800 nm附近具有平坦色散的光子晶体光纤的计算与设计

采用矢量有效折射率方法设计了在800 nm附近具有平坦色散的光子晶体光纤.将光子晶体光纤的总色散分为波导色散和材料色散两部分分别计算,并利用波导色散的比例性质来改变总色散.波长800 nm是广泛使用的钛宝石飞秒激光器的工作波长,该光纤对于研究飞秒激光在光子晶体光纤中的传输特性具有重要意义.     

光子晶体光纤色散调控方法的研究

文章采用全矢量有效折射法深入分析了光子晶体光纤结构参数及比例系数对波导色散、总色散的作用,总结了光子晶体光纤色散特性的调整方法,探索出特定色散特性光子晶体光纤的设计方法,并且设计了在800 nm处具有近零平坦色散的光子晶体光纤,该光纤对于研究飞秒激光的传输特性和应用具有一定的价值.     

环形结构塑料光子晶体光纤色散特性分析

利用有限差分光束传播法模拟了光波在环形结构塑料光子晶体光纤内的传输情况,讨论了基模有效折射率与光纤结构的关系,并分析了色散特性随孔间距、孔大小变化的一般规律,发现塑料光子晶体光纤的总色散主要来自材料色散,尤其在短波长范围内材料色散更是居于主导地位,但随波长的增大波导色散逐渐增大,可以设计零色散波长位于可见光波段的塑料光子晶体光纤,此光纤也能很好地应用到非线性领域.     

应用等效折射率模型研究光子晶体光纤

应用等效折射率模型研究了光子晶体光纤(PCF)的传播特性.介绍了光子晶体光纤的等效折射率模型.通过求解标量波动方程得到了光子晶体光纤包层基空间填充模的模式折射率,利用阶跃光纤的理论来研究光子晶体光纤的导模特性.应用此模型对不同结构光子晶体光纤包层区的等效折射率与波长的关系进行了讨论.包层区等效折射率与芯子的折射率差随波长的增加而增大,并由此阐述了光子晶体光纤的单模特性.数值分析得到光子晶体光纤的基模的模式折射率,并由此研究了光子晶体光纤的波导色散与结构参量的关系.分析表明,光子晶体光纤的波导色散随空气孔孔距的变化符合Maxwell方程的比例性质.空气孔的相对孔径对波导色散有重要的影响.这些分析表明光子晶体光纤具有可以灵活设计其色散特性的潜在应用前景.     

光子晶体光纤的色散特性分析

采用有效折射率模型分析了光子晶体光纤的色散特性，并给出了无限大空气玻璃微结构中基模的本征方程。分析结果表明光子晶体光纤具有奇异的色散特性，能在极大的波长范围内支持单模传输，在单模工作时可以具有反常波导色散。同时通过调整光子晶体光纤的结构参数(包括空气孔径和孔间距)可以移动零色散点的位置。最后讨论了大空气孔光子晶体光纤的特性及其在色散补偿中的应用。     

接近于零色散的色散平坦光子晶体光纤的数值模拟与分析

基于标量近似理论利用有效折射率方法对低空气填充率的光子晶体光纤 (PCF)的色散特性进行了数值模拟。发现通过调节光纤包层的空气穴节距或空气穴大小可以有效地调节光子晶体光纤的色散特性 ,可以实现光子晶体光纤零色散波长向短波方向 (小于石英材料的零色散波长 1 2 7μm)移动 ,甚至在光通信波段出现两个零色散波长 ;可以设计在光通信波段接近于零色散的色散平坦光子晶体光纤 ,其色散系数D的绝对值在 1 2～ 1 7μm波长范围小于 2 0 ps·km-1·nm-1,其色散斜率D′的绝对值小于 0 0 2 ps·km-1·nm-2 。     

光子晶体光纤色散特性的多极法研究

应用多极法对折射率导模型光子晶体光纤的色散特性进行了数值模拟.与实验数据对比,验证了该计算方法的准确性.研究了结构参量孔径d、孔距Λ和包层空气孔层数Nr对光子晶体光纤色散特性的影响;分析表明,通过改变包层空气孔直径d或空气孔间距Λ,可使光子晶体光纤零色散波长移动;当包层空气孔层数Nr较小时,Nr不同的各光纤色散特性差别极大;当Nr足够大时,将不再影响光子晶体光纤的色散特性.本文的计算和分析可以为设计适当色散特性的光子晶体光纤提供理论依据.     

