CMOS-fab-compatible mid-IR waveguide platform for gas / breath / hyperspectral sensing
Physics / mechanism
Pure germanium is transparent from ~1.8 μm out to ~14 μm — covering most of the molecular-fingerprint mid-IR band where silicon absorbs (silicon’s transparency cuts off around 4 μm at production-grade purity). Ge-on-Si waveguides leverage standard silicon photonic fab infrastructure with Ge epitaxy as an additional process step — already mature for Ge photodetectors integrated in silicon photonics.
The killer pitch: Ge-on-Si reuses the silicon-photonics ecosystem (CMOS fabs, design tools, foundries) for mid-IR applications, sidestepping the specialty-fab problem that limits chalcogenide. Combined with Quantum Cascade Lasers as the source side, a fully-integrated mid-IR PIC for chip-scale spectroscopy becomes feasible.
Competitive landscape
Frontier (open questions)
See frontmatter frontier: block.