异质双周期结构光子晶体光学特性

利用传输矩阵法研究了异质双周期结构一维光子晶体的带隙结构和光学传输特性。此光子晶体能形成512～960 nm的含5个极窄透射峰的光子带隙。重点研究了一种材料为复折射率时的光学传输特性,以及当结构发生轴向应变时的"介观压光效应"。结果表明:当复折射率虚部为负时,透射峰随虚部绝对值的增大先增大后减小,甚至出现衰减;虚部为正时,发生吸收现象。当光子晶体发生轴向应变时,透射峰随应变量的增加呈现近似L形变化,应变量很小时透射率几乎线性减小,波长越大透射峰变化越缓慢。

复介电双周期光子晶体的特性研究

利用传输矩阵法研究了复介电双周期光子晶体的带隙结构和光传输特性。研究发现:一维双周期光子晶体的光子带隙结构中在两光子晶体带隙交叠处具有很明显的两共振透射峰。当组成双周期光子晶体的一种介质为复介电且其虚部为负时,两共振透射模式都出现了较强的增益。随着复介电常量的虚部的增加,两透射增益先增加后减少,中间存在一极值点。而当组成双周期光子晶体的一种介质的复介电虚部为正时,表现为对两共振透射模式的吸收。这一结果为光子晶体同时实现双通道超窄带滤波器和光放大微器件提供了理论基础。

双原子正方晶格光子晶体边界模式的光传输特性（英文）

利用平面波展开法,发现双原子正方晶格光子晶体中ΓM方向边界面存在着快慢两类边界模式,并且通过计算色散关系和电场分布研究了边界参量对这两类边界模式传输特性的影响.依据两种模式的色散关系,计算了群指数和群速度色散参量,结果表明边界参量的变化对第一类边界模式传输特性的影响较小,该模式的平均群指数始终维持在5.0左右;第二类边界模式与第一类模式明显不同,边界参量的变化能够有效地影响到这种模式的传输特性,该模式的最大平均群指数可达178左右.利用时域有限差分法记录了不同时刻电场强度在边界附近的分布及监测点处的电场幅度变化情况,结果表明,两类模式都能够被限制在边界附近并向前传播,时域有限差分法得到的群速度与平面波展开法的结果完全吻合.

一维双周期光子晶体的特性分析

借助传输矩阵法研究一维光子晶体的光传输特性。当一维光子晶体为双周期时,两光子晶体禁带的交叠处将会出现明显的共振透射峰。当一维双周期光子晶体的一种组成介质的介电常数为复数并且其虚部为正时,两透射峰都将出现吸收现象。如果该介电常数虚部为负,则两透射峰都将出现放大现象。

含负折射率材料的一维双周期光子晶体带隙特性

基于传输矩阵法,对含负折射率材料的一维双周期光子晶体的带隙特性进行研究.与一维单周期光子晶体以及常规材料构成的一维双周期光子晶体的归一化透射率曲线相比较,可见含负折射率材料的一维双周期光子晶体在一个禁带周期内的禁带数量相对于前者明显增加了,其禁带宽度相对于后者明显增加,且更加平坦,其导带是一个尖锐的透射峰.进而分析了含负折射率材料的一维双周期光子晶体的带隙结构的形成机理,并进一步分析了含负折射率材料的一维双周期光子晶体的子周期长度、材料的相对折射率差和薄膜厚度对其禁带特性的影响.

基于异质双周期结构光子晶体加速度计的设计

对于异质双周期结构的光子晶体而言,不需要掺杂即可形成多条透射谱。理论结果显示,在实际应用范围内,透射率与光子晶体所受的轴向应力呈简单的线性关系。据此,设计了一种单悬臂梁结构的多量程、超灵敏的宽频带加速度计。在单悬臂梁根部所受应力最大处,用异质双周期光子晶体替代以往的压敏电阻,只需检测出透射光强与入射光强的比值,即可测出加速度。ANSYS软件仿真结果表明,当透射光强改变万分之一时,该加速度计可以感知0.01gn的加速度变化,测量量程可达100gn。从模态分析图中可以看到该加速度计可以稳定地工作,可用在自控、车辆、测试等领域。

非对称双芯光子晶体光纤特性分析

设计一种新型非对称双芯光子晶体光纤模型,利用有限元法及其双芯光纤的耦合特性分析其光子晶体光纤的光学特性,数值模拟了非对称双芯光子晶体光纤的有效折射率、双折射、耦合系数在一定结构参数下随波长的变化特性.数值模拟结果表明,选择合适的结构参数可以得到较高的双折射特性以及耦合特性,因此光子晶体光纤的非对称结构的特性分析对于光学器件的研制有重要意义.

