Propagation of elliptical Gaussian beam passing through apertured paraxial optical systems

The propagation of elliptical Gaussian beam passing through paraxial optical systems with aperture is investigated analytically by using tensor method. The approximate formula for propagation of elliptical Gaussian beam through hard apertured optical systems is derived based on the fact that the circ function can be expanded into a finite sum of complex Gaussian functions. The derived formula provides a convenient tool for treating the propagation and transformation of elliptical Gaussian beam through apertured optical systems. As an application example, the propagation properties of elliptical Gaussian beam through apertured fractional Fourier systems are discussed.     

就单摆问题引入大学物理教学新模式

单摆教学的过程中引入MATLAB数值计算的教学新模式,可以有效地改善大学物理教学的枯燥方式,有助于提高学生对大学物理课中抽象的、复杂的物理现象和规律的理解,也有助于促进对所学数学知识的实际应用.这种新教学模式是深化高等工程教育改革、加快新工科建设、促进创新型工科人才培养的有效手段.     

消毒灭菌的电离辐射与电磁辐射等物理技术比较分析北大核心CSCD

消毒灭菌技术广泛应用于食品工业、医疗领域、水处理等方面。相对于传统化学和热效应的消毒灭菌方法,γ射线、X射线、电子束、微波、低温等离子体、紫外线、高压脉冲电场等物理手段具有不污染环境、消毒灭菌温度低、没有化学残留物等优点而日益受到重视。但这些物理技术手段各有不同,本文首先介绍了γ射线、X射线、电子束、微波、低温等离子体、紫外线、高压脉冲电场等消毒灭菌的技术原理,然后对比了各自优缺点和应用领域。每种方法都有优势和不足,应针对不同的消毒灭菌对象而选择不同的方式。最后,展望了消毒灭菌的发展方向,提出了消毒灭菌在家庭日常消毒、医疗垃圾处理、有人状态下的室内空气消毒等方面的迫切需求。     

椭球粒子声辐射力计算及分析

针对水下椭球粒子,以声散射理论为基础,采用分波序列的方法,建立了椭球粒子声辐射力的理论计算模型。进而根据声辐射力计算公式,以刚性椭球粒子和液体椭球粒子为例,计算并分析不同Bessel波束作用下椭球粒子的轴向声辐射力函数特征。数值仿真计算结果表明,对于刚性椭球粒子,扁平椭球粒子相对于细长椭球粒子更有助于激发负声辐射力;对于液体椭球粒子,细长椭球粒子相对于扁平椭球粒子更加容易产生负声辐射力;对于不同介质的椭球粒子,不同的入射波束激发的负声辐射力的效果也存在明显的差异。该结果为复杂的尺寸和介质粒子声操控技术提供了理论的可行性。     

Beam Parameters for End Diffraction of TE0 Mode of Planar Waveguide

The relation between diffractive beam parameters and normalized frequency is analyzed that leads to two improved Tormulas for two kinds of mode-field halT-widths and several formulas for divergence angle as well as beam propagation factor. The numerical calculation indicates that the maximal relative error is less than 0.5% within a reasonable parameter range.     

Recent Advances in Spatial Self-Phase Modulation with 2D Materials and its Applications

In recent years, spatial self-phase modulation (SSPM) with two-dimensional (2D) materials has attracted the attention of many researchers as an emerging and ubiquitous nonlinear optical effect. In this review, the state of the art of 2D material-based SSPM is summarized. SSPM measures or tunes the nonlinearity of 2D materials, and it is also an effective approach to study the band structure of 2D materials. Several modified forms of SSPM, such as high-order, white-light-excited, vector field excited, and optically nonlinearly enhanced SSPM are also presented. Subsequently, the physical origin of the SSPM formation mechanism is compared and analyzed. Furthermore, the applications of SSPM with 2D materials, including passive photonic devices, generation of Bessel beams, and identifying the mode of the orbital angular momentum, are listed. Finally, several urgent problems of the SSPM with 2D materials, potential applications, and prospects for future development are presented.     

Radially polarized hyperbolic-cosine-Gaussian beam

Vector beams have attracted much interest recently. In this paper, focusing properties of the radially polarized hyperbolic-cosine-Gaussian beam are investigated. Simulation results show that the focal depth increases with increasing cosine parameter in the cosine term of the beam, while focal spot decreases simultaneously, namely, superresolution occurs. Focal depth increase velocity is quicker for larger cosine parameter, while the transverse focal spot shrinks more quickly for smaller cosine parameter. In addition, for two-portion concentric piecewise radially polarized hyperbolic-cosine-Gaussian beam with π phase shift in center circle portion, focal pattern evolves considerably with increasing cosine parameter, and the evolution principle differs for different radius of the center circle portion. Focal splitting and novel focal spots may appear. This kind of vector beam can be used in optical storage, optical manipulation, and lithography.     

Gauss光束通过单丝的Fresnel衍射

本文用数值计算方法研究了Ｇａｕｓｓ光束照射下的Ｆｒｅｓｎｅｌ衍射，尤其是单丝的衍射，导出主极大区有明显的三分裂特征，并将求得结果与已有平面波照射下的Ｆｒｅｓｎｅｌ单缝衍射进行对比，在相当宽的范围内，实验证实了我们的理论结果。     

An ultra-wideband coding polarizer for beam control and RCS reduction

Pancharatnam−Berry (PB) phase metasurface, as a special class of gradient metasurfaces, has been paid much attention owing to the robust performance for phase control of circularly polarized waves. Herein, we present an element-based polarizer for the first step, which enables the incident electromagnetic waves into the cross-polarized waves with the relative bandwidth of 71%, and the polarization conversion ratio exceeds 90% at 6.9−14.5 GHz. Then an eight-elements coding polarizer based on the PB phase is presented for the applications on beam control and radar cross section reduction. The simulated values indicate that the reduction of radar cross section is more than 10 dB at 6−16 GHz. Our work reveals the availability of manipulating the waves, beamforming in communication systems and electromagnetic stealth, and so on.     

Magnetic-Electric Metamirror and Polarizing Beam Splitter Composed of Anisotropic Nanoparticles

The emergence of new materials and fabrication techniques provides progress in the development of advanced photonic and communication devices. Transition metal dichalcogenides (e.g., molybdenum disulfide, MoS₂) are novel materials possessing unique physical and chemical properties promising for optical applications. In this paper, a metasurface composed of particles made of bulk MoS₂ is proposed and numerically studied considering its operation in the near-infrared range. In the bulk configuration, MoS₂ has a layered structure being a uniaxial anisotropic crystal demonstrating an optical birefringence property. It is supposed that the large-scale and uniform MoS₂ layers are synthesized in a vertical-standing morphology, and then they are patterned into a regular 2D array of disks to form a metasurface. The natural anisotropy of MoS₂ is utilized to realize the splitting of electric and magnetic dipole modes of the disks while optimizing their geometric parameters to bring the desired modes into overlap. At the corresponding resonant frequencies, the metasurface behaves as either an electric or a magnetic mirror, depending on the polarization of incident light. Based on the extraordinary reflection characteristics of the proposed metasurface, it can be considered an alternative to traditional mirrors and optical splitters when designing compact and highly efficient metadevices, which provide polarization and phase manipulation of electromagnetic waves on a subwavelength scale.