTO algorithm, which adheres to the ZOA method, yielded the lowest response. Optimization using GTO resulted in a 6.71% improvement in kerf deviation prediction accuracy compared to experimental values, while ZOA achieved a 2.37% improvement. Furthermore, GTO demonstrated superior computational efficiency, converging in 5.687 s, significantly faster than the 11.548 s required by ZOA. The optimal solution suggested by the GTO algorithm is further verified using a confirmation test on the random settings. In addition, the surface morphology of the laser-cut kerf surfaces was analyzed using SEM images. Through this, it is confirmed that the metaheuristic algorithm of GTO is more suitable for finding the optimum process parameters. Full article

Surface micro-texture has been shown to enhance wettability and reduce wear on cutting tools. However, there is limited research on how laser parameters impact the dimensional accuracy of surface texture and its wettability. This study focuses on producing arrayed groove textures on WC/Co cemented carbide surfaces using Nd: YAG laser, evaluating the effect of the laser parameters on surface topography and texture accuracy through microscopic observation and simulation. The results indicate that, with laser parameters such as a number of passes less than 5, approximately 16 W power, scanning speed of 100–150 mm/s, and pulse frequency of 30 kHz, the error between the groove width and laser spot diameter was 4.7%. Additionally, the study explores the impact of the groove texture on surface wettability using the solid droplet method and XPS analysis. Comparative experiments reveal that increased surface roughness enhanced oleophobicity, with surfaces exhibiting high texture accuracy and integrity showing improved oleophobic and spreading properties. Thus, the precise regulation of laser processes is crucial for maintaining surface texture integrity and enhancing surface wettability. Full article

This paper presents the design and experimental results of a long cavity length Nd:YAG laser with a large stable zone for water jet-guided laser (WJGL) applications. The design is based on the light transmission matrix and resonator stability conditions, aiming to achieve a large stable zone and a short cut-off thermal focal length (CTFL). A folded concave resonator is researched to enhance the cavity length, and the influence of the tunable cavity arm length on the oscillating beam in the resonator and in the YAG crystal is theoretically studied. Moreover, the effects of the output mirror curvature and the cavity arm length on the range of the stable area and the cut-off thermal focal length are also investigated. Experimental results show that a stable green laser output is obtained after second harmonic generation (SHG) with a pulse width ranging from 43 to 143 ns within the laser operating frequency range of 5–20 kHz. At an operation frequency of 10 kHz, the output power is 21.33 W, and the instability of the output power within 400 min is 0.88%. The laser source achieves a maximum power of 25.7 W at 20 kHz, and the maximum single pulse energy reaches 2.7 mJ at 6 kHz. Finally, this is used as the laser source to couple with a water jet with a diameter of 100 microns, achieving a lossless water conductivity transmission over 60 mm length. These results demonstrate the suitability of the designed laser source for WJGL technology research. In precision machining applications, this technology exhibits processing advantages of low thermal damage (~2 μm) and large depth (>10 mm), for 7075 aluminum alloy. Full article

We developed and evaluated an anodized-aluminum pressure-sensitive paint (AA-PSP) with new formulations of free-base porphyrin, ${\mathrm{H}}_2\mathrm{TCPP}$, as an optical unsteady pressure sensor. The luminophore ${\mathrm{H}}_2\mathrm{TCPP}$ has quite a short fluorescent lifetime (2.4 ns on the condition of the AA-PSP). The fluorescence spectroscopy result shows that the excitation wavelength of ${\mathrm{H}}_2\mathrm{TCPP}$ corresponds to violet-colored (425 nm) and green-colored (longer than 520 nm) lights. The pressure sensitivity is sufficiently high for the pressure sensor (0.33–0.51%/kPa) and the temperature sensitivity is very low (0.07–1.46%/K). The photodegradation of the AA-PSPs is not severe in both excitation light sources of the green LED and the Nd:YAG laser. The resonance tube experiment result shows the cut-off frequency of the AA-PSPs is over 9.0 kHz, and the results of the shock tube experiment show the 10 µs order time constant of the normal shock wave. Full article

