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Laser radiation impact on a solid surface and formation of micro- and nanostructures
摘要： The work is devoted to the problem of micro- and nanostructuring of the surface of solids as a result of exposure to laser radiation. The method of forming periodic surface structures by means of femtosecond laser processing is presented using the example of solving the problem of titanium structuring.
关键词： femtosecond laser processing,micro- and nanostructures,laser radiation,titanium structuring
更新于2025-09-12 10:27:22
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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) - Faster Femtosecond Laser Processing using a Dual-Focus SLM Emulated Lens
摘要： The generation of multiple beams is an established method to increase the processing speed of advanced laser-based material processing techniques. This multi-foci approach has shown promising results in laser micromachining, scanning microscopy, optical data storage, or optical tweezer arrays. Of particular interest is its application to manufacturing bigger objects where laser treatment is required over surfaces on the centimetre scale or larger. Using a Spatial Light Modulator (SLM), such parallelisation has been studied over the last few years by splitting the input beam into multiple beams (up to 1000 beams [1]) for simultaneous machining on a plane perpendicular to the propagation axis. This method is primarily based on holographic femtosecond laser processing [2] where computer-generated holograms (CGH) are displayed on an SLM. Further applications include phase distortion and lens aberration correction [3], or for four-dimension light shaping [4]. The SLM provides unique features for dynamic pulse shaping, more efficient use of the laser energy, or the machining of complex shapes.
关键词： spatial light modulator,laser micromachining,computer-generated holograms,dual-focus SLM,femtosecond laser processing
更新于2025-09-12 10:27:22
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Femtosecond Laser Surgery in Ophthalmology
摘要： This comprehensive, well-organized text encompasses the numerous applications of femtosecond lasers to anterior segment surgery. From the use of laser-assisted in situ keratomileusis flap creation, cataract surgery, and even femtosecond-assisted keratopigmentation, this text thoroughly reviews all aspects of technology, leaving no application uncovered, highlighting the great versatility and potential of this technology. Each of the chapters is written by 1 to 3 experienced ophthalmic surgeons, and the text is well edited to assure completeness and prevent redundancy.
关键词： anterior segment surgery,femtosecond laser,laser-assisted in situ keratomileusis,ophthalmology,cataract surgery
更新于2025-09-12 10:27:22
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6 GHz electromagnetic wave guiding along a femtosecond laser plasma filament
摘要： To study the electromagnetic (EM) wave guiding performance of the plasma filament generated by the intense femtosecond (fs) laser pulse, a 3D physical model of the wave-plasma interaction is built and discussed with the commercial simulation software XFDTD. Then, an experiment is conducted to verify the EM wave guiding performance of the fs laser plasma filament. Our investigation illustrates that the 6 GHz EM wave can propagate along the fs plasma filament, making the EM field enhance out of the rectangular waveguide and attenuate in the rectangular waveguide. Besides, the filament can cause 4.74 dB enhancement of the wave energy relative to freely propagating the signal. Furthermore, the experimental result indicates that the guiding performance of the plasma filament on the TE polarization wave is better than that on the TM one, which is consistent with the theoretical result. For TE polarization wave, the plasma filament can reduce the microwave signal in the waveguide, which is lesser than that of the Cu wire in the experiment. The research results confirm that the fs laser plasma filament can guide the EM wave with a better performance relative to freely propagating the signal.
关键词： waveguide,guiding,plasma filament,femtosecond laser,EM wave
更新于2025-09-12 10:27:22
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Simultaneous 3-D Surface Profiling of Multiple Targets by Repetition Rate Scanning of a Single Femtosecond Laser
摘要： We present an integrated scheme of 3-D surface profile measurements made at multiple sites concurrently by employing only a single fiber femtosecond laser as the common light source of low coherence scanning interferometry. This versatile use of an ultrashort mode-locked laser is enabled by linear scanning control of the pulse repetition rate on the source site, while diverse forms of unequal-path, non-symmetric measurements are taken with nanometer precision for different targets simply by delivering fr-scanned pulses through a fiber network. This proposed scheme has no restriction on the number of interferometer sites being integrated concurrently, allowing more diverse industrial applications of ultrashort lasers despite increased system cost and complexity.
关键词： Surface profiling,Low coherence scanning interferometry,Repetition rate scanning,Multiple targets,Femtosecond laser
更新于2025-09-12 10:27:22
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A New Optical Angle Measurement Method Based on Second Harmonic Generation with a Mode-Locked Femtosecond Laser
摘要： This paper proposes a new optical angle measurement method based on second harmonic generation with a mode-locked femtosecond laser source by taking use of the unique characteristic of high peak power and high-intensity electric field of the femtosecond laser pulses. The angle is measured from the second harmonic wave intensity, which is a function of the angle between the laser beam axis and the optic axis of a nonlinear crystal attached to the target of interest. It is found that the beta barium borate (BBO) crystal is suitable as the nonlinear crystal for this purpose through theoretical simulation. As the first step of research, an experimental demonstration is also carried out in such a way that a change of the second harmonic wave intensity due to the angular displacement of BBO crystal is measured to verify the feasibility of the proposed principle of the angle measurement method.
