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Sensing characteristics of long period grating by writing directly in SMF-28 based on 800?nm femtosecond laser pulses
摘要： A long period grating is fabricated in standard SMF-28 ?bers without hydrogen loading by adopting point-by-point direct writing based on femtosecond laser pulses with 800 nm wavelength and 100 fs pulse width. Its sensing characteristics is investigated and the sensing sensitivities to temperature, external refractive index (RI) and strain are systematically examined as well. The experimental results show that the sensing sensitivity of the long period grating to temperature, RI and strain is about 124 pm/°C with a linearity of 0.989 within temperature ranging from 20 °C to 800 °C, ?582.5 nm/RIU (refractive index unit) with a linearity of 0.998 in the RI ranging from 1.342 to 1.380, and ?9.45 × 10-4 dB/με with a linearity of 0.98 in the strain ranging from 0 to 2925 με, respectively. The high sensitivity of prepared LPG will have potential application values in sensing measurement of multi-parameters and in the ?eld of high temperature and harsh environments detection.
关键词： Refractive index (RI),Long Period Gratings (LPGs),Femtosecond laser,Strain sensing,Temperature sensitivity
更新于2025-09-12 10:27:22
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Femtosecond Laser Synthesis of Luminescent Carbon Dots from Toluene
摘要： Products of reactions in toluene induced by nonlinear absorption of femtosecond laser pulses are studied. Laser synthesis of carbon dots with characteristic sizes of several nanometers and luminescence in the visible spectrum is demonstrated. A relation between synthesis conditions, morphology, and composition of carbon dots and their optical properties is established. The possibility of single-stage laser synthesis of polyethylene glycol passivated carbon dots having an enhanced quantum yield and improved spectral characteristics of luminescence is demonstrated. The results of the work open up new opportunities for obtaining promising carbon nanomaterials and optimizing their optical properties through the use of femtosecond laser pulses.
关键词： carbon dots,luminescence,toluene,femtosecond laser,polyethylene glycol
更新于2025-09-12 10:27:22
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Pulse-Propagation Modeling and Experiment for Femtosecond-Laser Writing of Waveguide in Nd:YAG
摘要： In this work, unidirectional pulse propagation equation (UPPE) modeling is performed to study the nonlinear laser-mater interaction in silicon and Nd:Y3Al5O12 (Nd:YAG) crystals. The simulation results are validated with reported experimental results for silicon and applied to Nd:YAG crystals with experimental validation. Stress-induced waveguides are written in Nd:YAG crystals using 515 nm, 300 fs pulses at a 1 kHz repetition rate. Waveguides having a mean propagation loss of 0.21 ± 0.06 dB/cm are obtained, which is lower than the previous reported values for Type-II waveguides written in Nd:YAG crystals. The modeling and experimental results consistently show that the modi?cation (waveguide track) depth increases with input energy. A detailed analysis is presented to control the modal properties of the waveguide in the context of UPPE simulation.
关键词： stress-induced waveguide writing,nonlinear pulse propagation,femtosecond laser writing,Nd:YAG crystal
更新于2025-09-12 10:27:22
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Tribological performance of metal-reinforced ceramic composites selectively structured with femtosecond laser-induced periodic surface structures
摘要： The impact of femtosecond (fs) laser-induced periodic surface structures (LIPSS) on tribological properties was investigated for metal-reinforced ceramic composites (Al2O3-ZrO2-Nb). For this purpose, the metallic niobium (Nb) phase was selectively structured with LIPSS in an air environment with different values of the fs-laser peak fluence by near-infrared fs-laser radiation (λ = 1,025 nm, τ = 300 fs, frep = 1 kHz), taking advantage of the different light absorption behavior of ceramic and metal. The tribological performance was evaluated by reciprocating sliding tests in a ball-on-disc configuration using Ringer’s solution as lubricant. The surfaces were characterized before and after laser irradiation by optical microscopy, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy and by measuring the contact angle with Ringer’s solution. The LIPSS formation resulted in an increased wetting of the surface with the lubricant. Moreover, the selectively structured composite surfaces revealed a coefficient of friction significantly reduced by a factor of ~ 3 when compared to the non-irradiated surface. Furthermore, the formation of a laser-induced oxidation layer was detected with NbO as the most prominent oxidation state. Selectively structured composites with outstanding mechanical properties and enhanced tribological performance are of particular interest for biomedical applications.
关键词： femtosecond laser-induced periodic surface structures (LIPSS),tribology,wettability,ceramic matrix composites,coefficient of friction,selective surface structuring
更新于2025-09-12 10:27:22
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Femtosecond Laser Written Depressed-Cladding Waveguide 2 × 2, 1 × 2 and 3 × 3 Directional Couplers in Tm3+:YAG Crystal
摘要： Ion-doped crystal-based compact devices capable of beam splitting and coupling are enthralling for a broad range of classical and quantum integrated photonics applications. In this work, we report on the fabrication of depressed-cladding waveguide 2D 2×2, 1×2 and 3D 3×3 directional couplers in Tm3+:YAG crystal by femtosecond laser writing. The performances of the couplers are characterized at 810 nm, showing single-mode guidance, polarization independence, ?nely matched splitting ratios. These results open up new opportunities in the bene?cial fabrication of 3D circuits and devices in crystals.
