Individual optical multi-gas sensors as next generation second-order unobtrusive and continuous operation analytical instruments.

Three designs are shown of photonic nanostructured sensors as second-order analytical instruments. In all three designs, the first independent variable in sensor response is optical wavelength across the visible spectral range. The second independent variable is either (i) illumination angle, (ii) light polarization, or (iii) the operation temperature of the sensor. These illustrative designs of second-order gas sensors bring mathematical understanding to boost the multi-gas resolution achieved by individual material-based sensors through the transducer, material design, appropriate excitation conditions, and data analysis. Results presented should inspire new fundamental research and technological innovations in the areas of gas sensors, optics, materials science, nanofabrication, and data analysis. The strategic approach of expanding the dimensionality of the sensor response described will enable next-generation sensors to perform on par with traditional orthogonal-output analytical instruments, but with a continuous real-time data stream and unobtrusive, energy-efficient designs.