Research Projects

Confining the light beam in nanometer range and its interaction with atomic lattice holds the key for advancement in Nano lithography, surface enhancement of Raman spectroscopy (SERS, enhancement of non-linear optical effects, high resolution imaging, single molecule detection useful for quantum electronics/ biomedical applications. One of the most popular techniques to confine the light beam in nanometer range is based on adiabatic long tapered nano-fibers, wherein the concept of total internal reflection aided by metal coating is employed to break the diffraction limits and focus the light in atomic dimensions. The proposed project aims to design and develop an automated machine for fabrication of customized adiabatic/non-adiabatic and symmetric/asymmetric Nano fiber wires of desired profile and investigate the light propagation properties of these wires using continuous and femto- second laser pulses for super continuum generation/imaging applications. The proposal is also to develop a design recipe in terms of a mathematical model for predicting the conicoid shape of the tapered fiber fabricated under different operating conditions of speed and acceleration of the motors used in the manufacturing rig. The mathematical 3D taper profile fed to the programmed computer driven rig consisting of stepper motors, linear translation stages, in-house designed induction mini-furnace, and detectors for fabrication of different types of hyperbolic 3D profiles of nano fiber wires. During fabrication, one port of the optical fiber is spliced with the laser, as an input light source, and the unjacketed middle part is partially softened under high temperature and low pressure inside the mini-in-house designed furnace before stretching the heated fiber region adiabatically/non adiabatically with the help of the stepper motors attached with linear translation stages. The processes of heating the fiber and precisely pulling the heated fiber start simultaneously and it goes till the desired 3 D profile of the Nano wire, as per initial desired design taken from the mathematical model, is obtained. The output port of the nano wire is connected to the detectors/optical spectrum analyzer for analyzing its spectral properties online during the fabrication process. The profile of fabricated tapered wire would be characterized under the Scan Electron Microscope. PI has developed a microcontroller driven fiber taper fabrication rig indigenously capable of realizing tapers of waist diameter as ~ 2-micron. However, novelty of the present proposal is in terms of precision of computer aided nano scale manufacturing based on the taper profile fed to the indigenously developed program loaded on the computer. The spectral characteristics of the Nano tapered fiber would be investigated for super continuum generation, nano scale light focusing and other biomedical sensing applications by coating a suitable metal/liquid crystal display/graphene etc. on the nano tapers.