锗薄片内飞秒光偏转波谱技术

本文报道一种高灵敏飞秒时间分辨光偏转波谱技术。利用这一技术我们探测到锗薄片内超快的声子激发并精确测量了声脉冲的波形。我们观测到了光激发的电子—空穴等离子的超声传播。从实验数据我们推算出等离子的传播速度是锗内纵向声速的4倍。     

飞秒激光与超快现象（II）

文章介绍超快现象研究的新进展，其中在飞秒相干光谱学、强场物理和超快光电子技术等领域的迅速进展，向人们展示了超快现象的真实世界。     

飞秒激光与超快现象(Ⅱ)

文章介绍超快现象研究的新进展，其中在飞秒相干光谱学、强场物理和超快光电子技术等领域的迅速进展，向人们展示了超快现象的真实世界．     

141Pr+波长56908 nm谱线超精细结构测量

利用共线快离子束-激光高分辨光谱学测量了141Pr+波长为56908nm谱线的超精细结构光谱，由此得到超精细相互作用常数和参与跃迁激发态、亚稳态能级的超精细能级分裂-与已有的数据比较，在实验误差范围内一致，但测量精度提高了一个数量级- 关键词： 超精细结构 快离子束-激光光谱学 磁偶极矩和电四极矩超精细作用常数     

C掺杂FePt铁磁薄膜光诱导超快退磁动力学研究

FePt合金薄膜由于具有较强的磁各向异性而在磁信息和磁光信息存储中具有重要的应用.C掺杂可精确调控薄膜的磁各向异性,从而可有效地改变薄膜的矫顽场.通过超短激光脉冲与铁磁薄膜相互作用,可以获得非平衡状态下电子、自旋和晶格等自由度之间的动态耦合参数,这是研究超快磁记录材料的物理基础.本文基于瞬态磁光Kerr效应,研究了两种C掺杂浓度下FePt薄膜的超快磁光响应.实验结果表明:瞬态Kerr信号与外加磁场正相关,磁场反向,Kerr信号反号,而瞬态反射率与外加磁场无关;不同C掺杂的FePt薄膜的矫顽场不同,软磁的退磁时间显著小于硬磁薄膜的退磁时间.我们还观测到超快激光在铁磁薄膜中诱导频率约为49 GHz的相干声学声子,该声子的频率与外加磁场无关.实验结果为设计和研制新型磁光薄膜提供了实验依据.     

用超快电子衍射技术研究Al薄膜的超快动力学行为

超快电子衍射（UED）技术因其同时具有亚皮秒的时间分辨和亚毫埃的空间分辨能力,成为研究物质瞬态结构变化,特别是研究晶格材料超快动力学的有力工具.应用国内首台自行研制的UED系统,我们实时测量了超快激光脉冲激发下,20 nm金属Al多晶薄膜产生的相干声子和晶格热运动.实验结果显示,在晶格热运动加剧的同时,热应力的作用使晶格产生了相干振荡,并最终膨胀达到新的平衡位置.实验中测得的振荡周期以及晶格上升的温度与理论计算的结果符合较好,展示了UED技术在超快晶格动力学研究方面的广阔应用前景 关键词： 超快电子衍射 相干声子 晶格热运动     

143,145Nd+ 570.38 nm谱线的超精细结构作用常数测量

利用共线快离子束－激光高分辨光谱学方法测量了^143,145Nd^ 570.38nm谱线的超精细结构光谱，并得到了参与跃迁的上、下能级的超精细相互作用常数。     

基于折叠式超快非线性干涉仪的全光码型转换理论和实验研究

码型转换是实现非归零(NRZ)信号全光时钟恢复的关键技术.提出了一种基于折叠式超快非线性干涉仪的全光NRZ到伪归零(PRZ)信号转换的新型方案.基于半导体光放大器的分段模型和超快非线性干涉仪的传输函数，建立了该方案的理论分析模型，数值模拟了不同速率下的码型转换过程.实验实现了稳定的10，20和40 Gbit/s的NRZ到PRZ信号的码型转换，分析了影响码型转换输出特性的因素，理论分析结果与实验结果基本符合. 关键词： 超快非线性干涉仪 半导体光放大器 全光码型转换     

拓扑绝缘体薄膜在超快光器件中的应用(特邀)

随着超快光学的发展和对以Bi2Te3为代表的拓扑绝缘体材料研究的深入,近几年,将拓扑绝缘体薄膜应用于超快光器件的研究方向发展迅速并发表了一系列研究成果,本文综述了近年来基于拓扑绝缘体材料的超快激光及光器件的研究.从材料结构及制备方法出发,介绍了其独特的光学及光电特性,总结了其在超快激光及光器件中的应用研究进展,回顾和讨...     

半导体光放大器亚皮秒量级超快动态特性的研究

通过考虑脉冲频谱的增益色散，提出了一个分析亚皮秒光脉冲在半导体光放大器(SOA)中传输的新思路.分别对超快光脉冲在时域和频域内进行离散化，建立了一个更为合理的传输数值模型.基于该模型，观察到了脉冲频谱的明显漂移，并探讨了漂移量与脉冲载波波长、脉冲能量、脉冲宽度、SOA长度和注入电流等外部条件之间的关系，从理论上解释了文献没有证实的实验结果.同时，基于交叉增益调制原理，利用双光束结构，描述了载流子加热、光谱烧孔效应和双光子吸收等非线性效应引起的增益压缩.理论分析的结果为改善SOA的动态特性提供了指导. 关键词： 半导体光放大器 超快非线性效应 增益色散性     

Doppler-free optoacoustic spectroscopy

The first observation of Doppler-free optoacoustic spectroscopy is reported. As a first example the P (193) line of the 11-0 band of the B←X transition of ¹²⁷I₂ is used. The output of cw single mode dye laser is split into two equal intensity beams chopped at frequencies ω₁ and ω₂. The nonlinear compoment of the optoacoustic signal at the frequency (ω₁ + ω₂) is detected and Doppler-free resolution is obtained. Comparing the Doppler-free optoacoustic and fluorescence spectra of iodine measured under similar conditions, good agreement is found. Since optoacoustic and fluorescence methods complement each other, this opens up new possibilities for weakly or nonfluorescing molecules.     

