Whispering-gallery-modes in narrowband emission from B/N-PAH-doped geometrically arranged polymer photonic cavities, waveguides and splitters.

Polymer microcavity-based coupled-resonator optical waveguides (CROWs) with narrowband emission offer a promising approach for developing next-generation miniaturized photonic components. In a unique approach, a narrowband-emitting compound 9,9'-(4,4'-(tert-butyl)diphenylamino)dibenzo[b,d]borin-2-ylidene)dibenzonitrile (BCz-BN), with a full width at half maximum (FWHM) of 28.9 nm, was doped into polystyrene microspheres and assembled on a glass substrate. Using an atomic force microscope cantilever tip-based micromanipulation technique, we successfully created CROWs with distinct architectures for narrowband light transmission. Detailed micro-spectroscopy studies revealed CROWs capability to support optical whispering-gallery modes (WGMs) while retaining the narrowband emission of the doped fluorophore. Dimeric to pentameric, triangular, square, and Y-shaped BCz-BN-doped CROWs were realized, demonstrating efficient light-guiding, distribution and splitting. These fabricated waveguides provide a scalable platform for advanced photonic applications, including on-chip optical communication, biosensing and quantum optics, paving the way for advanced microscale optoelectronic devices.