fabrication and characterization of the fiber optical taper for a surface plasmon resonance sensor

for a fiber optical surface plasmon resonance (spr) sensor a short part of its cladding should be removed to coat a thin layer of a metal. usually this is problematic when an optical fiber with small core diameter is used. in this paper, a new method using µliter droplet of the hf acid for short fiber optical taper fabrication is reported. using this method in a multi-mode optical fiber with the core/cladding size of 50/125 µm a 2 mm long taper with 40 µm diameter is fabricated. roughness of its surface is investigated using an atomic force microscopy. the measured mean value of the roughness is about 8 nm. a 60 nm thin layer of pure silver is coated on the taper surface in order to investigate its performance using a fiber optical spr sensor.  using this spr fiber sensor measurement of the lead concentrations in water ranging from 0.1 to 10 part per million (ppm) is reported.