Laser optoacoustic spectroscopy of gold nanorods within a highly scattering medium

We describe a spectroscopic comparative analysis based on the optoacoustic technique over the wavelength range from 410nm to 1000nm using a Q-switched Nd:YAG pumped optical parametric oscillator tunable source on a gold nanostructure solution located within a highly scattering medium. The advantages of this method over standard spectroscopy techniques are the possibility to localize and monitor the spectroscopic response of absorbing materials located within turbid media. The operation is confirmed using a comparative analysis with the spectroscopic results obtained from a reference measurement scheme, based on a highly sensitive collimated optical transmission setup in parallel and under the same experimental conditions as the optoacoustic technique.     

Sub-Doppler optoacoustic spectroscopy

We report the observation of saturation Lamb-dips in the optoacoustic spectrum of CH₃OH and CO₂ excited by CO₂ laser. An intermodulation technique is used to get Doppler-free resolution of the lines. Because of the small sample size and the high sensitivity intermodulated optoacoustic spectroscopy compares favorably with other Doppler-free methods.     

Multichannel optoacoustic spectroscopy of molecular gases with pulsed lasers

This paper contains a review of results of the experimental investigation of linear and nonlinear absorption of atmospheric gases using the methods of multichannel optoacoustic spectroscopy with pulsed visible and IR lasers.     

Influence of the absorbed optical quanta energy on GHz ultrasound generation in GaAs

Experimental results of the investigation of the optoacoustic processes taetang place in GaAs semiconductor at ultrashort time scales are reported. Femtosecond laser has been used both for the generation (through the deformation potential mechanism by the interband absorption of laser radiation) and detection of GHz ultrasound waves. First experimental observation of an abrupt change in the phase of the photoexcited GHz ultrasound, when with increase of the energy of optical quanta direct generation of the electron-hole pairs in the side-valleys of GaAs becomes allowed by the energy and momentum conservation laws, is reported. We relate this observation, at least partially, to abrupt change in the ultrafast dynamics of photogenerated electron-hole plasma, in particular to deceleration of plasma diffusion when heavy carriers in the high energy side valley are photogenerated instead of light carriers in the lowest energy valley.     

Femtosecond infrared spectroscopy of semiconductors and semiconductor nanostructures

Infrared spectroscopy on ultrafast time scales represents a powerful technique to investigate the nonequilibrium dynamics of elementary excitations in bulk and nanostructured semiconductors. In this article, recent progress in this field is reviewed. After a brief introduction into electronic excitations below the fundamental bandgap and ultrafast processes in semiconductors, infrared pulse generation and the methodology of time-resolved infrared spectroscopy are reviewed. The main part of this paper is devoted to coherent optical polarizations and nonequilibrium excitations of the electronic system in the spectral range below the fundamental band gap. The focus is on the physics of single component plasmas, i.e. electrons or holes. In particular, intraband, inter-valence and intersubband transitions are considered. Processes of phase relaxation, carrier and energy redistribution are analyzed. The potential of ultrafast infrared technology and spectroscopy for future applications is discussed in the final part.     

Experimental study using optoacoustic spectroscopy (OAS) on spherical gold nanoparticles

In this paper a spectroscopic characterisation method based on the optoacoustic technique has been used to investigate the optical properties of two separate spherical gold nanoparticle (SGNP) solutions where an absorption peak located at 520 nm has been observed. This analysis has been carried out over the visible wavelength range from 410 to 650 nm using a Q-switched Nd:YAG pumped optical parametric oscillator (OPO). To verify the reliability of optoacoustic spectroscopy (OAS), the results obtained have been compared to those from more standard and limited spectrophotometer and reference collimated optical transmission schemes, where good agreement is shown. The experimental procedure presented here demonstrates the potential of this technique for integration along with optoacoustic imaging methods to identify physiological information for non-destructive in-vivo applications.     

Study of Organized Media Using Time-Resolved Fluorescence Spectroscopy

Many photophysical processes which occur on an ultrafast time scale in ordinary liquids become significantly retarded in organized assemblies, by two to three orders of magnitude. Recently many groups have applied ultrafast laser spectroscopy and theoretical methods to elucidate this dramatic phenomenon. Although the implications of this phenomenon in biology and chemistry are not yet fully understood, it has been demonstrated that ultrafast time-resolved fluorescence spectroscopy is a very powerful tool to study the microscopic properties of the organized assemblies and that water or other liquids confined inside these assemblies are fundamentally different from the corresponding liquid in bulk.     

使用共振多程光声池的CO_2和SF_6的无多普勒饱和吸收光谱

本文使用共振多程池的光声探测法对CO_2和SF_6分子的无多普勒饱和吸收光谱进行了实验研究.测量CO_2的吸收凹陷约为2.5MHz,实验中观察到5个SF_6的吸收凹陷、凹陷深率约为1.9MHz.两种情况的分辨率均大于10~7.     

液体光击穿阈值的研究

运用声学基础理论,讨论了激光入射到液体中,激光能量与声信号强度间的变化关系.发现激光能量与声信号强度之间存在着对数线形关系.根据液体中光声信号的连续性,得到了一种求取液体光击穿阈值的新方法.