- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
[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) - Superfilament Spatial Dynamics and Energy Deposition under Various Focusing Conditions
摘要： One of the distinctive features of femtosecond laser ?lamentation is intensity and plasma concentration clamping. Arising due to the dynamical competition between Kerr focusing and plasma defocusing this phenomenon limits the peak intensity to the values 1014 W/cm2 and plasma concentration level to 1016 – 1017 cm?3. Further increase of the beam power leads to the beam splitting and multi?lament formation rather than to an intense single ?lament with high plasma density. However it have been recently shown that fusing several ?laments by introducing additional weak focusing one can obtain signi?cant enhancement of energy deposition in the extended region around the focus resulting in higher plasma concentration and intensity [1,2,3]. This report aims to present the comprehensive picture of super?lament evolution including its formation from merging ?laments and dissipation stages. We discuss energy deposition during the multi?lament evolution and its dependency of the pulse energy as well as the in?uence of additional focusing conditions on super?lament formation.
关键词： femtosecond laser ?lamentation,super?lament,energy deposition,plasma concentration,focusing conditions
更新于2025-09-12 10:27:22
-
[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) - Talbot Effect in Embedded Gratings Inscribed with Femtosecond Laser in Transparent Media
摘要： Since the first refractive index modification of transparent materials was achieved via femtosecond laser micromachining, the fabrication of bulk inscribed 3D optical elements has been insistently pursued. This method has been extensively used to generate a variety of photonic devices such as waveguides, couplers or amplifiers, which enabled a large number of technological breakthroughs. In particular, the fabrication of glass embedded volume-phase gratings (VPG) has been studied in detail by many authors. Currently, the process for manufacturing VPGs involves the use of dichromated gelatin hologram recording, which is accomplished sealing the gelatin between two layers of glass. Using femtosecond laser inscribing technique, VPGs can be fabricated in a more direct, robust and environmental friendly way. Only a few studies have been reported on the near-field diffraction properties of the femtosecond laser fabricated VPGs. Among the different peculiarities that are observed in the microscale propagation of the light, one of the most studied phenomenon is the Talbot effect or also called self-imaging. Caused by the interference of waves with quadratic relative phases, when a grating is illuminated with a collimated monochromatic light, exact images of the illuminated grating are formed at a distance (cid:1852)(cid:3021) = p2/λ, where p is the period of the grating. In this presentation, we will show the fabrication of an embedded grating that generates a high contrast Talbot effect. VPGs with periods of 10 (cid:80)m and different Q parameters are fabricated with a 500 kHz diode-pumped ultrafast fiber amplifier Satsuma system of λ=1030 nm. The VPGs are fabricated in fused silica and nanocrystal doped glass (OG530). It is observed that the width, thickness and refractive index profile of the generated modification zone depends on the laser processing conditions such as pulse energy, repetition rate or processing depth. The gratings are characterized with far-field diffraction measurements and microscopy images of the cross-sections. Also, the near-field intensity profiles generated by the VPGs are measured to visualize the Talbot effect (Fig. 1 a). The experimental setup for the near-field includes a collimated 633nm laser beam and a 20× microscope objective selectively displaced with a resolution of 5 μm. The Talbot planes are formed at a distances of the order of ~ 100 (cid:80)m. The dependence of the contrast of the intensity profiles on the VPG laser processing condition is analyzed. Our results show that high contrast Talbot effect is achieved when the phase difference generated by the VPG is optimized (Fig. 1 b)).
