- 标题
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- 实验方案
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Nanotube mode-locked, wavelength and pulsewidth tunable thulium fiber laser
摘要： Mode-locked oscillators with highly tunable output characteristics are desirable for a range of applications. Here, with a custom-made tunable filter, we demonstrate a carbon nanotube (CNT) mode-locked thulium fiber laser with widely tunable wavelength, spectral bandwidth, and pulse duration. The demonstrated laser’s wavelength tuning range reached 300 nm (from 1733 nm to 2033 nm), which is the widest-ever that was reported for rare-earth ion doped fiber oscillators in the near-infrared. At each wavelength, the pulse duration can be regulated by changing the filter’s bandwidth. For example, at ~1902 nm, the pulse duration can be adjusted from 0.9 ps to 6.4 ps (the corresponding output spectral bandwidth from 4.3 nm to 0.6 nm). Furthermore, we experimentally and numerically study the spectral evolution of the mode-locked laser in presence of a tunable filter, a topic that has not been thoroughly investigated for thulium-doped fiber lasers. The detailed dynamical change of the mode-locked spectra is presented and we observed gradual suppression of the Kelly sidebands as the filter’s bandwidth is reduced. Further, using the polarization-maintaiing (PM) cavity ensures that the laser is stable and the output laser’s polarization extinction ratio is measured to exceed 20 dB.
关键词： thulium fiber laser,spectral bandwidth,polarization-maintaiing cavity,Kelly sidebands,tunable wavelength,pulse duration,Mode-locked oscillators,carbon nanotube
更新于2025-11-28 14:23:57
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nano structured films induced by laser plasma ionization deposition
摘要： This research explores the optical properties of a large group of silicon/silica nanofibrous thin films. A picosecond pulse laser was employed for indirect deposition of ablated silicon on glass substrates. Prominent parameters such as laser power, repetition rate, pulse duration and scanning speed were changed to vary the structural and compositional properties of synthesized nanofibrous thin films. Transmission and specular reflection measurements along with material characterization techniques, Raman and FTIR, were employed for better interpretation of the results. By and large, an increase in the values for repetition rate and scanning speed produced a corresponding increase in optical data intensity, while an increase in power and pulse duration produced a drop in the same data. The results show that degree of oxidation and inherent porous structure are driving the light interaction in thin samples, as indicated by the changes in intensity or spectrum shape. Observation of these trends enabled us to apply tunable fabrication procedures to obtain desired groups of nanofibrous thin films. Electron and optical microscopy as well as background knowledge certify tangled nano-wired morphology in most cases. Structures with highly desirable usages, such as in sensing technology, can be optimized by their porosity, density and thickness.
关键词： Optical spectroscopy,Thin film,Pulse duration,Pulsed laser,Nano-fibers
更新于2025-09-23 15:19:57
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Transition regime in the ultrafast laser heating of solids
摘要： Based on the phenomenological theory of heat diffusion, we show that the generated peak temperature Tmax after absorption of a laser pulse strongly depends on the pulse duration. We identify three different heat conduction regimes that can be identified via a simple parameter that depends only on the pulse duration and on material constants. The phenomenological approach is supported by numerical simulations of heat diffusion and measurements of the thermal surface expansion after transient grating excitation with 1 ps and 10 ns optical pulses.
