Characteristics of local photonic state density in an infinite two-dimensional photonic crystal

The local density of photonic states （LDPS） of an infinite two-dimensional （2D） photonic crystal （PC） composed of rotated square-pillars in a 2D square lattice is calculated in terms of the plane-wave expansion method in a combination with the point group theory. The calculation results show that the LDPS strongly depends on the spatial positions. The variations of the LDPS as functions of the radial coordinate and frequency exhibit “mountain chain” structures with sharp peaks. The LDPS with large value spans a finite area and falls abruptly down to small value at the position corresponding to the interfaces between two different refractive index materials. The larger/lower LDPS occurs inward the lower/larger dielectric-constant medium. This feature can be well interpreted by the continuity of electricdisplacement vector at the interface. In the frequency range of the pseudo-PBG （photonic band gap）, the LDPS keeps very low value over the whole Wiger-Seitz cell. It indicates that the spontaneous emission in 2D PCs cannot be prohibited completely, but it can be inhibited intensively when the resonate frequency falls into the pseudo-PBG.     

Controlling spontaneous emission with the local density of states of honeycomb photonic crystals

We calculated the local density of state for various positions in a photonic crystal of honeycomb lattice to study how the spontaneous emission rate of a radiating dipole is altered in the presence of the photonic crystal. The local density of states is found to be position-sensitive and its value can be enhanced or depressed relative to the density of states, depending on the location of the dipole. Our study shows that the density of states tends to underestimate the effect of a photonic crystal on the prohibition of light propagation, while on the contrary tends to overestimate the effect on the enhancement of light emission. The calculations also indicate that it is possible to tailor the spontaneous emission of an active medium by careful selecting its location in the photonic crystal. The results are helpful in determining the insertion location of the active medium and in evaluating the efficiency of active photonic crystal devices such as light-emitting diodes or lasers.     

用不同密度分布的发光分子探测光子晶体的全态密度

单一原子（分子）的自发辐射衰变的动力学性质强烈地依赖于其在光子晶体中的位置及其辐射偶极矩与所处位置场的相对方向.测量单一原子（分子）的自发辐射衰变特性只能反映光子晶体的局域态密度特征，而不能反映光子晶体的全态密度特征.理论上研究发现，通过引入含不同密度分布的发光分子可以探测到光子晶体的全态密度的部分细节甚至全部信息.按来源首次将全态密度分为两个部分，证明了特定的发光分子分布可以完善地反映其中的一部分或者全部，这为解释、设计加速或抑制原子（分子）自发辐射的实验提供了有益的指导. 关键词： 光子晶体 自发辐射 态密度 密度分布     

Modification of spontaneous emission rate of micrometer-sized light sources using hollow-core photonic crystal fibers

We investigate numerically and experimentally the modification of the spontaneous emission rate for micrometer-sized light sources embedded in a hollow-core photonic crystal fiber (HCPCF). The diameter of the light source is deliberately chosen such that they could be easily introduced into the central hole of the hollow-core photonic crystal fiber by capillary force. The photoluminescence from the microparticles is measured by using an inverted microscope in combination with a spectrometer. The modification of the spontaneous emission rate is observed in a wavelength region where there is no band gap. The experimental observations are consistent with the simulation results obtained by the plane wave expansion and finite-difference time-domain techniques.     

具有态守恒赝隙的光子晶体中两能级原子自发辐射的增强与抑制

论证了在赝带隙光子晶体中存在一个全频率域态总数守恒规则，在完全带隙光子晶体中还存在一个局域态总数守恒规则.态总数守恒规则指出，如果一个光子晶体的态密度在某些频率范围存在相对于等效介质态密度的谷，则一定由其他频率范围内相对于等效介质态密度的峰来补偿.使用符合态总数守恒规则的态密度模型，解释了态密度调制导致的自发辐射谱增强、抑制、变窄、红移、蓝移以及谱分裂等光子晶体中的量子光学现象.该理论比较适合研究在具有赝带隙的光子晶体中大量随机分布的发光原子或分子的自发辐射行为. 关键词： 光子晶体 自发辐射 态密度 光子赝带隙     

Theoretical study of enhancement and suppression of the fluorescent spectra of dye molecules in a photonic crystal with a pseudogap

We have investigated the analytical forms of the photonic density of states (DOS) in a photonic crystal in the interested frequency regime according to the rule of state conservation in a photonic crystal with pseudogaps, which states that, if a valley of the DOS appears in some range of frequencies, it must be compensated for by increasing over some other ranges. By using a model DOS with a state-conservative photonic pseudogap, we have also investigated the enhancement and suppression of spontaneous emission of two-level atoms with different frequency positions and widths of emission spectra in a state-conservative electromagnetic reservoir; and the DOS-induced suppression, enhancement, narrowing and redshifting or blueshifting of spontaneous emission spectra are naturally obtained.     

