Tailoring Multibounce Reflection Interference with Microscale Refractive Interfaces

Developing approaches to tailor iridescence generated
by microscale
structures is essential for applications ranging from sensors to security
materials. Here, we achieve tunable iridescence by combining microscale
refractory interfaces with concave microstructures to generate multibounce
reflection interference. By incorporating designed refractory interfaces,
we demonstrate the ability to control the distribution of illumination
angles entering the structured cavity thereby modulating the resulting
color and reflection efficiency. Experimental analysis of Janus droplets
combined with ray tracing simulations highlight how refractory elements
modify the optical paths of multibounce reflections and alter the
angle-dependent coloration. Additionally, we investigate the incorporation
of axion lenses that refract and focus light onto the microstructure
to increase reflection efficiency while maintaining color saturation.
The integration of refractory interfaces with reflective microstructure
cavities provides customizable routes to tailor the structural coloration
and reflection performance of multibounce reflection interference,
advancing the design of high-performance optical materials.