共查询到20条相似文献,搜索用时 593 毫秒
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结合飞秒激光在研究分子激发态弛豫动力学中的应用,介绍了几种飞秒时间分辨实验中确定泵浦激光脉冲与探测激光脉冲的相关函数和时间零点的方法.对于波长在可见波段的泵浦和探测激光脉冲,我们可以利用非线性光学的技术手段,探测泵浦光与探测光的和频光的强度随二者间的时间延迟的变化来确定相关函数和时间零点;对于波长在紫外甚至更短的波段的泵浦和探测激光脉冲,由于单脉冲能量比较低,目前还很难利用技术手段来测定泵浦激光与探测激光的相关函数及时间零点,可以利用某些原子气体(如Xe)或某些具有短寿命态的分子作平行实验进行间接测量. 相似文献
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纳秒激光诱导空气等离子体存在从紫外、可见、近红外乃至射频微波的宽谱段辐射,但目前的研究大多关注紫外到可见波段的光谱辐射。激光等离子体作为一种新型的红外辐射源具有很多优势,相比于红外干扰弹以及红外干扰手段而言,空气等离子体红外辐射源可以灵活布置,成本低廉,因此研究空气等离子体的红外辐射特性就很有必要。针对目前脉冲激光诱导空气等离子体的红外干扰研究需要,对激光波长为532 nm的纳秒脉冲激光诱导空气等离子体的红外辐射特性进行实验研究,探讨激光能量对空气等离子体红外辐射强度的影响规律,以及空气等离子体红外辐射的角度分布特性,分析了等离子体红外辐射的可能产生机制。实验结果表明,激光诱导空气等离子体在950~1 700 nm范围内的红外光谱为线状谱和连续谱的叠加。其中线状谱主要是氮和氧的中性原子谱线,并且氮原子红外辐射占主导。随着激光能量的增加,由于空气击穿产生的氧和氮原子数量增加,导致空气等离子体红外辐射的谱线强度逐渐增大。随着红外探测角度的变化,在探测角度为75°时,OⅠ 1 128.63 nm和NⅠ1 246.96和1 362.42 nm谱线强度达到最大,在探测角度为120°时,NⅠ 1 011.46和1 053.96 nm谱线强度达到最大,这是因为空气等离子体红外辐射强度随探测角度变化呈现空间非对称性,表明空气等离子体内不同粒子的空间分布呈现非对称性。 相似文献
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为实现长波红外无线激光通信,建立了基于脉宽调制的长波红外无线激光通信系统模型,对系统性能进行了分析,给出了系统误码率的计算公式.搭建了实验系统,对CO_2激光器的平均输出光功率随占空比的变化情况进行了分析,对不同占空比条件下接收端对应的激光平均脉冲宽度以及脉冲宽度受噪声影响的随机变化情况进行了分析,得到了激光输出平均光功率、平均脉冲宽度与占空比之间的关系,以及脉宽的分布规律,并将实验结果与理论分析结果进行了对比,在此基础上得到了脉宽最佳判决门限和系统各类工作参数同误码率之间的关系.结果表明,基于CO_2激光器的脉冲宽度调制能够实现长波红外无线激光通信. 相似文献
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本文分析计算了红外激光探测的信噪比、距离衰减、背景散射等性能指标,最后导出达到所需探测的激光输出功率公式。对于10.6微米波长的 CO_2激光器,在探测距离为4公里时,以碲镉汞红外探测器作为探测元件,所需的激光脉冲功率约为100瓦,脉冲宽度为100毫微秒。 相似文献
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Basanth S. Kalanoor 《Optics Communications》2010,283(20):4059-4063
Nonlinear optical properties of a standard dye IR26 have been studied by using the Z-scan technique to decipher the difference in the mechanism of nonlinear absorption on picosecond time scale at two wavelengths i.e. at 1064 nm and 532 nm. A prominent contribution of nonlinear absorption is observed in the Z-scan profiles at 1064 nm. The dye exhibits the mechanism of self-defocusing at 1064 nm in contrast to that of self-focusing at 532 nm. While the two photon absorption has been found to be the dominant mechanism of reverse saturable absorption at 1064 nm, the mechanism of excited state absorption is operating at 532 nm. Additionally, the optical phase conjugate geometry of degenerate four wave mixing (DFWM) technique has been used to measure the third order nonlinear susceptibility values at 532 nm to compare with those obtained from the Z-scan profiles. 相似文献
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Interaction of Nd:YAG laser, operating at 1064 or 532 nm wavelength and a pulse duration of 40 ps, with AISI 1045 steel was studied. Surface damage thresholds were estimated to be 0.30 and 0.16 J/cm2 at the wavelengths of 1064 and 532 nm, respectively. The steel surface modification was studied at the laser energy density of 10.3 J/cm2 (at 1064 nm) and 5.4 J/cm2 (at 532 nm). The energy absorbed from Nd:YAG laser beam is partially converted to thermal energy, which generates a series of effects, such as melting, vaporization of the molten material, shock waves, etc. The following AISI 1045 steel surface morphological changes and processes were observed: (i) both laser wavelengths cause damage of the steel in the central zone of irradiated area; (ii) appearance of a hydrodynamic feature in the form of resolidified droplets of the material in the surrounding outer zone with 1064 nm laser wavelength; (iii) appearance of periodic surface structures, at micro- and nano-level, with the 532 nm wavelength and, (iv) development of plasma in front of the target. Generally, interaction of laser beam with the AISI 1045 steel (at 1064 and 532 nm) results in a near-instantaneous creation of damage, meaning that large steel surfaces can be processed in short time. 相似文献
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Interaction of an Nd:YAG laser, operating at 1064 or 532 nm wavelength and pulse duration of 40 ps, with titanium implant was studied. Surface damage thresholds were estimated to 0.9 and 0.6 J/cm2 at wavelengths 1064 and 532 nm, respectively. The titanium implant surface modification was studied by the laser beam of energy density of 4.0 and 23.8 J/cm2 (at 1064 nm) and 13.6 J/cm2 (at 532 nm). The energy absorbed from the Nd:YAG laser beam is partially converted to thermal energy, which generates a series of effects, such as melting, vaporization of the molten material, shock waves, etc. The following titanium/implant surface morphological changes were observed: (i) both laser wavelengths cause damage of the titanium in the central zone of the irradiated area, (ii) appearance of a hydrodynamic feature in the form of resolidified droplets of the material in the surrounding outer zone with the 1064 nm laser wavelength and (iii) appearance of wave-like microstructures with the 532 nm wavelength. Generally, both laser wavelengths and the corresponding laser energy densities can efficiently enhance the titanium/implant roughness. This implant roughness is expected to improve its bio-integration. The process of the laser interaction with titanium implant was accompanied by formation of plasma. 相似文献
