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1.
多光子过程和自发辐射对激光诱导自电离的影响 总被引:1,自引:1,他引:0
利用反作用算符的方法,研究了一个单模激光场将原子从束缚能级激发到自电离能级的过程中,双光子过程和自发辐射过程的影响。研究结果表明:自发辐射对这种光电离过程的影响一般情况下是很小的,但光子能谱特性十分明确地表明,辐射主要来源于由态共振加强的喇曼过程;并显示了激光诱导自电离过程中的缀饰(Dressed)原子图像;双光子过程将使光电子能谱和光诱导自电离过程变得非常复杂,单光子和双光子过程所产生的光电子能谱,都具有多极大值结构。 相似文献
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蓝紫激光和中红外激光在基础研究和国防工程中有重要的应用前景。单光子吸收的碱金属蒸气激光器具有量子效率高、受激发射截面大和热管理性能好等优点,近些年来已成为激光领域中研究热点之一,目前已实现k W量级的输出。双光子吸收的碱金属蒸气激光器可实现蓝紫激光和中红外激光级联输出的特性,也引起越来越多的关注。本文从碱金属原子密度、泵浦光功率、偏振和频率失调量以及调控激光等几种影响因素出发,综述了双光子吸收碱金属蒸气激光的研究进展,在此基础上分析了影响激光输出特性的原因,最后对双光子吸收碱金属蒸气激光器的发展趋势进行了展望。 相似文献
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研究了利用反向泵浦-探测双光子吸收材料的方法来测量脉冲激光的相干时间,并测量量了23ps,532nm Nd:YAG激光脉冲的相干时间。实验和理论分析表明,光束相干作用增加了双光子吸收,利用此方法可测量其它脉宽激光的相干时间。 相似文献
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失谐量对双光子J-C模型中光场位相扩散及频率漂移的影响 总被引:7,自引:1,他引:6
通过考察失谐量对双光子Jaynes-Cummings(J-C)模型中光场位相的影响,论证了失谐量不仅会影响原子-光场耦合程度,而且还会导致光场频率发生漂移.并且讨论了双光J-C模型中光场位相特性与双光子激光频率特性之间的关系. 相似文献
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两能级原子与外部环境(热库)相互作用时,采用非旋波近似,研究原子与热辐射场单光子和双光子作用过程,利用小系统与库耦合行为的量子理论,计算原子约化密度矩阵非对角元,分析原子状态的消相干特性。 相似文献
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Ning CZ 《Physical review letters》2004,93(18):187403
We propose to make a two-photon laser based on intersubband (sublevel) transitions in semiconductor nanostructures. The advantages and feasibility of such a two-photon laser are analyzed in detail using the density matrix approach. Both one-photon and two-photon gains in a three subband quantum well structure are studied on the same footing to show how the two-photon gain can be maximized, while the competing one-photon gain is minimized. The results show that a sufficient two-photon gain can be achieved to overcome one-photon competition and the loss of a conventional semiconductor cavity, making intersubband transitions one of the very few feasible approaches to two-photon lasing. 相似文献
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Jiang M Sucha G Fermann ME Jimenez J Harter D Dagenais M Fox S Hu Y 《Optics letters》1999,24(15):1074-1076
We describe an erbium fiber laser that is passively mode locked by a novel, precision antireflection-coated semiconductor saturable-absorber mirror that incorporates an additional two-photon absorber. It is shown that passive mode locking evolves from a Q-switching instability. The results are achieved by use of saturable absorbers that provide a large (15%) nonlinear (saturable) loss. Exploiting two-photon absorption can substantially reduce the peak power of the Q-switched pulses, which results in improved reliability of the laser. Moreover, two-photon absorption can be used to produce an optimal stability range for saturable-absorber mode locking. 相似文献
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基于两双光子过程的相位共轭二阶极化干涉,从理论上研究了四能级系统在阿秒量级的不对称和频极化拍频(FASPB).在抽运光束为窄带情形下,场关联对FASPB信号影响很弱.在宽带情形下,FASPB信号表现出共振-非共振交叉关联,双光子信号展现出混合辐射-物质失谐的THz阻尼振荡,即当激光频率偏离双光子共振跃迁的条件时,信号将呈现阻尼振荡,而且其双光子自相关信号的包络还呈现最大值零延时不对称.还研究了由于两双光子自相关过程零延时的偏差导致的阿秒拍频信号的不对称性,和两个双光子信号的最大值分别向相反的方向偏离零延时点的现象.FASPB作为一种阿秒超快调制过程,从理论上说它可以扩展到任何两偶极禁戒跃迁激发态的能级和系统.
