Visually Adjusting Coupling Conditions in Light-Emitting Micro-Components

We demonstrate a directly visible approach to adjust the coupling conditions of photonic components based on fluorescent indication. Under an optical microscope, the fluorescence of the dye-doped polymer microfiber (PMF) is excited by the evanescent coupling method and is used to visualize the light path in the PMF. By simply moving the coupling position of input probe in a few microns according to the fluorescent indication, we adjust the coupling conditions of the components, such as Y beam splitter and Mach-Zehnder interferometer, and the splitting ratio varies from 1.8 to 0.8. Besides, we directly visualize and adjust the energy coupling of two overlapping PMFs in the pig-tail microring via the fluorescent indication. The fluorescent indication in PMF demonstrated here simplifies the adjusting process of the component based on free standing PMFs and promises a potential for directly visible adjusting in microfibers-based photonic circuit integration for photonic neural networks.