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Xian-Kun Cheng Qian-Jin Cui Yong Zhou Zhi-Min Wang Yong Bo Da-Fu Cui Zu-Yan Xu 《Optics Communications》2009,282(21):4288-5164
We report a stable high power and high beam quality diode-side-pumped CW green laser from intracavity frequency doubled Nd:YAG laser with LBO crystal. By using a advanced resonator, a large fundamental mode size in the laser crystal and a tight focus in the nonlinear crystal could be obtained simultaneously, which are favorable for high power and high beam quality CW green laser generation. The green laser delivered a maximum 532 nm output power of 40 W. The corresponding optical-to-optical conversion efficiency and electrical-to-optical conversion efficiency were 8.6% and 5.0%, respectively. Under 532 nm output power of 34 W, the beam quality factor was measured to be 1.6. 相似文献
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The demand for high data rate, security and reliable communication is driving the development of free space optic communication (FSO) technology. The atmospheric effects such as scintillation, absorption and scattering severely affect the availability and range of the FSO system. The atmospheric rain absorbs and scatters the laser beam energy resulting in attenuation of the propagating signal. Initial development of FSO technology primarily used wavelength from infrared spectrum. In the recent years, the interest in visible light carrier for FSO applications is consistently increasing. In this paper, the effect of rain over two optical wavelengths from the visible spectrum i.e. 532 nm and 655 nm has been experimentally evaluated and results for the specific rain attenuation at 532 nm and 655 nm wavelengths have been compared. 相似文献
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A novel technique for two-dimensional measurements of soot volume fraction and particle size has been developed. It is based
on a combined measurement of extinction and laser-induced incandescence using Nd:YAG laser wavelengths of 532 nm and 1064 nm.
A low-energy laser pulse at 532 nm was used for extinction measurements and was followed by a more intense pulse at 1064 nm,
delayed by 15 ns, for LII measurements. The 532-nm beam was split into a signal beam passing the flame and a reference beam,
both of which were directed to a dye cell. The resulting fluorescence signals, from which the extinction was deduced, together
with the LII signal, were registered on a single CCD detector. Thus the two-dimensional LII image could be converted to a
soot volume fraction map through a calibration procedure during the same laser shot. The soot particle sizes were evaluated
from the ratio of the temporal LII signals at two gate time positions. The uncertainty in the particle sizing arose mainly
from the low signal for small particles at long gate times and the uncertainty in the flame temperature. The technique was
applied to a well-characterized premixed flat flame, the soot properties of which had been previously thoroughly investigated.
Received: 21 June 2000 / Revised version: 11 September 2000 / Published online: 7 February 2001 相似文献
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Using nonlinear photoinduced anisotropy in bacteriorhodopsin (bR) film, we presented and demonstrated an image switch in which the output can be tuned continuously by the intensity of a pumping beam. A laser with wavelength 532 nm was used as the pumping beam, and a He-Ne laser at wavelength 632.8 nm was used as the probe beam. Without pumping light, a little of polarized probe beam can transmit the crossed polarizers and the output is very low. With the presence of pumping light, owing to photoinduced anisotropy in the bR film, a portion of the probe beam transmits the crossed polarizers, depending on the intensity of the pumping beam. For the low-intensity probe beam (0.44 mW/cm2), the output is dependent on a wide range of pumping beam (2-30 mW/cm2). On the contrary, for the high-intensity probe beam (0.80 mW/cm2), the output is dependent on a narrow range of pumping beam (2-7 mW/cm2). 相似文献
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The wavelength-dependent intensity of a light beam scattered by an isotropic homogeneous particle illuminated with an on-axis monochromatic polarized Gaussian beam is calculated in this paper. The vector spherical harmonics expansion and T transformation matrix are used to form the theoretical basis. Numerical results show that the angular intensity distribution is symmetric for an on-axis polarized Gaussian beam illumination upon an aqueous spherical particle at 473, 532 and 660 nm. For the specified aqueous spherical particle, the scattered intensity distribution decreases with increase in wavelengths. 相似文献