Two Modes Excited SPR Sensor Employing Gold-Coated Photonic Crystal Fiber Based on Three-Layers Air-Holes

Ahighly sensitive refractive index (RI) biosensor based on three-layers air-holes photonic crystal fiber (PCF) with gold film on the outer edge of the fiber cladding is proposed. The properties of modes coupling between fundamental mode (odd mode), cladding mode (even mode) and surface plasmon polaritons (SPPs) mode were theoretically simulated, respectively. Meanwhile, the effects of gold film thickness and cladding air-hole diameter on the sensor performance are analyzed in detail. When the energy of odd and even modes couple strongest to SPP mode with the gold film is 50 nm, the maximum sensitivities of this PCF sensor are 8400nm/RIU (odd mode) and 8500nm/RIU (even mode), respectively under the RI of 1.41. Compared with the traditional optical fiber sensor, this PCF sensor has the advantages of wide and real-time detection, compact and high RI sensing responsivity, which has the potential to be used in the field of environment quality-detection and biochemistry sensing.