Surface plasmon resonance based fiber optic hydrogen sulphide gas sensor utilizing nickel oxide doped ITO thin film

Fabrication and characterization of a surface plasmon resonance (SPR) based fiber optic sensor for the detection of hydrogen sulphide gas have been carried out. Three kinds of probes have been fabricated to optimize the performance of the sensor. These probes have common coating of silver layer over unclad core of the fiber while these have different over-layers of nickel oxide, indium tin oxide and nickel oxide doped indium tin oxide. The SPR spectra of all the probes and hence the resonance wavelengths have been found to shift toward the higher wavelength with the increase in the concentration of the hydrogen sulphide gas around the probe. The shift occurs due to the interaction of the hydrogen sulphide gas with the over-layer resulting in the change in its dielectric function. However, the maximum shift has been obtained in the case of nickel oxide doped indium tin oxide over layer. To achieve the highest sensitivity of the sensor, the thickness of the over-layer and the doping concentration of nickel oxide have been varied and optimized. Further, to test the selectivity, the experiments have been performed on various other gases. It has been found that the nickel oxide doped indium tin oxide probe is highly selective toward hydrogen sulphide gas.