QQ客服 官方微博 反馈留言

题名	超分辨激光远场光斑的压缩整形技术
作者	贾佳
学位类别	硕士
答辩日期	2003
授予单位	中国科学院上海光学精密机械研究所
导师	周常河
关键词	衍射光学 二元光学 超分辨 位相片 达曼光栅
其他题名	Superresolution laser beam shaping and compression technology in the far field
中文摘要	本硕士论文报道的工作就是采用超分辨技术的数学工具，对激光远场的衍射斑进行压缩和整形。本硕士论文取得的主要成果包括二个方面：第一，设计并加工了超分辨的位相板实现了小于爱里班0.8倍的激光通信远场光谱。第二，提出了一种新型的圆环形的达曼光栅，它能实现等强度的多级圆环谱的光强，给出了优化计算结果。并加工出了这样的位相板，用实验予以证实。具体描述如下：1．我们先用基本的衍射公式对孔径受限的基本衍射现象作了模拟计算，对轴上点的光强随距离的变化和孔径变化的调制关系作了理论研究，从而对远距离载波光束远场衍射斑的整体进行几何整形，提出最初的几何压缩指标：主斑压缩0.8，中心斑能量最大化。如果主斑压缩比太大接近于1，则压缩的效果不明显；如果压缩比太小，则主斑能量太小，不便于实验中观察。2．根据基本的衍射理论，远场爱里斑的大小由发射孔径大小、传播距离、激光波长所决定。在实际的激光通信系统中，这些变量都是固定的，从而爱里斑是固定不变的。我们首次把超分辨技术应用到激光通信远场的光斑压缩中来。我们对环形位相分布的位相片对远场的调制过程进行了大量的优化计算，从理论上证明了，适当半径和环形位相分布的位相片可以实现远场的衍射斑主斑的几何大小的压缩。我们还利用微光学技术制造了三环位相片，从实验上观察到了小数值孔径透镜下超分辨压缩的效果，这在超分辨领域的研究报道中是不多见的。理论和实验都证明了我们采用超分辨技术进行激光远场光斑压缩的有效性。3．我们提出了一种新型的衍射光学位相器件：圆环形的达曼光栅。这种器件的提出有两个方面的原因。其一，我们在超分辨压缩的研究中，比较深入地考察了环形位相分布的位相片对激光远场的调制关系，知道了改变环形位相片的半径和各环的位相值，可以使衍射场的能量在不同的衍射级次谱里转移。其二，我们知道达曼光栅产生的是一维和二维的等强度点的方形衍射场，它不是轴对称的，而大多数的光学系统都是轴对称的。这两者的结合，促使我们研究一种新型的光栅，实现了各级衍射谱峰值强度相等的环形衍射场。我们借助超分辨的数学工具，从理论上优化了从零阶到八阶的圆环形的达曼光栅的制造参数。我们利用微光学技术加工出了四阶的圆环形达曼光栅，并在实验上观察到了等强度圆环的衍射场。实验结果证明圆环形达曼光栅这一概念是完全正确的，也证明了理论分析和计算的正确性。这种新型的圆环形的达曼光栅将在圆孔型的光学信息处理技术中得到广泛的应用。
英文摘要	We report our works on the use of the superresolution technology for compression of the size and the control of the shape of the diffractive spot in the far field. The results of this dissertation are two aspects. The first is the design of the superresolution phase plate for 0.8 times compression of the central diffraction spot compared with the Airy spot, and the fabrication of the phase plate and experimental results are given, too. The second is the presentation of the equal-intensity circular spectrums in the far field, numerical optimization results and experimental verification of CDG are given, too. The details of these new results are described in the following: 1.2 We simulated the aperture-limited laser propagation along the axis with the diffraction theory. And we calculated the relation between the axial intensity, the propagation distance, and the size of the aperture of the emitting lens. We set up the criteria of the central spot compression criteria of G≥0.8 while the energy within the central spot (S) should be as larger as possible. 2. It is well known that the size of the Airy spot in the far-field is controlled by the aperture of a lens, propagation distance and the laser wavelength. So the Airy spot is fixed in the free-space communication system. We introduce diffractive superresolution technology to design the cheap pure-phase plate for realizing the smaller spot size than the usual Airy spot size, which can decrease the weight and size of the emitting lens. We have calculated 2,3,4,5 circulation zones for optimizing the highest energy compression (Strel ratio) with the constraint of the First zero ratio value G=0.8. Numerical results show that the 2 or 3-circular zone pure-phase plate can yield the highest Strehl ratio (S≈0.59) with the constraint of (7=0.8, but the 4,5 circular zone binary phase (0, π) plates are calculated to yield the result of 5≈0.57 with G=0.8. We have fabricated 2 and 3-circular zone binary phase plate with binary optics technology. Finally, we have established an experimental system for verification of the superresolution effect, and the free-space laser communication is simulated based on this experimental result with the advantages of the superresolution phase plate. 3. We have presented the circular Dammann grating that can realize the circular equal-intensity at the different orders in the far field. A set of parameters such as the order, the circular number, uniformity and diffraction efficiency has been defined to describe this novel diffractive phase elements. Numerical solution of binary-phase (0, π) circular Dammann grating are given. Experimental result of a 4-order circular Dammann grating made with lithographic technique is given. This novel diffractive optical elemental should be highly interesting for practical applications.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/16644]
专题	上海光学精密机械研究所_学位论文
推荐引用方式 GB/T 7714	贾佳. 超分辨激光远场光斑的压缩整形技术[D]. 中国科学院上海光学精密机械研究所. 2003.

个性服务

查看访问统计

相关权益政策

暂无数据

收藏/分享

除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。