Terahertz wave generating element and terahertz wave detecting element

Patent metadata

Field	Value
Publication number	US-2016246158-A1
Application number	US-201415027361-A
Country	US
Kind code	A1
Filing date	Sep 24, 2014
Priority date	Oct 9, 2013
Publication date	Aug 25, 2016
Grant date	—

Abstract

A terahertz wave generating element includes a nonlinear optical crystal generating terahertz waves by propagating light, and a coupling member propagating the generated terahertz waves. The coupling member includes a reflecting face reflecting at least part of the generated terahertz waves. The reflecting face is convex in a propagation direction of the generated terahertz waves. An angle at the coupling member side between the reflecting face and the propagation direction of the light is greater than 90 degrees−cos −1 (n g /n THz ) but smaller than 90 degrees at a plane including the light propagation direction. n g represents a group refractive index of the nonlinear optical crystal at a wavelength of the light, n THz the refractive index of the coupling member at a wavelength of the generated terahertz waves. A curvature radius of the reflecting face, in a reflection region reflecting the radius terahertz waves, is smaller the farther downstream in the light propagation direction.

First claim

1 . 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 and a transmission face configured to transmit the terahertz waves reflected at the reflecting face; 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 greater than 90 degrees−cos −1 (n g /n THz ) and smaller than 90 degrees at a plane including the propagation direction of the light, where n g represents a group refractive index of the nonlinear optical crystal at a wavelength of the light, and n THz 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.

2 . The terahertz wave generating element according to claim 1 ,
wherein the angle is not less than sin −1 (n e /n THz )+90 degrees-cos −1 (n g /n THz ) where n e 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.

3 . 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 (n e /n THz )+90 degrees−cos −1 (n g /n THz ) and smaller than 90 degrees at a plane including the propagation direction of the light, where n g represents a group refractive index of the nonlinear optical crystal at a wavelength of the light, n e 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 n THz 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.

4 . The terahertz wave generating element according to claim 1 ,
wherein the angle is 90 degrees−cos −1 (n g /n THz )/2±λ/8, where λ represents the wavelength of the terahertz waves generated by the nonlinear optical crystal.

5 . The terahertz wave generating element according to claim 1 ,
wherein the terahertz waves generated by the nonlinear optical crystal are totally reflected at the reflecting face.

6 . The terahertz wave generating element according to claim 1 ,
wherein the reflecting face includes a part of a curve formed by rotating a straight line or a curve of which the axis of rotation is the propagation direction of the light.

7 . The terahertz wave generating element according to claim 1 ,
wherein the reflecting face includes a part of a conical face of which the axis is the propagation direction of the light.

8 . The terahertz wave generating element according to claim 1 ,
wherein at least part of a cross-section of the reflecting face at a plane orthogonal to the propagation direction of the light through the coupling member is a part of a circle or ellipse.

9 . The terahertz wave generating element according to claim 1 ,
wherein the plane including the propagation direction of the light is perpendicular to the surface of the nonlinear optical crystal.

10 . The terahertz wave generating element according to claim 1 , further comprising:
a waveguide; wherein the waveguide includes the nonlinear optical crystal, and a clad layer which is disposed between the nonlinear optical crystal and the coupling member and which has a refractive index lower than the refractive index of the nonlinear optical crystal at the wavelength of the light.

11 . The terahertz wave generating element according to claim 1 ,
wherein the width of the nonlinear optical crystal is smaller than the wavelength of the terahertz waves generated by the nonlinear optical crystal.

12 . The terahertz wave generating element according to claim 1 ,
wherein the nonlinear optical crystal is configured so that the terahertz waves generated by the nonlinear optical crystal are input again, whereby a propagation state of light different from the light changes, whereby the terahertz waves generated by the nonlinear optical crystal are detected using the light of which the propagation state has changed.

13 . 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 (n g /n THz ) and smaller than 90 degrees at a plane including the propagation direction of the light, where n g represents a group refractive index of the nonlinear optical crystal at a wavelength of the light, and n THz 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.

14 . 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

Assignees

• Canon Kk

Inventors

• Kajiki Kousuke

Classifications

• G02F1/37 Primary

  for second-harmonic generation {(G02F1/3532 takes precedence)} · CPC title

• G02F1/365

  in an optical waveguide structure (G02F1/377, {G02F1/395} take precedence) · CPC title

• G01N21/55

  Specular reflectivity · CPC title

• G02F2001/3503

  Physics · mapped topic

• G02F1/3534 Primary

  Three-wave interaction, e.g. sum-difference frequency generation (G02F1/3532 takes precedence) · CPC title