Polarized light separation element and optical reception device

A polarization splitting device comprising:

• a substrate having a transmitting property for object light;
• and
• a polarization splitting layer made of a material having a transmitting property for the object light and with a refractive index higher than that of the substrate, having a structure element pattern including a plurality of structure elements each having two-fold rotational symmetry, and formed on an upper surface of the substrate, wherein
• the polarization splitting device has a configuration of a transmission type in which one surface of a lower surface of the substrate and an upper surface of the polarization splitting layer is set as a light incident surface, and another surface is set as a light output surface,
• the polarization splitting layer is configured to split first to sixth polarization components included in the object light incident from the light incident surface, and focus the first to sixth polarization components respectively at first to sixth focal positions different from each other on a focal plane set on the light output surface, and wherein
• the structure element pattern includes:
• a first structure element pattern including a plurality of first structure elements, and configured to focus the first polarization component and the second polarization component respectively at the first focal position and the second focal position;
• a second structure element pattern including a plurality of second structure elements, and configured to focus the third polarization component and the fourth polarization component respectively at the third focal position and the fourth focal position;
• and
• a third structure element pattern including a plurality of third structure elements, and configured to focus the fifth polarization component and the sixth polarization component respectively at the fifth focal position and the sixth focal position, and wherein
• a pattern of a linear shape or a triangular shape constituted by the first structure element, the second structure element, and the third structure element is set as a unit pattern, and a plurality of unit patterns are two-dimensionally arranged on the upper surface of the substrate.