Gas refractive index sensor with an integrated prism and a microlens array

A novel sensor for measuring the refractive index of gas is realized by the integration of a prism and a micro-lens array. The proposed sensor is constructed in a single optical path setup and relies on neither a spectrometer nor other spectrum-sensing devices. In the proposed sensor, the gas is injected into the chamber equipped with the prism, and the wavefront of the exit probe beam is decomposed by the microlens array to realize multi-focalization. The developed sensor is utilized to measure the refractive indexes of the air and nitrogen. The refractive index of nitrogen using the proposed sensor is in agreement with data reported previously. By considering twice the standard deviation, a precision of 4.70 × 10 –6 RIU is achieved for the refractive index measurement of nitrogen