Terahertz wave generator

1. A terahertz wave generator for generating a terahertz wave, comprising:

a generating layer for generating carriers by incident excitation light, wherein the excitation light reflected by the generating layer reenters the generating layer;

a waveguide layer for permitting the excitation light to pass through; and

a first confinement layer for making the excitation light reflected by the generating layer to reenter the generating layer,

wherein:

the generating layer, the wave guide layer, and the first confinement layer are laminated in the stated order,

the generating layer is formed of a photoconductive semiconductor,

the waveguide layer is formed of a material that permits the excitation light entering the generating layer and a terahertz wave generated by the excitation light entering the generating layer to pass through, and

the first confinement layer is formed of a material that reflects the excitation light propagating in the waveguide layer and the terahertz wave propagating in the waveguide layer.

2. A terahertz wave generator according to claim 1 , wherein the excitation light that enters the generating layer at a first position is reflected, and the reflected excitation light enters the generating layer at a second position that is different from the first position.

3. A terahertz wave generator according to claim 1 , further comprising a second confinement layer formed of a material that reflects the terahertz wave generated in the generating layer,

wherein the second confinement layer, the generating layer, the waveguide layer, and the first confinement layer are laminated in the stated order.

4. A terahertz wave generator according to claim 1 , wherein the generating layer has an optical thickness of one tenth or smaller of a wavelength of the terahertz wave generated from the generating layer.

5. A terahertz wave generator according to claim 1 , wherein the waveguide layer has a refractive index with respect to the excitation light that is smaller than a refractive index with respect to the excitation light of the generating layer.

6. A terahertz wave generator for generating a terahertz wave, comprising:

a generating layer for generating carriers by incident excitation light, wherein the excitation light reflected by the generating layer reenters the generating layer, the excitation light that enters the generating layer at a first position is reflected, and the reflected excitation light enters the generating layer at a second position that is different from the first position;

a waveguide layer for permitting the excitation light to pass through;

a first confinement layer for making the light reflected by the generating layer at the first position to enter at the second position; and

a second confinement layer formed of a material that reflects the terahertz wave generated in the generating layer,

wherein the second confinement layer, the generating layer, the waveguide layer, and the first confinement layer are laminated in the stated order, and

wherein the second confinement layer is an electrode for applying an electric field to the generating layer.

7. A terahertz wave generator according to claim 6 , wherein the excitation light that enters the generating layer at a first position is reflected, and the reflected excitation light enters the generating layer at a second position that is different from the first position.

8. A terahertz wave generator according to claim 6 , wherein the generating layer has an optical thickness of one tenth or smaller of a wavelength of the terahertz wave generated from the generating layer.

9. A terahertz wave generator according to claim 6 , wherein the waveguide layer has a refractive index with respect to the excitation light that is smaller than a refractive index with respect to the excitation light of the generating layer.

10. A terahertz wave generator for generating a terahertz wave, comprising:

a generating layer for generating carriers by incident excitation light, wherein the excitation light reflected by the generating layer reenters the generating layer, the excitation light that enters the generating layer at a first position is reflected, and the reflected excitation light enters the generating layer at a second position that is different from the first position;

a waveguide layer for permitting the excitation light to pass through;

a first confinement layer for making the light reflected by the generating layer at the first position to enter at the second position; and

an adjustment layer for adjusting an absorption ratio of the excitation light absorbed by the generating layer,

wherein the generating layer, the adjustment layer, the waveguide layer, and the first confinement layer are laminated in the stated order.

11. A terahertz wave generator according to claim 10 , wherein the excitation light that enters the generating layer at a first position is reflected, and the reflected excitation light enters the generating layer at a second position that is different from the first position.

12. A terahertz wave generator according to claim 10 , further comprising a second confinement layer formed of a material that reflects the terahertz wave generated in the generating layer,

wherein the second confinement layer, the generating layer, the waveguide layer, and the first confinement layer are laminated in the stated order.

13. A terahertz wave generator according to claim 10 , wherein the generating layer has an optical thickness of one tenth or smaller of a wavelength of the terahertz wave generated from the generating layer.

14. A terahertz wave generator according to claim 10 , wherein the waveguide layer has a refractive index with respect to the excitation light that is smaller than a refractive index with respect to the excitation light of the generating layer.

15. A terahertz wave generator for generating a terahertz wave, comprising:

a generating layer for generating carriers by incident excitation light, wherein the excitation light reflected by the generating layer reenters the generating layer, the excitation light that enters the generating layer at a first position is reflected, and the reflected excitation light enters the generating layer at a second position that is different from the first position; and

a waveguide layer for permitting the excitation light to pass through;

a first confinement layer for making the light reflected by the generating layer at the first position to enter at the second position,

wherein the generating layer, the wave guide layer, and the first confinement layer are laminated un the stated order, and

wherein the waveguide layer includes a first waveguide layer for propagating the excitation light and a second waveguide layer for propagating the terahertz wave.

16. A terahertz wave generator according to claim 15 , wherein the excitation light that enters the generating layer at a first position is reflected, and the reflected excitation light enters the generating layer at a second position that is different from the first position.

17. A terahertz wave generator according to claim 15 , further comprising a second confinement layer formed of a material that reflects the terahertz wave generated in the generating layer,

wherein the second confinement layer, the generating layer, the waveguide layer, and the first confinement layer are laminated in the stated order.

18. A terahertz wave generator according to claim 15 , wherein the generating layer has an optical thickness of one tenth or smaller of a wavelength of the terahertz wave generated from the generating layer.

19. A terahertz wave generator according to claim 15 , wherein the waveguide layer has a refractive index with respect to the excitation light that is smaller than a refractive index with respect to the excitation light of the generating layer.