基于衍射条纹非对称性的表面波衰减系数的测量

通过采用将入射光掠入射到频率为几百赫兹的衰减低频液体表面波上,观察到了清晰的间距分布具有明显非对称性的衍射条纹。当入射光掠入射到低频液体表面上时,衍射图样非对称分布具有普遍性。理论上得到了考虑表面波衰减影响后观察屏处衍射光强分布的解析表达式。理论结果表明:衍射图样的这种非对称分布与衍射级次、入射光波波长、液体表面波波长及表面波衰减系数有关;正负级次衍射亮条纹距离中央零级亮条纹的间距体现表面波衰减信息;正衍射级次之间以及负衍射级次之间的条纹间距体现表面波波长信息。利用所提出的方法实现了对几百赫兹液体表面波的衰减系数的实时便捷测量。     

干涉法测量低频表面波的衰减系数

对于频率为几十赫兹的低频衰减液体表面波,结合激光干涉法和激光扫描法,实验得到反衬度很高的调制干涉图样,理论上给出了干涉图样的条纹宽度,条纹分布范围与表面声波振幅之间的解析关系,实时测量了液体表面波的衰减系数.     

多振源低频液体表面波声光效应研究

同时利用两个振源,在液体表面上产生两列低频表面波,实现了多振源条件下表面声光效应,观察到清晰、稳定、反衬度高的声光衍射条纹.当引起两列表面波的两个振源频率具有倍数关系时,声光衍射条纹的极大值位置与较小频率的振源单独存在时所产生表面波的极大值位置相同,与较大频率的振源单独存在时所产生表面波的极大值位置部分相同.当引起两列表面波的两个振源频率不具备倍数关系时,不仅观察到单振源的衍射条纹,而且也观察到了双振源的干涉条纹.理论上得到多振源衍射光场和表面波波长、振幅之间的解析表达式,理论规律与实验结果吻合较好.     

低频液体表面波激光衍射条纹的特征

用激光衍射法实现了低频液体表面波稳定、清晰、反衬度非常高的条纹,并发现了缺级现象.理论上分析了表面波的光衍射效应,得到了衍射光场和表面波之间的解析表达式,表达式包括衍射因子和干涉因子.通过对衍射因子和干涉因子的分析,得到衍射条纹空间分布与表面波波长的关系、条纹的半角宽度与入射激光光斑覆盖表面波的个数和入射方向的关系、衍射光强度与表面波振幅的关系,并解释了条纹缺级现象.     

小振幅低频液体表面波的光学干涉效应的研究

实验上实现了频率为几十赫兹的低频液体表面波的光干涉调制研究,得到了稳定、清晰的干涉图样。理论上对表面波干涉现象进行了分析,得出了条纹分布的解析表达式,较合理的解释了干涉图样的分布现象。该方法适用于低频液体表面波的特性研究,通过分析实验图样,可以对液体的表面张力等特性参数进行研究。     

低频水下声信号的激光探测

根据表面波声光效应的原理,提出了一种低频水下声信号的激光探测技术,并建立了实验装置。在几十赫兹的低频段,对水下声源所产生的表面声波进行了探测。实验过程中,利用MATLAB软件对拍摄的衍射图样进行扫描分析,得到了衍射图样中条纹的像素差。根据波长与条纹间距的解析关系式,得到了低频液体表面声波波长,其大小在毫米量级。利用计算机编程,根据最小二乘法拟合色散关系的回归曲线,测量结果与理论色散关系吻合。该方法具有实时、非接触的特点。     

低频液体表面波衍射条纹的不对称性

实验上实现了低频液体表面波的光衍射,当表面波波长远大于入射光波波长时,得到了稳定、清晰的衍射图样,并首次发现了衍射条纹具有明显的不对称分布.理论上对表面波衍射的近似条件进行了分析,得出了各级衍射条纹角宽度的解析表达式,解释了衍射条纹的非对称分布.衍射图样的不对称分布具有普遍规律,可观察的明显程度与表面波的波长和光波波长的比值有关,在能观察到衍射效应的条件下,当表面波波长远大于光波波长,非对称分布越明显,当表面波波长远接近光波波长时,衍射条纹可近似的看成是对称分布的.     

干涉亮条纹强度的不均匀分布

建立了低频液体表面声波的激光干涉测量系统,实验上不仅得到了清晰、稳定的干涉条纹,而且首次发现干涉条纹的强度分布具有空间不均匀性,干涉条纹被限定在一定的空间区域内,中心干涉条纹强度最小,向两边强度逐渐增大,在两边界位置达到极大.根据波动光学原理,得到了干涉条纹分布的解析表达式,并给出了低频表面波振幅、波长与干涉条纹空间限度、干涉条纹间距的数学表达式.理论规律与实验结果吻合较好.     

利用表面波对激光的衍射效应测水波频率和波速

利用液体表面波（surfaceacousticwaves,SAW）对激光的衍射效应,建立起一种新的低频液体表面波频率的光学测量方法;同时对表面波的传播速度进行了测量,拟合数据对波速和波长之间的关系进行了研究。     

液体对微振动的放大效应

根据表面波声光效应的原理,实验上建立了固体表面微振动的激光衍射测量系统.当激光斜入射到微振动引起的液体表面波上,观察到了清晰、反衬度非常高的衍射图样.利用MATLAB软件对拍摄的衍射图样进行扫描,得到了衍射光斑的光强分布图,并根据衍射图样宽度与表面波振幅的解析关系式,求出了液体表面波的振幅,其大小在微米量级.改变样品池中液体的深度,测得不同深度下液体表面波的振幅,给出了表面波振幅与液体深度之间的解析关系,并发现了液体对微振动的放大效应.利用液体对微振动的放大效应,求出了固体表面微振动的振幅,实现了固体表面微振动的探测.     