关键词： transparent media,self-imaging,volume-phase gratings,femtosecond laser,Talbot effect,embedded gratings
更新于2025-09-12 10:27:22
-
[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) - An Increase in Refractive Index Contrast in a Waveguide Inscribed in Tellurite Glass by Means of Sub-Nanosecond Bursts of Femtosecond Pulses
摘要： Femtosecond laser direct writing (FLDW) of waveguides in dielectric glasses and crystals is well-recognized technique for manufacturing of compact laser sources, optical sensors, labs-on-a-chip and optical chips for quantum computing [1]. For this technology the main obstacle to compaction of optical circuits and an increase in the number of elements on an optical chip is constraint of the refractive index contrast Δn between the core and the cladding of a waveguide that is given by the nature of FLDW. Insufficient RIC also restricts application of the depressed cladding waveguides in mid-IR due to mode leakage [2]. The largest ever-obtained refractive index change is associated with ion migration in a phosphate glass under the thermal regime of laser writing, and it is as high as +0.03 [3]. Recently we found that simultaneous actions of rarefaction and electronic excitation lead to enhanced negative refractive index change in the laser modified spots in silica glass and sapphire [4], wherein the required conditions were produced by a sub-nanosecond burst of femtosecond laser pulses. Here we report on FLDW of a low loss waveguide with enhanced refractive index contrast in 70TeO2-22WO3-8Bi2O3 glass inscribed by bursts of pulses with exponentially decaying amplitudes in each burst and pulse separation of 10 ps. The depressed cladding waveguide composing of 14 parallel tracks with reduced refractive index was inscribed at wavelength of 1030 nm (Fig.1.(a)). The maximum refractive index change Δn produced by train of ordinary pulses in the investigated glass was as high as -0.002 [2]. Mapping of refractive index change in tracks inscribed by the bursts with different burst energies and pulse separation intervals is shown in Fig.1(c) The range of the parameters was found for which the burst produced smooth tracks of negative refractive index change, and its amplitude is increased by factor of 3 in comparison with tracks inscribed by ordinary pulses. The maximum index change Δn was obtained with pulse separation interval of 10 ps. Beside enhanced refractive index change the burst train inscribed tracks with reduced cross section. That is, the track height is less at least by a factor of 3 in comparison with one inscribed by ordinary pulses under the same energy for a burst and an ordinary pulse (Fig1(a),(b)). We consider that the enhanced index change and the reduced track height are inevitably accompanied by strong localization of energy deposition through a reduction in peak pulse intensity that allowed avoiding destructive Kerr self-focusing. We consider that the new technique of FLDW paves the way for better confinement of radiation in a depressed cladding waveguide writing waveguides with well deterministic architectures. The increase in the waveguide non-linearity and extension of operation range to mid-IR is inevitably expected.
关键词： sub-nanosecond bursts,tellurite glass,depressed cladding waveguide,refractive index contrast,Femtosecond laser direct writing
更新于2025-09-12 10:27:22
-
[Laser Institute of America ICALEO? 2016: 35th International Congress on Applications of Lasers & Electro-Optics - San Diego, California, USA (October 16–20, 2016)] International Congress on Applications of Lasers & Electro-Optics - Controlling the wettability of stainless steel by surface texturing using a high power femtosecond fiber laser
摘要： In this work, stainless steel samples have been textured by a simple and fast one-step laser process. The particularity of this process is the use of an ultrashort pulsed laser technology, combining a high power pulses at high repetition rate. An improved productivity can thus be considered. Successive ablations by IR laser pulses allow to generate dual-scale surface structures. Hierarchical structures, composed of micro-hills on which are superimposed periodic nano-ripples, have been produced at the repetition rate of 50 kHz, by a repeated irradiation of a crossed pattern of parallel lines. In order to increase the process throughput, repetition rates of 100, 250 and 500 kHz have been tested. After an adaptation of the process parameters, topographies with the same dimensions of structures have been created. The presence of these structures modifies the wetting properties of the material. Immediately after laser irradiation the surface becomes hydrophilic; however this wetting state evolves to become superhydrophobic with contact angles higher than 160° and water droplets unable to adhere to the surface. The temporal evolution of the wettability results from the combination of the surface roughness and the chemical composition of this surface. The modeling of the wetting behavior of water droplet, deposited on grooves structures, shows the enhancement of the initial wettability of the surface.
关键词： wettability,superhydrophobic,femtosecond laser,stainless steel,surface texturing
更新于2025-09-12 10:27:22
-
Controllable fabrication of unidirectional liquid spreading surface through confining plasma eruption and femtosecond laser double pulses
摘要： The e?cient and simple fabrication of a self-driven, continuous, and controllable unidirectional liquid spreading surface is an enormous challenge. In this paper, we present a maskless, one-step, and controllable method to fabricate unidirectional high-speed liquid spreading surfaces. The method con?nes the eruption of plasma by using oblique glass and femtosecond (fs) laser double pulses. The oblique glass is used to regulate plasma density via plasma con?nement, and the double-pulse is used to control the ?nal processing energy by changing pulse delay. The gradient structure size can be controlled by adjusting the laser energy, pulse delay and the tilted glass angle. Moreover, It has even can both achieved a high-speed and unidirectional spreading. A 1 μL droplet ?ows approximately 7 mm in 640 ms with no increase of the corresponding width using the gradient grating structure fabricated under double pulses with a pulse delay of 1 ps. Using di?erent gradient channel assembly, a selective ?ow along designed direction can be achieved. The selective ?ow phenomenon is observed through customized liquid diode. By manufacturing continuous and adjustable gradient structure, the method is potential to control liquid ?ow in microsystem.
