一维对称光子晶体的简正耦合模

对一维对称光子晶体中的色散介质采用洛仑兹振子模型,通过考虑色散介质层两侧的边界条件,得到了表征色散介质层的转移矩阵.对线性层及色散δ层均采用传输矩阵的方法,研究了一维含色散介质的光子晶体微腔中的简正耦合模.由于光与色散介质的相互作用,纵腔模将分裂成简正耦合模.通过改变色散介质的相关参数,详细研究了简正耦合模频率的移动、均匀展宽效应和失谐效应.发现两个简正的耦合模的频率间距主要依赖于振子的耦合强度,与约化的振子的HWHM线宽无关.失谐效应则会使其中的一个峰降低,而另一个峰相对拉高,这一现象可以通过Fabry-Pérot腔得到很好的解释.     

含色散与非线性媒质的光子晶体的简正耦合模

利用传输矩阵方法及对色散媒质采用洛伦兹振子模型，研究了一维含色散媒质的光子晶体的简正耦合模，并计算了该结构的复有效折射率。在光学双稳态中，与仅含非线性媒质的光子晶体相比，得到了低得多的阈值入射光强。     

含色散介质的一维光子晶体微腔中简正耦合模的物理图像

对一维光子晶体中的色散介质采用洛伦兹振子模型,对线性层及色散δ层均采用传输矩阵的方法,研究了一维含色散介质的光子晶体微腔中的简正耦合模.通过改变洛伦兹振子和微腔之间的失谐频率,分析了简正耦合模频率的变化情况.在失谐频率比较大时,光与洛仑兹振子间的耦合作用较小,简正耦合模中的一个接近腔模频率,而另一个则接近洛仑兹振子的共振频率;在失谐频率比较小时,光与洛仑兹振子间的耦合作用较大,简正耦合模与未耦合的腔模频率和洛仑兹振子的共振频率之间的差别较为明显.最后通过引进该结构的复有效折射率,对含色散介质的系统,由于带隙中间的共振模被湮灭并分裂为左右两个耦合模,其复有效折射率虚部在原共振峰处跃变为一较大值,而在新生成的两个耦合模附近趋近于零,光与色散介质相互耦合而形成的腔极化激元的物理图像十分清晰.     

光子晶体晶粒尺寸和排列结构对随机激光辐射特性的影响

研究了光子晶体对随机激光器的输出特性的调控,并分析了光子晶体的晶粒尺寸和排列结构等对调控作用的影响.对于同一随机介质而言,上下表面用同种材料不同晶粒尺寸的光子晶体覆盖,结果显示:晶粒尺寸合适的光子晶体会使光在系统中来回振荡从而得到很好的放大,使系统中的光与随机增益介质的相互作用加强,激光阈值降低;同时还对激光模式有较强的调制能力,能在一定程度上抑制自发辐射,使之向所需要的频率内辐射.但如果光子晶体的晶粒尺寸与随机增益介质结构匹配不当,则光子晶体对激光模式调制能力较弱,光场能量不能有效地被局域在系统中,系统 关键词： 有限时域差分法 光子晶体 随机激光 辐射特性     

与色散介质毗邻的一维半无限光子晶体表面态

运用Bloch定理和传输矩阵方法,研究了与色散介质毗邻的由两种材料组成的半无限一维光子晶体局域表面态的电场和色散关系.和以空气为背景的一维光子晶体相比,毗邻色散介质的光子晶体表面模色散曲线在一定堆积次序下会在较低的带隙中发生断开,较高带隙中的表面模群速度在不同堆积次序下会有很大差异.当与色散介质毗邻的物质折射率较大时,较高带隙中的表面模群速度较小;与色散介质毗邻的物质折射率较小时,较高带隙中表面模的群速度较大.     

Superprism properties in 2D polymer photonic crystals at high normal frequencies

The superprism effects of higher bands, i.e., for normal frequencies of higher than one, in two-dimensional (2D) polymer photonic crystals (PCs) are investigated. It is shown that in a polymer PC of triangular symmetry with filling factor of about 31%, the gradual transition of the hexagonal into triangular equi-frequency dispersion contours leads to a strong superprism in the 6th band at a normal frequency of 1.2. This dispersion is more prominent than those observed in the lower bands in 2D PCs. Also, this requires a lattice constant longer than the concerned wavelength. Furthermore, in a 2D polymer PC with a filling factor of about 83% a strong discontinuous superprism effect occurs at normal frequencies higher than one, which is due to an abrupt transition between two modes with the refraction angles of opposite signs. The effect can be exploited for switching applications as demonstrated in the paper.     