Acoustooptic multiplication of the frequency shift of optical radiation on the basis of bragg polarization splitting

A technique for the acoustooptic multiplication of the frequency shift of an optical beam is proposed. The technique is based on the cascade diffraction of the beam by a single acoustic wave with the use of Bragg polarization splitting in a uniaxial crystal. The fundamental possibility of the practical realization of the technique is confirmed experimentally by using anisotropic acoustooptic diffraction in LiNbO₃.     

基于相位共轭的动态体全息衍射特性的实时非破坏性测量

基于相位共轭技术,提出了一种动态体全息衍射特性的实时测量方法.在光学系统设计中,通过调整使得物光和参考光较强,而与参考光共轭的再现光非常弱（约为参考光的1/1 000）,借助非常微弱的共轭再现光实现了动态体全息的非破坏性实时测量.三束光的强度和偏振态可通过1/4波片、偏振片和衰减片进行调节和组合,可记录光强调制型或偏振态调制型体全息.本方法适合于光致折射率变化和光致变色材料体全息的测量.     

Spatial-carrier phase-shifting digital holography utilizing spatial frequency analysis for the correction of the phase-shift error

We propose a single-shot digital holography in which the complex amplitude distribution is obtained by spatial-carrier phase-shifting (SCPS) interferometry and the correction of the inherent phase-shift error occurred in this interferometry. The 0th order diffraction wave and the conjugate image are removed by phase-shifting interferometry and Fourier transform technique, respectively. The inherent error is corrected in the spatial frequency domain. The proposed technique does not require an iteration process to remove the unwanted images and has an advantage in the field of view in comparison to a conventional SCPS technique.     

Plane-wave analysis of the near field of light diffracted by ultrasound.

Although the phenomenon of light diffraction by ultrasound has been studied very extensively during the last 40 years, almost all investigations were concentrated on the individual far field (Fraunhofer) diffraction orders. In the present paper, the basic theory is developed for studying the near field (Fresnel region) of light diffracted by an arbitrary plane ultrasonic wave and the fundamental periodicity properties are stated. The general plane-wave theory of Raman-Nath has been taken as a starting point. From the analysis, the near field of the diffracted light is seen to be highly sensitive to variations of the ultrasonic amplitude and this feature provides a useful technique for observing weak ultrasonic waves. In particular, for the specific case of Raman-Nath-type diffraction, a procedure is presented allowing the reconstruction of the time waveform of the ultrasonic wave from the diffracted light intensity signal.     

Diffraction of a plane electromagnetic wave at a schwarzschild black hole

Using the technique of Debye potentials a rigorous solution of the diffraction problem is given as a superposition of an incident wave, strongly connected with the Coulomb scattering wave function, and a scattered wave, which is purely outgoing for large distances. The solution fulfils the boundary conditions to be the light of a very distant star and to be purely ingoing at the Schwarzschild horizon. The phase shifts of the partial waves are evaluated in the WBK approximation.     

基片衍射对会聚激光驻波场中原子波包几率密度演化的影响

针对激光会聚铬原子沉积实验,运用标量衍射理论,通过数值模拟研究了基片衍射对会聚激光驻波场中原子波包几率密度演化的影响。结果显示基片衍射的影响会随激光中轴线与基片沉积表面距离b0的变化而变化。相对于非衍射情况,衍射效应会提高激光驻波场中会聚平面内原子波包几率密度分布的中心值,同时减小其半峰全宽。当参量b0=－0.2w0(w0为高斯光束的束腰半径)时,原子波包几率密度的会聚平面和基片沉积表面完全重合。此处,衍射时原子波包几率密度分布的中心值为1.26,其半峰全宽为5.62 nm,两者分别为非衍射时的1.1倍和0.94倍。     

Time-resolved detection of atoms diffracted from a standing light wave

We present a time-resolved experimental observation of the diffraction of metastable helium atoms from a nearly resonant standing light wave. The application of a time-resolved detection technique and a pulsed source allows to resolve high diffraction orders, which are populated in the atom-light interaction. Furthermore, the rms momentum transfer from the light field on the atom as a function of the interaction time is investigated. Future applications of this technique may be the detailed investigation of the motion of atoms in standing light waves and the detection of correlations between spontaneously emitted photons and atoms.Dedicated to H. Walter on the occasion of his 60th birthday     

Diffraction grating eigenvector for translational and rotational motion

Future energy scaling of high-energy chirped-pulse amplification systems will benefit from the capability to coherently tile diffraction gratings into larger apertures. Design and operation of a novel, accurate alignment diagnostic for coherently tiled diffraction gratings is required for successful implementation of this technique. An invariant diffraction direction and phase for special moves of a diffraction grating is discussed, allowing simplification in the design of the coherently tiled grating diagnostic. An analytical proof of the existence of a unique diffraction grating eigenvector for translational and rotational motion that conserves the diffraction direction and diffracted wave phase is presented.