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Femtosecond Laser Electronic Excitation Tagging Velocimetry in a Large-Scale Hypersonic Facility
摘要： Femtosecond laser electronic excitation tagging (FLEET) is a nonintrusive optical diagnostic technique that has been demonstrated to provide direct measurement of velocity and other transport properties in unseeded air and nitrogen flows. A portable FLEET system that uses a single laser for production of N2 tracers and a single camera for tracking their motion in real time has been developed and deployed. The system performance for high-speed velocimetry in unseeded nitrogen flow has been evaluated at the AEDC Hypervelocity Wind Tunnel 9. Instantaneous velocity measurements at 1 kHz repetition rate were performed during 21 tunnel runs at Mach 10 and 14, both in freestream and in a turbulent boundary layer. The freestream velocities measured with FLEET displayed excellent agreement with the velocities computed using the standard Tunnel 9 data reduction methodology. The turbulent boundary-layer velocity profiles measured with FLEET also showed good agreement with PIV measurements and boundary-layer computational modeling.
关键词： nonintrusive optical diagnostic,Femtosecond laser electronic excitation tagging,velocimetry,FLEET,hypersonic flow
更新于2025-09-19 17:13:59
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3D polarization-dependent waveguide arrays in LiNbO3 crystal produced by femtosecond laser writing
摘要： Waveguide arrays are basic photonic elements in integrated optics. We propose a 3D hybrid-integrated waveguide array based on the femtosecond laser writing of lithium niobate (LiNbO3) crystals by engineering the layout of laser-induced tracks. The cross section of the structure is a cross-shaped geometry. The light propagation through this waveguide array shows polarization-dependent behaviors, which enables mode-coupling along either the vertical or the horizontal direction under excitation of linearly polarized light. This work opens new way to produce polarization-dependent optical devices in photonic systems by using femtosecond laser writing of LiNbO3.
关键词： Femtosecond laser writing,waveguide arrays,polarization-dependent devices,lithium niobate (LiNbO3)
更新于2025-09-19 17:13:59
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Femtosecond Laser-inscribed Non-volatile Integrated Optical Switch in Fused Silica based on Microfluidics-controlled Total Internal Reflection
摘要： We demonstrate a non-volatile optical power switch, fabricated by femtosecond laser inscription in a fused silica substrate, with switching operation based on microfluidics-controlled total internal reflection. The switch consists of crossed waveguides and a rectangular, high aspect ratio microfluidic channel, located at the waveguide crossing. The switching between total internal reflection and transmission at the channel wall is determined by the refractive index of the medium inside the channel. Femtosecond laser inscription allows for co-integration of low-loss optical waveguides and channels with smooth sidewalls and thus the fabrication of low insertion loss switches that are broadband and show low polarization dependent losses. The measured total internal reflection loss of the fabricated switch is about 1.5 dB at the wavelength 1550 nm. The loss due to transmission through the channel filled with refractive index matching liquid is about 0.5 dB. Detailed finite time domain and beam propagation method difference simulations of the switch’s performance indicate that the losses can be further reduced by optimizing its geometry, together with further adjusting the inscription parameters.
关键词： Fused silica,Non-volatile,Single mode waveguides,Total internal reflection,Microfluidics,Femtosecond laser inscription,integrated optical switch
更新于2025-09-19 17:13:59
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Combined Femtosecond Laser-Assisted Cataract Surgery and 27-Gauge Transconjunctival Sutureless Vitrectomy
摘要： Purpose. To report the outcomes of combined surgery using femtosecond laser-assisted cataract surgery (FLACS) and sutureless 27-gauge pars plana vitrectomy with intravitreal tamponade. Methods. This retrospective clinical study involved 23 eyes of 23 patients on whom combined vitreoretinal surgery was performed. Patients were initially given the femtosecond laser treatment that was performed after selection of capsulotomy and lens fragmentation patterns. The capsulotomy diameter was chosen as 4.9 mm in all patients. After the femtosecond laser, the sutureless phacovitrectomy procedure was performed. At the end of surgery, perfluoropropane or sterile air tamponade was applied. Results. The mean age of patients was 66.43 ± 7.61 (range, 54–83) years. Fifteen patients were females (65.2%). The mean follow-up was 16.09 ± 4.71 (range, 9–25) months. The most common surgical indication was epiretinal membrane (65.3%). The mean preoperative best-corrected visual acuity (BCVA) was 0.71 ± 0.44 (range, 1.7–0.3) logMAR, and the mean postoperative BCVA at 6 months was 0.16 ± 0.14 (range, 0.4–0) logMAR (p < 0.001). The mean target sphere refractive error was ?0.24 ± 0.16 (range, ?0.50–0.11) D, and the mean postoperative spherical equivalent refractive error was ?0.14 ± 0.39 (range, ?1.00–0.50) D at 6 months (p = 0.196). All intraocular lenses (IOLs) remained well centered in the capsular bag during surgery and follow-up. There was no iris capture, posterior synechiae, capsular opacification, or pseudophakic cystoid macular edema. The only complication related to femtosecond laser was two cases of subconjunctival haemorrhage related with suction. Conclusions. FLACS is a safe and effective technique providing the advantage of repeatable, precise capsulorhexis shape and size to achieve a well-centered and stable IOL postoperatively. These advantages can certainly improve the results of vitrectomy, especially in gas-filled eyes. FLACS and 27-gauge sutureless combined surgery may be a future trend in appropriate cases.
