Suspended Germanium-on-Silicon Photonic Integrated Circuits Operating in the Long-Wave Infrared and Their Use for Ethanol Sensing

2026-04-22

Pen-Sheng Lin

Per‐Erik Hellström

Charalampos Zervos

Frank Niklaus *

Kristinn B. Gylfason *

DOI：10.1021/acsphotonics.6c00154

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Germanium-based integrated photonics is gaining attention due to its potential for mid-infrared wavelength applications, including environmental sensing, industrial gas monitoring, defense, and security. However, current germanium-on-silicon platforms face significant propagation losses at wavelengths above 8 μm, and gas sensing in this regime using a germanium waveguide has not been demonstrated to date. To address this challenge, we introduce a suspended germanium-on-silicon platform, where an 11 μm deep suspension gap ensures optical mode isolation from the lossy silicon substrate. The waveguide has a low propagation loss of 3.5 dB/cm at a wavelength of 9.2 μm. Furthermore, we demonstrate on-chip ethanol gas sensing in the long-wave infrared range with a detection limit of 925 ppm using this platform. Our method paves the way for extending the operating wavelength range of germanium-on-silicon integrated photonics into the long-wave infrared.

Keywords:

Ethanol

Infrared light

Photonics

Quantum mechanics

optical gas sensors

ethanol gas sensors

silicon photonics

germanium waveguide

absorption spectroscopy

mid-IR waveguide

Suspended Germanium-on-Silicon Photonic Integrated Circuits Operating in the Long-Wave Infrared and Their Use for Ethanol Sensing

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