共查询到20条相似文献,搜索用时 203 毫秒
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本文提出一种新型函数光子晶体, 其折射率是空间位置函数. 由费马原理, 我们给出光在一维、 二维和三维函数光子晶体中的运动方程, 以及一维函数光子晶体的色散关系、 带隙结构和透射率, 再利用传输矩阵理论研究函数光子晶体周期数、 入射角和介质层的厚度等对透射率和禁带结构的影响, 计算发现通过选择不同的折射率空间分布函数, 可以得到比传统光子晶体更宽或更窄的禁带结构. 这样为我们设计不同带隙结构的光子晶体提供理论依据. 相似文献
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非磁化等离子体光子晶体的禁带周期特性研究 总被引:12,自引:1,他引:11
用时域有限差分法(Finite-Different Time-Domain,FDTD)中的电流密度卷积(Current Density Convolution,JEC)算法讨论了一维非磁化等离子体光子晶体的禁带周期特性,分析了非磁化等离子光子晶体的周期结构和等离子体参量对其禁带周期的影响.以微分高斯脉冲为激励源,用电磁波通过非磁化等离子体光子晶体后所得的透射系数来讨论非磁化等离子体光子晶体的禁带周期特性.结果表明,通过改变参量可以获得不同的禁带周期特性. 相似文献
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用特征矩阵法研究了带缺陷的一维光子晶体的透射性质,并提出了新的可调谐光滤波器的概念.一维光子晶体(L1H1)m带有Lc-H2(L2H2)n形式的缺陷时,在光子晶体中间出现了窄的透射峰,其他级次的干涉峰则随着覆盖层H2(L2H2)n周期数的增大而减弱并消失.当耦合层Lc厚度变化时,在光子晶体禁带边缘附近出现两个高透射率区域.高透射率区域透射峰的特性由光子晶体和覆盖层的性质决定.当光子晶体禁带宽度较小时,两个高透射率区域接近,形成具有约150nm调谐范围的区域,因此可制备以一维光子晶体为基础的新型可调谐光滤波器.
关键词:
光子晶体
可调谐光滤波器
特征矩阵 相似文献
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一维光子晶体非线性色散特性的分析 总被引:10,自引:8,他引:2
从无限周期一维光子晶体的色散关系和有限周期光子晶体的透射系数两个方面,对有限和无限周期光子晶体有效折射率的实部和虚部特性曲线分别进行了计算和分析.结果表明一维光子晶体的色散曲线与弹性电偶极子的经典色散曲线类似,在光子晶体的导带为正常色散,而在禁带呈现反常色散.并且用简约布里渊和扩展布里渊区色散曲线对文献报道中存在的两种矛盾的计算结果进行了理论的探讨.解释了导致对一维光子晶体有效折射率计算存在两种不同结果的原因. 相似文献
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紫外区全角度光子晶体反射镜 总被引:3,自引:3,他引:0
根据角域叠加原理,在石英玻璃基板上用全介质膜系实现了紫外区域全角度一维光子晶体反射镜的设计。采用两个不存在全角度反射带的一维光子晶体在角域上叠加,通过传输矩阵方法,从理论上计算合成光子存在全角度禁带,禁带波长范围328.95~352.11nm,相对带宽为6.80%。实验上采用HfO2和SiO2两种薄膜材料,用电子束蒸发的方法在石英玻璃基板上制备合成光子晶体。若透射率在1%以下为光子晶体禁带,则禁带波长范围从331.2~350.4nm,相对带宽5.63%。从而证明了角域叠加设计的正确性。 相似文献
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设计了一种因掺杂而具有超窄带滤波特性的光子晶体滤波器和一种复周期结构的梳状多通道光子晶体滤波器。在两种均匀介质交替分布的周期结构中间插入一层折射率不同的介质膜后,通过传输矩阵法的数值计算,发现采用前后不对称的周期结构并调节参数,可以在1 550 nm处找到一个透射率接近100%的极窄的透过峰,因而可得到一种超窄带光子晶体滤波器。另外,在以高低两种折射率的介质交替分布,并以两种单独的单元周期合并组成一个复周期,然后进行周期重复构成的光子晶体中,利用通道数等于复周期数减1的规律,并配合各层厚度的调节,设计出在1 550 nm附近梳状8通道和16通道的光子晶体滤波器,各通道透过峰的透射率均接近100%,由此设计出一种梳状多通道光子晶体滤波器。 相似文献
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The properties of optical parametric amplification (OPA) based on non-collinear double quasi-phase matching (NDQPM) with single periodically poled KTP (PPKTP) have been investigated theoretically. The NDQPM includes two different non-linear processes: one is optical parametric generation (OPG) and the other is difference frequency generation (DFG). The investigation of our numerical simulation focuses on the gain bandwidth of dependence upon non-collinear angle, grating period and crystal temperature. At a certain non-collinear angle and grating period with fixed temperature, there exists a broadest gain bandwidths of output mid-infrared pulse at 526 nm pump wavelength and certain signal wavelength in PPKTP. These are an optimal values of non-collinear angles and grating period. By accurately tuning the non-collinear angle or temperature near the optimal non-collinear angle, broadband mid-infrared tuning is obtained and an optimal operation of NDQPM can be realized. In this paper, the solutions of the coupled equations of the cascaded processes were discussed, and the spatial-temporal frequency (STF) band of the output idler pulse is analyzed by taking angular dispersion of amplified pulse beam into account. The idler pulse with a certain angular dispersion can improve the OPA bandwidth significantly. So, optical parametric chirped-pulse amplification can be realized in this configuration. For a broadband NDQPM both the acceptance angles and the acceptance temperature are smaller and the gain bandwidth is sensitive to non-collinear angles and temperature, it is important to control the precision of the non-collinear angles and the temperature in experiment. 相似文献
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We have investigated the spectral properties of multilayer interference systems formed by multiple repetition of the symmetric three-component period ABCBA. The problem of synthesizing structures, in whose spectral characteristics suppression of adjacent fifth-, sixth-, and seventh-order high-reflection bands is observed, has been solved. It has been shown that there exist only nine options of layer thicknesses in a period. It should be noted that only in six cases upon suppression of fifth-, sixth-, and seventh-order high-reflection bands is the first-order reflection band preserved. The values of the refractive indices of layers at which the problem has a solution have been found. The refractive indices of layers in all the nine cases are described by different relations defining the dependence of the refractive index of one of the components on the randomly chosen refractive indices of the other components. 相似文献
