共查询到19条相似文献,搜索用时 169 毫秒
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利用飞秒脉冲自相关技术研究了高质量三维胶体光子晶体中的慢光速和超光速效应.实验中使用的胶体光子晶体是采用压力控制的绝热沉积技术(PCIHVD)制备的、由聚苯乙烯小球组成的人工蛋白石结构.由于其中的缺陷和位错密度很低,它们具有很高的通带透过率和陡峭的能带边缘.测量了从通带到带边直至带隙中央群速度的变化,在只有20层左右小球的样品中观察到低至0.43c的慢光速以及高至1.34c的超光速现象.此外,利用时域有限差分(FDTD)方法对短脉冲在三维光子晶体中的群速度进行了数值模拟,并且和
关键词:
三维胶体光子晶体
慢光速
超光速
脉冲自相关 相似文献
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将二维三角晶格光子晶体波导和微腔结构结合,优化设计了一种二维三角晶格光子晶体共振耦合腔波导,运用时域有限差分法(FDTD)模拟共振耦合腔波导TE偏振光的透射谱,通过透射谱得到传输光的透射率和群速度。结果表明,合适参数的二维三角晶格共振耦合腔波导在波长1.551μm处的群速度为c/130、透射率为20.1%,在波长1.502μm处的群速度为c/50、透射率为29.2%。运用平面波展开法(PWE)计算的该波导的能带结构对慢光特性进行了分析。这种慢光特性的光子晶体波导将在光存储、光延迟及光子集成等方面有潜在的应用价值。 相似文献
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矩形孔光子晶体波导慢光特性 总被引:1,自引:0,他引:1
在线缺陷光子晶体波导中,利用矩形孔和椭圆孔分别替代临近线缺陷的第二行和第一、三行圆形孔,构成矩形孔光子晶体波导结构.利用平面波展开法对波导的慢光特性进行仿真分析,研究矩形孔的非对称性对慢光带宽和色散特性的影响.研究表明,在慢光区域平均群折射率变化为±10%的情况下,与圆形孔线缺陷波导相比,得到的导模能更好地限制在禁带中,而且当矩形孔宽度参量小于高度参量时,导模可以得到归一化延迟带宽积更大、带宽更宽、色散更小的慢光.通过对波导中矩形孔参量的优化,得到的慢光归一化延迟带宽积最大为0.402,此时带宽为44.4nm,群速度色散为8.0ps2/mm. 相似文献
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在单线缺陷结构中引入两个附加的相邻介质柱,构成一种新型的光子晶体耦合腔波导结构.通过平面波展开法对波导结构的的慢光特性进行了仿真分析,研究了平移线缺陷上下两侧介质柱,以及改变腔体的长度对器件色散特性和群速度的影响.结果表明:与平移缺陷上下两侧介质柱相比,通过改变腔体的长度,不仅可将光群速度低到0.03c(c为真空下的光速),而且器件的有效波长范围接近20nm.利用时域有限差分法得到波导结构的传输场分布图,研究波长的选取对入射激励光在光子晶体耦合腔波导中传输场的影响,发现结构参量优化后的光子晶体耦合腔波导仍然具有良好的传输特性. 相似文献
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采用4×4传输矩阵法研究了两种结构一维磁光子晶体的光隔离特性.结构一在外加磁场与光路光轴方向呈52.0°时,用7.96μm的总厚度在中心波长附近0.95nm范围内实现了光隔离,在此范围之内法拉第旋转角和透射率分别在45°~50.65°和97.01%~99.96%之间波动,结构仅包含43层光学薄膜,易于实际制备;结构二在外加磁场与光路光轴方向呈32.7°时,用11.54μm的总厚度在中心波长附近0.85nm范围内实现了光隔离,在此范围之内法拉第旋转角和透射率分别在45°~48.55°和98.85%~100%之间波动,结构包含73层光学薄膜,与结构一相比,该结构具有更高的透射率和更平坦的光谱.用这两种结构的一维磁光子晶体代替目前商用磁光隔离器中的块状磁光介质,可实现磁光隔离器的集成化. 相似文献
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在对周期性结构进行谐波分析的基础上,导出了非截面二维光子晶体排列矩形波导的本征值方程. 基于此方程,可以对该类光子晶体波导的所有可能模式进行分析. 分析认为,非截面二维光子晶体排列矩形波导内能存在的模式包括E(y),TEy,H(y)和TMy模式;改变波导高度,可以实现E(y)模式和H(y)模式与其他模式通带的完全分离. 然而改变任一结构参数,都不能使E(y)和H(y)的各个模式通带,以及E(y)1模式和H(y)1模式的通带完全隔离. 波导单模工作的带宽由E(y)1和E(y)2模式的低端截止频率决定.
