共查询到20条相似文献,搜索用时 31 毫秒
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A promising method for the generation of a supercontinuum with a high spectral power density based on the spectral broadening
of ultrashort pulses in a fiber amplifier is considered. The advantage of the method, as compared to the conventional way
of the supercontinuum generation in a microstructure fiber, is a lower pulse spectral broadening rate, which allows one to
achieve higher SC spectral power densities. The initial stage of the supercontinuum generation in an ytterbium fiber amplifier
(a fiber core diameter of 7 μm) with side pumping from an array of laser diodes with a total power of 8 W at a wavelength
of 976 nm is experimentally studied. Yb:KYW laser pulses with a duration of 250 fs, a central wavelength of 1046 nm, and an
average power of 150 mW have been supplied to the input of the amplifier. In this case spectrally broadened radiation with
an average spectral power density of higher than 65 mW/nm and a spectrum width of 50 nm has been obtained. 相似文献
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Xia C Kumar M Kulkarni OP Islam MN Terry FL Freeman MJ Poulain M Mazé G 《Optics letters》2006,31(17):2553-2555
A mid-infrared supercontinuum (SC) is generated in ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF...) fluoride fibers from amplified nanosecond laser diode pulses with a continuous spectrum from approximately 0.8 microm to beyond 4.5 microm. The SC has an average power of approximately 23 mW, a pump-to-SC power conversion efficiency exceeding 50%, and a spectral power density of approximately -20 dBm/nm over a large fraction of the spectrum. The SC generation is initiated by the breakup of nanosecond laser diode pulses into femtosecond pulses through modulation instability, and the spectrum is then broadened primarily through fiber nonlinearities in approximately 2-7 m lengths of ZBLAN fiber. The SC long-wavelength edge is consistent with the intrinsic ZBLAN material absorption. 相似文献
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Using the example of a neural system that generates a conditional Markov sequence of delta pulses, the procedure for the derivation
of the expression for the spectral power density of such a signal is shown. 相似文献
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T. Saiki S. Motokoshi K. Fujioka H. Fujita C. Yamanaka 《Optics Communications》2009,282(13):2556-2984
Laser pulses with high repetitive rate generated from a Q-switch microchip Nd:YAG oscillator were amplified by Active mirror composed of Nd/Cr:YAG ceramic pumped by CW arc-lamp. The laser pulses were amplified, and saturation of averaged output laser power was observed. Repetitive ratio of injected laser pulses was changed from 20 to 100 kHz. Averaged output laser power and gain were measured, and gain coefficient and power-extraction efficiency were evaluated. Output laser power was calculated and compared to experimentally measured one, and the calculated results are consistent with the experimental ones. For amplification of laser pulses with high repetitive ratio, this laser material can realize very high laser gain with low pumping power density and high optical-optical conversion efficiency under CW-lamp-light pumping. 相似文献
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High power femtosecond pulses in the Vacuum Ultra Violet (VUV) have been generated through the nonlinear interaction of femtosecond KrF pulses with xenon and argon gas. Under near resonant two photon excitation of xenon by a femtosecond KrF laser, parametric four wave mixing processes lead to VUV pulses at 147 and 108 nm with pulse energies in the 10 µJ range. Tuning is demonstrated by mixing the KrF pulse with a 500 fs dye laser pulse at 497 nm, resulting in 165 nm emission. In argon, a three photon resonance leads to third harmonic generation at 83 nm and micro joule level pulses near 127 nm generated by a six wave mixing process. Since the spectra of the VUV pulses show an ionization-induced blue shift with increasing KrF laser intensity, the VUV pulses can be shown to have temporal duration less than the pulse width (450 fs) of the KrF laser. Blue shifting of the third harmonic of the KrF laser in argon is dominated by a reduction in the neutral gas density rather than by an increase in the electron density. 相似文献
