基于Hilbert变换实现数字全息高精度相位重建

为了提高数字全息相位重建精度,研究了基于Hilbert变换重建相位的理论和方法,并通过像面数字全息实验对该方法的有效性进行了验证,同时与数字全息常规重建方法得到的结果进行了比较.结果表明:Hilbert变换本身具有消除直流项的作用,对利用频域滤波滤除零级谱后的全息图进行Hilbert变换,能够彻底消除零级衍射项的干扰,从而提高相位重建精度.与常规重建结果相比,基于Hilbert变换的相位重建结果的标准偏差降低了14.0%.本文结果对提高数字全息相位重建精度具有重要的指导意义.     

不同气氛下LaMnO_3缓冲层后退火效应研究北大核心CSCD

在第二代高温涂层导体离子束辅助沉积技术(IBAD)路线中,LaMnO_3(LMO)作为超导层的生长面,直接影响到YBCO的性能,为改善LMO的织构、形貌等,对磁控溅射法制备的LMO薄膜进行了后退火处理,本实验系统研究了后退火处理对LMO物相、织构、表面形貌等的影响,并进一步研究了后退火效应对超导层的影响.结果表明后退火处理有助于改善LMO表面形貌,优化LMO微结构,在潮湿Ar-5%H2气氛下,LMO缓冲层改善率最高,在经湿Ar-5%H2后退火处理的LMO缓冲层上制备的超导层具有最佳的性能,在77K自场下,临界电流密度达到1.2 MA/cm^2.     

Enhanced Surface-Plasmon-Polariton Interference for Nanolithography by a Micro-Cylinder-Lens Array

A practical interference lithography scheme based on surface plasmon polaritions （SPPs） is suggested. In this scheme, a micro-cylinder-lens array is employed to generate the evanescent wave （EW） carrying much energy. When the top of the cylinder lenses are in close contact with a metal film coated on a resist, the energy of EW will launch strong SPPs and form enhanced interference nanopatterns in the resist. The simulation results confirm that a high quality nanopattern with a critical dimension of λ/7 can be achieved in the resistance. The anaJysis results indicate that the height of the cylinder lenses can provide a large tolerance to decrease the fabrication difficulty of this element.     

Perfect digital holographic imaging with high resolution using a submillimeter-dimension CCD sensor

In order to improve the resolution of digital holography with a common-dimension charge-coupled device (CCD) sensor, the point spread functions are briefly derived for the commonly used and practical post-magnification, pre-magnification, and image-plane digital holographic microscopic systems. The ultimate resolutions of these systems are analyzed and compared. The results show that the ultimate lateral resolution of pre-magnification digital holography is superior to that of post-magnification digital holography in the same conditions. We also demonstrate that the ultimate lateral resolution of image-plane digital holography has no correlation with the photosensitive dimension of the CCD sensor, and it is not significantly related to the pixel size of the sensor. Moreover, both the ultimate resolution and the imaging quality of image-plane digital holography are superior to that of pre- and post-magnification digital holographic microscopy. High-resolution imaging, whose resolution is close to the ultimate resolution of the microscope objective, can be achieved by image-plane digital holography even with a submillimeter-dimension sensor. This system, by which perfect imaging can be achieved, is optimal for commonly used digital holographic microscopy. Experimental results demonstrate the correctness of the theoretical analysis.