Low-power supercontinuum generation in Ge-rich SiGe waveguides from 4 to 13 μm wavelength

The development of on-chip spectroscopic systems has attracted a lot of attention in recent years. Such systems require broadband mid-infrared sources, resulting in the exploration of mid-infrared supercontinuum generation. This study focuses on reducing the pump peak power to obtain on-chip octave-spanning supercontinua at wavelengths from 4 to 13 μm, leveraging the high nonlinear refractive index and low propagation losses of Ge-rich graded SiGe photonic circuits. Two distinct platforms are explored, one grown in an industrial-scale epitaxy tool and the other using low-energy plasma-enhanced chemical vapor deposition. These silicon-compatible platforms are used to design nonlinear waveguides exhibiting anomalous group velocity dispersion, enabling soliton fission based octave-spanning supercontinuum generation at a record-low peak power of 311 W in this wavelength range. This work paves the way toward chip-based commercially available supercontinuum sources in the mid-infrared.