关键词： Wettability gradient surface,Liquid diode,Plasma con?nement,Unidirectional liquid,Double pulse,Femtosecond laser
更新于2025-09-12 10:27:22
-
Comparison of the selected parameters of the anterior segment of the eye between femtosecond laser-assisted cataract surgery, microincision cataract surgery, and conventional phacoemulsification
摘要： The purpose of our study was to compare the selected parameters of the anterior segment of the eye in patients after femtosecond laser-assisted cataract surgery (FLACS) with the results of microincision cataract surgery (MICS) and conventional phacoemulsi?cation surgery (CPS). This single-center prospective randomized comparative observational study included 87 patients. Patients were randomly selected into group A (FLACS), group B (MICS) and group C (control group). All the surgeries were performed by the same experienced surgeon. Preoperative and postoperative parameters were evaluated: best-corrected visual acuity (BCVA), endothelial cell density (ECD), endothelial cell loss percentage (ECL%), central corneal thickness (CCT), central anterior and posterior corneal astigmatism induction, posterior corneal elevation map were measured. Intraoperative parameters: effective phacoemulsi?cation time (EPT), balanced salt solution use (BSS use), total surgical time and suction time were analyzed. Examination was performed preoperatively and on the ?rst, seventh day, one and six months postoperatively. The follow up period was 6 months. There was no statistically signi?cant difference in BCVA, central anterior and posterior astigmatism induction between studied groups. The ECL% was statistically signi?cant lower in the group A on the 7th day, 1 month and 6-months postoperatively (P < .05). The CCT was statistically signi?cant lower in the group A and in the group B than in the group C on the 7th postoperative day (P = .002). However, in the 6 months follow-up there was no statistically signi?cant difference in the CCT between studied groups (P = .133). We observed statistically signi?cant difference in change of the posterior corneal elevation map at the periphery assessed within the 90° to 120°meridian range between group A, group B and group C at every timepoint postoperatively (P < .05). The EPT and BSS use were statistically signi?cant lower whilst total surgery time was statistically signi?cant higher in the FLACS group (P < .05). To conclude in the 6 months follow-up there was statistically signi?cant difference found between eyes undergoing FLACS, MICS and CPS with respect to the posterior corneal elevation map assessed within the studied range, ECL%, EPT, BSS use and total surgery time. Postoperative BCVA, central anterior and posterior astigmatism induction, CCT were comparable between studied groups.
关键词： conventional phacoemulsi?cation surgery,femtosecond laser-assisted cataract surgery,clinical outcomes,manual phacoemulsi?cation,intraoperative parameters,microincision cataract surgery
更新于2025-09-12 10:27:22
-
Femtosecond Laser-Assisted Deep Lamellar Descemet Membrane Endothelial Keratoplasty for the Treatment of Endothelial Dysfunction Associated With Posterior Stromal Scarring
摘要： To describe an alternative surgical approach, femtosecond laser-assisted deep lamellar Descemet membrane endothelial keratoplasty (Femto-DL-DMEK), for the treatment of posterior corneal stromal scarring associated with endothelial diseases. Case report of a 52-year-old man with pseudophakic bullous keratopathy and posterior corneal scarring secondary to viral endotheliitis who underwent Femto-DL-DMEK. The surgical technique was as follows: First, a manual lamellar dissection plane was created at approximately 75% to 85% depth through a 5.0-mm superior scleral incision. One week later, using a femtosecond laser, an intersecting posterior side cut of 8.2 mm diameter was created. Subsequently, the dissected posterior recipient disk was removed from the anterior chamber through a 3.2-mm limbal incision. Finally, an 8.0-mm DMEK graft was placed. The patient’s uncorrected distance visual acuity improved from 20/200 (0.15; decimal) preoperatively to 15/25 (0.6) after surgery; corrected distance visual acuity improved from 20/200 (0.15) to 20/25 (0.9) with a residual refraction of +1.0–0.50 at 140 degrees. Endothelial cell count was 2062 cell/mm2 6 months after surgery. No intra- or postoperative complications were noted. As long as the anterior and mid-stroma are unaffected, those with endothelial diseases associated with opacification of the posterior stroma can benefit from endothelial keratoplasty through a Femto-DL-DMEK procedure, avoiding all well-known drawbacks of penetrating keratoplasty.
