Fabrications of Tapered Optical Fibers by Laser Induced Photopolymerization Technique

Abstract

Taper shaped optical fibers have been much investigated because it may enhance the evanescence wave formation on the surface of the fiber, which can be utilized for sensing. In this paper, we report the fabrication of tapered optical fiber by employing laser induced photopolymerization(LIP) technique from hybrid organo-siloxane polymer precursor. This precursor was prepared by the sol-gel method for creating the inorganic cross-links. The photopolymerization process then made the organic cross-links and transformed it into the solid phase. The taper structure formation was strongly dependent on the laser power and time duration. A typical condition for taper structure formation was the laser power of 2 μW and the fiber drawing speed in the range of 20 μm/s - 40 μm/s.The resulted tapers lengths were around 1.5 mm-5.5 mm with the diameter around 100 μm at the beginning of the taper and less than 5 μm at the end of the taper. The optical propagation and evanescent wave profile in this kind of tapered optical fiber was also studied computationally by using Finite Difference Time Domain (FDTD) method.