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Abstract Iridescent color-shift pigments have been used in some industrial applications, e.g., for cosmetics and packaging. To achieve environmental-friendly and lasting color, thin-film interference is used to generate structural color. By maximizing the refractive index (RI) difference between the thin films (i.e., using an ultralow RI film), super-iridescent structural color can be produced. While the lowest refractive index of a naturally occurring solid dielectric is close to 1.37 (i.e., MgF₂), we synthesized highly porous dielectric SiO₂aerogel to achieve ultralow-RI (n ~ 1.06) and demonstrated a high-refractive index/low-refractive index/absorber (HLA) trilayer structural color. The achieved structural color is highly iridescent and capable of tracing a near-closed loop in CIE color space. By tuning the refractive index, thickness, and geometry of the aerogel layer, we control the reflection dip’s shape, therefore producing a wide range of vivid and iridescent colors. 

Abstract High‐quality‐factor microring resonators are highly desirable in many applications. Fabricating a microring resonator typically requires delicate instruments to ensure a smooth side wall of waveguides and 100‐nm critical feature size in the coupling region. In this work, a new method “damascene soft nanoimprinting lithography” is demonstrated that can create high‐fidelity waveguide by simply backfilling an imprinted cladding template with a high refractive index polymer core. This method can easily realize high Q‐factor polymer microring resonators (e.g., ≈5 × 10⁵around 770 nm wavelength) without the use of any expensive instruments and can be conducted in a normal lab environment. The high Q‐factors can be attributed to the residual layer‐free feature and controllable meniscus cross‐section profile of the filled polymer core. Furthermore, the new method is compatible with different polymers, yields low fabrication defects, enables new functionalities, and allows flexible substrate. These benefits can broaden the applicability of the fabricated microring resonator.