共查询到20条相似文献,搜索用时 0 毫秒
1.
A. V. Kuznetsov A. S. Kuzakov E. F. Martynovich 《Bulletin of the Russian Academy of Sciences: Physics》2016,80(1):64-67
The formation of fluorescent channels with color centers in LiF crystals under the action of the multiple filamentation of femtosecond laser pulses is studied experimentally and theoretically for pulse powers around four orders of magnitude higher than the critical self-focusing value. 相似文献
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A. A. Ionin S. I. Kudryashov S. V. Makarov L. V. Seleznev D. V. Sinitsyn 《JETP Letters》2009,90(6):423-427
The propagation of focused femtosecond laser pulses with supercritical peak powers in air has been investigated by the methods
of optical visualization, profilometry, and calorimetry. Laser pulses with supercritical powers create a bundle of submillimeter
filaments with a diameter of about 5 μm ahead of the lens focus; the maximum number of filaments in the beam cross section
and their length increase linearly and sublinearly, respectively, with the radiation peak power. The optical visualization
and calorimetry indicate that the plasma channels of filaments are optical contrast (a plasma density of 1018–1019 cm−3), ensuring the refraction of laser radiation incident on them. 相似文献
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Shock-wave generation upon axicon focusing of femtosecond laser radiation in transparent dielectrics
A. A. Babin A. M. Kiselev D. I. Kulagin K. I. Pravdenko A. N. Stepanov 《JETP Letters》2004,80(5):298-302
It is shown experimentally that the axicon focusing of intense femtosecond laser pulses in transparent dielectrics leads to efficient excitation of shock waves. A method is developed for measuring the dynamics of shock waves, which uses a frequency-chirped probe pulse and has high spatial (~1 μm) and time (~10 ps) resolutions. The initial stage of the evolution of an intense (up to 10 GPa) shock wave is studied by this method. 相似文献
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We report on a systematic study of the laser polarization effect on a femtosecond laser filamentation in air.By changing the laser's ellipticity from linear polarization to circular polarization, the onset position of laser filament formation becomes farther from the focusing optics, the filament length is shorter, and less laser energy is deposited. The laser polarization effect on air filaments is supported by a simulation and analysis of the polarization-dependent critical power and ionization rates in air. 相似文献
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V. Jukna J. Galinis G. Tamosauskas D. Majus A. Dubietis 《Applied physics. B, Lasers and optics》2014,116(2):477-483
We carried out experimental and numerical study of the ultrafast supercontinuum generation by filamentation of 120 fs, 800 nm laser pulses in sapphire under variable focusing conditions. We demonstrate that the supercontinuum spectra produced in loose focusing conditions have much larger infrared extent, while the spectral blueshift remains fairly the same. Our numerical simulations reproduce the experimental results in great detail and disclose that the input beam focusing conditions affect only the nonlinear propagation of the leading sub-pulse, which emerges after the pulse splitting event, and which is responsible for the redshifted spectral broadening. 相似文献
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实验研究了平顶飞秒激光经圆锥透镜后在熔融石英中的成丝及超连续辐射.与高斯飞秒激光的成丝对比发现,平顶飞秒激光可以获得在圆锥透镜焦深区域内强度分布更为均匀的等离子体细丝,这一特征更有利于飞秒激光在固体介质中进行微纳加工等领域的应用.并且,在不损伤熔融石英的条件下,平顶飞秒激光成丝可以获得更高能量、更高转换效率的超连续辐射,这是因为若产生光强相近的细丝,平顶飞秒激光所需的初始激光能量更高,此激光能量下产生的细丝长度更长、均匀性更好. 相似文献
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《中国光学快报(英文版)》2021,(8)
The spatial distribution of the forward-propagating amplified spontaneous emission(ASE) of nitrogen molecular ions during femtosecond laser filamentation in air is studied via numerical simulations. The results suggest that the divergence angle and signal intensity are extremely sensitive to the external focal length. Concurrently, we show that the optical Kerr effect plays a significant role in concentrating the directivity of ASE signals, particularly in cases of loose focusing. Furthermore,the simulations demonstrate that ASE signals are enhanced for a tight focus, although the corresponding filament length is shorter. The main physical mechanism underlying this process is the competition between the plasma defocusing and optical Kerr effects. The result is important for filamentation-based light detection and ranging applied to remote sensing. 相似文献
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《中国光学快报(英文版)》2015,(7)
The influence of air turbulence on the transverse wandering of a single femtosecond laser filament is studied by numerical simulation.The results show that the average transverse displacement of the single filament(δr} is proportional to the square root of turbulent structure constant and the relations between δr and the propagation distance can be fit by a power function.In addition,by using an axicon as a focusing optics,the wandering of a single filament is suggested to be stronger than the free-propagation case. 相似文献
