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991.
An explanation of optical unitary transformation is presented for general nonoverlapping-image multimode interference(MMI) couplers with any number of input and output ports. The light transformation in the MMI coupler can be considered as an optical field matrix acting on an input light column vector. We investigate the general phase principle of output light image. The complete proof of nonoverlapping-image MMI coupler's optical unitarity along with the phase analysis of matrix element is provided. Based on a two-dimensional finite-difference time-domain(2 D-FDTD) simulation,the unitary transformation is obtained for a 4× 4 nonoverlapping-image MMI coupler within a deviation of 4× 10~(-2) for orthogonal invariance and 8× 10~(-2) for transvection invariance in the C-band spectral range. A compact 1 × 4 splitter based on cascaded MMI coupler is proposed, showing a phase deviation less than 5.4° while maintaining a low-loss performance in C-band spectra. 相似文献
992.
We utilized a set of fused silica thin plates to broaden the spectrum of 1kHz, 30 fs Ti:sapphire amplified laser pulses to an octave. Following the compression by chirped mirror pairs, the generated few-cycle pulses were focused onto an argon filled gas cell. We detected high order harmonics corresponding to a train of 209 as pulses, characterized by the reconstruction of attosecond beating by interference of two-photon transition(RABITT) technique. Compared with the conventional attosecond pulse trains, the broad harmonics in such pulse trains cover more energy range, so it is more efficient in studying some typical cases, such as resonances, with frequency resolved RABITT. As the solid thin plates can support high power supercontinuum generation, it is feasible to tailor the spectrum to have different central wavelength and spectral width, which will make the RABITT source work in different applications. 相似文献
993.
聚合物纳米复合材料以其质量轻、易加工成型、耐化学腐蚀等优秀特性成为电磁屏蔽材料的研究热点. 复合材料的导电性是影响电磁屏蔽性能的关键因素,而聚合物基体中导电网络结构则决定了材料内部的电子传输效率,从而在很大程度上决定材料导电性能. 合理的结构设计可以解决纳米填料在基体中易团聚、难分散的问题,实现低渗滤阈值、高导电性能/电磁屏蔽与多功能化的统一. 我们围绕聚合物纳米复合材料的关键科学问题展开研究,取得一些创新性研究成果: (1)通过填料/基体界面调控,实现复合材料连续导电网络的构筑,制备系列低渗滤阈值聚合物导电复合材料;(2)发展三维导电结构预先构筑新方法,制备出高效导电网络,实现电磁屏蔽复合材料结构功能一体化设计与制备;(3)提出构建多界面结构策略,实现聚合物电磁屏蔽复合材料的轻量化设计. 本专论针对我们研究成果进行总结,并对高性能电磁屏蔽纳米复合材料的发展前景进行展望. 相似文献
994.
Zhang Qi-Yan;Li Han-Song;Guo Bao-Hua;Guo Zhao-Xia;Yu Jian 《高分子科学》2020,38(6):593-598
Electromagnetic interference (EMI) shielding materials are in great demand in electronic equipment and our surrounding environment to resist the increasing serious radiation pollution. Compared with their metal counterparts, conductive polymer composites (CPCs) have unique advantages of lightweight, corrosive resistance, low cost, and excellent processability, and are therefore an ideal choice for developing high-performance EMI shielding materials. However, CPCs based EMI shielding materials are limited to high filler loading, which caused poor mechanical properties and processability. Here, we demonstrate a facile and highly scalable approach to develop high-performance EMI shielding materials with low filler loading by using miscible poly(phenylene oxide)/polystyrene (PPO/PS) blend as the matrix. In contrast to PS/carbon nanotubes (CNTs) composites, PPO/PS/CNTs composites show much higher EMI shielding effectiveness caused by good dispersion of CNTs and highly interconnected conductive network. An excellent EMI shieling effectiveness of 23−25 dB is achieved for PPO/PS/10%CNTs composites with a thickness of only 375 μm, which is superior to most of reported polymer/CNTs composites prepared by melt-compounding. In addition, the results show that although absorption is the major shielding mechanism, the contribution of reflection is also important and closely related to the connectivity of conductive network, as well as the electrical conductivity of the CPCs. 相似文献
995.
996.
997.
基于空间光调制器的飞秒激光时空干涉方法,改变800nm飞秒激光能流密度和累积脉冲数,在316镜面不锈钢上高效率、高质量地制备了面积为5mm×5mm的双尺度的类鲨鱼皮肤微纳米仿生结构,并研究了该结构在不同激光照射条件下的润湿性。在激光能流密度为1.37J/cm2,累积脉冲数为30~40的条件下,不锈钢表面碳元素含量最多增加了13.22%,润湿性由亲水（接触角88°）转变为超疏水,接触角高达165°。本研究利用灵活、高效的飞秒激光时空干涉加工方法,得到了稳定的超疏水表面,为仿生结构制备提供了新思路。 相似文献
998.
针对现有可逆信息隐藏嵌入率低,无法一次隐藏多张不同图像问题,提出一种密文域光学多图像可逆信息隐藏方法。将多张不同类型、不同大小图像进行数据报重组得到重组多图像,无需提供任何信息可在一定噪声下重构多图像。载体图像经非对称双随机相位编码得到加密图像,再将重组多图像光强缩小1000倍,与加密图像级联干涉得到载密图像,利用级联矢量分解可从载密图像中无损还原重组多图像和加密图像。载密图像可用解密密钥进行解密,也可用隐藏密钥无损还原重组多图像,当同时具有解密密钥与隐藏密钥时可无损还原载体图像,实现完全可逆、可分离。实验表明,当嵌入率为128比特/像素时,载密图像峰值信噪比大于32dB,且可无损还原隐藏图像与载体。在1/ 2
999.
《中国物理 B》2021,30(9):94209-094209
We perform a theoretical study on dynamic interference in single photon ionization of ground state hydrogen atoms in the presence of a super-intense ultra-fast chirped laser pulse of different chirp types(equal-power and equal-FWHM laser pulses) by numerically solving the time-dependent Schr ¨odinger equation in one dimension. We investigate the influences of peak intensity and chirp parameters on the instantaneous ionization rate and photoelectron yield, respectively. We also compare the photoelectron energy spectra for the ionization by the laser pulses with different chirp types. We find that the difference between the instantaneous ionization rates for the ionization of hydrogen atom driven by two different chirped laser pulses is originated from the difference in variation of vector potentials with time. 相似文献
1000.
《中国物理 B》2021,30(10):104204-104204
We investigate theoretically single photon transport in one-dimensional waveguide coupled to a pair of cavities, which are denoted by the first cavity and the auxiliary cavity. Two cases with no atom and one atom embedded in the first cavity are discussed. The Fano dips in the transmission spectrum and locations of transparency window are calculated. When no atom is embedded in the first cavity, there exists a transparency window under the condition that the first cavity and the auxiliary cavity are not resonant. The locations of the transparency window and Fano line type depend strongly on the eigen frequency of the auxiliary cavity and the coupling strength between the auxiliary cavity and the waveguide. When one atom is embedded in the first cavity, we show that the transparency window exists even though the first cavity, the atom and the auxiliary cavity are resonant. The Fano line type is strongly dependent on the eigen frequency of the auxiliary cavity and the coupling strength. Our results have potential applications in design of quantum devices at the level of single photon,such as single photon switch and single photon routers. 相似文献