关键词： laser heating,heat diffusion,thermal surface expansion,pulse duration
更新于2025-09-23 15:19:57
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[Laser Institute of America ICALEO?? 2014: 33rd International Congress on Laser Materials Processing, Laser Microprocessing and Nanomanufacturing - San Diego, California, USA (October 19a??23, 2014)] International Congress on Applications of Lasers & Electro-Optics - Laser ablation cutting of thin silicon subtrates with tunable ultra-short pulsed lasers from 200FS-10PS
摘要： In this paper the influence of the pulse duration in a range of 200 fs up to 10 ps on the cutting process of thin silicon is investigated. The experiments are carried out with a Light Conversion Pharos with various pulse duration between 190 fs and 10 ps. The laser is operated at the second harmonic wavelength of 515 nm and a repetition rate of 200 kHz. Although the ablation threshold, which is determined with the method of Liu [1], amounts 0.27 J/cm2 for 0.2, 1 and 10 ps, one can find extremely different ablation behavior during the cutting experiments. It turns out that independent from pulse energy and pulse overlap the shortest pulse duration at 200 fs leads to a deeper cutting depth and furthermore to a higher cutting speed. This difference can be explained with higher pulse peak intensities and shorter interaction time between laser and material for the 200 fs pulse duration. Nevertheless the general ablation geometry is very similar for all tested pulse durations. We explain this with a simple geometric model. This model considers the projection from a Gaussian beam profile in an existing cutting kerf.
关键词： cutting process,laser ablation,ultra-short pulsed lasers,pulse duration,thin silicon substrates
更新于2025-09-23 15:19:57
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Gas-vapor Interplay in Plasmonic Bubble Shrinkage
摘要： The understanding of the shrinkage dynamics of plasmonic bubbles formed around metallic nanoparticles immersed in liquid and irradiated by a resonant light source is crucial for the usage of these bubbles in numerous applications. In this paper we experimentally show and theoretically explain that a plasmonic bubble during its shrinkage undergoes two different phases: first, a rapid partial bubble shrinkage governed by vapor condensation and, second, a slow diffusion-controlled bubble dissolution. The history of the bubble formation plays an important role in the shrinkage dynamics during the first phase, as it determines the gas-vapor ratio in the bubble composition. Higher laser powers lead to more vaporous bubbles, while longer pulses and higher dissolved air concentrations lead to more gaseous bubbles. The dynamics of the second phase barely depends on the history of bubble formation, i.e. laser power and pulse duration, but strongly on the dissolved air concentration, which defines the concentration gradient at the bubble interface. Finally, for the bubble dissolution in the second phase, with decreasing dissolved air concentration, we observe a gradual transition from a R(t) ∝ (t0 ? t)1/3 scaling law to a R(t) ∝ (t0 ? t)1/2 scaling law, where t0 is the lifetime of the bubble and theoretically explain this transition.
关键词： dissolved air concentration,laser power,pulse duration,plasmonic bubbles,vapor condensation,shrinkage dynamics,diffusion-controlled dissolution
更新于2025-09-23 15:19:57
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Study of laser-driven magnetic fields with a continuous wave Faraday rotation diagnostic
摘要： Magnetic ?elds driven by a laser in coil targets were studied for laser energies of (cid:2)25 J and two pulse durations of 2.8 ns and 70 ps. Axial magnetic ?elds in the coils were measured by continuous wave Faraday rotation diagnostics. The diagnostics indicated magnetic ?elds of 6–14 T in the coil and currents of 10–20 kA. Magnetic ?elds were compared for similar laser targets, focusing conditions, and laser energies. A 30-times increase in the intensity of the laser beam by reducing the pulse duration resulted in an increase in the magnetic ?eld and current by a factor of 2. The relaxation time of the magnetic pulse was on the sub-microsecond scale.
关键词： coil targets,magnetic field measurement,laser-driven magnetic fields,pulse duration,Faraday rotation diagnostics
更新于2025-09-19 17:13:59
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Terahertz radiation emission from three-color laser-induced air plasma
摘要： Based on the photocurrent model, terahertz (THz) radiation generation in three-color (fundamental (ω), second-harmonic (2ω), and third-harmonic (3ω)) laser-induced air plasma is studied using particle in cell simulation. Our simulation results show that the amplitude of THz radiation in the three-color laser scheme is several times larger than the amplitude of THz radiation in the two-color laser scheme (fundamental (ω), second harmonic (2ω)). In addition, the effect of the phase difference between the first and second harmonics (?2) and the phase difference between the fundamental and third harmonics (?3) on THz generation is investigated in order to obtain the optimum conditions. It is indicated that the effect of ?3 on THz radiation strongly depends on ?2 in the three-color scheme and it is found that the THz radiation is maximum in the case with ?2 = π/6 and ?3 = π/6. The influence of laser wavelength and pulse duration on THz generation is also studied. Our results reveal that the THz radiation increases proportionally to the square of the laser wavelength. Moreover, it is shown that THz radiation increases by increasing pulse duration.
