Design and analysis of slow-light Bloch slot waveguides for on-chip gas sensing

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Abstract
The performance of on-chip gas sensors based on light absorption is mainly determined by the light–gas interaction. In this paper, slow-light Bloch slot waveguides (BSW) are proposed to improve sensing performance. The sensing performance is enhanced in two mechanisms. On the one hand, light is confined in the slot to increase the overlap of the mode field and the gas; on the other hand, the slow-light effect is achieved by adjusting the subwavelength grating period to increase the group index. By joint engineering the evanescent fields and group index, for a low pump power of 10 mW and a propagation loss of 3 dB/cm, the detection limit of 0.034 ppm in the near-infrared and the detection limit of 0.29 ppm in the mid-infrared at the optimum propagation length of 1.45 cm are obtained, respectively. The proposed BSW provides a promising platform for high-performance gas sensing.
Funding Information
  • Wuhan Municipal Science and Technology Bureau (2018010401011297)
  • National Natural Science Foundation of China (61605179)
  • Electrostatic Research Foundation of Liu Shanghe Academicians and Experts Workstation, Beijing Orient Institute of Measurement and Test (BOIMTLSHJD20181001)
  • China University of Geosciences, Wuhan (G1320311998, ZL201917)
  • Natural Science Foundation of Hubei Province (2019CFB598)