Patent ID: 8735823

Claim:
A terahertz-wave element comprising: a waveguide that includes an electro-optic crystal and allows light to propagate therethrough; and a coupling member that causes a terahertz wave to enter the waveguide, wherein a propagation state of the light propagating through the waveguide changes as the terahertz wave enters the waveguide via the coupling member, wherein the waveguide includes a core layer and a cladding layer, wherein the cladding layer is interposed between the coupling member and the core layer, and wherein a<d<λ eq /10 is satisfied where d denotes a thickness of the cladding layer, a denotes a thickness corresponding to 1/e 2 of a light intensity of the light in the core layer, e being the base of natural logarithm and λ eq denotes an equivalent wavelength in the cladding layer with respect to a wavelength corresponding to a maximum frequency of the terahertz wave.