Optical device

An optical device, comprising:

• a photoelectric conversion layer comprising a plurality of photodiodes;
• an anti-reflection layer disposed on the photoelectric conversion layer;
• an underlying layer disposed above the anti-reflection layer;
• a bottom meta layer disposed on the underlying layer and comprising a plurality of bottom meta units and a filling between the bottom meta units, wherein the filling continuously extends from the underlying layer, and a material of the filling is the same as a material of the underlying layer;
• a top meta layer disposed above the bottom meta layer and comprising a plurality of top meta units and a plurality of air recesses, wherein the plurality of air recesses are respectively disposed between two adjacent top meta units;
• and
• an internal space layer connecting the top meta units to the bottom meta units, wherein a refractive index of the internal space layer is the same as a refractive index of the bottom meta units.