光子晶体线缺陷波导中的慢光研究

研究了线缺陷光子晶体波导中的慢光现象。运用平面波展开法对线缺陷光子晶体波导结构进行了模拟计算,分析了填充因子作为敏感结构参量,其变化对色散性质和群速度的影响。发现光子晶体的填充因子决定了光子晶体带隙中导模的传输特性。随着填充因子的增加,光子晶体波导中的群速度先增大再减小。可以证明,通过改变光子晶体的填充因子,群速度可以达到0.01c以下。     

Ge_(20)Sb_(15)Se_(65)硫基光子晶体平板波导的宽带慢光特性研究

通过改变最内层两排空气孔的半径,研究了Ge20Sb15Se65硫基光子晶体平板波导的宽带慢光特性。利用三维平面波展开法,通过计算得到波导的能带结构、群折射率和色散,并分析了它们与内层空气孔半径大小的关系。同时优化第一层和第二层空气孔的半径大小,得到了群速度色散为零的对称型硫系光子晶体波导结构,并在20%的变化范围内获得大小分别为125、40和18的群折射率,对应通信波长处的带宽分别为1.7、5.6、9.7 nm,并讨论了折射率对光子晶体波导慢光性能的影响。并为高非线性、低色散的宽带慢光硫基光子晶体平板波导器件的设计及制备提供了理论基础。     

正方形栅格全固态光子晶体光纤色散的研究

为了研究正方形栅格全固态光子晶体光纤色散特性,基于全矢量有限元法,对其色散特性进行了数值模拟.通过改变正方形栅格全固态光子晶体光纤的结构参量,分析比较了它们的色散特点,并通过改进结构得出一种零散波长在1.55μm的四方栅格全固态光子带隙光纤.结果表明,四方栅格全固态光子带隙光纤色散具有3个零色散点,其零色散波长随高折射率棒直径d的增大而向长波方向移动,其色散平坦程度随棒间距Λ的减少而变得更加平坦.这为全固态光子晶体光纤的设计和制作提供了理论依据.     

Wavelength dispersion characteristics of single-mode fibers in low-loss region

Wavelength dispersion characteristics of single-mode silica fibers in a very low-loss region, including zero dispersion wavelengths, are studied in detail using a "difference method." Wavelength dispersion of single-mode fibers is compared for fibers with same material dispersion but with different waveguide structure. Material dispersion is evaluated by extracting waveguide dispersion from experimental results. Effects of waveguide dispersion on the zero dispersion wavelength of the single-mode fiber in a longer wavelength region are clearly analyzed. Single-mode fiber design consideration is given from the wavelength dispersion point of view.     

Broadband Mach–Zehnder interferometer design using microstructured optical fibers for multi-channel DPSK demodulation

Microstructured optical fibers (MOFs) are typically all silica optical fibers with air holes. Tremendous interest in these fibers has been generated because of potential applications in optical communications, remote sensing, frequency metrology and optical coherence tomography. A feature of MOFs is that waveguide dispersion can be modified significantly by means of geometrical parameters, namely, the positions and sizes of the different holes. We propose here an innovative MOF design whose waveguide dispersion inversely matches the material dispersion of silica to obtain broadband zero group velocity dispersion from 1400 to 1650 nm. One application of this fiber is in the demodulation of differential phase shift keying (DPSK) signals. We propose a novel Mach–Zehnder interferometer design using a small section of zero-dispersion fiber providing a wavelength-independent time delay and address all practical considerations. The constant free spectral range of the interferometer would allow the demodulation of multiple evenly spaced wavelength-multiplexed DPSK-encoded channels in a telecommunication link instead of one demodulator per channel.     

