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Blue laser annealing can be used to obtain a high-mobility thin-film transistor (TFT) through a laser annealing (i.e., LTPS: low-temperature Poly-Si) process. However, the laser annealing process’s low productivity (as well as high cost) is an issue because the high output power of blue lasers still needs to be addressed. Therefore, productivity can be improved if blue laser energy is efficiently supplied during the laser annealing process using a continuous wave laser instead of a conventional pulsed excimer laser. We developed a blue laser light source (440 ± 10 nm) using the wavelength beam combining (WBC) method, which can achieve a laser power density of 73.7 kW/cm2. In this semiconductor laser, when the power was increased s by 2.9 times, the laser scanning speed was increased by 5.0 times, achieving twice the productivity of conventional lasers. After laser annealing, the size of the crystal grains varied between 2 and 15 μm, resulting in a crystallization rate of 100% by Raman scattering rsult and low resistivity of 0.04 Ωcm. This increase in production capacity is not an arithmetic increase with increased power but a geometric production progression.

The production of brighter coherent XUV radiation by intense laser pulses through the process of high-harmonic generation (HHG) is one of the central challenges in contemporary nonlinear optics. We study the generation and spatial propagation of high harmonics analytically and via ab initio simulations. We focus on the length scales defining the growth of the harmonic signal with propagation distance and show that the well-known coherence length limits HHG only for relatively low driving intensities. For higher intensities, the photoionisation of the medium, naturally accompanying HHG, leads to essentially transient phase matching and laser frequency blue shift. By systematically taking both of these factors into account, we demonstrate that the behaviour of the harmonic signal at higher intensities is defined by another length scale—the blue-shift length. In this generation regime the XUV intensity at a given frequency first grows quadratically and then saturates passing the blue-shift length, but the total harmonic efficiency continues growing linearly due to the linear increase of the harmonic line bandwidth. The changeover to this generation regime takes place for all harmonic orders roughly simultaneously. The rate of the efficiency growth is maximal if the atomic dispersion is compensated by photoelectrons near the centre of the laser pulse. Our theory offers a robust way to choose the generation conditions that optimise the growth of the harmonic signal with propagation.

Hairpin winding technology is a crucial part of the contemporary electric drives used for traction applications. The contacting of the hairpin couples requires a fast process with high quality and cleanliness in the processing environment. High-brilliance NIR sources provide industrially accepted solutions with high productivity, while spatter, porosity, and material burst defects remain open issues to be resolved. The use of conduction mode welding may provide a more stable process in the absence of keyhole fluctuations. The blue wavelength at high power can provide the means for a conduction mode weld with high absorptivity despite low irradiance, sufficiently deep and wide as required by the hairpin welding applications. This work investigates the use of a 3 kW blue diode laser with 720 µm spot size for the welding of pure Cu hairpin couples. The work systematically investigates the melting capacity of the blue laser beam from bead-on-plate experiments to the hairpin welds with elliptical trajectories and an increasing number of scans. The results show that the blue laser is capable of producing the weld beads with sufficient size using scan speeds between 50 and 150 mm/s and a number of rotations between 2 and 7, characterized by low porosity and reduced material ejection. The process was observed to be relatively slower compared to keyhole welding but proved to be favorable for reducing spatter generation. The conduction-based welding is also provided to correlate more easily the external dimensions of the weld bead to weld strength and electrical resistance. Such features are highly appealing for an easier process of quality assessment.

Blue diode laser irradiation has significant potential for realization of high vaporization efficiency with minimal thermal damage because of the strong blue light absorption of hemoglobin and the resulting shallow tissue penetration. This study presents an in silico framework for designing laser parameters, specifically pulse duration and power, for efficient vaporization under low-power irradiation conditions while minimizing thermal tissue damage. Computational simulations of laser-tissue interactions using the Monte Carlo light transport with dynamic optical properties model were conducted to evaluate vaporization and coagulation performance under various irradiation conditions. In addition to vaporization volume, the fraction of coagulated tissue was also calculated as a measure of thermal tissue damage. The in silico designs were validated experimentally through irradiation experiments performed on porcine liver tissue. Computational simulations revealed a non-monotonic relationship between pulse duration and vaporization volume at constant energy, as well as distinct trends for vaporization and coagulation. The experimental results confirmed the effectiveness of the simulation-derived parameters, and supported the practical utility of the proposed in silico design approach. The proposed in silico design approach enables quantitative analysis of vaporization and coagulation responses and can guide the development of safe and effective laser treatment protocols.

