Optical spectral response for relative humidity measured with polyvinylpyrrolidone-coated Mach-Zehnder interferometer

We measure the optical spectral behavior of Mach-Zehnder interferometer formed on a planar waveguide while changing the ambient humidity level and temperature. The proposed sensor has an asymmetric structure by etching the overclad of only one side of the interferometer. Then, the etched region is coated by Polyvinylpyrrolidone polymer layer. Therefore, changes in boundary condition between core and PVP layer introduces different interference pattern with respect to the ambient humidity level and temperature.