双缺陷光子晶体禁带结构特性研究

用特征矩阵法研究了带有双缺陷的一维光子晶体的禁带结构特性。由于两缺陷间存在相互作用,其禁带结构的性质受到两缺陷间隔光学厚度及缺陷层折射率的影响。定义了描述两缺陷间相互作用强弱的关联系数,进而分析了关联系数与两缺陷层间相隔光学厚度及缺陷层折射率的关系。通过数值计算和计算机模拟,确定了光子晶体结构的特征间隔光学厚度。

双周期渐变光子晶体结构及其纳米聚焦效应

利用3+3光束双锥干涉法设计了双周期渐变光子晶体结构阵列,并研究了它的纳米聚焦效应。通过调整内锥角和内外锥的增量角来改变光子晶体晶格的小周期及光子阵列的大周期,通过调整光束强度、偏振方向来实现渐变光子晶体晶格结构、形状等参数的改变。采用傅里叶变换的方法研究了光子晶体结构对光场的纳米聚焦效应。该结构对于提高发光二极管的提取效率、光显示、光耦合及光集成具有非常重要的意义。

基于双锥干涉法的双周期渐变光子晶体透镜聚焦特性研究

构建双锥干涉模型设计双周期渐变光子晶体(GPC)结构,基于该结构的渐变光强分布设计了介质柱尺寸渐变的GPC透镜,并研究了内外锥干涉角对GPC周期及透镜聚焦特性的影响。研究发现,干涉光束内外锥角正弦差决定透镜大周期,而外锥角则直接影响小周期。当透镜大周期固定时,小周期越小,聚焦效果越好;而小周期固定时,大周期越小,透镜数值孔径越大。所设计的透镜可实现亚衍射极限聚焦,该研究有助于透镜在光耦合、光集成、光显示以及成像方面的应用。

可调光子晶体研究进展

可调光子晶体是光子晶体研究中的一个新领域 .文章简单介绍了当前可调光子晶体的发展状况 ,阐述了其调制机理及存在的问题 ,同时论述了可调光子晶体的发展趋势 .

增益平坦的全光波长转换技术研究

为避免多路波长转换实现增益平坦时引起的码间串扰和非线性影响,利用喇曼增益效率系数在L波段近似为常数的非对称双芯光子晶体光纤(ATC-PCF),设计了一种增益平坦的全光波长转换方案。建立了基于ATC-PCF中受激喇曼散射(SRS)效应的多路波长转换理论模型,给出了多路波长转换器的原理框图,并通过Matlab进行仿真分析。结果表明:所设计的波长转换器平坦度为0.3359dB,带宽为60nm。当泵浦光功率为1.6W、光纤长度为1.5km时,平坦度都可以保持在1dB内,为设计增益平坦的多路波长转换器提供了新的理论基础。

A kind of photonic crystal fiber with high birefringence and low cofinement loss

The triangular-lattice highly birefringent photonic crystal fibers(PCFs) with gradually increasing diameter of the air holes along radial axis are put forward. The modal birefringence, dispersion and confinement loss of the fundamental mode are simulated by full vector Galerkin finite element method(FEM) with a perfectly matched layer(PML). The results show that this PCF can keep low confinement loss when the rings of air holes are few. When the wavelength is 1.55 μm , the birefringence, the confinement loss of quick-axis and slow-axis are 1.365×10-3, 0.017 dB/m and 0.051 dB/m, respectively. A new way is proposed to fabricate polarization-mainting fibers with high performance.

测量多种气体体积分数的PCF传感器结构

为提高气体体积分数传感器的灵敏度、抑制光纤的模间干扰,设计了双通道边孔型结构,利用COMSOL软件建立气体体积分数传感模型的方法和损耗谱分析法,研究不同结构参数和镀膜厚度对光纤气敏特性的影响,进行理论分析和实验验证,调整薄膜材料厚度和光纤气孔尺寸,通过分析光纤双折射变化规律得到最优的各类参数方案。结果表明,该传感器对氢气的探测灵敏度为0.36nm/%,对甲烷的探测灵敏度为2.89nm/%,且线性度高。该光子晶体光纤气体传感器具有灵敏度高、响应速度快等优点,还能同时对两种气体进行检测,应用范围广,为研发实际生活及工业领域相关气敏性薄膜和实现一根光纤传感器同时检测3种甚至更多种气体体积分数提供了参考思路。

Design of a fiber polarizer based on an asymmetric dual-core photonic crystal fiber

We propose a novel optical polarizer based on an asymmetric dual-core photonic crystal fiber(PCF) with triangular lattice air-holes.The fiber is designed as that the effective indices of modes in the two cores are matched at one polarized state but mismatched at another polarized state.As a result,one of the polarization states is coupled to the other core and transferred into a high-order mode.The transmission properties of the polarizer are investigated by the semi-vectorial beam propagation method(SV-BPM).Numerical results demonstrate that a device length of 11.3 mm shows extinction ratio as low as-20 dB with bandwidth as great as 80 nm ranging from 1.51 mm to 1.59 mm.

