Experimental system for visualizing and measuring fields of density change with holographic interferometry using BSO single-crystal

研究了利用BSO单晶全息干涉测量密度变化场的实验系统。在这种情况下，一个重要的问题是对BSO全息图的高衍射效率和全息干涉条纹的高对比度的要求。首先对BSO晶体的全息记录特性进行了理论和实验研究。获得高衍射效率的重要因素（外加电场、陷阱密度、空间频率、吸收系数和偏振特性）变得清晰。实验研究了晶体厚度和材料参数（阱密度、μ τ值）对衍射效率和光折变响应的影响。为了提高全息干涉条纹的对比度，测量了BSO晶体衍射波和透射波的偏振度。利用He-Ne气体激光器测量了BSO晶体的全息记录特性，该光源可用于透明物体的全息干涉测量。利用He-Ne激光对BSO单晶进行全息干涉测量，测量透明物体的折射率变化。通过干涉测量，可以实时地观察到酒精中驻波的波前，因为条纹会由于折射率的变化而发生位移。通过CCD相机记录条纹的位移，并通过傅里叶变换方法进行数字图像处理，确定条纹的相位。观察了峰值声压的线性分布，并测量了振幅和超声波长。此外，还测量了超声波在酒精中的瞬态声压变化。

Experimental system for visualizing and measuring fields of density change with holographic interferometry using BSO single-crystal is investigated. In this case an important problem is requirement of high diffraction efficiency of the BSO hologram and high contrast of holographic interference fringes. At first, hologram recording characteristics of the BSO crystal are investigated theoretically and experimentally. The important factors for obtaining high diffraction efficiency (applied electric field, trap density, spatial frequency, absorption coefficient and polarization property) becomes clear. Next influence of thickness of crystal and material parameter (trap density, values of mu tau) to diffraction efficiency and photorefractive response are investigated experimentally. Polarization of diffracted wave and transmitted wave from BSO crystal are measured for improvement of contrast of holographic interference fringes.Hologram recording characteristics to BSO crystal by He-Ne gas laser are measured and the light source can be used to holographic inferometric measurement of transparent objectsRefractive index change of transparent object is measured by holographic interferometry with BSO single-crystal using He-Ne laser. Wave fronts of standing ultrasonic waves in alcohol can be visualized at real time as the fringe shifts due to the index change by the interferometry.The fringe shifts are recorded through CCD camera and by the digital image processeing with Fourier transform method the phase of the fringes are determined. The linear distributions of peek sound pressure are observed and measured the amplitude and the ultrasonic wave length.Farther, transient sound pressure changes of traveling ultrasonic wave in the alcohol are measured by the method.