Reflective filter comprising a periodic array structure having an equivalent refractive index and display panel having the same, display device and control method thereof

A control method of a reflective filter, wherein the reflective filter comprises:

• a substrate, a first dielectric layer located on one side of the substrate and having a first refractive index, a periodic array structure located on one side of the first dielectric layer away from the substrate and in direct contact with the first dielectric layer and a second dielectric layer whose material is a variable refractive index material, the periodic array structure comprises a plurality of solid material patterns spaced apart by gaps, the second dielectric layer covers the periodic array structure and fills the gaps, a first refractive index of the first dielectric layer is lower than an equivalent refractive index nneff of the periodic array structure with the gaps filled with the variable refractive index material, and the equivalent refractive index nneff is:
• nneff=√{square root over (f×na2+(1−f)×nv2)}
• where f is a ratio of a projection area of the solid material patterns of the periodic array structure on the substrate relative to a projection area of an entirety of the periodic array structure on the substrate, na is a refractive index of a material of the solid material patterns, and nv is a refractive index of the variable refractive index material;
• the control method comprises the steps of:
• in response to the reflective filter receiving a display signal, controlling a refractive index of a variable refractive index material in the reflective filter so that incident light is enabled to form a reflection peak of a designated color light or disenabled to form a reflection peak of a designated color light on a surface of the first dielectric layer adjacent to the periodic array structure, so as to realize a display requirement corresponding to the display signal.