Design and Fabrication of High-Refractive-Index-Contrast All-Polymer Optical Microcavities

Polymer microcavities based on distributed Bragg reflectors (DBRs) represent a versatile platform for the fabrication of lightweight, flexible, and fully solution-processable photonic structures.[1] However, the relatively low refractive-index contrast typically achievable in polymer systems often limits optical confinement and the performance of the photonic architectures.[2] In this work, we investigate high-contrast all-polymer microcavities based on alternating layers of Aquivion (AQ) and poly(N-vinylcarbazole) (PVK), fabricated by sequential spin coating. Due to the relatively large refractive-index contrast between the two polymers (Δn ≈ 0.33), the resulting structures exhibit enhanced photonic confinement while maintaining the advantages of polymer-based fabrication.[3] These DBRs were employed to achieve fully solution-processed planar microcavities incorporating TDBC J-aggregates dispersed in a polyvinyl alcohol (PVA) matrix as the cavity defect layer.[4] Different architectures were explored by varying the number of DBR bilayers to evaluate the influence of cavity design on the optical response. The structures were characterized by angle-resolved reflectance and transmittance spectroscopy and analysed through transfer-matrix modelling. The results highlight the key role of refractive-index contrast and cavity design in controlling optical confinement. The resulting optimized microcavities exhibit strong exciton-photon coupling, demonstrating the potential of this materials platform for advanced photonic devices. [5,6]