【作者】 喻霞；

【导师】 陈克求；

【作者基本信息】 湖南大学 ， 物理学， 2012， 博士

【摘要】 低维周期和准周期超晶格中光传输特性量子结构调控在设计光电子器件方面有着重要的应用前景，优化光学元件是改善光束质量有效的手段。本文着重研究了如下几个问题：含缺陷周期和准周期超晶格对光输运性质调控，优化设计衍射光学元件提高在光束整形，长焦深以及光束分离和聚焦等多种功能中的光学性能。获得了如下有意义的结果：研究了由左右手材料组成的准周期超晶格光传输性质，展现了共振传输和光子带隙。发现当介质的介电常数和磁导率与频率无关时，传输谱呈现理想透射峰和宽的光子带隙；随着准周期结构序列增加，带隙加宽，出现更多的全透峰值和透射峰；左手材料的引入，使带隙覆盖整个频率区域，除了满足相位π/2的整数倍的点；带隙宽度及透射率均对入射角很敏感，随着入射角增大，传输谱均向低频端移动，高频区域透射率降低；随着材料光学厚度增加，模式劈裂，出现更多的新的传输通道。当引入介电常数和磁导率与频率有关的负折射率材料时，传输谱呈现更多的光学带隙和传输通道。研究了准周期结构缺陷对有限超晶格中光波传输特性的调控。当介电常数和磁导率与频率无关时，缺陷的引入使得带隙中出现缺陷模式，随着缺陷阶数增加，带隙加宽，新的传输通道出现；缺陷为左手材料时，透射率降低，出现更完美和更宽的带隙；带隙宽度和缺陷态的性质都依赖于入射角的变化，随着入射角增大，带隙变宽，中间缺陷模式向高频端移动；当折射率是频率色散并且为负时，出现不对称的丰富的传输带隙。为设计多通道滤波和宽带滤波器件等方面提供了重要的参考价值。一种改进的加权杨顾算法被用于实现在分数傅里叶变换区域和自由空间光束整形，模拟设计衍射相位元件实现不同分数阶和不同参数的高斯光束和空心高斯光束最优的达到均匀平顶矩形光束。对于不同的分数阶和不同的腰斑半径，加权杨顾算法都最优的实现光束整形，提高光束整形质量，降低误差函数和光强不均匀性；对于不同的初始相位，误差函数都趋向于0值点，有效的避免循环过程中陷入局部极值点，降低对初始值的敏感性。我们利用优化算法设计衍射Axicon实现不同光束长焦深，发现优化设计的衍射Axicon实现焦深区域更宽范围的轴向高强度分布，获得更高的横向分辨率。设计三种不同波长入射光束，都能在预设焦深范围实现长焦深，多次加权后实现焦深区域均匀强度分布；对于均匀光束和高斯光束都能实现预设范围长焦深；两个预设焦深设计，两种光束都在预设焦深范围内都达到了较好的焦深效果。我们优化设计的Axicon可提高不同波长，不同人射光束在不同预设位置长焦深性能。利用优化算法设计光学元件实现不同波长光束分离和聚焦，扩展相位分布，发现多种波长都能实现分离并能在预设位置聚焦且能量损耗小。对于三个到五个不同的入射波长，实现分离，并能在预设位置聚焦；对于不同波长，在任意的预设位置都能较好的分离和聚焦。更多还原

【Abstract】 The quantum structure manipulation of optical transmission properties inlow-dimensional periodic and quasiperiodic superlattices has important applicationforeground in the design of optoelectronic devices. Optimization design of opticalelements can effectively improve the beam quality. In this thesis, we focus on thefollow issues: light propagation properties in periodic and quasiperiodic superlatticeswith structural defect, optimization design of diffractive optical elements for beamshaping, long focal depth and wavelength demultiplexing and focusing. Some mainresults achieved in this thesis are summarized as follows:A three-component quasiperiodic superlattice structures composing of both positiveand negative refractive index materials are shown to display resonant transportbehavior and optical band gaps. When the structure is composed of non-dispersiverefractive index material, the number of the resonant transmission peaks increases andthe optical band gap becomes broader with the increasing of the medium generation.The band gap covers all the wavelength except for some singular wavelength pointswhen the structure is composed of negative refractive index materials. Moreover, it isfound that the spectrum shifts to low frequency for oblique incidence. And with theincreasing of the optical thickness, the band gap splits and new perfect transportchannels emerge. For a more realistic dispersive negative refractive index material,the transmission coefficients are characterized by a rich transmission profile withoutsymmetry, more wide band gaps and abundance transmissive channels appear.We investigate the optical transmission properties in finite periodic superlatticemodulated with three-component quasiperiodic defect structure. The results show thatwhen the multilayered defect is composed of frequency-independent refractive indexmaterial, more band gaps appear with the growing of the number of the defect order,and new guided channels emerge. Perfect and more wide band gap can be observedwhen the structural defect is composed of negative refractive index materials.Moreover, the band gap can be adjusted by the incident angle and the spectrum shiftsto high frequency for oblique incidence. For a more realistic frequency-dependentrefractive index, the transmission spectra are characterized by a rich transmissionprofile without symmetry.An improved approach named as weighted YangGu(YG) algorithm for the design of diffractive phase element (DPE) that implement beam shaping in the fractionalFourier transform domain and free space is presented. Modeling designs of the DPEare carried out for several fractional orders and different parameters of the beam foroptimization converting a Gaussian profile and hollow Gaussian profile into a uniformbeam. We found that our algorithm can improve the beam shaping effect, reduce theerror function, and increase light intensity imhomogeneous. For different initial phase,the error function tends to nearly zero points. It can be effective for avoiding thesearch process to local extreme point and decreasing the sensitivity to initial phase.We use an optimization weighted YG algorithm for the design of diffractive Axiconwith long focal depth and high lateral resolution. Modeling designs of the diffractiveAxicons are carried out uniform and Gaussian beam for optimization implementing onlong focal depth. For three different wavelengths incident beam, can realize long focaldepth in the predesignated focal range. After more than once weighted, we found thatour algorithm can increase focal depth, achieve an uniform plateau profile in thedomain of focal depth.We use the optimization algorithm design optical elements for wavelengthseparation and focus. A variety of wavelength can be separated and are able to focus atthe predesignated positions and energy consumption is small. For four differentincident wavelengths, they can also be separated and focus at arbitrary predesignatedpositions after expansion the phase distribution.更多还原