Suspended waveguide-enhanced near-infrared photothermal spectroscopy for ppb-level molecular gas sensing on a chalcogenide chip

Kaiyuan Zheng; Hanyu Liao; Fengbo Han; Xueying Wang; Yan Zhang; Jiaxin Gu; Pengcheng Zhao; Haihong Bao; Shaoliang Yu; Qingyang Du; Lei Liang; Chuantao Zheng; Wei Jin; Lijun Wang

doi:10.1038/s41377-026-02196-7

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Suspended waveguide-enhanced near-infrared photothermal spectroscopy for ppb-level molecular gas sensing on a chalcogenide chip

Original Articles

- Suspended waveguide-enhanced near-infrared photothermal spectroscopy for ppb-level molecular gas sensing on a chalcogenide chip
- Light: Science & Applications Vol. 15, Issue 4, Pages: 1305-1316(2026)
- Affiliations：
  
  1.Department of Electrical and Electronic Engineering and Photonics Research Institute, The Hong Kong Polytechnic University, 999077 Hong Kong, China
  2.Photonics Research Center, The Hong Kong Polytechnic University Shenzhen Research Institute, 518071 Shenzhen, China
  3.Zhejiang Lab, 311121 Hangzhou, China
  4.State Key Laboratory of Integrated Optoelectronics, JLU Region, College of Electronic Science and Engineering, Jilin University, 130012 Changchun, China
  5.State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 130033 Changchun, China
- Author bio：
  
  Qingyang Du (qydu@zhejianglab.edu.cn)
  Chuantao Zheng (zhengchuantao@jlu.edu.cn)
  Wei Jin (wei.jin@polyu.edu.hk)
- Funds：
- DOI：10.1038/s41377-026-02196-7
  CLC：
- Received：13 August 2025，
  
  Revised：2025-12-22，
  
  Accepted：13 January 2026，
  
  Online First：17 February 2026，
  
  Published：30 April 2026
- Accepted：
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Zheng, K. Y. et al. Suspended waveguide-enhanced near-infrared photothermal spectroscopy for ppb-level molecular gas sensing on a chalcogenide chip. Light: Science & Applications, 15, 1305-1316 (2026).
DOI：

Zheng, K. Y. et al. Suspended waveguide-enhanced near-infrared photothermal spectroscopy for ppb-level molecular gas sensing on a chalcogenide chip. Light: Science & Applications, 15, 1305-1316 (2026). DOI： 10.1038/s41377-026-02196-7.

摘要

Abstract

On-chip waveguide sensors have attracted significant attention recently due to their potential for high-level integration. However

so far

on-chip gas sensing based on traditional laser absorption spectroscopy has demonstrated low detection sensitivity

due to weak light-gas interaction over a limited interaction distance. On-chip photothermal spectroscopy (PTS) appears to be a powerful technique to achieve higher sensitivity; its performance is yet constrained to parts-per-million (ppm)-level due to a small fraction of evanescent field in the light-gas interaction zone and fast thermal dissipation through the solid substrate. Herein

we demonstrated suspended chalcogenide glass waveguide (ChGW)-enhanced PTS that overcomes these limitations

enabling highly sensitive parts-per-billion (ppb)-level molecular gas sensing. We fabricated a nanoscale suspended ChGW with a low loss of 2.6 dB/cm using a CMOS-compatible two-step patterning process. By establishing an equivalent PTS model to guide the optimization of the ChGW geometry

we achieved a 4-fold increase in the absorption-induced heat source power and a 10.6-fold decrease in the equivalent heat conductivity

resulting in a 45-fold enhancement in photothermal phase modulation efficiency over the non-suspended waveguides. Combining with a high-contrast waveguide facet-formed Fabry-Perot interferometer

we achieved an unprecedented acetylene detection limit of 330 ppb

a large dynamic range close to 6 orders of magnitude

and a fast response of less than 1 s. The overall system exhibits a noise-equivalent absorption coefficient of 3.8×10

−7

−1

setting a new benchmark for photonic waveguide gas sensors to the best of our knowledge. This work provides a key advancement towards prototyping an integrated sensor-on-a-chip for highly sensitive and background-free photonic sensing applications.

关键词

Keywords

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