光子晶体光纤的色散特性分析

为了探讨靠近纤芯区域的第1层、第2层和第3层空气孔的直径对光子晶体光纤色散特性的影响,采用有限元法进行了理论分析。结果表明,适当调节第1层、第2层和第3层空气孔的直径,可以使零色散点在1100nm～1800nm之间的任何位置上移动。还可以设计在1270nm～1800nm较宽的波长范围内接近零色散的色散平坦光子晶体光纤。这一结果对光子晶体光纤的设计具有重要的作用。     

Photonic crystal fiber with novel dispersion properties

Our recent research on designing microstruc-tured fiber with novel dispersion properties is reported in this paper. Two kinds ofphotonic crystal fibers (PCFs) are introduced first. One is the highly nonlinear PCF with broadband nearly zero flatten dispersion. With introducing the germanium-doped (Ge-doped) core into highly non-linear PCF and optimizing the diameters of the first two inner rings of air holes, a new structure of highly non-linear PCF was designed with the nonlinear coefficient up to 47 W-1·km-1 at the wavelength 1.55 μm and nearly zero flattened dispersion of ±0.5 ps/(km·nm) in telecom-munication window (1460-1625nm). Another is the highly negative PCF with a ring of fluorin-doped (F-doped) rods to form its outer ring core while pure silica rods to form its inner core. The peak dispersion - 1064 ps/(km·nm) in 8 nm full width at half maximum (FWHM) wavelength range and -365ps/(km·nm) in 20nm (FWHM) wavelength range can be reached by adjusting the structure parameters. Then, our recent research on the fabrication of PCFs is reported. Effects of draw parameters such as drawing temperature, feed speed, and furnace temperature on the geometry of the final photonic crystal fiber are investigated.     

Spectrally Sliced Pulse Source Based on Supercontinuum Generation in Dispersion-Flattened Photonic Crystal Fiber

Designed is dispersion-flattened photonic crystal fiber（PCF） with small normal dispersion for generating flat wideband supercontinuum （SC）, and demonstrated is spectrally sliced pulse source which utilizes supereontinuum generated in dispersion-flattened photonic crystal fiber. The results show that the fiber characterized by flattened dispersion with small normal dispersion is suitable for flat wideband supercontinuum generation. In the process of spectral broadening, self-phase modulation plays a dominant role. By filtering the supercontinuum, multi-wavelength pulses can be obtained over a wide spectral range.     

高非线性色散平坦光子晶体光纤的研究

利用矢量等效折射率法计算了空气孔间距和空气填充率对非线性系数以及波导色散的影响,通过计算发现孔间距对波导色散曲线的走向起决定性作用,而空气填充率的影响主要是使得波导色散大小和位置发生变化,同时减小孔间距以及增大空气填充率都会提高非线性系数,最终设计出了几种不同特性的800nm处色散平坦高非线性光子晶体光纤。     

Dispersion Properties in Total Internal Reflective Photonic Crystal Fiber

The dispersion properties in the short wavelength region of total internal reflective photonic crystal fiber have been studied by using the models of the equivalent twin waveguide soliton coupling, effective refractive index，effective normalized frequency and dispersion management solitons. It is shown that the dispersion in the cladding waveguide of the total internal reflective photonic crystal fiber is a positive dispersion，and the dispersion of its core waveguide is a negative dispersion. The method of the compensated probing laser diffraction by the phase hole induced by the stationary pumping laser in the cladding waveguide enables the average dispersion value of the total internal reflective photonic crystal fiber to be close to zero and the zero dispersion point to shift to the short wavelength region.     

高非线性色散平坦微结构光纤的研究

利用矢量等效折射率法计算了空气孔间距和包层空气填充率对微结构光纤的非线性系数以及结构色散的影响,通过计算发现孔间距对结构色散曲线的走向起决定性作用,而包层空气填充率的影响主要是使得结构色散大小和位置发生变化,同时减小孔间距以及增大包层空气填充率都会提高非线性系数,最终设计出了几种不同特性的800nm处色散平垣高非线性微结构光纤。     

零模间色散三芯光子晶体光纤

为了研究纤芯掺杂低折射率材料后三芯光子晶体光纤中任意两超模之间的模间色散特性,采用全矢量有限元法进行了仿真,取得了模间色散系数、零模间色散波长随纤芯折射率和结构参量变化的数据。结果表明,通过调节纤芯折射率、纤芯直径、空气孔直径以及孔间距这4个结构参量,可以使任意两超模间的模间色散在两个常用波段1.31m和1.55m处为0。该结果对于消除基于模分复用的光纤不同模式间因为模间色散导致的脉冲失真和实现零模间色散的模分复用技术是有帮助的。