Waveguide integrated optical modulators in the mid-infrared wavelength range are of significant interest for molecular spectroscopy. This is because on-chip synchronous detection can improve the performance of detection systems and can also be used for free-space communications where optical modulators working in atmospheric transparency windows are needed. Here we report optical modulation in a mid-infrared photonic circuit, reaching wavelengths larger than 8 µm. Optical modulation in the wavelength range from 5.5 to 11 µm is shown, relying on a broadband Ge-rich graded-SiGe platform. This demonstration experimentally confirms the free-carrier absorption effect modeling. These results pave the way towards efficient high-performance electrically-driven integrated optical modulators in the mid-infrared wavelength range.

分子光谱学对中红外波长范围内集成波导的光调制器非常感兴趣。这是因为片上同步检测可以提高检测系统的性能，并且还可以用于需要在大气透明窗口中工作的光调制器的自由空间通信中。在这里，我们报告了中红外光子电路中的光学调制，其波长大于8 µm。图中显示了在5.5至11 µm波长范围内的光调制，它依赖于富含Ge的宽带渐变SiGe平台。该演示实验证实了自由载流子吸收效应模型。这些结果为在中红外波长范围内实现高效的高性能电驱动集成光学调制器铺平了道路。