Surface plasmon resonance methane sensor based on the D-type photonic quasi-crystal fiber with double-layer films

A high-sensitivity photonic quasi-crystal fiber surface plasmon resonance (PQF-SPR) methane sensor is designed and analyzed. The six-fold Penrose PQF has a D-type structure with two grooves on which TiO2 and Au films are deposited, and methane-sensitive film containing cryptophane-E is coated on the surface of the D-type structure. The characteristics of the sensor are analyzed by the finite element method and the influence of different coating materials (Au-TiO2, Au-MgF2, Au-ITO) on the sensitivity and FOM of the sensor is analyzed and compared. The results show that the PCF-SPR sensor with the dual Au-TiO2 film has better sensing properties. The maximum wavelength sensitivity and average wavelength sensitivity reach 40 nm/% and 34.74 nm/% in the methane concentration range of 0–3.5 % respectively. These properties are significantly better than those of similar sensors reported recently, and the sensor thus has large potential in the development of high-sensitivity and miniaturized methane sensors.