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Applying the finite element analysis on the photonic band-gap materials with a cavity at the center for two types of structures, circular and square shape holes with the same cross section, filtering operation of these structures is simulated and compared. Any variations in the structure parameters, such as cavity length, period and hole dimensions, change the transmission peak and frequency bandwidth of these structures. The effects of rotation of square holes and ellipticity of circular holes on filtering operation are studied. Other new structures such as tapered, shortened and non-uniform rotated structures are proposed and filtering characteristics of them are discussed. It is found that, by rotating the square holes around their axis, it is possible to have a blue-shift in the transmission peak wavelength without notable variations in the filter peak and bandwidth. It is concluded that the increase of elliptical holes diameters length causes the decrease of transmission peak and increase of bandwidth with blueshift of the peak wavelength. This shift is larger for one of the elliptical diameter values considered that is along the waveguide length. 相似文献
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提出了利用准相位匹配晶体进行宽带脉冲倍频,再根据准相位匹配晶体的极化周期与倍频脉冲输出中心波长的相位匹配关系来精确测量准相位匹配晶体极化周期的新方法。理论分析了准相位匹配晶体的极化周期与倍频脉冲的光谱关系、倍频容许带宽与晶体长度的关系。研究表明:宽带脉冲倍频后输出的脉冲峰值波长对应于角度的调谐曲线具有对称性;对于长度为10 mm的极化晶体,其倍频容许带宽不到0.2 nm。实验中,采用了国产PPKTP晶体试验片,晶体尺寸为10 mm×7 mm×1 mm,理想极化周期9 300 nm。结果表明:对于中心波长为537.25 nm的倍频光,其对应的实际晶体极化周期为9 303.9 nm,大于晶体加工时的理想值;当倍频脉冲光谱测量精度为0.01 nm时,准相位匹配晶体的极化周期测量精度达到0.1 nm,远高于一般光学显微镜的观测精度。 相似文献
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Study on guided-mode resonance characteristic of multilayer dielectric grating with broadband and wide using-angle 下载免费PDF全文
Guided-mode resonance in a diffraction band of multilayer
dielectric gratings may lead to a catastrophic result in laser
system, especially in the ultrashort pulse laser system, so the
inhibition of guided-mode resonance is very important. In this paper
the characteristics of guided-mode resonance in multilayer
dielectric grating are studied with the aim of better understanding
the physical process of guided-mode resonance and designing a
broadband multilayer dielectric grating with no guided-mode
resonance. By employing waveguide theory, all guided-wave modes
appearing in multilayer dielectric grating are found, and the
incident conditions, separately, corresponding to each guided-wave
mode are also obtained. The electric field enhancement in multilayer
dielectric grating is shown obviously. Furthermore, from the
detailed analyses on the guided-mode resonance conditions, it is
found that the reduction of grating period would effectively avoid
the appearing of guided-mode resonance. And the expressions for
calculating maximum periods, which ensure that no guided-mode
resonance occurs in the requiring broad angle or wavelength range,
are first reported. The above results calculated by waveguide theory
and Fourier mode method are compared wit each other, and they are
coincident completely. Moreover, the method that relies on waveguide
theory is more helpful for understanding the guided-mode resonance
excited process and analyzing how each parameter affects the
characteristic of guided-mode resonance. Therefore, the effects of
multilayer dielectric grating parameters, such as period, fill
factor, thickness of grating layer, {\it et al.}, on the guided-mode
resonance characteristic are discussed in detail based on waveguide
theory, and some meaningful results are obtained. 相似文献
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Influence of defect states on band gaps two-dimensional phononic crystal in the of4340 steel in an epoxy 下载免费PDF全文
The band structures of a new two-dimensional triangle-shaped array geometry of 4340 steel cylinders of square cross section in an epoxy resin were studied by the plane-wave expansion and supercell calculation method. The band gaps of this type of phononic crystals with different defects were calculated such as defect-free, 60 crystal linear defect states, 120 crystal linear defect states, and 180 crystal linear defect states. It was found that the band gap will emerge in different linear defects of the phononic crystals and the bandwidth of linear defect states is larger than that of the free-defect crystal by about 2.14 times within the filling fraction F = 0.1-0.85. In addition, the influence of the filling fraction on the relative width of the minimum band gap is discussed. 相似文献
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本文基于密度泛函理论研究了扶手椅型碳化硅纳米管(SiCNT)的电子结构、成键机制以及其光学性质。研究结果表明:当碳和硅的原子比为1∶1时,SiCNT的结构最为稳定,并且表现出诸多的优良性质。通过分析计算结果我们发现,SiCNT是间接带隙材料,并且管子的带隙随着直径的增加而增加。从SiCNT的轨道图谱中我们看到碳和硅原子之间属于sp2杂化,同时硅原子周围的电子密度明显要低于碳原子周围的电子密度。对能态密度的计算我们得知碳原子和硅原子分别主导价带和导带。与其它纳米管(BN)有所不同,SiCNT的光学性质更接近于各向同性材料。 相似文献