共查询到20条相似文献,搜索用时 62 毫秒
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将PG玻璃材料制作成的椭圆纤芯引入光子晶体光纤中心,设计了一种石墨烯包层结构的高双折射光子晶体光纤.基于有限元法对该光纤的双折射特性进行了数值模拟,研究了光纤孔径比、孔间距和纤芯椭圆对双折射特性的影响,并以该光子晶体光纤的模场面积和限制性损耗为依据进行了优化.研究结果表明:在波长1 550nm处,光纤双折射率高达0.13,满足高双折射要求;两偏振方向模场面积小于0.7μm2,限制性损耗低于10-6 dB/km.该光纤可有效保持光在传输系统中的偏振状态,为高稳定性超连续谱的产生提供依据. 相似文献
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设计了一种基于肖特玻璃SF57的新型高双折射光子晶体光纤,在纤芯和包层同时引入椭圆空气孔,并且在包层的最内层对称地引入两个圆形空气孔.通过改变空气孔的间距和椭圆率,采用全矢量有限元法研究了该光纤的双折射、限制损耗和色散特性.数值研究发现,在纤芯中引入小椭圆空气孔,可极大地提高双折射的数值.通过优化光纤的结构参数,当孔间距Λ为1.60μm,椭圆率η为0.5时,在波长1.55μm处,双折射高达5.22×10-2,限制损耗低至8.82×10-10dB/m,且该光纤在1.0~2.2μm的波长范围内保持正常色散,可用于宽带色散补偿.该设计对研究新型背景材料的光子晶体光纤具有一定的意义. 相似文献
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设计了一种高双折射高非线性多零色散波长的全内反射光子晶体光纤,采用有限元法研究了这种光纤的有效模面积、非线性、色散和双折射特性.计算结果表明,通过设置合适的结构参数,该光纤可在波长1.55μm处获得2.54×10-2的双折射,也可在X,Y偏振方向分别获得50.22 W-1·km-1和54.61 W-1·km-1的高非线性系数.另外,该光纤在近红外波段出现了两个零色散波长,其中的一个零色散波长出现在1.55μm附近.本设计为获得高双折射高非线性多零色散波长的光子晶体光纤提供了一种新的结构,其在偏振控制、非线性光学、色散管理和超连续谱传输方面具有广泛的应用前景. 相似文献
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提出了以包层为椭圆空气孔的矩形结构光子晶体光纤,采用有限元法分析了光子晶体光纤的双折射和损耗特性.研究表明:当光子晶体光纤中心缺失两个空气孔,即Λx=1.0μm,Λy=2.0μm时,在1.55μm处双折射可以达到1.98×10-2;在芯区引入小的椭圆空气孔时,双折射与引入椭圆空气孔的大小、长短轴的比例和空气孔的位置有关;芯区引入空气孔后,使光模场发生了形变,同时减少了向包层的泄漏,其损耗相比未引入空气孔小;增加包层的层数,发现包层层数对光纤双折射和损耗几乎没有影响,当包层层数N4时,损耗小于10-3量级. 相似文献
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设计了一种高双折射高非线性光子晶体光纤, 采用全矢量有限元法研究了这种光纤的基模模场、双折射、非线性、有效模面积及色散特性. 数值研究发现, 减小孔间距Λ的大小, 在波长1550 nm 处, 该光纤可获得10-2 数量级的双折射B, 比普通的椭圆保偏光纤高约两个数量级; 同时, 该光纤可获得42 W-1·km-1 的高非线性系数γ. 另外,分别在可见光和近红外波段出现了两个零色散波长, 在波长800–2000 nm 之间具有良好的色散平坦特性. 这种设计为获得高双折射高非线性超平坦色散光子晶体光纤提供了一种新的方法, 该光纤在偏振控制、非线性光学和色散控制方面具有广泛的应用前景.
关键词:
光子晶体光纤
高双折射
高非线性
有限元法 相似文献
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设计了一种新型近椭圆内包层(NEIC)结构的高双折射偏振保持光子晶体光纤(PCF),并利用带有各向异性完全匹配层吸收边界条件的全矢量有限元法(FEM)对这种光纤的特性参数进行了数值分析.结果表明这种结构的光子晶体光纤在1.55μm的双折射系数高达2.0×10-3,在长轴和短轴方向上的模场直径分别为9.2μm和2.4μm.同时当短轴方向最内层空气孔的孔径在1.30—1.18μm范围内变化时(孔径变化范围~10%),其双折射系数的劣化小于1.2×10-5,表明这种结
关键词:
光子晶体光纤
双折射
近椭圆内包层
偏振稳定性 相似文献
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A multi-conjugate adaptive optics (MCAO) can offer a possibility of widening field of view (FOV) characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle's expressions of two deformable mirrors (DMs) MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance. 相似文献
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Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use. 相似文献
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A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands. 相似文献
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40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm. 相似文献
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Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser. 相似文献
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Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored. 相似文献
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Xin Kang 《中国光学快报(英文版)》2008,6(2)
An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography. 相似文献
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The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films. 相似文献
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References: 《声学学报:英文版》2008,27(1):85-96
Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation. 相似文献