2 input/output microfibres SNAP experiment:fabrication and characterization

This work described the application of two microfibers for the first time to experimentally investigate tunneling phenomena in SNAP. The axial WGM distribution along a SNAP fiber is governed by 1D time-independent Schrödinger equation. The transmission spectrum of microfiber orthogonally coupled with SNAP fiber were measured with 1μm incremental step microfiber scanning along SNAP fiber. The microfibers were fabricated with sapphire tube and CO2 laser heat-and-pull setup. Uniform SNAP fibers prepared with hot sulphuric/nitric acid stripping shows the general trend of exponential decay.However, the problem of deep cracks prevented the accurate determination of tunneling time. Symmetric SNAP double resonators with nano-engineered radius variations along uniform SNAP fibers were fabricated using CO2 laser annealing technique. The observed energy level splitting due to the effect of resonant tunnelling between equal energy levels demonstrates the ultra-precise-tuning of height, shape and separation of the double resonators. The transmission surface plots for both S11 and S12 closely matches the theoretical SNAP model based on Levenberg-Marquardt least squares fitting algorithm and bare Green’s function construction method. The reviewed tunneling time literature is intended as a self-contained framework for further SNAP tunneling time research