设计了一种基于多模干涉(MMI)耦合输入/输出结构的跑道型双微环串联谐振滤波器, 并采用紫外光敏聚合物材料SU-8作波导芯层, 聚合物CYTOP为下包层, 在硅基底上完成了器件的制备。器件的波导端面尺寸为2 μm×1 μm, 与设计值相符, 扫描电镜显示所制备的器件波导侧壁陡直度较高。直波导传输损耗的测试结果表明, 在1550 nm波长, 直波导传输损耗约为2.0 dB/cm。测试并获得了多模干涉结构和器件的通光及输出光谱图。测试结果表明, MMI结构在较宽的波长范围内实现了接近50∶50的功分比, 微环谐振滤波器的通光性能良好, 实现了滤波功能, 器件的自由光谱区FSR实际值约为0.94 nm, 与设计参数值很接近。研究结果表明采用聚合物SU-8制备小波导尺寸微环谐振器的器件简便可行。

In this paper, a micro-ring resonant filter(MRRF),consisting of two cascaded coupled racetrack rings and using MMI as input/output coupling structure, was designed and fabricated on the Si substrate by using a UV sensitive polymer material SU-8 as the core material of the waveguide and polymer material CYTOP as the bottom cladding layer. According to the scanning electron microscope (SEM) results, the cross sectional size of waveguide of the device is 2 μm×1 μm, which is in accordance with the designed value, the waveguide shows high sidewall quality. The propagation loss of straight optical waveguide is measured to be 2.0 dB/cm at 1550 nm wavelength. The near field optical pattern from the output port of MMI structure and the output spectrum of the MRRF were obtained. The measured results show that the power ratio of the MMI was close to 50∶50 in a relatively wide range of wavelengths, and the filtering was realized, the measured free spectral range FSR of device is about 0.94 nm, which is close to the designed value. The study results show that it is simple and feasible for fabricating MRRF with fine waveguide by using SU-8.