Optical stack and optical device

Abstract

An optical stack comprises a first optical layer having a first principal surface and a second principal surface opposite to the first principal surface, a plurality of first internal low refractive index layers arranged discretely along a first direction, the plurality of first internal low refractive index layers being inclined to the first principal surface, and a second optical layer arranged to sandwich the plurality of first internal low refractive index layers between the first and second optical layers, wherein each of the plurality of first internal low refractive index layers has a refractive index lower than a refractive index of the first optical layer and lower than a refractive index of the second optical layer, and each of the plurality of first internal low refractive index layers directs part of light entering each of the plurality of first internal low refractive index layers from the first optical layer, by total internal reflection, toward the side of the first principal surface.

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