Insensitivity to Humidity in Fabry–Perot Sensor With Multilayer Graphene Diaphragm

We developed a novel open-cavity Fabry-Perot (F-P) interferometer with multilayer graphene diaphragm suspended on the endface of a ferrule. The insensitivity to relative-humidity (RH) ranging from ~20%RH to 70%RH was investigated in terms of the wavelength shift and power change in interference spectrum, along with the balanced air pressure on both sides of the graphene membrane. The measured wavelength shift of 0.02 nm/%RH and maximum power change of 0.02 dB/%RH demonstrated the humidity-insensitive response of at least one order lower than those for previously reported F-P humidity sensors using porous hydrophilic films. Furthermore, the fitted coupled interaction between dominated temperature and minor humidity yielded a good fitting R-square of about 99.5%. These measurements could shed light on the environmental adaptability of F-P sensors using graphene or other 2-D nanomaterials.