关键词： posterior corneal scarring,cornea,endothelial failure,Femtosecond laser,endothelial keratoplasty,transplant,DMEK
更新于2025-09-12 10:27:22
-
Microfluidic Channels Fabrication Based on Underwater Superpolymphobic Microgrooves Produced by Femtosecond Laser Direct Writing
摘要： A strategy is proposed here to fabricate microfluidic channels based on underwater superpolymphobic microgrooves with nanoscale rough surface structure on glass surface produced by femtosecond (fs) laser processing. The fs laser-induced micro/nanostructure on glass surface is able to repel liquid polydimethylsiloxane (PDMS) underwater, with the contact angle (CA) of 155.5 ± 2.5° and CA hysteresis of 2.7 ± 1.5° to a liquid PDMS droplet. Such phenomenon is defined as the underwater “superpolymphobicity”. Microchannels as well as microfluidic systems are easily prepared and formed between the underwater superpolymphobic microgrooves-textured glass substrate and the cured PDMS layer. Because the tracks of the laser scanning lines are programmable, arbitrary-shaped microchannels and complex microfluidic systems can be potentially designed and prepared through fs laser direct writing technology. The concept of “underwater superpolymphobicity” presented here offers us a new strategy for selectively avoiding the adhesion at the polymer/substrate interface and controlling the shape of cured polymers, none of these applications can find analogs in previously reported superwetting materials.
关键词： femtosecond laser,microfluidic channels,underwater superpolymphobicity,microfluidic systems,PDMS
更新于2025-09-12 10:27:22
-
[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) - Femtosecond Laser Assisted Fabrication of Visible Wavelength All-Dielectric Nano-Membrane Metasurfaces
摘要： Metamaterials allow control and tailoring the optical response of natural materials to achieve unprecedented functionalities. These artificial electromagnetic media are engineered by structuring materials on a subwavelength scale. Metamaterials have conventionally been made out of noble plasmonic metals. Intrinsically, plasmonic metamaterials suffer from high energy dissipation due to ohmic losses at ultraviolet to visible spectral frequencies. Therefore, in recent years, all-dielectric resonant metamaterials typically made from high-index dielectrics have been explored widely as they can potentially alleviate such losses, while allowing similar functionalities. One of the factors constraining their widespread use is slow and high-cost production techniques required to achieve nanoscale structures across large areas in reasonable timescales. Here we demonstrate that laser direct writing can be used as a viable alternative to FIB and EBL for implementation of optical metasurfaces. Our proposed approach allows manufacturing all-dielectric metasurfaces with flexible geometry and high uniformity at mm2/min throughput rates. Laser direct writing relies on removing the material via irradiation with an intense light source producing a contaminant free nano-patterned surface. The patterning was performed using femtosecond laser pulses with a bandwidth centred at 515 nm (a second harmonic of the Yb:KGW laser). The laser beam was focused with a 0.6 NA objective lens producing a spot size of 430 nm. Optimized experimental conditions allowed us to fabricate arrays of holes directly in free-standing, 50 nm thick SiN membranes, which exhibit strong optical resonances in the visible spectral range. Each perforation is achieved with a single femtosecond laser pulse, providing for an area of 1×1 mm2 to be patterned within 10 minutes. Our writing technique allowed us to inscribe holes with sub-200 nm in diameter, which is well below the diffraction limit. The periods of arrays ranged from 300 to 1000 nm allowing us to achieve optical resonances in the visible with high resonance quality factors up to 46 (for a metasurface period of 520). Quality factor is defined here as Q = λR/Δλ, where λR is the reflection resonance wavelength and Δλ is the half-maximum linewidth). The asymmetry in the structure, which leads to polarization dependent resonance, stems from a linearly polarized laser beam resulting in asymmetric intensity distribution at the focal point. Although our proof of principle demonstration is limited to dielectric nanomembranes, this technique can be easily extended to fabrication of metasurfaces in semiconductors and metals due to the nonlinear character of femtosecond laser pulse interaction with materials. In conclusion, we have demonstrated feasibility and versatility of femtosecond laser processing for developing scalable optical metasurfaces.
关键词： metasurfaces,all-dielectric,optical resonances,femtosecond laser,metamaterials
更新于2025-09-12 10:27:22
-
A Monolithic Gimbal Micro-Mirror Fabricated and Remotely Tuned with a Femtosecond Laser
摘要： With the advent of ultrafast lasers, new manufacturing techniques have come into existence. In micromachining, the use of femtosecond lasers not only offers the possibility for three-dimensional monolithic fabrication inside a single optically transparent material, but also a means for remotely, and arbitrarily, deforming substrates with nanometer resolution. Exploiting this principle and combining it with flexure design, we demonstrate a monolithic micro-mirror entirely made with a femtosecond laser and whose orientation is tuned in a non-contact manner by exposing some part of the device to low energy femtosecond pulses. Given the non-contact nature of the process, the alignment can be very precisely controlled with a resolution that is many orders of magnitude better than conventional techniques based on mechanical positioners.
关键词： femtosecond laser machining,tunable optics,repositioning,integrated optics,monolithic,micro-optics,non-contact,fused silica,flexures
更新于2025-09-12 10:27:22