A gold-deposited surface plasmon resonance-based optical fiber sensor system using various light-emitting diodes

The performance of a simple gold (Au)-deposited optical fiber sensor system based on surface plasmon resonance (SPR) is presented. Our sensor system comprises a light-emitting diode (LED) and a photodiode (PD) as the light source and the detector, respectively. The response curves and sensor properties of the Au-deposited optical fiber with a Au film thickness of 45 nm obtained by using three LEDs with 563, 660, and 940 nm emissions were investigated. The sensor properties depend strongly on the wavelength of the incident light and can be controlled by changing the LED emission wavelength. The response curves of the sensor obtained at the three wavelengths and calculated using SPR theoretical equations were compared with those obtained by experimentation. Our sensor system represents a new SPR-based refractometer with performance almost equal to that of an Abbe refractometer. To demonstrate its usefulness, ethanol concentrations in various spirits were measured and the results compared with those as labeled.