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Beam optimization in a 25 TW femtosecond laser system for high harmonic generation
摘要： It has been demonstrated in the past that high fluxes of extreme ultraviolet (XUV) light could be obtained by driving high harmonic generation (HHG) with high energy lasers. However, the peak intensity at the focal point of a femtosecond laser with more than 100 mJ can be too high for phase-matched HHG in gases. We propose a method to optimize the spatial profile at focus by adding customized wavefront terms. An XUV pulse energy of 5.6 μJ was obtained from HHG when a larger off-focus spot of a 500 mJ Ti: Sapphire laser beam was applied in an argon gas cell.
关键词： wavefront correction,extreme ultraviolet,femtosecond laser,high harmonic generation,Ti: Sapphire laser
更新于2025-09-23 15:21:01
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Development of a continuously tunable titanium-sapphire laser system for the ARIEL laser ion source
摘要： A concept for continuously tunable titanium-sapphire (Ti:Sa) lasers using dispersion prisms is under investigation for the ARIEL (Advanced Rare IsotopE Laboratory) laser ion source at TRIUMF (Canada’s particle accelerator center). Wavelength selection for pulsed Ti:Sa lasers used in hot cavity laser resonance ionization spectroscopy is usually done with birefringent filters (BRFs) and etalons or diffraction gratings. For resonance ionization spectroscopy a laser system allowing a continuous wavelength scan is necessary. Tunable lasers based on BRFs and etalons have high output powers however require synchronized optimization for continuous laser wavelength scans and are therefore laborious to use in scanning applications. Diffraction grating tuned lasers can provide continuous wavelength scan over 200 nm range but typically have lower output laser power due to the grating deformation under high pumping power. Aiming to overcome both shortcomings a laser design based on prisms as dispersing element has been revisited. Simulations on the beam path and optical reflectivity are done which show that these losses can be minimized to around 0.04 % for a tuning range from 700 nm up to 920 nm. Further improvement on the tuning range and reduction on the linewidth will be pursued.
关键词： Titanium-sapphire laser,Tunability,Prisms
更新于2025-09-23 15:21:01
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[IEEE 2019 SBFoton International Optics and Photonics Conference (SBFoton IOPC) - Sao Paulo, Brazil (2019.10.7-2019.10.9)] 2019 SBFoton International Optics and Photonics Conference (SBFoton IOPC) - Evaluation of the Adhesive Strength in Dentin after Irradiation with Ti:Sapphire Ultrashort Laser Pulses
摘要： This study was done to evaluate whether the irradiation of dentine with ultrashort laser pulses prior to adhesive procedures contributes to increase the adhesive resistance to microtraction essays. Twenty-four human teeth (third molars) were used, divided into 4 groups (n=6): standard adhesive procedures with etch-rinse adhesive were used in the control group, and in the experimental groups, the dentin was irradiated by 25 fs pulses prior to the adhesive procedures, with varying fluences. One tooth from each group was used to evaluate its surface roughness. After 24h, the teeth were sectioned with perpendicular cuts, producing toothpicks that were submitted to the microtraction test. The results showed that the groups irradiated with fluences under 4 J/cm2 presented similar results among themselves, comparable to the control group, while the group irradiated with 8 J/cm2 showed lower adhesive strength. We propose that the adhesive strength and surface roughness reduction resulting from the fluence increase is probably related to the shielding arising from an electron plasma formation during the ablation, decreasing the material removal efficiency. Nevertheless, the lower energy densities did not affect the adhesiveness, maintaining values similar to the control.
关键词： dentin,femtoseconds laser pulses,microtensile bond strength,adhesion,Ti:Sapphire laser irradiation
更新于2025-09-19 17:13:59
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A comparative clinical trial to evaluate efficacy and safety of the 308‐nm excimer laser and the gain‐switched 311‐nm titanium:sapphire laser in the treatment of vitiligo
摘要： Background/purpose: Ultraviolet B (UVB) laser irradiation in a targeted manner is a reasonable treatment option for localized vitiligo. Recently, narrow‐band UVB gain‐switched 311‐nm titanium:sapphire lasers (TSL) were developed for the treatment of localized vitiligo. We aimed to compare efficacy, patient satisfaction, and safety between the conventional 308‐nm excimer laser (EL) and gain‐switched 311‐nm TSL in patients with vitiligo. Methods: The 13‐paired lesions from 10 patients who had small vitiligo patches were included in this prospective intra‐patient comparison trial. Each pair was randomly assigned to each laser treatment group and treated twice weekly for 12 weeks. The global photographic assessments by dermatologists, objective numerical assessments by imaging analyzer, and patient's satisfaction were used to evaluate the effectiveness. Adverse effects were also investigated at every visit. Results: All treated lesions showed improvement of about 50% after 12 weeks. There was no significant difference between EL‐ and TSL‐treated groups. Patient satisfaction and preference among the groups were also similar. Regarding safety, there were no serious adverse effects requiring cessation of the treatments; however, the severity score for persistent erythema (lasting >24 hours) was significantly lower in the TSL group than in the EL group. Conclusions: The gain‐switched 311‐nm TSL exhibited similar efficacy to the 308‐nm EL in treating vitiligo as well as improved safety. Therefore, the 311‐nm TSL is considered as a candidate device to replace the EL as a new and promising treatment option for localized vitiligo.