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Different conical emission (CE) patterns are obtained experimentally at various incident powers and beam sizes of pump laser pulses with pulse durations of 7fs, 44fs and 100fs. The results show that it is the incident power but not the incident power density that determines a certain CE pattern. In addition, the critical powers for similar CE patterns are nearly the same for the laser pulses with the same spectral bandwidth. Furthermore, as far as a certain CE pattern is concerned, the wider the spectral bandwidth of pump laser pulse is, the higher the critical power is. This will hopefully provide new insights for the generation of CE pattern in optical medium. 相似文献
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S. Henin Y. Petit J. Kasparian J.-P. Wolf A. Jochmann S. D. Kraft S. Bock U. Schramm R. Sauerbrey W. M. Nakaema K. Stelmaszczyk P. Rohwetter L. W?ste C.-L. Soulez S. Mauger L. Bergé S. Skupin 《Applied physics. B, Lasers and optics》2010,100(1):77-84
We experimentally and numerically characterize multiple filamentation of laser pulses with incident intensities of a few TW/cm2. Propagating 100 TW laser pulses over 42 m in air, we observe a new propagation regime where the filament density saturates. As also evidenced by numerical simulations in the same intensity range, the total number of filaments is governed by geometric constraints and mutual interactions among filaments rather than by the available power in the beam. 相似文献
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分析研究了空间光孤子脉冲化后在反常群速色散的克尔非线性平面光波导中的传输特性和稳 定性.当空间光孤子脉冲的时间宽度等于某一临界值时,脉冲发生自陷,小于该值时,脉冲 发生扩散,大于该值时,脉冲发生塌陷.空间光孤子的阶数越高,这个临界值越小.当空间光 孤子脉冲的时间宽度等于某一特定值时,脉冲塌陷最快,与这个特定值相差越大,塌陷越慢 .空间光孤子的阶数越高,这个特定值越小.脉冲自陷后的峰值光强、时间和空间宽度与输入 时的值有明显的不同.
关键词:
脉冲自陷
脉冲塌陷
光孤子 相似文献
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J. Kerdiles 《Optical and Quantum Electronics》1969,1(4):193-195
In this experiment, the transmission of the saturable absorber of a mode-locked laser is modulated optically by a train of ultra-short pulses emitted by another laser, with some power reflected inside the cavity to initiate the emission. The laser threshold is only attained during the opening time of the modulator, and stimulated emission is prevented at any other time. Once pulses are formed, the photon density is sufficiently high for auto-modulating the dye.Q-switching of the laser is only realised if the difference between the time of a round-trip in the cavity and the period of modulation is less than ±17 psec. The emission is a series of pulses of 5.2 nsec period lasting for 60 nsec. The total energy in all pulses is 60 mJ for a neodymium doped glass rod of 8 mm diameter.We describe a method for measuring the noise of the series of pulses using a saturated photo-cell. We find a ratio of 100 between the energy of one pulse and the energy emitted between two pulses. 相似文献
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O. M. Kugaenko L. A. Vasilieva 《Bulletin of the Russian Academy of Sciences: Physics》2016,80(12):1459-1464
Optoacoustic means are used to study the kinetics of laser damage accumulation in potassium chloride crystals. This approach allows us to observe the accumulation of changes in KCl crystals when it is irradiated by a series of laser pulses of subthreshold intensity in a variety of actions (alloying, applying an external electric field, UV illumination). Number of laser pulses N cr required to destroy a specimen at the same density of radiation power depends on density power I as N ~ I ?4. Results are explained by the formation and accumulation of structural defects during photochemical reactions under the action of laser radiation. 相似文献
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The results of a study of degradation of the surface of gallium arsenide resulting from irradiation with a power excimer laser at power densities ranging from the threshold power to the power level causing local melting of the surface are presented. Two degradation mechanisms have been identified, one of which causes the formation of a thin near-surface layer of modified nonstoichimetric gallium arsenide at a power level higher than 1×107 W/cm2 and the other of which causes the formation of a separate gallium phase. The formation of the separate gallium phase can be produced either by a single pulse of laser radiation with a power density exceeding 2.7×1011 W/cm2 or by a few less powerful pulses. An empirical relationship has been established between the power density and the number of pulses causing the formation of the separate gallium phase. It has also been established that as a result of laser irradiation at the boundary of “cold” and “hot” gallium arsenide, periodically ordered defects in the form of blocks aligned along the [100] directions emerge. 相似文献
