Patent ID: 7304916

Claim:
An optical head, comprising: a first propagation section made of a first low extinction material and installed along an optical axis from an incident point to an emergent point of light, where the first low extinction material has a complex refractive index whose imaginary part is virtually negligible; a pair of second propagation sections which are made of a second low extinction material and sandwich the first propagation section in at least one cross-axis direction intersecting the optical axis, where the second low extinction material has a complex refractive index whose imaginary part is virtually negligible and whose real part is larger than the real part of the complex refractive index of the first propagation section; a pair of first confining sections which are made of a material with light propagation capability lower than the light propagation capability of the second propagation sections, with zero light propagation capability being acceptable and further sandwich the first propagation section and the second propagation sections from outside the second propagation sections in the cross-axis direction; and a pair of third propagation sections which are made of a material with light propagation capability higher than the light propagation capability of the first confining sections and further sandwich the first confining sections from outside in the cross-axis direction, and are thicker in the cross-axis direction than the first confining sections.