关键词:
波导
光子晶体
本征值方程
模式 相似文献
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A two-dimensional photonic crystal coupled-cavity waveguide is designed and optimized, the transmission spectrum is calculated by using the finite-difference time-domain method, and the group velocity of c/1856 is obtained. To our knowledge, this value of group velocity is the lowest group velocity in a photonic crystal waveguide calculated from its transmission spectrum so far. The result is confirmed by the photonic band structure calculated by using the plane wave expansion method, and it is found that the photonic crystal waveguide modes in a photonic band structure are in accordance with those in the transmission spectrum by using the finite-difference time-domain method. The mechanism of slow light in the coupled-cavity waveguide of photonic crystal is analysed. 相似文献
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《Photonics and Nanostructures》2014,12(1):75-82
In this paper, we investigate coupling of light to slow modes in a photonic crystal power splitter composed of a Y-junction and two 60° bends. First, a combination of two cascaded bends which is commonly used in integrated photonic crystal circuits is studied in slow light frequency regime. We propose a structure that its transmission spectrum covers the high group-index frequencies near the band edge. Also, by structural modifications, high transmission near to 95% is achieved in slow light bandwidth. Next, we study the complete structure of a photonic crystal power splitter with parallel outputs based on a Y-junction integrated with two 60° bends. Using modified bends and reducing sharpness of Y-junction, the efficiency of splitting increases in both high and low group-index frequency bands. The optimized structure has an average efficiency of 82% in slow mode regime. This structure can be used in photonic crystal based slow light devices, such as Mach-Zehnder interferometers. 相似文献
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We study the transmission properties for the waveguide bends composed by a circular photonic crystal. Two types (Y and U type) of the waveguide bends utilizing the circular photonic crystal are studied. It has been shown, compared with the conventional photonic crystal waveguide bends, transmission properties for these bends can be significantly improved. Over a 6.4% bandwidth, less than 1-dB loss/bend are observed. U bent waveguide, i.e., 180° bend, can be easily realized with low loss using the circular photonic crystal. 相似文献
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A line defect waveguide formed by a new kind of two-dimensional photonic crystal with combinations of gradient varied dielectric was designed and the properties of slow light will been studied by using the Plane Wave expansion Method (PWM). The result shows that the group velocity is slower when the corresponding combination of gradient dielectric constants are with higher dielectric constant and lower interval. In our new structure of photonic crystal, the corresponding group velocity can reach as low as 0.06c (c: light velocity in vacuum), two orders magnitude lower than light velocity. Meanwhile, the group velocity dispersion effect is relatively small. 相似文献
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高品质因子和高传输效率的二维光子晶体耦合腔波导研究 总被引:2,自引:1,他引:1
基于时域有限差分方法,通过仿真计算设计了一种具有较高品质因子和传输效率的二维光子晶体耦合腔波导结构。通过改变二维光子晶体波导微腔结构中隔绝波导与微腔的空气孔的半径和数量,在获得近似90%的传输效率的同时,使得品质因子达到了8.20×104。为了使品质因子在大幅度提高的同时,传输效率只有小幅度的降低,在波导微腔结构中引入了链式微腔。将链式微腔结构与传统的波导微腔结构相结合,使这种新形式的耦合腔结构的品质因子提高了1个数量级,传输效率仅下降了约40%。 相似文献
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Shengli Pu Haotian Wang Ning Wang Xianglong Zeng 《Applied physics. B, Lasers and optics》2013,112(2):223-229
A line-defect waveguide within a two-dimensional magnetic-fluid-based photonic crystal with 45o-rotated square lattice is presented to have excellent slow light properties. The bandwidth centered at $ \lambda_{0} $ = 1,550 nm of our designed W1 waveguide is around 66 nm, which is very large than that of the conventional W1 waveguide as well as the corresponding optimized structures based on photonic crystal with triangular lattice. The obtained group velocity dispersion $ \beta_{2} $ within the bandwidth is ultralow and varies from ?1,191 $ a/(2\pi c^{2} ) $ to 855 $ a/(2\pi c^{2} ) $ (a and c are the period of the lattice and the light speed in vacuum, respectively). Simultaneously, the normalized delay-bandwidth product is relatively large and almost invariant with magnetic field strength. It is indicated that using magnetic fluid as one of the constitutive materials of the photonic crystal structures can enable the magnetically fine tunability of the slow light in online mode. The concept and results of this work may give a guideline for studying and realizing tunable slow light based on the external-stimulus-responsive materials. 相似文献
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In this paper, theoretical and numerical analysis of low-loss right angle waveguide bends and T-junctions based on ultra-compact photonic crystal ring resonators (PCRR) is presented. Desirable characteristics are obtained by designing the waveguide bends and T-junctions as low-Q resonant cavities with certain symmetries and small radiation loss. A simple analysis, based on coupled mode theory (CMT) in time, is used to explain the operation principles which agree qualitatively with the numerical results. These structures have high transmission efficiency over a large bandwidth in third communication window. Also effects of changing the ring size on power splitter transmission characteristics are discussed. The perfect transmission and zero reflection conditions are discussed by applying coupled mode theory. Results obtained by the finite difference time domain (FDTD) simulations are consistent with those from the coupled mode theory. 相似文献
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研究了单光子晶体界面介质波导中的慢光效应.芯层-空气层界面的全内反射效应以及光子晶体基底的禁带效应共同形成了对光场能量的横向约束.用基于超元胞的平面波展开法计算得到了导模色散曲线,并据此对其色散、群速以及群速色散性质做了详尽分析.由于利用了色散曲线慢光区域内拐点附近低群速色散的部分,该单光子晶体界面介质波导具有良好的慢光特性.对两个不同导模计算得到的平均群速分别为c/98和c/376,可用相对频带宽度分别达到2.1×10-3和4.1×10-4.另外,该慢光结构可以侧向耦合的方式克服光子晶体慢光波导耦合困难的缺点. 相似文献
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C. Jiang 《Applied physics. B, Lasers and optics》2011,102(1):49-52
An uniform silicon waveguide is proposed featuring ultralow-dispersion slow light. The core of the waveguide consists of one
silicon trip and two pairs of air/silicon strip and the cladding is composed of several alternative silicon and air strips,
which form a transverse band gap to confine propagating light in the core. The waveguide has several nearly linear photonic
bands in a large frequency range, which can support broadband slow modes with a group velocity of 0.03–0.08c and tolerable group velocity dispersion. 相似文献