二维平板光子晶体直波导的制备和光传输特性的测量

利用聚焦离子束刻蚀的方法在SOI(silicon on insulator)基片上制备了W3型二维光子晶体直波导.观察并测量了近红外激光通过光子晶体波导的散射图形和透过谱.实验结果说明，激光在有引入引出脊形波导的光子晶体直波导中具有很好的传输特性. 关键词： 光子晶体波导 光子带隙 脊型波导     

Photonic band structures of two-dimensional photonic crystals with deformed lattices

Using the plane-wave expansion method, we have calculated and analysed the changes of photonic band structures arising from two kinds of deformed lattices, including the stretching and shrinking of lattices. The square lattice with square air holes and the triangular lattice with circular air holes are both studied. Calculated results show that the change of lattice size in some special ranges can enlarge the band gap, which depends strongly on the filling factor of air holes in photonic crystals; and besides, the asymmetric band edges will appear with the broken symmetry of lattices.     

二维非线性光子晶体中的高阶准相位匹配谐频

在二维正方晶格的周期性极化铌酸锂晶体中，通过调节基频光波长实现了皮秒光束的高阶共线及非共线准相位匹配谐频过程，在垂直于入射光束的方向上观察到了多对红、绿、蓝三种颜色的谐频光斑.同时，通过改变晶体的入射角度也实现了基频光的高阶谐频过程.实验与理 论符合得很好，这一结果对光电子集成及紧凑器件的研究发展有重要的指导意义. 关键词： 高阶准相位匹配 二维非线性光子晶体 频率转换     

大小周期正方格子复合结构的光子带隙特性

把具有宽完全带隙的粗锐复合的周期常数为a的二维正方格子再与周期常数为a₂的大周期简单正方格子复合，发现大周期正方格子起缺陷作用.并发现当a₂<5a时,缺陷态明显地随入射角度变化.此变化随a₂的增大而减少.用FDTD方法计算了其透射和反射谱,结果表明缺陷峰透射率与a₂的大小成反比.另外还发现: 缺陷峰结构与大周期正方格子的圆柱直径的关系曲线与a₂关系不大.通过调节大周期正方格子的圆柱的直径，可获得单 关键词： 光子晶体 光子能隙 复式结构 缺陷态     

Mach–Zehnder interferometers in photonic crystals

Photonic crystal technology allows the creation of optical waveguides with low sharp-bending losses as well as ultra-low group velocity. This last property is particularly interesting to develop highly-compact optical devices based on the controlled modification of the optical phase of the signals traveling through the waveguides. Among these devices, the Mach–Zehnder interferometer acquires fundamental importance because it can be used as a building block of more complex optical devices and functionalities such as optical filters, wavelength demultiplexers, channels interleavers, intensity modulators, switches and optical gates. In this paper, the performance of a Mach–Zehnder interferometer consisting of two coupled-cavity waveguides with different lengths created in a two-dimensional photonic crystal is theoretically analyzed. We also provide simulation results using a finite-difference time-domain code that confirm the theoretical analysis. The main limitations in the performance of the structure are addressed and discussed.     

Conservative finite-difference scheme for the problem of propagation of a femtosecond pulse in a nonlinear photonic crystal with nonreflecting boundary conditions

Conservative finite-difference schemes are constructed for the problems of self-action of a femtosecond laser pulse and of second-harmonic generation in a one-dimensional nonlinear photonic crystal with nonreflecting boundary conditions. The invariants of the governing equations are found taking into account these conditions. Nonreflecting conditions substantially improve the efficiency of conservative finite-difference schemes used in the modeling of complex nonlinear effects in photonic crystals, which require much smaller steps in space and time than those used in the case of linear propagation. The numerical experiments performed show that the boundary reflects no more than 0.01% of the transmitted energy, which corresponds to the truncation error in the boundary conditions. The amplitude of the reflected pulse is less than that of the pulse transmitted through the boundary by two (and more) orders of magnitude. The simulation is based on the approach proposed by the authors for the given class of problems.     

光子晶体光纤超连续谱产生的实验研究

报道了利用掺钛蓝宝石飞秒激光器产生重复频率为80MHz,脉宽为10fs的超短激光脉冲在10cm长光子晶体光纤产生超连续谱的实验,获得展宽范围为450nm到1100nm的连续谱。实验中观察到孤子自频移和高阶孤子分裂现象,非孤子辐射与随后光谱向短波方向的拓展有密切关系。     

Flexibly Enhanced Photonic Spin Hall Effect via Selective Brewster Angle

The manipulating of photonic spin Hall effect (SHE) plays a crucial role for development of spin-dependent nanodevices and systems. Since the photonic SHE is generally enhanced near the Brewster angle, the choice of incident angle usually has low flexibility with natural materials due to their dielectric constants. Herein, an efficient method to flexibly enhance the photonic SHE by utilizing selective Brewster angle in an anisotropic metamaterial is proposed. Through adjusting the thickness ratio of two media in metamaterial, the Brewster angle can be flexibly adjusted in a broad range (nearly 0–90°). With the selective Brewster angle, the spin-dependent transverse shift can be enhanced at nearly arbitrary incident angles. Furthermore, based on this structure, a binary encoding system is demonstrated, realizing information conversion around incident angles. This research work provides more possibilities for applications in manipulating photonic SHE.     

Chiral-Quantum-Optics-Based Supervised Learning

Based on the excellent control of single photons realized by atom-photon-chiral couplings,a novel quantum-optics scheme for supervised learning is proposed. The single-photon rotating and phase-shift operations, which can be controlled by another single photon, are realized by proper atom-photon-chiral couplings. Then, an algorithm to perform the supervised learning tasks, composed by integrating the realized gates, and implemented by the tunable gate parameters, is realized.     

Method of measuring one-dimensional photonic crystal period-structure-film thickness based on Bloch surface wave enhanced Goos-Hänchen shift

This paper puts forward a novel method of measuring the thin period-structure-film thickness based on the Bloch surface wave (BSW) enhanced Goos-Hänchen (GH) shift in one-dimensional photonic crystal (1DPC). The BSW phenomenon appearing in 1DPC enhances the GH shift generated in the attenuated total internal reflection structure. The GH shift is closely related to the thickness of the film which is composed of layer-structure of 1DPC. The GH shifts under multiple different incident light conditions will be obtained by varying the wavelength and angle of the measured light, and the thickness distribution of the entire structure of 1DPC is calculated by the particle swarm optimization (PSO) algorithm. The relationship between the structure of a 1DPC film composed of TiO₂ and SiO₂ layers and the GH shift, is investigated. Under the specific photonic crystal structure and incident conditions, a giant GH shift, 5.1×10³ times the wavelength of incidence, can be obtained theoretically. Simulation and calculation results show that the thickness of termination layer and periodic structure bilayer of 1DPC film with 0.1-nm resolution can be obtained by measuring the GH shifts. The exact structure of a 1DPC film is innovatively measured by the BSW-enhanced GH shift.