Ring resonator of surface modes based on photonic crystals

We design a compact ring resonator of surface modes based on photonic crystals (PCs). The structure is formed by sandwiching a surface mode ring waveguide (SMRW) into two parallel surface mode waveguide (SMW) based on two dimensional (2D) PCs. The SMRW is created on the surface of a circular photonic crystal (CPC) structure, where the wave propagates with high transmission efficiency. As a fundamental mode is introduced in the input SMW, at certain frequencies, the SMRW modes are enhanced because of resonance and the light-waves are coupled to the output SMW. It is demonstrated by the simulation results that the surface mode ring resonator has a low radiation loss with a very small size because of the good wave-guiding of surface mode based on PCs, and can be used in the future wavelength division multiplex (WDM) optics communication systems.     

Photonic band gap of one-dimensional periodic structure containing dispersive left-handed metamaterials

Band structures of one-dimensional(1D)photonic crystals(PCs)containing dispersive left-handed metamaterials are studied theoretically.The results show that the structure possesses a type of photonic band gap originating from total internal reflection(TIR).In contrast to photonic band gaps corresponding to zero average refractive index and zero phase.the TIR gap exhibits sharp angular effect and has no polarization effect.It should also be noted that band structures of transverse electric(TE) and transverse magnetic(TM) mode waves are exactly the same in the PCs we studied.     

Tunneling modes in photonic crystals with anisotropic single-negative metamaterials

We study tunneling modes in a one-dimensional photonic crystal (1DPC) with multilayered periodic structures containing dispersive anisotropic single-negative (ASNG; permittivity- or permeability-negative) metamaterials. A defect layer is introduced into the proposed structure, and some unusual properties are found in contrast with that of a tunneling mode in PCs with isotropic single-negative (SNG) gaps.     

Kerr缺陷一维耦合腔光波导的双稳态方向性

本文提出一种只在一层高折射率介质层中掺杂Kerr介质的一维耦合腔光波导.利用一维传输矩阵理论和非线性传输矩阵方法研究了此结构的光学双稳态.根据一维传输矩阵理论分析了此结构的线性特性,包括低频带边模的偏移及场分布的特点,讨论了此结构实现双稳态的原理.研究发现:由于缺陷层中场分布与入射光方向密切相关,而缺陷层光场的局域,将激发Kerr介质的三阶非线性效应,从而改变了缺陷层的折射率,所以不同方向的入射光具有不同的双稳态阈值.利用非线性传输矩阵方法研究了光学双稳态特性.结果表明:由于缺陷层的位置导致缺陷模正方向（由左到右）入射的场分布大于反方向（由右到左）入射的场分布,正方向的阈值低于反方向的阈值,相差一倍.     

Multiwavelength ultralow-threshold lasing in quantum dot photonic crystal microcavities

We demonstrate multiwavelength lasing of resonant modes in linear (L3) microcavities in a triangular-lattice 2D photonic crystal (PC) slab. The broad spontaneous emission spectrum from coupled quantum dots, modified by the PC microcavity, is studied as a function of the intensity of incident optical excitation. We observe lasing with an ultralow-threshold power of approximately 600 nW and an output efficiency of approximately 3% at threshold. Two other resonant modes exhibit weaker turnon characteristics and thresholds of approximately 2.5 and 200 microW, respectively.     

Optical multistability in 1D photonic crystals with nonlinear Thue–Morse structure

A 1D photonic crystal structure contains 16 layers, 8 common dielectric layers and 8 layers with nonlinear medium, with an arrangement similar to the 5th generation, Thue–Morse multilayer is presented. The properties of photonics band gap, field distribution and optical multistability are investigated. On the band gap, 5 resonant modes is observed. On the behavior of output intensity versus input intensity around resonant frequencies, the multistability response observed. When the frequency of incident field is close to the resonant frequency, the threshold intensity of multistability is decreased.     

L-band polarization-controlled multiple dissipative solitons generation in a normal dispersion fiber ring laser

A polarization-controlled multiple dissipative solitons generation in a normal dispersion fiber ring laser operating in L-band is demonstrated. The fiber laser is passively mode-locked with nonlinear polarization rotation (NPR) technique. Depending on the rotations of the PCs, the number of the pulses circulating in the laser cavity can be tuned from 1 to 4. The experimental results suggest that the generation of multiple pulses is caused by the soliton shaping of dispersive waves induced by the variations of spectral filtering effect.     