2维光子晶体谐振腔的分析与模拟

为指导光子晶体谐振腔的设计,运用3维电磁场仿真软件HFSS模拟了2维光子晶体谐振腔,分析了影响2维光子晶体谐振腔的主要特性参数,主要包括所插介质杆的排列结构、介电常数及其半径和间距。研究表明,在其它条件保持不变时,若增大介质杆半径,则同一模式频率没有同一的变化规律;若增大介质杆介电常数,则出现的规则模式减少,并且没有基模出现,同一个模式,频率明显降低;若增大介质杆间距,则计算的频率间隔减小,对其它参数影响不大,只是同一模式的频率略有减小。     

High-Q cavity based on gradated one-dimensional photonic crystal

A high quality-factor （Q） cavity based on a one-dimensional （1D） photonic crystal with gradated elliptical holes was designed using FDTD simulation. Different gradient profiles of the mirror holes were found to correspond to different Q- values of the cavities. A simple strategy is proposed to construct high-Q cavities by using an S-shaped gradient profile for the elliptical holes＇ minor axes, such as a cosine function or Gaussian function. Using such a strategy, a Q value exceeding two million is obtained with only ten mirror holes in a cavity.     

The local density of states in finite size photonic structures, small particles approach

The local density of states is studied with the help of the local perturbation method for vector and scalar wave fields propagating in finite size photonic structures. The local density of states is numerically calculated for one-, two-, and three-dimensional finite size photonic structures considering them as made of small particles.     

硅基二维平板光子晶体高Q微腔的制作和光谱测量

利用微加工技术, 在SOI上制作出了高Q值的光子晶体微腔, Q值可以达7×10⁴以上, 为后续的光与物质相互作用和量子信息方面的实验奠定了基础. 实验结果与理论模拟符合得较好. 通过三维时域有限差分法模拟, 得到光子晶体微腔的Q值为1.2×10⁵左右. 关键词： 光子晶体 微腔 微加工     

二维等离子体填充金属光子晶体腔体特性

设计了等离子体填充的二维金属光子晶体特殊开放腔体结构,并采用粒子模拟技术(PIC)建立了基于等离子体填充腔体结构物理模型,分析了等离子体填充下二维腔体的各模式场分布特性,以及等离子体的引入对腔体内各模式工作频率、电场幅值的影响。结果表明:腔体内各模式的电场强度随等离子体密度的增加而减弱,模式频率随背景等离子体归一化频率的提高而增加,工作模式的产生与激励方式密切相关。     

2维光子晶体谐振腔的分析与模拟

 为指导光子晶体谐振腔的设计,运用3维电磁场仿真软件HFSS模拟了2维光子晶体谐振腔,分析了影响2维光子晶体谐振腔的主要特性参数,主要包括所插介质杆的排列结构、介电常数及其半径和间距。研究表明,在其它条件保持不变时,若增大介质杆半径,则同一模式频率没有同一的变化规律;若增大介质杆介电常数,则出现的规则模式减少,并且没有基模出现,同一个模式,频率明显降低;若增大介质杆间距,则计算的频率间隔减小,对其它参数影响不大,只是同一模式的频率略有减小。     

二维光子晶体耦合腔阵列的慢波效应研究

设计了一种六角晶格二维光子晶体耦合腔阵列,平面波展开法计算能带表明,处于禁带中的耦合缺陷腔模的色散曲线在光子晶体平面内所有k矢量方向更加平坦.模拟了横电波沿ΓK方向的透射谱.与光子晶体单缺陷腔相比,耦合腔阵列结构的缺陷腔模透射率提高三个量级以上,而群速度降低一个量级,得到0.007c的结果.该慢波效应在构造微型可调谐光延迟器和低阈值光子晶体激光器等方面具有潜在的应用前景. 关键词： 光子晶体 耦合腔阵列 慢波 透射率     

低频强场作用下三维光子晶体中二能级原子的自发辐射性质

研究了处于三维光子晶体中，且在强相干的低频场的驱动下的单个二能级原子的自发辐射性质.由于低频场的影响，使得原子产生了在跃迁过程中吸收或发射一个低频光子的衰减渠道.这些跃迁导致了自发辐射的量子干涉，再加上光子晶体能带带边的作用，自发辐射被显著抑制.原子的布居俘获依赖于原子上能级与能带带边的相对位置，低频场的频率和原子不同跃迁通道间的相对跃迁强度. 关键词： 光子晶体 二能级原子 自发辐射     

光子晶体垂直腔面发射激光器的电流分布研究

对氧化限制型外腔式光子晶体垂直腔面发射激光器注入到有源区的电流密度分布进行了分析研究.提出三维电流分布计算模型,研究了光子晶体结构对电流密度分布和器件串联电阻的影响.研究发现,光子晶体孔刻蚀深度越深,电流分布圆对称性越差,引起的串联电阻越大.不同光子晶体图案对电流分布的均匀性和圆对称性也有很大的影响.该模型对于研究、设计氧化限制型外腔式光子晶体垂直腔面发射激光器提供了一个有用的分析方法.     

