Photonics in the Mid-Infrared: Challenges in Single-Chip Integration and Absorption Sensing

Photonics has been extensively exploited in the visible and near-infrared spectral ranges. Sensing of liquids and gases is a promising area for advancing of the photonics also in the mid-infrared spectral range (MIR). Of particular interest is the realization of Si-based MIR devices and their integration on a single chip. In this paper, the fundamental material challenges for the fabrication of photonic and opto-electronic devices in the mid-infrared are discussed. An approach for development, characterization, and integration of numerous photonic components for the spectral range λ = 4-6 μm is presented. Using Si, SiOx, and Si
₃
N
₄
as a material base, it is illustrated that fully Si-compatible active and passive devices are possible, which can be readily integrated onto a silicon chip. Finally, a compact mathematical model is provided for evanescent sensing of fluids with rib and photonic crystal waveguides.