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Suspended Germanium-on-Silicon Photonic Integrated Circuits Operating in the Long-Wave Infrared and Their Use for
Pen-Sheng Lin1, Per-Erik Hellström2, Charalampos Zervos3
1Department of Micro and Nanosystems, School of Electrical Engineering and Computer Science, KTH Royal Institute of Technology, Stockholm SE-10044, Sweden.
ACS Photonics
|May 11, 2026
Summary
Researchers developed a suspended germanium-on-silicon platform for mid-infrared applications. This new platform significantly reduces propagation loss, enabling effective gas sensing in the long-wave infrared spectrum.
Area of Science:
- Integrated photonics
- Mid-infrared optics
- Chemical sensing
Background:
- Germanium-on-silicon photonics shows promise for mid-infrared applications like environmental sensing.
- Existing platforms suffer high propagation losses above 8 μm, limiting their use.
- Gas sensing in this wavelength range using germanium waveguides remains undemonstrated.
Purpose of the Study:
- To overcome propagation loss limitations in germanium-on-silicon platforms.
- To enable gas sensing applications in the long-wave infrared (LWIR) spectrum.
- To demonstrate a novel suspended germanium-on-silicon platform.
Main Methods:
- Fabrication of a suspended germanium-on-silicon platform with an 11 μm suspension gap.
- Optical characterization of the waveguide's propagation loss at 9.2 μm.
- On-chip demonstration of ethanol gas sensing in the LWIR range.
Main Results:
- Achieved a low propagation loss of 3.5 dB/cm at 9.2 μm.
- Demonstrated on-chip ethanol gas sensing with a detection limit of 925 ppm.
- Successfully isolated the optical mode from the silicon substrate.
Conclusions:
- The suspended germanium-on-silicon platform effectively reduces propagation loss in the LWIR.
- This technology enables practical gas sensing applications in the long-wave infrared.
- Paves the way for extending germanium-on-silicon integrated photonics to longer wavelengths.