关键词： phacovitrectomy,epiretinal membrane,intravitreal tamponade,femtosecond laser-assisted cataract surgery,27-gauge transconjunctival sutureless vitrectomy
更新于2025-09-19 17:13:59
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Modulating Ca <sup>2+</sup> release in the dorsal root ganglion neurons using femtosecond laser
摘要： The calcium ion (Ca2+) is a ubiquitous second messenger that is responsible for regulating a wide range of cellular and biological processes, including cell proliferation and cell death, gene expression, muscle contraction and neurotransmission. Here, we demonstrate the change of intracellular Ca2+ release in dorsal root ganglion (DRG) neurons in vitro by femtosecond laser stimulation using confocal microscopy combined with special fluorescence probe Fluo-3/AM. The results showed that relative fluorescence intensity increased significantly after the axons of DRG neurons was performed with photostimulation. It demonstrated that femtosecond laser stimulation could affect the intracellular Ca2+ release in the sensory neurons and might be used to treat pain by modulating intracellular Ca2+ release in DRG neurons.
关键词： dorsal root ganglion (DRG) neurons,femtosecond laser stimulation,intracellular Ca2+
更新于2025-09-19 17:13:59
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A prospective comparative study on endothelial cell loss and morphology after femtolaser-assisted cataract surgery and phacoemulsification
摘要： Purpose To compare changes in endothelial cell count and morphology at 6 months follow-up in eyes undergoing femtosecond laser-assisted cataract surgery (FLACS) and conventional phacoemulsi?cation. Design Prospective, comparative and open-label study. Methods All consenting patients between 50 and 75 years of age with uncomplicated cataract underwent either FLACS [Catalys Precision Laser System (OptiMedica Corp.; Abbott Medical Optics)] or conventional phacoemulsi?cation [Bausch ? Lomb Stellaris(cid:3) (Rochester, USA)] based on their preference and were followed up on day 15 and at 2 and 6 months postoperatively. The endothelial cell count (ECC), % of hexagonal cells and coef?cient of variation were noted at baseline and at each follow-up visit and compared between groups. Results A total of 187 eyes of 187 patients (n = 98 in phaco vs. n = 89 in FLACS) were enrolled. At 15 days follow-up, there was a signi?cant decline in the endothelial cell count in both groups (187 ± 156 in phaco vs. 193 ± 240 in FLACS, p < 0.001). In the ECC remained stable (8% decline in phaco vs. 7.7% decline in femto, p = 0.87) till last follow-up at 6 months. The %hexagonal cells also decreased signi?cantly at 15 days post-op (p < 0.001) but did not show any change in subsequent visits. The coef?cient of variation in ECC did not change signi?cantly throughout the study period. Eyes with higher endothelial cell count at baseline tended to lose more cells (b = 25.7 cells/mm3, 95% CI 16–35 cells, p = 0.01) irrespective of age and type of surgery. Conclusions Both procedures are equally safe with < 10% ECC loss at 6 months. Longer studies are required to determine in?uence of FLACS on ECC.
关键词： Hexagonal cells,Phacoemulsi?cation,Endothelial cell count (ECC),Femtosecond laser-assisted cataract surgery (FLACS)
更新于2025-09-19 17:13:59
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In Vitro Bioactivity and Biocompatibility of Bio-Inspired Ti-6Al-4V Alloy Surfaces Modified by Combined Laser Micro/Nano Structuring
摘要： The bioactivity and biocompatibility play key roles in the success of dental and orthopaedic implants. Although most commercial implant systems use various surface microstructures, the ideal multi-scale topographies capable of controlling osteointegration have not yielded conclusive results. Inspired by both the isotropic adhesion of the skin structures in tree frog toe pads and the anisotropic adhesion of the corrugated ridges on the scales of Morpho butter?y wings, composite micro/nano-structures, including the array of micro-hexagons and oriented nano-ripples on titanium alloy implants, were respectively fabricated by microsecond laser direct writing and femtosecond laser-induced periodic surface structures, to improve cell adherence, alignment and proliferation on implants. The main di?erences in both the bioactivity in simulated body ?uid and the biocompatibility in osteoblastic cell MC3T3 proliferation were measured and analyzed among Ti-6Al-4V samples with smooth surface, micro-hexagons and composite micro/nano-structures, respectively. Of note, bioinspired micro/nano-structures displayed the best bioactivity and biocompatibility after in vitro experiments, and meanwhile, the nano-ripples were able to induce cellular alignment within the micro-hexagons. The reasons for these di?erences were found in the topographical cues. An innovative functionalization strategy of controlling the osteointegration on titanium alloy implants is proposed using the composite micro/nano-structures, which is meaningful in various regenerative medicine applications and implant ?elds.
