Precision Thermo-Welding of Polymer Microspheres into Periodically Organized, Hybrid, Mechanically Rollable Coupled-Resonator Optical Waveguides

Abstract: Polymer microspherical resonators that trap light are crucial structures for on-chip and on-board integration in nanophotonic applications. Using advanced micromanipulation and thermo-welding methods, we successfully create welded polystyrene-based coupled-resonator optical waveguides (CROWs) with customized lengths, shapes, and optical characteristics. Through the thermal fusion of blue, green, and red fluorophore-doped polystyrene microspheres, multi-fluorescent cohesive units are created from dimeric to henicosameric periodic arrangements. Detailed micro-spectroscopy studies reveal CROWs' capability to support optical whispering-gallery modes. The periodic arrangements of different fluorophore-doped resonators within the CROW facilitate efficient guided transmission of light via both active and passive mechanisms in opposite directions. The welded structures exhibit mechanically driven rolling motion, confirming their integration as cohesive units. These findings highlight the versatility and performance of thermo-welded polymer microsphere-based waveguides, paving the way for scalable, low-cost photonic devices in sensing, modulation, and light guiding, emphasizing their role in future integrated photonics.