Terahertz wave generating element and terahertz wave detecting element

A terahertz wave generating element comprising:

• a nonlinear optical crystal configured to generate terahertz waves by light propagating therethrough;
• and
• a coupling member through which the terahertz waves generated by the nonlinear optical crystal propagate;
• wherein the coupling member includes a reflecting face configured to reflect at least a part of the terahertz waves generated by the nonlinear optical crystal;
• wherein the reflecting face is convex in a propagation direction of the terahertz waves generated by the nonlinear optical crystal;
• wherein an angle at the coupling member side between the reflecting face and a propagation direction of the light is not less than sin−1 (ne/nTHz)+90 degrees−cos−1 (ng/nTHz) and smaller than 90 degrees at a plane including the propagation direction of the light, where ng represents a group refractive index of the nonlinear optical crystal at a wavelength of the light, ne represents a refractive index of an external matter of the coupling member at the wavelength of the terahertz waves generated by the nonlinear optical crystal, and nTHz represents the refractive index of the coupling member at a wavelength of the terahertz waves generated by the nonlinear optical crystal;
• and wherein a radius of curvature of the reflecting face, in a reflection region where the terahertz waves generated by the nonlinear optical crystal are reflected, is smaller the farther downstream in the propagation direction of the light.

A terahertz wave detecting element comprising:

• a nonlinear optical crystal configured to change a propagation state of light by input of terahertz waves;
• and
• a coupling member configured to guide the terahertz waves to the nonlinear optical crystal;
• wherein the coupling member includes a transmission face configured to transmit the terahertz waves and a reflecting face configured to reflect at least a part of the terahertz waves transmitted through the transmission face;
• wherein the reflecting face is convex in a direction opposite to the propagation direction of the terahertz waves input to the nonlinear optical crystal;
• wherein an angle at the coupling member side between the reflecting face and a propagation direction of the light is greater than 90 degrees−cos−1 (ng/nTHz) and smaller than 90 degrees at a plane including the propagation direction of the light, where ng represents a group refractive index of the nonlinear optical crystal at a wavelength of the light, and nTHz represents the refractive index of the coupling member at a wavelength of the terahertz waves generated by the nonlinear optical crystal;
• and wherein a radius of curvature of the reflecting face, in a reflection region where the terahertz waves generated by the nonlinear optical crystal are reflected, is greater the farther downstream in the propagation direction of the light.

A terahertz wave detecting element comprising:

• a nonlinear optical crystal configured to change a propagation state of light by input of terahertz waves;
• and
• a coupling member configured to guide the terahertz waves to the nonlinear optical crystal;
• wherein the coupling member includes a reflecting face configured to reflect at least a part of the terahertz waves input to the nonlinear optical crystal;
• wherein the reflecting face is convex in a direction opposite to the propagation direction of the terahertz waves input to the nonlinear optical crystal;
• wherein an angle at the coupling member side between the reflecting face and a propagation direction of the light is not less than sin−1 (ne/nTHz)+90 degrees−cos−1 (ng/nTHz) and smaller than 90 degrees at a plane including the propagation direction of the light, where ng represents a group refractive index of the nonlinear optical crystal at a wavelength of the light, and nTHz represents the refractive index of the coupling member at a wavelength of the terahertz waves generated by the nonlinear optical crystal;
• and wherein a radius of curvature of the reflecting face, in a reflection region where the terahertz waves generated by the nonlinear optical crystal are reflected, is greater the farther downstream in the propagation direction of the light.

A terahertz wave generating element comprising:

• a crystal including at least one selected from a group consisting of LiNbOx, LiTaOx, NbTaOx, KTP, DAST, ZnTe, GaSe, and GaAs;
• and
• a coupling member through which terahertz waves propagate, the terahertz waves being generated from the crystal as a result of light propagating through the crystal;
• wherein the coupling member includes a reflecting face configured to reflect at least a part of the terahertz waves generated from the crystal and a transmission face configured to transmit the terahertz waves reflected at the reflecting face;
• wherein the reflecting face includes a part of a conical face that has an apex on a downstream side of a propagation direction of the light.