Detecting at least one chosen gas in ambient atmosphere comprises passing optical wave through material whose refractive index varies under effect of gas and measuring perturbation

摘要

An optical wave (11a) passes through a material (5, 8) which has a refractive index (n, N) which varies under the effect of the gas to be detected so its presence in the material perturbs the wave propagation conditions. The perturbation of the optical wave is measured and at least the presence or absence of the chosen gas in the atmosphere (13) is deduced. The material and the optical wave are linked by an optical coupling through a prism (15) and a diffraction grating, with a waveguide. The perturbation is measured by measuring flux or by measuring modifications in the wave propagation. An independent claim is made for a device to carry out the above process, comprising an optical detector (3) containing at least one layer of material sensitive to the gas, linked optically to an optical wave source and in gaseous communication with ambient atmosphere which may contain the gas to be detected. The device also contains a device for evaluating the presence or absence of the gas, including a device for detecting and preferably measuring the perturbation of the optical wave under the effect of the variation of refractive index of the material. The optical detector includes a support substrate and the layer of sensitive material has a diffraction grating formed in it defining the means of optical coupling.