Optical information reproduction device, optical information reproduction method, and information recording medium

An optical information reproduction device that reproduces information recorded on an information recording medium including at least a substrate and a recording layer, the optical information reproduction device comprising:

• a light source configured to emit reproduction light;
• a plasmon resonance element including a resonance section arranged adjacent to a recording region of the recording layer, the resonance section causing plasmon resonance between the recording region and the resonance section;
• a photodetector configured to detect reflected light or transmitted light from the plasmon resonance element on which the reproduction light is irradiated;
• and
• a reproduction unit configured to determine, on the basis of a detection signal from the photodetector, whether the recording region is in a recorded state or an unrecorded state, and reproduce information recorded in the recording region.