Blue lasers are integral to a variety of applications, including marine communication, underwater resource exploration, cold laser processing, laser medicine, and beyond. Vertical external cavity surface-emitting lasers (VECSELs) have the advantages of high output power and tunable wavelength, and can output blue laser via frequency doubling. In this article, a new type of intracavity beam control external-cavity structure is introduced. The laser beam waist is effectively adjusted by intracavity beam control, and the frequency conversion efficiency is improved. A laser cavity stability analysis model was developed to investigate the impact of laser cavity lens parameters and relative positions on stability. The external resonant cavity of VECSELs utilizes two optical lenses to position the beam waist near the laser output coupling mirror and locates the frequency doubling crystal at a high optical power density position to optimize frequency conversion efficiency. The VECSEL straight external-cavity structure achieves a frequency conversion efficiency of up to 60.2% at 488 nm, yielding a blue laser output exceeding 1.3 W. The full width at half maximum of the 488 nm spectrum measures approximately 0.23 nm. This intracavity beam-controlled direct external-cavity structure effectively mitigates laser mode leakage and shows potential for the development of an efficient and compact blue laser source.

IntroductionIn light-emitting diode (LED) and LASER colonoscopy, linked color imaging (LCI) and blue light/laser imaging (BLI) are used for lesion detection and characterization worldwide. We analyzed the difference of LCI and BLI images of colorectal lesions between LED and LASER in a multinational study.MethodsWe prospectively observed lesions with white light imaging (WLI), LCI, and BLI using both LED and LASER colonoscopies from January 2020 to August 2021. Images were graded by 27 endoscopists from nine countries using the polyp visibility score: 4 (excellent), 3 (good), 2 (fair), and 1 (poor) and the comparison score (LED better/similar/LASER better) for WLI/LCI/BLI images of each lesion.ResultsFinally, 32 lesions (polyp size: 20.0 ± 15.2 mm) including 9 serrated lesions, 13 adenomas, and 10 T1 cancers were evaluated. The polyp visibility scores of LCI/WLI for international and Japan-expert endoscopists were 3.17 ± 0.73/3.17 ± 0.79 (p = 0.92) and 3.34 ± 0.78/2.84 ± 1.22 (p < 0.01) for LED and 3.30 ± 0.71/3.12 ± 0.77 (p < 0.01) and 3.31 ± 0.82/2.78 ± 1.23 (p < 0.01) for LASER. Regarding the comparison of lesion visibility about between LED and LASER colonoscopy in international endoscopists, a significant difference was achieved not for WLI, but for LCI. The rates of LED better/similar/LASER better for brightness under WLI were 54.5%/31.6%/13.9% (International) and 75.0%/21.9%/3.1% (Japan expert). Those under LCI were 39.2%/35.4%/25.3% (International) and 31.3%/53.1%/15.6% (Japan expert). There were no significant differences in the diagnostic accuracy and the comparison score of BLI images between LED and LASER.ConclusionsThe differences of lesion visibility for WLI/LCI/BLI between LED and LASER in international endoscopists could be compared to those in Japanese endoscopists.

ObjectiveTo explore the feasibility, safety and effectiveness of the 450-nm blue diode laser (BL), novel blue laser in the treatment of upper tract urothelial carcinomas (UTUCs) and other lesions in a porcine model.Material and methodsFor in vitro experiment, the ureter tissue was vaporised and coagulated with BL, green-light laser (GL) and Ho:YAG laser (Ho). The efficiency, width and depth of vaporisation, and depth of coagulation were recorded and compared. For in vivo experiments, four swines weighing 70 kg were used. In the acute group, different modes of operations were performed to evaluate the thermal damage, perforation and bleeding. In the chronic group, the overall appearance of the ureter and laser wound healing were observed by the naked eyes and H&E staining 3 weeks after surgery.ResultsIn in vitro study, the BL showed a higher efficiency of tissue vaporisation and less tissue coagulation for fresh ureter compared to GL and Ho. In the in vivo study, the power of BL set at 7 W was better, and the thickness of thermal damage varied with different surgery types in the range of 74–306 μm. After 3 weeks, the wound healed well static in vaporisation (SV), moving vaporisation (MV) and H&E staining indicated mucosal healing rather than scar healing.Conclusion5–10W blue diode laser achieved a higher efficiency of tissue vaporisation and less tissue coagulation in a porcine model, indicating its potential application in the endoscopic surgery of UTUC as an optional device with high performance and safety.

