一种晶体光纤基模色散特性的矢量法分析

利用矢量有效折射率方法(矢量法)对光子晶体光纤基模的色散特性进行了数值模拟，并与双正交归一基矢量法以及标量有效折射率方法(标量法)的模拟结果进行了对比.发现所用矢量法的结果与双正交归一基矢量法的结果符合很好，而标量法在低空气填充率f或较高归一化波数A/λ时是一种较好的近似，在空气填充率f较高或归一化波数A/λ较低时，要得到精确的结果必须利用矢量法对光子晶体光纤的特性进行模拟.讨论了光子晶体光纤包层有效折射率与光纤结构的关系. 关键词： 光子晶体光纤 矢量法 有效折射率 色散     

Investigation on Guided-Mode Characteristics of Hollow-Core Photonic Crystal Fibre at Near-Infrared Wavelengths

Guided-mode characteristics of hollow-core photonic crystal fibre （HC-PCF） are experimentally and theoretically investigated. The transmission spectrum in the range from 755 to 845nm is observed and the loss is measured to be 0.12dB/m at 800nm by cut-back method. Based on the full-vector beam propagation method and the full-vector plane-wave method, the characteristics of mode field over propagation distance 1 m are simulated, and the results show that the propagation efficiency can be above 80%. Compared with the fundamental guided mode well confined in air core within shorter propagation distance, the second-order guided mode leaks into the cladding region and gradually attenuates due to larger refractive index difference. The primary loss factors in HC-PCF and the corresponding solutions are elementarily discussed.     

传输可见光的空芯光子带隙光纤的研究

利用全矢量平面波展开法(FVPWM)对采用改进的两次堆积法制备的空芯光子带隙光纤进行了数值模拟.在特定传播常数β下,光纤在500—1000 nm的波段内出现多条宽窄不同的有效光子带隙.依据有效折射率的不同,部分带隙中的空气-导模将以不同的形式存在.经过实验测试,发现测得的带隙位置相对于模拟结果向短波段发生了较明显的移动,主要原因被认为是光纤结构的纵向不均匀性和包层节点处间隙孔的存在. 关键词： 空芯光子带隙光纤 全矢量平面波展开法 有效光子带隙 空气-导模     

Supercontinuum Generation in Holey Microstructure Fibres with Random Cladding Distribution by Femtosecond Laser Pulses ＊

It is reported that supercontinuum spectrum from 440 to 1050 nm can be generated in holey microstructure fibres (HMFs) with random cladding distribution by Ti:sapphire femtosecond laser pulses with central wavelength of 800 nm. Based on the method of the effective refractive index and the analogy of step-index fibre, we have calculated the effective mode area and the group velocity dispersion (GVD). It is found that the HMFs have specifically ability of localizing light and controlling GVD. The mechanism of supercontinuum generation in the HMFs with random cladding distribution is that the balance between the GVD and the self-phase modulation in the anomalous dispersion region leads to formation of solitons and fission of high order solitons.     

中红外散射的基质折射率效应研究

本文利用Mie散射理论对中红外波段三种不同类型散射体的散射和消光进行了研究,发现基质在三种不同类型散射体的散射和消光中所起作用完全不同。对于无吸收的高折射率散射体,基质折射率越大面积散射比(或面积消光比)越低;对于反常色散散射体,基质折射率越大面积散射比和面积肖光比越高;而对于金属散射体,基质折射率的大小对于散射和消光影响极小。     

全固双层芯色散补偿光子晶体光纤的研究与设计

为了补偿光纤色散对高速信号传输的限制,提出一种全固双层芯色散补偿光子晶体光纤.首先对该光纤模式耦合特性进行理论分析,然后利用多极法进行模拟计算,得到该光纤包层结构参数与色散值以及相位匹配波长之间的关系,并对其规律进行研究.通过优化光纤结构参数,得到在1 550nm处,色散值达到-32 620ps/(nm·km)、损耗为0.29dB/km、与标准单模光纤的熔接损耗为4.77dB的色散补偿光纤.该光纤可补偿1 910多倍长度的SMF-28单模光纤的色散,补偿能力远大于常规色散补偿光纤.与空气孔-石英结构色散补偿光子晶体光纤相比,全固色散补偿光子晶体光纤具有易制备、易与传统通信光纤熔接等优点.     

Ultra-violet and mid-infrared continuum generation by cross-phase modulation between red-shifted solitons and blue-shifted dispersive waves in a photonic crystal fiber

Using a photonic crystal fiber with a zero dispersion wavelength of the fundamental mode at 780 nm designed and fabricated in our lab, the ultraviolet and mid-infrared continua are generated by cross-phase modulation between red-shift solitons and blue-shift dispersive waves. The dependences of continuum on the pump power and wavelength are investigated. With the pump working at 820 nm, when the pump power increases from 300 to 500 mW, the bandwidths of ultraviolet and mid-infrared continua change from 80 to 140 nm and 100 to 200 nm, respectively. The wavelength of ultraviolet continuum is below 246 nm, and the wavelength of mid-infrared continuum exceeds 2500 nm. Moreover, the influences of pump power on wavelength and conversion efficiency of different parts of continua are also demonstrated.     

具有三个及四个零色散波长光子晶体光纤的仿真研究

利用多极法对光子晶体光纤的色散特性进行了模拟, 通过设计合适的结构参数, 得到了具有3个零色散波长的单模光纤.对中心纤芯有1个微小空气孔光子晶体光纤的色散特性进行了分析, 设计出了具有4个零色散波长的色散曲线.分析了零色散波长随光纤结构的变化规律, 这些零色散波长的位置和间距可以在很大波长范围内灵活调节. 具有多个零色散波长的光纤可以得到色散值极低的超平坦色散曲线. 多个零色散波长光纤能产生丰富的相位匹配曲线, 可以有效地控制光孤子及超短脉冲的四波混频及共振散射产生的光谱特性.     

用于光纤传像束的折-衍混合光学耦接器研究

在光学耦接器设计中引入衍射面,根据衍射光学元件的三级像差理论,分析了衍射面初始结构参量的求解规律,通过理论计算和ZEMAX光学软件的优化,给出工作波长0.4~0.7 μm,焦距27.5 mm,光学长度为64 mm,采用一个衍射面的耦接器设计实例.该耦接器适用于单丝直径16 μm,截面直径为6 mm的光纤传像束.对设计结果的分析表明,折-衍混合耦接器不仅在光学性能方面优于传统的光学耦接器,而且在尺寸和重量上有非常显著的减少.     

GeO2-Sb22O3-K22O玻璃空芯光纤材料的光学特性研究

系统地研究了传输CO2激光用的新型光纤材料GeO2-Sb2O3-K2O玻璃空芯光纤的光学特性。通过理论计算,得到了该材料nr＜1的波长范围,消光系数Ｋ和损耗系数a,通过工艺和材料的选择,使a理论值达到0.05 dB/m。同时讨论了HE11,TM01,TE01模式损耗和频率的关系。