RESUMO
This paper presents a nitrogen dioxide detection device based on gas absorption spectroscopy by connecting two integrating spheres as a gas cell, observing the feasibility of the tandem integrating spheres as a gas cell, and taking a single integrating sphere as a gas cell for comparison experiments. Theoretical knowledge of the effective path length of tandem integrating spheres was established, and the theoretical derivation was further verified by experiments investigating the relationship between absorbance and gas concentration. This work makes it possible to develop a gas sensor that can reduce the volume of the gas cell and keep the effective optical path length unreduced.
RESUMO
A novel integrated surface plasmon resonance (SPR) sensor that combines an optical waveguide platform and an ultra-thin spectrometer is proposed. The core of the proposed method is a special-shaped optical waveguide structure that employs a wedge-shaped incident surface, which changes the position of the total reflection of the incident light on the sagittal plane without affecting the direction of propagation on the tangential plane. The parameters of the sensing module with the integrated SPR sensor and spectrometer module were designed and optimized to achieve higher performance in a compact optical waveguide platform. An experimental system was built based on the theoretical model, and the spectral sensitivity of the system was analyzed before sample detection, and the results showed that the spectral resolution in the working range could reach 9.9 nm. The refractive index sensitivity of this novel SPR sensor was 3186 nm/RIU with good stability by detecting different concentrations of sodium chloride samples. This new structure does not require an external spectrometer, thereby enabling an increase in the compactness of the SPR sensing system. The proposed method can provide a novel idea for the miniaturization of SPR sensors.