Optical element, and optical device and terahertz time-domain spectroscopic apparatus including the same

An optical element configured to be irradiated with light and to generate or detect a terahertz wave in response thereof, the optical element comprising:

• a semiconductor layer having an energy band gap larger than a photon energy of the light;
• and
• a plurality of electrodes formed in electrical contact with the semiconductor layer,
• wherein at least one of the electrodes forms a Schottky junction between the electrode and the semiconductor layer, the Schottky junction having a barrier height smaller than the photon energy of the light, and
• wherein at least part of a junction surface between the electrode that forms the Schottky junction and the semiconductor layer includes:
• a light irradiation surface arranged to be irradiated with the light from a surface of the semiconductor layer without the electrodes, and
• a portion of a coupling structure arranged to be coupled to the terahertz wave that is generated or detected through the irradiation with the light.