关键词： Angle measurement,Second harmonic generation,Femtosecond laser
更新于2025-09-12 10:27:22
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Mass Producible Low-Loss Broadband Optical Waveguides in Eagle2000 by Femtosecond Laser Writing
摘要： Optical waveguides were fabricated in alkaline earth boro-aluminosilicate glass, by femtosecond laser direct writing, with varying pulse energy and scan velocity. A spectral characterization, from 500 nm to 1700 nm, was made in order to determine their losses and understand its dependence on the processing parameters. Three major loss mechanisms were identified. At longer wavelengths, loss is mainly due to weak coupling. On the other hand, the behavior at shorter wavelengths is governed by propagation loss due to Rayleigh scattering, which was shown to be practically eliminated (<0.05 dB· cm?1· μm4) at higher scan velocities. Bulk absorption was also found to have an influence in the propagation losses at higher wavelengths. The combination of intermediate pulse energies (between 125-250 nJ) and high scan velocities (above 6 cm/s) allowed the fabrication of optical waveguides offering low losses across the entire range of wavelengths tested, facilitating applications that require larger wavelength working bands. Furthermore, since optimal fabrication conditions are achieved at higher scanning velocities, mass production with reduced fabrication times can be achieved.
关键词： femtosecond laser direct writing,Rayleigh scattering,propagation loss,Coupling loss,Mie scattering,integrated optics,low-loss broadband optical waveguides,mass production
更新于2025-09-12 10:27:22
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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) - Stitchless Support-Free Fabrication of Free-Form Micromechanical Structures using Femtosecond Laser 3D Lithography
摘要： Femtosecond laser based 3D nanolithography is gaining popularity in huge variety of fields. However, further improvements are needed to push it from laboratory level use into a wide spread adaptation. These include increasing fabrication throughput without sacrificing quality of a final product and making the most challenging, free-movable 3D structures easy to print. In this work we present several advances needed to achieve these goals. First, linear stage and galvo-scanners synchronization is employed to produce stitch-free mm-sized structures with features down to micrometers. Furthermore, resolution bridge method is used to determine feature sizes acquired by varying objective numerical apertures (NA) from 0.8 NA to 1.4 NA. This way voxel size can be tuned in the range from 330 nm to 1.7 μm in transverse and 1.9 μm to 7.9 μm in longitudinal directions. At 1 cm/s translation velocity it results in voxel volumes from 0.017 μm3 to 3.759 μm3 with structuring rates at 2426 μm3/s and 104767 μm3/s respectively. This two orders of magnitude tunability is exploited to fabricate various functional structures. For instance, deformable microcantilevers and microsprings capable of sustaining multiple deformation cycles were created using 0.8 NA objective chosen for faster printing with acceptable resolution. Performance and longevity of these elements were characterized in both qualitative and quantitative manner. Furthermore, the hard gel form of the SZ2080 photopolymer used in this work allowed to perform support-free structuring of free-movable micromechanical components employing high-resolution structuring achievable with 1.4 NA objective. Possibility to forgo usage of supports needed with liquid resins eliminates the need to remove supports after printing making the whole process simpler. To demonstrate the potency of this approach movable mm-sized micromechanical spider and squid were fabricated, showing possibility to print true 3D hinge-like microstructures (feature size down to micrometers). Such structures have huge potential in the fields of sensors and microrobotics as mechanically induced deformation of movement can be employed as either means to detect outside force or provide a basis for self-propelling functional structures.
关键词： micromechanical structures,free-movable 3D structures,support-free structuring,Femtosecond laser,3D nanolithography
更新于2025-09-12 10:27:22
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Simulation of Self-focusing of Femtosecond Laser Pulses with Normal Dispersion in Air Using the Diffraction-Beam Tube Approach
摘要： Based on numerical simulation and qualitative analysis, the effect of the group velocity dispersion on the formation of light structures during self-focusing and filamentation of femtosecond Ti:sapphire laser pulses in air is studied. The main features of the filamentation have been determined at various pulse duration, initial beam radii, and peak radiation powers based on the results of numerical solutions of the nonlinear Schr?dinger equation in a Kerr-plasma dissipative dispersion medium and using the diffraction-beam tube approach. Dispersion is detected in the cases where the dispersion length is not a minimum at the scale of the process. It is shown that the relative (normalized to Rayleigh length) coordinate of the beginning of filamentation increases as the dispersion distortions of the pulse increase, and the filamentation channel length is reduced. For shorter laser pulses (tens of femtoseconds), the filamentation ceases as the laser beam radius increases. The size of the energy-replenishing diffraction-beam tube and the angular divergence of postfilamentation light channels increase for this class of pulses.
关键词： filamentation,self-focusing,femtosecond laser pulses,diffraction-beam tube,normal dispersion
更新于2025-09-12 10:27:22
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Controlling multiphoton excited energy transfer from Tm <sup>3+</sup> to Yb <sup>3+</sup> ions by a phase-shaped femtosecond laser field
摘要： The ability to control the energy transfer in rare-earth ion-doped luminescent materials is very important for various related application areas such as color display, bio-labeling, and new light sources. Here, a phase-shaped femtosecond laser field is first proposed to control the transfer of multiphoton excited energy from Tm3+ to Yb3+ ions in co-doped glass ceramics. Tm3+ ions are first sensitized by femtosecond laser-induced multiphoton absorption, and then a highly efficient energy transfer occurs between the highly excited state Tm3+ sensitizers and the ground-state Yb3+ activators. The laser peak intensity and polarization dependences of the laser-induced luminescence intensities are shown to serve as proof of the multiphoton excited energy transfer pathway. The efficiency of the multiphoton excited energy transfer can be efficiently enhanced or completely suppressed by optimizing the spectral phase of the femtosecond laser with a feedback control strategy based on a genetic algorithm. A (1 + 2) resonance-mediated three-photon excitation model is presented to explain the experimental observations. This study provides a new way to induce and control the energy transfer in rare-earth ion-doped luminescent materials, and should have a positive contribution to the development of related applications.
关键词： energy transfer,rare-earth ions,femtosecond laser,luminescent materials,multiphoton absorption
更新于2025-09-12 10:27:22