关键词:
阿秒和频
极化拍
四能级
双光子 相似文献
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Laser actions and photon statistics far a nondegenerate two-photon laser in an effective three-level stomic system with arbitrary detunlng are Investigated both semiclassically and quantum meehmleally, Due to the two-photon effect, the radiation field easily displays a sub-Foissonian statlstieal distribution. The laser actions for a two-photon and a sihgle-photon loss mechanisms are compared. It is found that the detailed balance in the single-photon loss mechanism can still be preserved in the case that a first-order phase transtion takes place. 相似文献
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We experimentally demonstrate two-photon absorption with broadband down-converted light (squeezed vacuum). Although incoherent and exhibiting the statistics of a thermal noise, broadband down-converted light can induce two-photon absorption with the same sharp temporal behavior as femtosecond pulses, while exhibiting the high spectral resolution of the narrow band pump laser. Using pulse-shaping methods, we coherently control two-photon absorption in rubidium, demonstrating spectral and temporal resolutions that are 3-5 orders of magnitude below the actual bandwidth and temporal duration of the light itself. Such properties can be exploited in various applications such as spread-spectrum optical communications, tomography, and nonlinear microscopy. 相似文献
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We report on a low-noise diode laser oscillator at 972?nm actively stabilized to an ultrastable vibrationally and thermally compensated reference cavity. To increase the fraction of laser power in the carrier we designed a 20?cm long external cavity diode laser with an intracavity electro-optical modulator. The fractional power in the carrier reaches 99.9%, which corresponds to an rms phase noise of φ(rms)2=1?mrad2 in 10?MHz bandwidth. Using this oscillator, we recorded 1S-2S spectra in atomic hydrogen and have not observed any significant loss of the excitation efficiency due to phase noise multiplication in the three consecutive two-photon processes. 相似文献
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Application of a femtosecond self-sustaining mode-locked Ti:sapphire laser to the field of laser scanning confocal microscopy 总被引:3,自引:0,他引:3
P. F. Curley A. I. Ferguson J. G. White W. B. Amos 《Optical and Quantum Electronics》1992,24(8):851-859
Developments in ultrafast Ti:sapphire laser technology can be applied in the investigation of nonlinear optical processes. We describe the application of a self-sustaining femtosecond Ti:sapphire laser as an illumination source in the field of confocal laser scanning fluorescence microscopy (LSM). We present spectra for various fluorescent stains under two-photon excitation and present LSM images of stained samples under mode-locked illumination. The potential for such a system as a non-destructive technique for studying live cells in biomedical research is discussed. 相似文献
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In this paper, we have developed an analytical model to study the temperature distributions in IR optical materials heated by laser pulses. Our model takes into account the two-photon absorption (TPA). The calculations are based on a three-dimensional model of heat diffusion in solids using the integral transform method. We find out the rigorous analytical expression of the thermal field when one considers both one- and two-photon absorption. The model is valid for any laser–solid system whose interaction can be described by the generalized Beer–Lambert law. Specific results are presented for an application of the model to ZnSe sample. We find out that TPA can produce detectable temperature variation. 相似文献
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A three level scheme interacting with three laser fields is considered. It is found that two competing processes contribute
to the absorption/dispersion on a particular transition: (i) one-photon processes governed by the field applied to that transition,
and (ii) two-photon processes governed by the two laser fields applied to two other transitions. Interference between the
two processes can be both constructive and destructive. It is shown that the net absorption/gain and dispersion can be controlled
by the relative phases of the laser fields. 相似文献
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We investigate the adaptive optimization of broadband laser pulses, using a closed-loop learning algorithm in which the merit function is derived from two-photon absorption in semiconductors. Photoluminescence experiments with CdS thin films and photocurrent measurements of a GaAsP photodiode have been performed. The experimental data demonstrate that reliable and accurate pulse compression to the bandwidth limit can be achieved, unperturbed by nontrivial phase effects. Therefore two-photon absorption proves to be an easy-to-implement alternative to second-harmonic generation for the compression of broadband laser pulses. 相似文献