A joint research team led by Prof. Wei Jin, Associate Director of Photonics Research Institute (PRI) and Chair Professor of Photonic Instrumentation in the Department of Electrical and Electronic Engineering of PolyU, and Prof. Chuantao Zheng of Jilin University, has developed a novel on-chip photothermal spectroscopy sensor for high sensitivity gas detection.
On-chip waveguide sensors have attracted considerable attention due to its ultra-compact footprint and potential for large-scale integration. However, existing waveguide gas sensors are primarily based on direct absorption spectroscopy which suffer from limited sensitivity and measurement range. The team demonstrated a new method for high sensitivity on-chip gas measurement by using photothermal spectroscopy. This technique detects photothermal phase change resulting from non-radiative relaxation upon light absorption by gas molecules, presenting itself as an indirect technique capable of circumventing the limitations of direct absorption measurement.
By selecting chalcogenide glass (ChG) as the core-layer material and fabricating thermally-isolated ChG-on-SU8 waveguide for thermal field accumulation, the team has demonstrated a remarkable acetylene detection sensitivity of 4 parts-per-million and a dynamic range exceeding 5 orders of magnitude, which outperform traditional direct absorption sensor by nearly 2 and 3 orders of magnitude, respectively.
The research findings have been recently published in Laser & Photonics Reviews. Further investigation is underway to optimize the waveguide structure, improve thermal accumulation and understand deeper the optical-thermal-phase transfer mechanism. The team looks forward to collaborating with the industry in further development of the integrated on-chip sensors and applications.
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