Mid-infrared (mid-IR) spectroscopy is a nearly universal way to identify chemical and biological substances, as most of the molecules have their vibrational and rotational resonances in the mid-IR wavelength range. Commercially available mid-IR systems are based on bulky and expensive equipment, while lots of efforts are now devoted to the reduction of their size down to chip-scale dimensions. The demonstration of mid-IR photonic circuits on silicon chips will benefit from reliable and high-volume fabrication to offer high performance, low cost, compact, low weight and power consumption photonic circuits, which is particularly interesting for mid-IR spectroscopic sensing systems that need to be portable and low cost.
In this context, the INsPIRE project will address a new route towards key advances in the development of chip-scale integrated circuits on silicon for the mid-IR wavelength range. The original idea is to use nonlinear optical properties in Ge/SiGe quantum well (QW) active devices combined with Ge-rich-SiGe waveguides. The objectives of the INsPIRE project are far beyond the state of the art, by targeting the monolithic integration of passive and active devices for operation in the 3 to 15 µm wavelength range.
As a main cornerstone we will demonstrate an optical photonic circuit based on Ge/SiGe QWs relying on a mid-IR light emitter combined with a mid-IR spectrometer and a detector array. The integration will be performed using Ge-rich-SiGe waveguides allowing the extension of the wavelength range up to 15 µm.
Such demonstration, which will constitute a breakthrough for establishing chip-scale circuits for the mid-IR photonics, requires a deep knowledge and understanding of Ge/SiGe optical properties. In particular, second- and third-order nonlinear optical properties of Ge/SiGe QW structures will be investigated in a wide spectral range from 3 to 15 µm.