Near-field light generator and thermally-assisted magnetic recording head

A near-field light generator comprising:

• a waveguide including a core through which light propagates, and a cladding provided around the core;
• a first gap part and a second gap part each made of a dielectric material that has a refractive index lower than that of the core;
• and
• a plasmon generator, wherein:
• the core has a first evanescent light generating surface and a second evanescent light generating surface that are disposed such that the plasmon generator is interposed therebetween;
• the first evanescent light generating surface generates first evanescent light based on the light propagating through the core;
• the second evanescent light generating surface generates second evanescent light based on the light propagating through the core;
• the plasmon generator has an outer surface, the outer surface including:
• a front end face;
• a first plasmon exciting part that is opposed to the first evanescent light generating surface with a predetermined spacing therebetween;
• and a second plasmon exciting part that is opposed to the second evanescent light generating surface with a predetermined spacing therebetween;
• the first gap part is interposed between the first evanescent light generating surface and the first plasmon exciting part;
• the second gap part is interposed between the second evanescent light generating surface and the second plasmon exciting part;
• the plasmon generator is configured so that a first surface plasmon is excited on the first plasmon exciting part through coupling with the first evanescent light, a second surface plasmon is excited on the second plasmon exciting part through coupling with the second evanescent light, the first and second surface plasmons propagate to the front end face, and near-field light is generated from the front end face based on the first and second surface plasmons;
• a cross section of the plasmon generator parallel to the front end face, the cross section having a periphery defined in part by the first and second plasmon exciting parts, is in the shape of a quadrangle that is made up of a first side, a second side, a third side, and a fourth side;
• and
• the first side is defined in its entirety by the first plasmon exciting part, the second side is defined in its entirety by the second plasmon exciting part, the third side connects between one end of the first side and one end of the second side, and the fourth side connects between the other end of the first side and the other end of the second side.