电光聚合物在全光技术实现THz波产生与检测中的研究进展

研究和开发基于超短波和低能量激光系统的高振幅、宽频带的太赫兹系统一直是太赫兹应用领域的一个热点。与传统电光晶体材料相比,以电光聚合物薄膜作为太赫兹波产生和检测的最大的优势在于： 一方面电光聚合物不具有晶格结构相应的不存在声子的吸收和太赫兹折射率的散射问题,避免光谱间隙的产生;另一方面电光聚合物薄膜与已用于宽频太赫兹系统中的超薄电光晶体材料相比,更易于加工和处理。另外,可以自行设计得到低相位失配和高电光系数的电光聚合物材料,得到高效率和宽频带的太赫兹辐射源。可以预见,电光聚合物在这一领域的应用必将有宽阔的发展空间和学术研究意义。介绍电光聚合物的电光效应及二阶非线性生色团合成等相关理论问题基础上,综述了近二十多年来,电光聚合物在基于全光技术实现太赫兹波产生与检测系统中的研究进展,主要包括: 掺钛蓝宝石飞秒激光激发下,共聚型和主客体型电光聚合物实现太赫兹波产生与检测;光纤飞秒激光激发下,主客体型电光聚合物实现太赫兹波的产生与检测。     

Near-field optical observations of surface plasmon wave interference at subwavelength hole arrays perforated in Au film

We image optical near-field patterns at subwavelength circular hole arrays in Au film by using scanning near-field optical microscopy in near-infrared wavelengths.Periodical oscillation features are found in the near-field images at the air/Au interface and exhibit two typical kinds of standing wave oscillation forms at the wavelengths corresponding to the transmission minimum and maximum in the transmission spectrum,and the latter one originates from the excitation and interference of a surface plasmon wave at the metallic hole arrays.Our work indicates that monitoring optical near-field patterns can help to reveal many interesting properties of surface plasmon waves at metallic nanostructures and understand their underlying physical mechanisms.     

Controlling the focusing properties of a triangular-lattice metallic photonic-crystal slab：

This paper studies the focusing properties of a two-dimensional photonic crystal (PC) slab consisting of a triangular lattice of metallic cylinders immersed in a dielectric background. Through the analysis of the equifrequency-surface contours and the field patterns of a point source placed in the vicinity of the PC slab, it finds that both the image distance and image quality can be controlled by simply adjusting the refractive index of the background material.     

Near-field imaging of a square-lattice metallic photonic-crystal slab at the second band

Imaging properties of a two-dimensional photonic crystal slab lens are investigated through the finite-difference time-domain method. In this paper, we consider the photonic crystal slab consisting of a square lattice of square metallic rods immersed in a dielectric background. Through the analysis of the equifrequency-surface contours and the field patterns of a point source placed in the vicinity of the photonic crystal slab, we find that a good-quality image can form at the frequencies in the second TM-polarized photonic band. Comparing the images formed at different frequencies, we can clearly see that an excellent-quality image is formed by the mechanisms of simultaneous action of the self-collimation effect and the negative-refraction effect.     

Optical properties of the direct-coupled Y-branch filtersby using photonic crystal slabs

We fabricated a new type of two-dimensional photonic crystal slab filter. The resonant cavities were directly put into the waveguide arms. The optical transmissions of the filters were measured and the results show that the optimized two-channel filters give good intensity distribution at the output ports of the waveguide. A minimum wavelength spacing of 5~nm of the filter outputs isrealized by accurately controlling the size of the resonant cavities.     

通过熵产率构建的两类损失模型计算精度比较

本文采用雷诺平均及雷诺平均-大涡模拟方法对一直叶栅进行数值模拟,分别对比分析了两类基于熵产率构建的损失模型结果。一类为假设模拟结果的湍流耗散等于湍流生成构建的模型,称为Moore模型;另一类为通过湍流模型参数直接求解湍流耗散率构建的模型,称为K-B模型。经过对比4°攻角下当地损失系数及2°、4°、7°攻角下积分损失可发现,无论是雷诺平均还是雷诺平均-大涡模拟方法模拟,Moore模型均与K-B模型在定性及定量上有一定差距。     

Quantum mechanical solution to spectral lineshape in strongly-coupled atom-nanocavity system

The strongly coupled system composed of atoms, molecules, molecule aggregates, and semiconductor quantum dots embedded within an optical microcavity/nanocavity with high quality factor and/or low modal volume has become an excellent platform to study cavity quantum electrodynamics (CQED), where a prominent quantum effect called Rabi splitting can occur due to strong interaction of cavity-mode single-photon with the two-level atomic states. In this paper, we build a new quantum model that can describe the optical response of the strongly-coupled system under the action of an external probing light and the spectral lineshape. We take the Hamiltonian for the strongly-coupled photon-atom system as the unperturbed Hamiltonian $\bm{H}$₀ and the interaction Hamiltonian of the probe light upon the coupled-system quantum states as the perturbed Hamiltonian $\bm{V}$. The theory yields a double Lorentzian lineshape for the permittivity function, which agrees well with experimental observation of Rabi splitting in terms of spectral splitting. This quantum theory will pave the way to construct a complete understanding for the microscopic strongly-coupled system that will become an important element for quantum information processing, nano-optical integrated circuits, and polariton chemistry.     

Enhanced light absorption of silicon in the near-infrared band by designed gold nanostructures

A scheme to enhance near-infrared band absorption of a Si nanoparticle by placing the Si nanoparticle into a designed gold nanostructure is proposed. Three-dimensional （3D） finite-difference time-domain simulations are employed to calcu- late the absorption spectrum of the Si nanostructure and maximize it by generating alternate designs. The results show that in the near-infrared region over 700 nm, the absorption of a pure Si nanoparticle is very low, but when the same nanoparticle is placed within an optimally designed gold nanostructure, its absorption cross section can be enhanced by more than two orders of magnitude in the near-infrared band.     

三联吡啶-萘酰亚胺二元化合物的合成及其与DNA的相互作用

本文合成了两种三联吡啶修饰的萘酰亚胺化合物NPI1和NPI2,并利用紫外-可见吸收光谱(UV-Vis)、圆二色光谱(CD)、荧光共振能量转移(FRET)等方法研究了它们与双链CT DNA和Htelo G-四链体DNA的相互作用。实验结果表明,化合物NPI1和NPI2对G-四链体DNA具有很好的结合能力和选择性,溶液中的碱金属离子种类和萘酰亚胺基团上的取代基对NPI1和NPI2与DNA的作用有很大的影响。在含K+的缓冲液中,NPI2与G-四链体的结合常数达到1.06×108 L/mol,是与双链CT DNA结合常数的268倍。圆二色谱结果表明在不含碱金属离子的溶液中,NPI1和NPI2可诱导Htelo DNA形成反平行结构G-四链体。Autodock分子对接模拟表明NPI1和NPI2可以通过堆积作用、静电作用、氢键等作用方式与G-四链体结合,使得它们对G-四链体具有很高亲和性(Ka>107 L/mol)。