Luminescence enhancement from Si-based materials by introducing a photonic crystal double-heterostructure slot waveguide microcavity

We demonstrate a novel SOI-based photonic crystal（PC） double-heterostructure slot waveguide microcavity constructed by cascading three PC slot waveguides with different slot widths,and simulate the luminescence enhancement of sol-gel Er-doped SiO2 filled in the microcavity by finite-difference time-domain（FDTD） method.The calculated results indicate that a unique sharp resonant peak dominates in the spectrum at the expected telecommunication wavelength of 1.5509 mm,with very high normalized peak intensity of ~108.The electromagnetic field of the resonant mode exhibits the strongest in the microcavity,and decays rapidly to zero along both sides,which means that the resonant mode field is well confined in the microcavity.The simulation results fully verify the enhancement of luminescence by PC double-heterostructure slot waveguide microcavity theoretically,which is a promising way to realize the high-efficiency luminescence of Si-based materials.

The polarization-dependent supercontinuum generation in photonic crystal fibers with high birefringence and two-zero dispersion

A polarization-dependent supercontinuum spectrum source of light from the UV to infrared region has been generated in our photonic crystal fiber with birefringence B=2.23×10 3.By tuning the polarization direction of the input pulse,it is found that the width of the supercontinuum spectrum changes dramatically with the input polarization directions.At the same time,we qualitatively explain the blue-shift peak and the red-shift peak in the experimental spectrum using phase matching conditions on dispersive waves,stoke waves and the pump wave.In addition,we also found that supercontinuum spectrum generation,to some extent,is dependent on the pump wavelength and average power of the pump.The spectrum is broadened with the increase of average power,but unchanged after average power reaches a certain value;when the pump wavelength is located in the anomalous dispersion and further away from the zero-dispersion wavelength,the spectrum of the supercontinuum is wider.

Crystal structures,two-photon absorption and theoretical calculation of a series of bis-vinylpyridine compounds synthesized by one-step solid state reaction

Three bis-vinylpyridine compounds (4,4′-bis(2-vinylpyridine)biphenyl L1,4,4′-bis(3-vinylpyridine) biphenyl L2,and 4,4′-bis (4-vinylpyridine)biphenyl L3) were synthesized by one-step solid-state reactions at room temperature,giving nearly quantitative yields. The compounds obtained were fully characterized by IR,MS and NMR spectroscopies. The structures of L2 and L3 were determined by single crystal X-ray diffraction analysis. No noticeable solvatochromism was observed in either one-photon absorption or one-photon excited fluorescence spectra. All of the compounds have high fluorescence quantum yields and long fluorescence lifetime. The linear and nonlinear optical properties of the compounds were investigated both experimentally and theoretically. Interestingly,the position of the nitrogen atom from pyridine influences their two-photon absorption across-sections.

Numerical study on pulse trapping in birefringent photonic crystal fibers

Using an adaptive split-step Fourier method,the coupled nonlinear Schrdinger equations have been numerically solved in this paper.The nonlinear propagation of an ultrashort optical pulse in the birefringent photonic crystal fibers is investigated numerically.It is found that the phenomenon of pulse trapping occurs when the incident pulse is deviating from the principal axis of the fiber with some angle.Owing to the birefringence effect,the incident pulse can be regarded as two orthogonal polarized pulses.The phenomenon of pulse trapping occurs because of the cross phase modulation(XPM) between the two components.As a result,the bandwidth of the supercontinuum(SC) decreases compared with the case that the incident pulse is input along the principal axis.When the polarization direction of the incident pulse is parallel to the fast axis,the bandwidth of the supercontinuum is maximal.

A novel high birefringence equal diameter circular-hole photonic crystal fiber

A novel equal diameter circular-hole photonic crystal fiber(PCF) with high birefringence is proposed and numerically analyzed by employing the finite-element method. The proposed PCF's birefringence is 10^(-3), which can reach 2 orders higher than that of traditional high birefringence fiber, and this equal diameter circular-hole structure reduces the difficulty of the actual drawing process. The effect of different parameters on the birefringence of this PCF is investigated, and the application of the Sagnac interferometer based on fiber filling technology in temperature sensing is studied. The result shows that the high birefringence PCF can be used in both optical communication and optical sensing fields.