聚合物Y分支脊形波导的单模条件

Single Mode Condition of Polymeric Y-junction Rib Waveguide

有机聚合物光波导近年来成为研究的热点,它为实现下一代的光电集成回路提供了另外一种选择。它所具有的一系列优点如下:(1)与传统的材料相比,有机聚合物光波导容易在各种衬底上制作,其制作成本也得以降低,并且使得与有源器件如激光器、调制器、探测器的单片集成成为可能;(2)有机聚合物波导材料的折射率可以进行调整以满足耦合损耗和弯曲损耗的折中选择;(3)此外,有机聚合物的热光系数比S iO2大一个数量级,而其导热系数却比S iO2和S i小得多。有机聚合物Y分支是强度调制器和光开关等器件的重要组成。光波导器件在和单模光纤一起使用时要求其实现单模传输,这样可以减少耦合损耗。利用变分有效折射率法计算了聚合物Y分支脊形波导的光场分布。变分有效折射率法是变分法(VM)和有效折射率法(EIM)的结合,它结合了两种方法各自的优点,能够很精确地模拟光场分布情况。利用变分有效折射率法验证了满足单模传输的脊形波导结构参数:芯层厚度为1.5μm,脊高为0.2μm,脊宽为5μm。

Polymeric optical waveguide has become the hotspot in recent years, it provide an alternative approach for realizing the next generation of optoelectronic integrated circuits because of a series of merits ： （ 1 ） In comparison with the traditional material, polymer waveguides are easy to fabricate on almost any substrate of interest which reduces manufacturing costs and opens the possibility of single-chip integration with active components, such as lasers, modulators, and detectors ; （2） The refractive indexes of polymer waveguide materials can be adjusted widely to address the compromise between coupling losses and bending losses; （3）Additionally, the thermo-optical coefficient of polymer materials can be greater than that of SiO2 and far more than an order of magnitude, while polymers＇ thermal conductivities are a fraction of SiO2 and silicon＇s. Polymeric Y-junction waveguide is the key component in fabricating polymeric electro-optic devices, such as intensity modulators, optical switches and so on. Single mode propagation is an important requirement for optical waveguide devices for use with single-mode fiber, it can reduce the coupling loss. In this paper, a technique is used for calculating the field distribution of the polymeric Y-junction rib waveguide. The technique is based on the combination of the effective index method （EIM） and the variational method （VM）, it is mixed between the advantages of each method and avoided their disadvantages, where EIM can make the calculations procedures simple but it has some difficult to find the field distribution, other wise, VM can be used with very good accuracy to find the field distribution. An algorithm is implemented to study the effect of the structure parameters on the field distribution of the polymeric Y-junction rib waveguide. The obtained single mode rid waveguide structure parameters are ：the core thickness is 1.5 μm, the rib height is 0.2 μm, and the rib width is 5 μm.