Vertical cavity surface emitting laser transverse mode and polarization control by elliptical holes photonic crystal

The polarization of traditional photonic crystal (PC) vertical cavity surface emitting laser (VCSEL) is uncontrollable, resulting in the bit error increasing easily. Elliptical hole photonic crystal can control the transverse mode and polarization of VCSEL efficiently. We analyze the far field divergence angle, and birefringence of elliptical hole PC VCSEL. When the ratio of minor axis to major axis b/a=0.7, the PC VCSEL can obtain single mode and polarization. According to the simulation results, we fabricate the device successfully. The output power is 1.7 mW, the far field divergence angle is less than 10°, and the side mode suppression ratio is over 30 dB. The output power in the Y direction is 20 times that in the X direction.     

Topological photonic states in gyromagnetic photonic crystals: Physics,properties, and applications

Topological photonic states (TPSs) as a new type of waveguide state with one-way transport property can resist backscattering and are impervious to defects, disorders and metallic obstacles. Gyromagnetic photonic crystal (GPC) is the first artificial microstructure to implement TPSs, and it is also one of the most important platforms for generating truly one-way TPSs and exploring their novel physical properties, transport phenomena, and advanced applications. Herein, we present a brief review of the fundamental physics, novel properties, and practical applications of TPSs based on GPCs. We first examine chiral one-way edge states existing in uniformly magnetized GPCs of ordered and disordered lattices, antichiral one-way edge states in cross magnetized GPCs, and robust one-way bulk states in heterogeneously magnetized GPCs. Then, we discuss the strongly coupling effect between two co-propagating (or counter-propagating) TPSs and the resulting physical phenomena and device applications. Finally, we analyze the key issues and prospect the future development trends for TPSs in GPCs. The purpose of this brief review is to provide an overview of the main features of TPSs in GPC systems and offer a useful guidance and motivation for interested scientists and engineers working in related scientific and technological areas.     

Vertical cavity surface emitting laser transverse mode and polarization control by elliptical hole photonic crystal

The polarization of traditional photonic crystal(PC) vertical cavity surface emitting laser(VCSEL) is uncontrollable,resulting in the bit error increasing easily.Elliptical hole photonic crystal can control the transverse mode and polarization of VCSEL efficiently.We analyze the far field divergence angle,and birefringence of elliptical hole PC VCSEL.When the ratio of minor axis to major axis b/a = 0.7,the PC VCSEL can obtain single mode and polarization.According to the simulation results,we fabricate the device successfully.The output power is 1.7 mW,the far field divergence angle is less than 10°,and the side mode suppression ratio is over 30 dB.The output power in the Y direction is 20 times that in the X direction.     

圆柱形散射子二维光子晶体的态密度与局域态密度

二维光子晶体只有赝带隙,因此能否利用二维光子晶体有效控制原子自发辐射是令人感兴趣也是有实际意义的问题。其中最重要的因素是态密度和局域态密度的性质。采用平面波展开结合晶体群论的方法计算了二维正方格子光子晶体的态密度和局域态密度。其中散射子为空气圆柱,放置在均匀的电介质背景上。结果显示两个特点:第一,总态密度和局域态密度在原来二维光子晶体赝带隙处虽然已经不为零,但是取值明显低于赝带隙范围之外的值,即存在一个准光子带隙。第二,局域态密度在空气散射子界面处发生突变,空气散射子区域的局域态密度相对较大,这可由电位移矢量的连续性来理解。由于这两个特点在其他二维光子晶体中也被发现过,它们可能是普遍存在的。     

立体耦合光子晶体薄板微腔的高Q值特性研究

利用微腔之间的立体耦合,提出了基于无源材料硅的双层光子晶体薄板H1(DLPCS-H1)腔,薄板之间为空气层.使用三维时域有限差分方法和Padé近似方法分析了DLPCS-H1腔的偶极模的场分布和品质因子.通过对中间空气层高度的优化使DLPCS-H1腔的偶极模的品质因子得到了显著的提高,大约为单层光子晶体薄板H1腔的偶极模的品质因子的4倍.此外,还研究了三层光子晶体薄板H1腔,它的偶极模的品质因子约为单层光子晶体薄板H1腔的偶极模的品质因子的7倍.