Silicon nitride integrated photonics from visible to mid-infrared spectra

Recently, silicon nitride (Si3N4) photonic integrated circuits (PICs) are of a great interest due to their extremely low waveguides losses. The number of Si3N4 integrated photonics platform applications is constantly growing including the Internet of Things (IoT), artificial intelligence (AI), light detection and ranging (LiDAR) devices, hybrid neuromorphic and quantum computing. Their heterogeneous integration with a III-V platform leads to a new advanced large scale PICs with thousands of elements. Here, we review key trends in Si3N4 integrated circuits technology and fill an information gap in the field of state-of-the-art photonic devices operating from visible to mid-infrared spectra. A comprehensive overview of Si3N4 integrared circtuis microfabrication process details (deposition, lithography, etching, etc.) is introduced. Finally, we point out the limits and challenges of silicon nitride photonics performance in an ultrawide range providing routes and prospects for their future scaling and optimization.