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R. A. Smith V. Barrow J. Edwards G. Kiehn O. Willi 《Applied physics. B, Lasers and optics》1990,50(3):187-192
The scaling of recombination XUV lasers to shorter wavelengths requires laser plasmas produced at initial electron densities close to solid. With pump laser pulses longer than a few tens of picoseconds the hydrodynamic motion of the plasma during the interaction makes this difficult to achieve. In contrast, when picosecond laser pulses are used the laser energy is absorbed close to solid density since the plasma expansion is insignificant during the laser pulse. This results in hot near solid density plasmas which are needed for hydrogenic recombination X-ray lasers operating in the water window. Experimental observations have shown that a fully ionized aluminium plasma with a temperature of about 400 eV and a density well above 1023 cm–3 is produced when an aluminium target is irradiated with a single 3.5 ps high power KrF laser pulse. 相似文献
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O. I. Buzhinskij V. A. Barsuk L. B. Begrambekov N. S. Klimov V. G. Otroshchenko A. B. Putric 《Physics of Atomic Nuclei》2016,79(7):1187-1192
The effect of the QSPA-T pulsed plasma irradiation on the crystalline boron carbide B4C coating was examined. The duration of the rectangular plasma pulses was 0.5 ms with an interval of 5–10 min between pulses. The maximum power density in the central part of plasma stream was 1 GW/m2. The coating thickness varied from 20 to 40 μm on different surface areas. Modification of the surface layers and transformation of the coating at elevated temperature under plasma pulse irradiation during four successive series of impulses are described. It is shown that the boron carbide coating withstood the full cycle of tests under irradiation with 100 plasma pulses with peak power density of 1GW/m2. Constitutive surface deterioration was not detected and the boron carbide coating kept crystal structure B4C throughout the irradiation zone at the surface depth no less 2 μm. 相似文献
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Experiments were conducted to measure the arrival time and the power density spectra of wide-band ultrasonic pulses as scattered by a circular, cylindrical, solid inclusion in a matrix of aluminium. Cavities of 3.18 and 6.35 mm diameter were alternately filled with four different solids possessing a wide range of acoustic properties. Results show that the time history and the spectral analysis of the scattered pulses can be used to determine the size of the cavity or the wave velocity in the solid inclusion. 相似文献
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We report the observation of spectral broadening induced by 200 femtosecond laser pulses with the repetition rate of 1 kHz at the wavelength of 532 nm in semi-insulating 4H–SiC single crystals.It is demonstrated that the full width at half maximum of output spectrum increases linearly with the light propagation length and the peak power density,reaching a maximum 870 cm~(-1)on a crystal of 19 mm long under an incident laser with a peak power density of 60.1 GW/cm~2.Such spectral broadening can be well explained by the self-phase modulation model which correlates time-dependent phase change of pulses to intensity-dependent refractive index.The nonlinear refractive index n_2 is estimated to be1.88×10~(-15)cm~2/W.The intensity-dependent refractive index is probably due to both the nonlinear optical polarizability of the bound electrons and the increase of free electrons induced by the two-photon absorption process.Super continuum spectra could arise as crystals are long enough to induce the self-focusing effect.The results show that SiC crystals may find applications in spectral broadening of high power lasers. 相似文献
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Beaudou B Gerôme F Wang YY Alharbi M Bradley TD Humbert G Auguste JL Blondy JM Benabid F 《Optics letters》2012,37(9):1430-1432
We report on power handling oriented design of kagome lattice hollow-core fiber and demonstrate through it for the first time nanosecond laser pulses induced spark ignition in a friendly manner. Two different core designs and transmission bands are investigated and evaluated. The energy threshold damage was measured to be in excess of the 10 mJ level and the output power density is approaching the TW/cm2 after focusing; demonstrating the outstanding ability of such fiber for high power delivery. 相似文献