含色散介质的一维光子晶体微腔的光学特性和模式调节

采用时域有限差分(FDTD)法计算了含色散介质一维光子晶体微腔的透射谱,研究了缺陷模的频移特性。通过与无色散光子晶体微腔透射谱相比较,发现了介质色散导致的缺陷模频移现象,并详细地分析了中心频率、色散强度和衰减系数等色散介质参量和缺陷模频移的依赖关系。模拟结果显示,缺陷模的频移决定于中心频率、色散强度和衰减系数等色散介质参量的大小,通过合理的调节这些参量,可以有效地调节缺陷模的频率。     

随机性对部分随机介质激光器阈值的影响

基于速率方程和Maxwell方程相结合的模型，采用时域有限差分法(FDTD)研究了介质的随机性和层数对部分随机介质激光器阈值的影响.模拟结果显示，当抽运速率超过阈值时，出现一个或者多个振荡模；随机性或者系统的尺度增加时，振荡模数量也增加；部分随机介质激光器的阈值在一定的随机强度和层数下将达到最小值，它与完全随机情况下的结论有所不同.对所得到的结论给出了物理解释.这些结果对于制作随机激光器和光集成潜在应用价值. 关键词： 激光物理 随机激光器 阈值 时域有限差分法     

Properties of defect modes in one-dimensional photonic crystals containing a graded defect layer

The properties of defect modes in one-dimensional photonic crystals (PCs) containing a graded defect layer are studied theoretically. The relative permittivity and magnetic permeability of the graded defect layer vary continuously along the direction perpendicular to the surface of the layer. The effect of the linear gradation profiles of the relative permittivity and permeability are studied in detail. It is shown that the defect modes appear inside the forbidden band gaps in its transmission spectra and the gradation profiles of the relative permittivity and permeability affect the defect modes significantly. By changing the gradation parameters, the intensity and position of the defect modes can be tuned. Therefore, introducing a graded defect layer in one-dimensional PCs provides possible mechanism for tuning the defect modes. This may be useful in the design of channeled filters.     

Spectral linewidths of two mode lasers

By application of quasilinear response theory the spectral linewidths of two mode lasers near their threshold are calculated. Use is made of an adaequate fluctuation-dissipation relation. The laser is described by a fluctuation Hamiltonian with intensity and phase coupling of the modes. Incidentally the two modes' intensity fluctuation linewidths (given earlier) are rederived, and a formerly given result on the detuned single mode laser is corrected. For the phase coupled two mode laser we find a third threshold between the photon thresholds and, for large pumping, a linewidth factor 1/2.     

High-Efficiency Bistable Switching Based on One-Dimensional Photonic Crystals with Single-Negative Materials

We study theoretically the nonlinear responses of one-dimensional photonic crystals （PCs） composed of alternating two kinds of single-negative （permittivity-negative and permeability-negative） materials embedded with a Kerrtype nonlinear defect layer. In conventional PCs, it is difficult to realize a bistable switching with both low threshold and quick response time. However, in PCs with single-negative materials, by changing the ratio of the thicknesses of the two types of layers, with the decreasing size of the structure, the switching response time is shortened and the threshold intensity decreases simultaneously.     

Interface and propagating optical phonon mixing modes in a wurtzite GaN-based quantum dot

The polar optical phonon vibrating modes of a quasi-zero-dimensional (Q0D) wurtzite cylindrical quantum dot (QD) are solved exactly based on the dielectric continuum model and Loudon’s uniaxial crystal model. The result shows that there exist four types of polar mixing optical phonon modes in the Q0D wurtzite cylindrical QD systems, which is obviously different from the situation in blende cylindrical QDs. The dispersive equations for the interface-optical-propagating (IO-PR) mixing modes are deduced and discussed. It is found that the dispersive frequency of IO-PR mixing modes in wurtzite QD just take a series of discrete values due to the three-dimensional confined properties. Moreover, once the radius or the height of the QD approach infinity, the dispersive equations of the IO-PR mixing modes in the wurtzite Q0D cylindrical QD can naturally reduce to those of the IO and PR modes in Q2D QWs or Q1D QWWs systems. This has been analyzed reasonably from both physical and mathematical viewpoints. The analytical expressions obtained in the paper are useful for further investigating phonon influence on physical properties of the wurtzite Q0D QD systems.