关键词： bioinspired surfaces,biocompatibility,cell adherence,femtosecond laser,bioactivity,cell alignment,Ti-6Al-4V,LIPSS
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Nonlinear compression of ultra-high-power laser pulses
摘要： Nowadays the peak power of PW lasers is limited by the damage threshold of optical compressor diffraction gratings. A promising way to overcome the difficulty and increase peak power is to use an additional pulse shortening after optical compressor without significant energy loses. The discussed method is called CafCA – Compression after Compressor Approach. CafCA possesses three undisputed merits: simplicity and low cost, negligible pulse energy loss, and applicability to any high-power lasers without changing their optical schemes. The key idea of the approach is to broaden spectrum of powerful laser pulses exactly after grating compressor and correct spectral phase with help of reflected dispersion devices (chirped mirrors in particular). The idea has been known since the end of 1960s but its application to lasers with a peak power higher 1 TW has been restricted by a number of physical reasons. The reasons and ways of its overcoming are discussed in the paper. We analyze the recent experimental results that demonstrate the CafCA efficiency in the range up to 200 TW.
关键词： temporal compression,self-phase modulation,PW-level femtosecond laser pulses
更新于2025-09-19 17:13:59
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Comparison of Excimer Laser Versus Femtosecond Laser Assisted Trephination in Penetrating Keratoplasty: A Retrospective Study
摘要： Introduction: To compare the impact of non-mechanical excimer-assisted (EXCIMER) and femtosecond laser-assisted (FEMTO) trephination on outcomes after penetrating keratoplasty (PK). Methods: In this retrospective study, 68 eyes from 23 females and 45 males (mean age at time of surgery, 53.3 ± 19.8 years) were included. Inclusion criteria were one surgeon (BS), primary central PK, Fuchs’ dystrophy (FUCHS) or keratoconus (KC), no previous intraocular surgery, graft oversize 0.1 mm and 16-bite double running suture. Trephination was performed using a manually guided 193-nm Zeiss Meditec (EXCIMER group: 18 MEL70 excimer laser in the FUCHS, 17 KC) or 60-kHz IntraLaseTM femtosecond laser (FEMTO group: 16 FUCHS, 17 KC). Subjective refractometry (trial glasses) and topography analysis (Pentacam HR; corneal Casia SS-1000 AS-OCT; TMS-5) were performed preoperatively, before removal of the first suture (11.4 ± 1.9 months) and after removal of the second suture (22.6 ± 3.8 months). Results: Before suture removal, mean refractive/AS-OCT topographic astigmatism did not differ significantly between EXCIMER and FEMTO. After suture removal, mean refractive/astigmatism Pentacam/AS-OCT topographic was significantly higher (6.2 ± 2.9 D/7.1 ± 3.2 D/7.4 ± 3.3 D) than in the EXCIMER patients (4.3 ± 3.0 D/4.4 ± 3.1 D/4.0 ± 2.9 D) (p B 0.005). Mean corrected distance visual acuity increased from 0.22 and 0.23 preoperatively to 0.55 and 0.53 before or 0.7 and 0.6 after suture removal in the EXCIMER and FEMTO groups, respectively. Differences between EXCIMER and FEMTO were only pronounced in the KC subgroup. Conclusion: Non-mechanical EXCIMER trephination seems to have advantages regarding postoperative corneal astigmatism and visual acuity compared with FEMTO trephination, especially in KC. A bigger sample size and longer follow-up are needed to evaluate the long-term impact of EXCIMER and FEMTO trephination on postoperative topographic and visual outcomes.
关键词： Excimer,Visual acuity,Femtosecond,Laser,Penetrating keratoplasty,Ophthalmology,Astigmatism
更新于2025-09-19 17:13:59
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Influences of nanosecond pulse pre-irradiation on femtosecond laser damage resistance of gold pulse compression grating
摘要： The gold pulse compression gratings (PCG) used in the Bidirectional Grating Compressor (BGC) suffers a nano- and femtosecond dual pulses irradiation. In the case that the ns pre-pulse comes 10 nanoseconds early before the fs pulse, experiments were conducted to investigate damage behaviors under the dual pulse irradiation. 1-on-1 laser induced damage threshold (LIDT) of the ns–fs dual pulses and fs single pulse were tested and compared. Scanning Electron Microscope (SEM) was employed to capture damage onset and exam the damage macro- and micro-morphologies. The mono-shot method, comparison between the damage zone and spatial distribution of laser pulses, was employed to analyze the difference of the damage onset fluences for the two cases thoroughly. It was found that there is no degradation of laser damage resistance due to the ns pre-pulse. Instead, a slightly increase (～10%) of fs LIDT caused by the ns pre-pulse was found.
关键词： Femtosecond laser damage,Nano- and femtosecond dual beam processing,Nanosecond pre-pulse,Gold-coated pulse compression gratings,Bidirectional grating compressor
更新于2025-09-16 10:30:52