Magnesium diboride (MgB₂) thin films on r-cut sapphire (r-Al₂O₃) single crystals were fabricated by a precursor, which was obtained at room temperature via a pulsed laser deposition (PLD) method using a Nd:YAG laser, and an in situ postannealing process. The onset superconducting transition, T_c^onset, and zero-resistivity transition, T_c^zero, were observed at 33.6 and 31.7 K, respectively, in the MgB₂ thin films prepared by a Mg-rich target with a ratio of Mg:B = 3:2. The critical current density, J_c, calculated from magnetization measurements reached up to 0.9 × 10⁶ A cm⁻² at 20 K and 0 T. The broad angular J_c peak was found at 28 K when the magnetic fields were applied in a direction parallel to the film surface (θ = 90°). This could be indicative of the granular structure with randomly oriented grains. Our results demonstrate that this process is a promising candidate for the fabrication of MgB₂ superconducting devices. Full article

Electro-optical modulators are effectively used for ultrafast pulse lasers operation control. The scheme of picosecond pulse-periodic high-peak-power Nd:YAG lasers is composed of an active-passive mode-locked and negative feedback-controlled master oscillator and regenerative amplifier based on common end-diode-pumped Nd:YAG crystal. A double-crystal thermally compensated Pockels cell based on KTP crystals of the Y-cut direction is employed as a key control element. The cell was assembled using a pair of equal-length crystals grown according to high-resistivity technology. The scheme provides output pulses with energy up to 1.6 mJ, a duration of 25 ps at repetition rates tunable from 0 to 200 Hz. The laser operation stages are analyzed in detail. The scheme looks attractive and promising for developing advanced ultrafast laser systems with higher repetition rates, peak and, accordingly, average power levels. The Pockels cell based on KTP crystals expands the line of available fast electro-optical control elements, along with the previously used RTP ones. The factors limiting laser pulse energy and repetition rate are discussed. Parasitic nonlinear conversion in the crystals of the Pockels cell along the axis may play an essential role. The results of comparative measurements of the second and third harmonics made with the Pockels cells based on KTP and RTP crystals of both X-cut and Y-cut directions are presented. The minimum second and third harmonics efficiency levels observed in the Y-cut Pockels cells of the KTP crystal seem to be their important advantage. Full article

Cobalt chromium (CoCr) alloy tubes have been widely used in manufacturing of vascular stents, due to their excellent bio-mechanical properties, especially their high strength. In recent years, fiber lasers have been used in the micro-machining of vascular stents, given their better cutting quality than neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers. A comparison study of CoCr fiber laser cutting with oxygen and argon is presented, and the differences, such as surface topography, chemical composition, and kerfs geometry, between the oxygen cuts and argon cuts are studied. Three types of topographies are obtained for the oxygen cuts, and the underlying reason for the different topographies are discussed. The influences of key parameters including power, repetition rate, pulse width, and cutting speed on the cutting quality are analyzed. The present research can also provide an optimization guideline for the micro-profiling of CoCr vascular stents. Full article

The aim of this paper is to fabricate micro-gears via laser shock punching with Spitlight 2000 Nd-YAG Laser, and to discuss effects of process parameters namely laser energy, soft punch properties and blank-holder on the quality of micro-gears deeply. Results show that dimensional accuracy is the best shocked at 1690 mJ. Tensile fracture instead of shear fracture is the main fracture mode under low laser energy. The soft punch might cause damage to punching quality when too high energy is employed. Appropriate thickness and hardness of soft punch is necessary. Silica gel with 200 µm in thickness is beneficial to not only homogenize energy but also propagate the shock wave. Polyurethane films need more energy than silica gel with the same thickness. In addition, blank-holders with different weight levels are used. A heavier blank-holder is more beneficial to improve the cutting quality. Furthermore, the simulation is conducted to reveal typical stages and the different deformation behavior under high and low pulse energy. The simulation results show that the fracture mode changes under lower energy. Full article