A 450-nm blue laser may be suitable to treat benign prostate hyperplasia (BPH) due to its haemoglobin absorption characteristic. The present study compared a novel high-power 450-nm semiconductor blue laser with other lasers marketed for in vitro soft tissue ablation, to evaluate the safety and efficacy of the 450-nm laser in BPH surgery. With the in vitro tissues on an experimental platform in water, the vaporization efficiency and coagulation layer thickness of the novel 450-nm laser and commercially available 532-nm, 980-nm, and 1470-nm lasers were measured at the same power (120 W). The damage to the adjacent tissue and the working noise were also measured. The vaporization efficiency was proved to be 450-nm laser > 532-nm laser > 1470-nm laser > 980-nm laser. Comparison of coagulation layer thickness was as follow: 980-nm laser > 1470-nm laser > 532-nm laser > 450-nm laser. The degree of tissue damage caused by the 450-nm and 532-nm lasers increased with the decrease in distance and increase in time (these are safe when a sufficient distance and short irradiation time are maintained). The heating ability of 980-nm and 1470-nm lasers was much greater than that of 450-nm and 532-nm lasers. The working noise was lower in 450-nm and 1470-nm lasers. The novel 450-nm laser has the advantages of highly efficient tissue vaporization, creating a thin coagulation layer, and low working noise. These characteristics suggest that the novel 450-nm laser may be a promising choice for the surgical treatment of BPH.

The advent of Blue LASER technology in otorhinolaryngology has transformed the management of various ear, nose and throat (ENT) disorders. Its distinct wavelength (445 nm) offers superior tissue selectivity, minimizing collateral damage and optimizing surgical outcomes compared to traditional LASERs. Blue Light LASER’s ability to target haemoglobin and melanin reduces intraoperative bleeding, scarring, and thermal damage. Its precision and versatility make it a valuable tool in addressing complex ENT pathologies. However, limitations, such as shallow penetration and potential risks of thermal damage, necessitate careful application. While it requires specialized training and consideration of its limitations, its benefits in reducing complications and improving recovery times highlight its potential in modern surgical practices. The article aims to analyse the key characteristics of Blue LASER in ENT pathology, presenting also a case of a 57-year-old male with lingual tonsil hypertrophy and obstructive sleep apnea who underwent Blue LASER surgery for tongue base reduction.CONCLUSION. Blue LASER technology ushers in a new era in ENT surgery. However, a thorough evaluation of its benefits and limitations is crucial to fully harness its potential in clinical applications.

The need for thin foil welding is increasing significantly, particularly in the electronic industries. The technologies that are currently available limit the joining processes in terms of materials and their geometries. In this paper, a series of trials of fusion welding (bead-on- plate) of commercially pure titanium (CPTi) foils were conducted using a blue diode laser (BDL) welding method. The power used was 50 W and 100 W for 0.1 mm and 0.2 mm thick foils, respectively. Following welding, various samples were prepared to examine the weld profiles, microstructures, hardness, tensile strength, and fracture surface characteristics. The results showed that the base metal (BM) had an annealed microstructure with equiaxed grains, while the weld zones contained martensite (α’) with large grains. The hardness increased in both regions, from around 123 HV to around 250 HV, in the heat-affected zone (HAZ) and fusion zone (FZ) areas. The tensile tests revealed that the strengths of the welded samples were slightly lower than the unwelded samples, i.e., UTS = 300–350 MPa compared with 325–390 MPa for the unwelded samples. Fracture took place within the BM area. All of the samples, welded and unwelded, showed identical fracture mechanisms, i.e., microvoid coalescence or ductile fracture. The weld zone experienced very small strains (elongation) at fracture, which indicates a good weld quality.