关键词： crystal,femtosecond laser writing,directional coupler,depressed-cladding waveguide,integrated photonics,yttrium aluminum garnet,quantum memory
更新于2025-09-12 10:27:22
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Leak in the curved suction contact glass of a femtosecond laser during small-incision lenticule extraction
摘要： We report a case of a leak in the curved suction contact glass of a VisuMax femtosecond laser that occurred during small-incision lenticule extraction (SMILE). As a result, creation of the anterior surface of the lenticule was not complete. One month later, a cap was created using the flap mode; the flap side cut was manually stopped after the flap cut was made. After laser in situ keratomileusis flap creation, the refractive lenticule was manually removed using microforceps, similar to the uneventful SMILE procedure. To our knowledge, this is the first report of a leak in the curved suction contact glass during SMILE that was successfully treated.
关键词： femtosecond laser,small-incision lenticule extraction,leak,suction contact glass,SMILE
更新于2025-09-12 10:27:22
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Plasma formation and relaxation dynamics in fused silica driven by femtosecond short-wavelength infrared laser pulses
摘要： Laser-induced plasma formation and subsequent relaxation in dielectric solids is the precursor to structural modi?cations serving as the basis for direct laser writing of functional optical micro- and nanostructures. Based on an experimental arrangement combining a time-resolved transmission measurement with a cross-phase modulation measurement, we isolate the plasma formation and relaxation dynamics in the bulk of amorphous fused silica excited by femtosecond short-wavelength infrared (k ? 2100 nm) laser pulses. Whereas the relaxation time of the generated subcritical electron-hole plasma was so far assumed to be constant, our ?ndings indicate an intensity-dependent relaxation time. We attribute this intensity dependence to vibrational activation of the medium, leading to detrapping of trapped carriers and a reduced trapping probability.
关键词： plasma formation,femtosecond laser pulses,relaxation dynamics,fused silica,short-wavelength infrared
更新于2025-09-12 10:27:22
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Tomographic analysis of anterior and posterior surgically induced astigmatism after 2.2?mm temporal clear corneal incisions in femtosecond laser–assisted cataract surgery
摘要： To evaluate surgically induced astigmatism (SIA) of temporal clear corneal incisions (CCIs) on anterior and posterior corneal curvature after femtosecond laser–assisted cataract surgery (FLACS) using Scheimpflug tomographic measurements.
关键词： clear corneal incisions,Scheimpflug tomography,femtosecond laser–assisted cataract surgery,surgically induced astigmatism
更新于2025-09-12 10:27:22
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Femtosecond-Laser-Induced Precipitation of CsPbBr3 Perovskite Nanocrystals in Glasses for Solar Spectral Conversion
摘要： Inorganic perovskite quantum dots (QDs) and nanocrystals (NCs) have attracted much attention in recent years because of their high photoluminescence quantum yield (PL QY), narrow full width at half maximum, and wide tunability cross the whole visible range. In this work, space- and size-controlled precipitation of CsPbBr3 perovskite NCs was realized through femtosecond laser direct writing method. Precipitation of CsPbBr3 NCs in glasses was confirmed by the energy dispersive spectroscopy, transmission electron microscope analysis and photoluminescence (PL). Growth of CsPbBr3 perovskite NCs in glass was modulated by fs laser irradiation parameters such as repetition rate, pulse energy, and scanning rate, and PL in the range spanning from blue to green was achieved. With well-designed arrangement of CsPbBr3 NCs and the reduction of self-absorption emission, solar concentrator fabricated by fs laser irradiation can realize the spectral conversion and enhance the quantum efficiency of solar cells.
关键词： Glass,All-inorganic perovskite,Spectral conversion,Solar concentrator,Femtosecond laser,Photoluminescence,CsPbBr3,Nanocrystals
更新于2025-09-12 10:27:22
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Multi-Purpose Nanovoid Array Plasmonic Sensor Produced by Direct Laser Patterning
摘要： We demonstrate a multi-purpose plasmonic sensor based on a nanovoid array fabricated via inexpensive and highly-reproducible direct femtosecond laser patterning of thin glass-supported Au films. The proposed nanovoid array exhibits near-IR surface plasmon (SP) resonances, which can be excited under normal incidence and optimised for specific applications by tailoring the array periodicity, as well as the nanovoid geometric shape. The fabricated SP sensor offers competitive sensitivity of ≈ 1600 nm/RIU at a figure of merit of 12 in bulk refractive index tests, as well as allows for identification of gases and ultra-thin analyte layers, making the sensor particularly useful for common bioassay experiments. Moreover, isolated nanovoids support strong electromagnetic field enhancement at lattice SP resonance wavelength, allowing for label-free molecular identification via surface-enhanced vibration spectroscopy.
关键词： refractive index and gas sensing,nanovoid arrays,direct femtosecond laser printing,plasmonic sensors
更新于2025-09-12 10:27:22