Wavelength selective filter, display, optical device, and method of producing wavelength selective filter

A method of producing a wavelength selective filter, comprising the steps of:

• forming a concavo-convex structure layer using a first low refractive index material, the concavo-convex structure layer having concavo-convex elements on a surface, the concavo-convex elements being composed of a plurality of protrusions and recesses arranged having a subwavelength period;
• forming a high refractive index layer using a high refractive index material having a refractive index higher than that of the first low refractive index material, the high refractive index layer being formed on a surface of the concavo-convex structure layer, and including a first grating high refractive index region located on a bottom of the concavo-convex structure of the concavo-convex structure layer to form a subwavelength grating, and a second grating high refractive index region located on a top of the concavo-convex structure to form a subwavelength grating;
• and
• forming a low refractive index layer using a second low refractive index material having a refractive index lower than that of the high refractive index material, the low refractive index layer being formed on a surface of the high refractive index layer, and having a surface shape following a concavo-convex structure on the surface of the high refractive index layer, wherein
• the step of forming the concavo-convex structure layer includes forming the concavo-convex structure layer by pressing an intaglio plate against a coating layer containing a resin which is the first low refractive index material, and removing the intaglio plate after the resin is cured to transfer the concavo-convex structure of the intaglio plate to the resin;
• the step of forming the high refractive index layer includes forming the high refractive index layer by physical vapor deposition, whereby the high refractive index layer includes an intermediate high refractive index region extending on a side surface of the concavo-convex element between the first grating high refractive index region and the second grating high refractive index region, and the second grating high refractive index region extends outside the intermediate high refractive index region when viewed in a direction parallel to a thickness direction of the high refractive index layer, and
• the step of forming the low refractive index layer includes forming the low refractive index layer by physical vapor deposition.

An optical device, comprising:

• a filter layer including a plurality of filter regions composed of a wavelength selective filter and
• a light receiving layer including a plurality of photoelectric conversion elements disposed corresponding to each of the filter regions, the photoelectric conversion elements being configured to receive transmitted light from the filter regions, wherein
• the plurality of filter regions include a plurality of the filter regions configured to reflect light in different wavelength ranges and/or a plurality of the filter regions in which the concavo-convex elements have arrangement directions different from each other, wherein the wavelength selective filter, comprises:
• a concavo-convex structure layer having a concavo-convex structure on a surface, the concavo-convex structure being composed of a plurality of concavo-convex elements arranged having a subwavelength period, the concavo-convex elements including protrusions and recesses;
• a high refractive index layer located on the concavo-convex structure and having a surface shape following the concavo-convex structure, the high refractive index layer including a first grating high refractive index region located on a bottom of the concavo-convex structure to form a subwavelength grating, and a second grating high refractive index region located on a top of the concavo-convex structure to form a subwavelength grating;
• and
• a low refractive index layer located on the high refractive index layer and having a surface shape following a concavo-convex structure on a surface of the high refractive index layer, wherein
• the high refractive index layer has a refractive index higher than both of refractive indices of the concavo-convex structure layer and the low refractive index layer.