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Wavelength division with three-dimensional couplers fabricated by filamentation of femtosecond laser pulses 总被引:1,自引:0,他引:1
Refractive-index changes can be induced by filamentation of 800-nm, 1-kHz femtosecond laser pulses in silica glass. Two-dimensional translation of a 40-microm-long filament leads to the formation of a curved waveguide because of bending by the previously induced refractive-index change. The fabrication of 2-mm directional couplers to split the coupled beam into 1:1 at a wavelength of 632.8 nm is demonstrated. The realization of three-dimensional directional couplers and wavelength division in the output from the couplers is also demonstrated. 相似文献
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Broadband and energetic terahertz (THz) pulses can be remotely generated in air through filamentation. We review such THz generation and detection in femtosecond Ti-sapphire laser induced remote filaments. New results are presented on the direct relationship between THz generation in a two color filament and induced N2 fluorescence through population trapping during molecular alignment and revival in air. This further supports the new technique of remote THz detection in air through the sensitive measurement of N2 fluorescence. 相似文献
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R. Inoue 《Applied Surface Science》2010,257(2):476-480
Micro-ablation of crystalline silicon was performed by irradiating a silicon substrate with femtosecond laser pulses of wavelengths 786 nm or 393 nm focused using a conical axicon assisted with a convex lens. Focusing the laser beam close to the tip of the axicon by means of the lens significantly improved the efficiency of concentration of laser pulse energy at the central spot of the resulting Bessel-Gaussian intensity distribution. As a result, micron-sized holes were formed with the diameter determined by the ablation threshold in the calculated fluence profile. It is possible to predict hole size from the laser pulse energy and the wavelength. Crystalline particles, a few tens of nanometers in size, were formed near the ablated zone. 相似文献
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R. A. Akhmedzhanov I. E. Ilyakov V. A. Mironov E. V. Suvorov D. A. Fadeev B. V. Shishkin 《JETP Letters》2009,88(9):569-573
Experimental results on the generation of terahertz radiation in the gas breakdown by high-power quasi-monochromatic laser pulses focused by an axicon lens are presented. A theoretical model developed for the terahertzradiation generation includes the nonlinear interaction of a femtosecond pulse with an ionized gas and the excitation of transverse oscillations of the plasma column. The results of the theoretical analysis are compared with the experimental data. 相似文献
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Akhmedzhanov R. A. Ilyakov I. E. Mironov V. A. Suvorov E. V. Fadeev D. A. Shishkin B. V. 《JETP Letters》2008,88(9):569-573
JETP Letters - Experimental results on the generation of terahertz radiation in the gas breakdown by high-power quasi-monochromatic laser pulses focused by an axicon lens are presented. A... 相似文献
17.
A systematic research on intensity clamping phenomenon was conducted both in air and argon by using a TW level femtosecond
laser. Though the laser peak power was increased from 0.1 up to 1.5 TW in the experiment, highly stabilized peak intensity
inside the filament was observed in both gases. The peak intensities inside filaments were experimentally determined to be
about 6.4 × 1013 W/cm2 (f = 20 cm) in air and 1.2, 1.3, and 1.7 × 1014 W/cm2 when different focal lenses (f = 100, 60, and 20 cm) were used in argon, respectively. 相似文献
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Yoshiki Nakata Takuya Hiromoto Noriaki Miyanaga 《Applied Physics A: Materials Science & Processing》2010,101(3):471-474
Mesoscopic nanomaterials with a size ranging from a few nanometers to hundreds of nanometers were generated on a metallic
thin film by interfering femtosecond (fs) laser processing. Because the nanomaterials seemed to demonstrate liquid behavior,
we named their structure nano water drop. The structure is considerably similar to that of a real water drop observed with a high-speed camera. Using the phase shift
between interfering beams, a duplicate structure was generated. This is a new surface modification technique, using a top-down
approach. 相似文献
19.
This work reports a temporal characteristic of a laser pulse undergoing filamentation in air. The diagnostic method is based
on two-photon fluorescence measurement. The results show that the pulse duration, chirp rate and beam radius could be simultaneously
quantitatively retrieved. This simple technique would be useful in practice to trace the underlying dynamics of filamentation
in air. 相似文献
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首次提出圆顶轴棱锥这一新型光学元件.由衍射理论分析了平面波通过圆顶轴棱锥后的光场强度分布,用软件对光强分布进行仿真.结果表明,平行光通过圆顶轴棱锥后可以形成多个局域空心光束(bottle beam),由于球面波能量在焦点附近高度集中,所得的bottle beam在焦点附近强度极大.通过仿真对比得知用圆顶轴棱锥产生的bottlebeam的暗域周围光强远大于用两束Bessel光束干涉所得,大幅度提高了bottle beam囚禁粒子的效率.通过比较这两种方法产生的bottle beam对粒子囚禁的散射力,证实了圆顶轴棱锥产生bottle beam在粒子囚禁方面更具优势. 相似文献