Optical interference control for selectively suppressing higher-order modes in all-dielectric tri-layered structures for reflective RGB colors

초록

We present a method to selectively suppress unwanted higher-order resonances in all-dielectric tri-layer structural color filters, achieving reflective red (R), green (G), and blue (B) colors through controlled optical interference. By applying a gradient-based optimization technique, we fine-tune the designs to improve color purity by eliminating undesired resonances outside the passband of the tri-layer structure. The filters are composed of a low-refractive-index (LRI) layer sandwiched between two high-refractive-index (HRI) layers. Higher-order modes in the HRI layers and the fundamental mode in the LRI layer are exploited to generate B and G colors. For the R color, the reverse configuration is used: the HRI layers employ the fundamental mode, and the LRI layer operates in a higher-order mode, which introduces an unwanted peak at lambda = 450 nm, significantly affecting color purity. To address this, we reduce the LRI thickness to half of the quarter-wave thickness (QWT) and increase the HRI thickness to a quarter of the QWT, shifting interference from constructive to destructive at lambda = 450 nm while preserving constructive interference at lambda = 642 nm. This effectively suppresses the higher-order mode, resulting in a pure R color. Our study provides valuable insights into the optical design of multilayer thin-film structures, with potential applications in reflective displays, image sensors, and colored solar cells. (c) 2025 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.

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