关键词： 308‐nm Excimer laser,gain‐switched 311‐nm titanium:sapphire laser,vitiligo
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Comparison of SC Fibers for fs Ti:Sapphire Based Hyperspectral CARS Microscopy
摘要： Hyperspectral coherent anti-Stokes Raman scattering (CARS) microscopy is a rapidly developing field enabling label-free, chemically selective bio-imaging based on Raman signatures. A significant factor limiting its clinical application is the complexity of current laser sources. A solution immediately relevant to two-photon excited fluorescence imaging laboratories is coherently broadening a fs Ti:Sapphire laser seed in a fiber to provide the Raman wavelengths via spectral-focusing (SF) CARS. The NKT fiber with two Zero Dispersion Wavelengths (ZDWs) is one option but the spectrum exhibits low Power Spectral Density (PSD) because of the large (>800 nm) spectral broadening. Here we perform the first systematic comparison sweeping (i) input pump power, (ii) pump wavelength and (iii) fiber length comparing the coherent SC from a femtoWHITE-CARS (2 ZDWs) fiber, a fiber with one ZDW offset above the seed wavelength, and an all-normal dispersion (ANDi) fiber. Starting with the seed laser polarisation aligned to a principal fiber axis, we show the total experimentally measured spectral output and importantly the polarisation resolved spectral component on the orthogonal axis, which is a measure of the nonlinear power-dependent depolarisation. This orthogonal component will degrade the efficiency of the CARS signal but still contributes to the bio-toxicity that limits the maximum power for imaging. Finally, we show representative SF-CARS microscopy images to showcase the power of this technique.
关键词： fiber optics,spectral-focusing,Ti:Sapphire laser,Hyperspectral CARS microscopy,supercontinuum generation
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Comparative Study of the Pump Beam Quality Effect on the Slope Efficiency in Kerr-Lens Mode-Locked Ti:Sapphire Laser
摘要： A comparative study of the pump beam quality effect on the slope efficiency in Kerr-lens mode-locked Ti:sapphire laser is presented. The Ti:sapphire laser is a very attractive candidate for ultrafast laser applications because of its broad emission bandwidth and high gain. The main factor that limits the efficiency of Ti:sapphire lasers is the poor absorption of the pump beam in the Ti:sapphire crystal. The pump beam quality is a key parameter for the efficiency of the laser. In this work, we compared a 1.0 μm green and a 1.0 μm from a green laser in order to investigate the effects of spatial beam properties on the pumping efficiency in a Ti:sapphire laser. The beam quality factors of green and green lasers were measured to be 1.2 and 1.1, respectively. After the special beam combination, the combined beam was focused into a 2-mm-long Ti:sapphire crystal. The focused beam diameters of the green and green lasers were 24 μm and 22 μm in the slow axis and 22 μm and 23 μm in the fast axis, respectively. The slope efficiency of 21.1% more for the green laser than the green laser was achieved. After the beam combination, the slope efficiency of 24.8% was achieved. The positive effect of higher beam quality on the slope efficiency was demonstrated.
关键词： pump beam quality,Kerr-lens mode-locking,Ti:sapphire laser,slope efficiency
更新于2025-09-12 10:27:22
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Experimental study of proton acceleration from thin-foil on a table top Ti:Sapphire
摘要： Table-top lasers of moderate energies (0.1- 0.5 J) are promising, cost-effective laser-driven sources of MeV-energy protons and ions accelerators, but many applications of laser-accelerated ion beams will not only require a low cost, compact system but also require operation at high repetition rates (>10 Hz). This paper focus the effort to characterize and optimize proton acceleration processes using 3 TW/55 fs, table-top Ti:Sapphire (Ti:Sa) laser capable to operate at 10 Hz, with this intention the maximum proton energy obtained, in a single shot, was evaluated by irradiating a variety of flat targets, from thin film to sub-micrometric film membranes designed for our purposes in a high density target array. The presented work is a previous stage and this study has the intention to be the prelude of the technological challenge, both in laser technology as well target design capable of operating at high repetition rates.
关键词： Ti:Sapphire laser,proton acceleration,thin-foil targets,high repetition rates
更新于2025-09-09 09:28:46