Liu Jinyuan, Zhang Ziyang
College of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027, China.
Laboratory of Photonic Integration, School of Engineering, Westlake University, Hangzhou 310024, China.
Polymers (Basel). 2023 Oct 15;15(20):4093. doi: 10.3390/polym15204093.
Germanium (Ge) nanostrip was embedded in a polymer and studied as a waveguide. The measurements reveal that this new type of semiconductor/polymer heterogeneous waveguide exhibits strong absorption for the TE mode from 1500 nm to 2004 nm, while the propagation loss for the TM mode declines from 20.56 dB/cm at 1500 nm to 4.89 dB/cm at 2004 nm. The transmission characteristics serve as an essential tool for verifying the optical parameters (-, refractive index, and extinction coefficient) of the strip, addressing the ambiguity raised by spectroscopic ellipsometry regarding highly absorbing materials. Furthermore, the observed strong absorption for the TE mode at 2004 nm is well beyond the cut-off wavelength of the crystalline bulk Ge (~1850 nm at room temperature). This redshift is modeled to manifest the narrowing of the Tauc-fitted bandgap due to the grain order effect in the amorphous Ge layer. The accurate measurement of the nanometer-scale light-absorbing strips in a waveguide form is a crucial step toward the accurate design of integrated photonic devices that utilize such components.
锗（Ge）纳米带被嵌入聚合物中并作为波导进行研究。测量结果表明，这种新型的半导体/聚合物异质波导对1500纳米至2004纳米的TE模式表现出强烈吸收，而TM模式的传播损耗则从1500纳米处的20.56分贝/厘米降至2004纳米处的4.89分贝/厘米。传输特性是验证纳米带光学参数（-、折射率和消光系数）的重要工具，解决了光谱椭偏仪对高吸收材料所提出的模糊性问题。此外，在2004纳米处观察到的TE模式的强烈吸收远超过晶体块状锗的截止波长（室温下约为1850纳米）。这种红移被建模为由于非晶锗层中的晶粒有序效应导致Tauc拟合带隙变窄。以波导形式对纳米级光吸收带进行精确测量是朝着准确设计利用此类组件的集成光子器件迈出的关键一步。
