Ultrafast miniature fiber-tip Fabry–Perot humidity sensor with thin graphene oxide diaphragm

We demonstrate here an ultrafast, miniature, and high-performance fiber-tip Fabry–Perot (F-P) humidity sensor with ∼300 nm-thick graphene oxide (GO) diaphragm suspended onto the end face of a capillary tube with an inner diameter of 50 μm and a cavity length of ∼100 μm. The sensitivity to relative humidity (RH) spanning from ∼10%RH to ∼90%RH was examined based on the wavelength shift in the interference spectrum. Due to the intrinsic hydrophilicity of the porous GO membrane, the developed sensor exhibited an average wavelength variation of ∼0.2 nm∕%RH, which indicated a relatively broad and readily detectable RH linear measurement range. More prominently, an ultrahigh response time of 60 ms was achieved over other alternative F-P humidity sensors previously reported, to our knowledge.