关键词： Photocurrent model,Particle in cell simulation,Phase difference,Pulse duration,Terahertz radiation,Laser wavelength,Three-color laser
更新于2025-09-19 17:13:59
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[Laser Institute of America ILSC? 2019: Proceedings of the International Laser Safety Conference - South Kissimmee, Florida, USA (March 18–21, 2019)] International Laser Safety Conference - Computer modelling to support laser safety analysis of pulse trains with varying peak power and pulse duration
摘要： Neither the international laser safety standard IEC 60825-1 Edition 3.0 nor the standard ANSI Z136.1-2014 provide specific rules on how to apply the pulse reduction factor C5 (resp. CP) to irregular pulse trains, featuring both varying peak power as well as varying pulse duration. Without specific guidance, the analysis has to be performed based on restrictive approaches, such as counting all pulses and giving them the same weight, even the ones with smaller peak power and lower energy. Preliminary work, presented at the ILSC 2017, focused on pulse trains with varying peak power. The present study provides guidance on how to analyze irregular pulse patterns - both in terms of peak power and pulse duration - in a less restrictive way.
关键词： peak power,IEC 60825-1,ANSI Z136.1,pulse duration,laser safety,pulse trains
更新于2025-09-16 10:30:52
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Effect of spectral filtering on pulse duration in dissipative soliton resonance (DSR) regime of modelocked fiber laser
摘要： The effect of spectral filtering on pulse duration in an all-normal-dispersion laser operating in a dissipative soliton resonance (DSR) regime is studied numerically and compared with the results obtained by solving the analytical expressions. It is observed that the spectral filtering reduces the pulse duration in the DSR regime. The numerically simulated trend of the variation of flat-top pulse duration as a function of the gain for different spectral transmission bandwidths of the filter shows good qualitative agreement with the experimental results.
关键词： modelocked fiber laser,pulse duration,spectral filtering,dissipative soliton resonance
更新于2025-09-16 10:30:52
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[Laser Institute of America ICALEO? 2014: 33rd International Congress on Laser Materials Processing, Laser Microprocessing and Nanomanufacturing - San Diego, California, USA (October 19–23, 2014)] International Congress on Applications of Lasers & Electro-Optics - ITO patterning using advanced green and infrared pulsed fiber lasers
摘要： Laser patterning of Indium Tin Oxide (ITO) deposited on bulk substrates enables a chemical waste free, high throughput process that is widely used in flat panel and touch panel display devices. To attain economic viability and meet the need for narrow touch sensor borders with high quality ITO patterning, the width, uniformity, and throughput of the scribing lines are key quality parameters. In this talk we report on the advances in pulsed nanosecond fiber lasers at wavelengths of 532 and 1064-nm with optimized parameters for meeting theses critical requirements. Specifically, near diffraction-limited beam quality, high peak power capabilities, short pulses, and fast transient response are necessary to produce consistent scribed lines in the order of 10?m in width with smooth edges. The results of our study demonstrate the advantage of using the IR laser as a robust, cost-effective solution for scribing lines with a width in between 15-25?m. However, the ability to focus the beam of the green laser more tightly makes it the preferred candidate for meeting the 10?m width target.
关键词： 1064nm,PRF,532nm,nanosecond,ITO patterning,peak power,pulse duration,fiber lasers,beam quality
更新于2025-09-16 10:30:52