Terahertz wave generation method and terahertz wave generation device

Patent metadata

Field	Value
Publication number	US-11073740-B2
Application number	US-201816637774-A
Country	US
Kind code	B2
Filing date	Jul 30, 2018
Priority date	Aug 10, 2017
Publication date	Jul 27, 2021
Grant date	Jul 27, 2021

Abstract

A terahertz-wave generation method of generating a terahertz wave in a direction satisfying a non-collinear phase-matching condition by making pump light incident on a nonlinear optical crystal capable of generating a terahertz wave by optical parametric effect, makes the pump light incident on the nonlinear optical crystal so that a peak excited power density is equal to or greater than a predetermined terahertz-wave lasing threshold and equal to or less than a predetermined laser damage threshold, and an average excited power density, is equal to or less than a predetermined photorefractive effect occurrence threshold, the pump light having a pulse width of 10 ps or more, the pulse width of 1 ns or less, and a repetition frequency of 1 kHz or more.

First claim

The invention claimed is:

1. A terahertz-wave generation method of generating a terahertz wave in a direction satisfying a non-collinear phase-matching condition by making pump light incident on a nonlinear optical crystal capable of generating a terahertz wave by optical parametric effect, the method comprising:
making the pump light incident on the nonlinear optical crystal so that a peak excited power density is equal to or greater than a predetermined terahertz-wave lasing threshold and equal to or less than a predetermined laser damage threshold, and an average excited power density is equal to or less than a predetermined photorefractive effect occurrence threshold, the pump light having a pulse width of 10 ps or more, the pulse width of 1 ns or less, and a repetition frequency of 1 kHz or more.

2. The terahertz-wave generation method of claim 1 , wherein
at least one of the peak excited power density and the average excited power density is changed by changing power of the pump light.

3. The terahertz-wave generation method of claim 1 , wherein
at least one of the peak excited power density and the average excited power density is changed by changing light flux diameter of the pump light at an incident surface of the nonlinear optical crystal.

4. The terahertz-wave generation method of claim 1 , wherein
the terahertz-wave lasing threshold is 500 MW/cm 2 .

5. The terahertz-wave generation method of claim 1 , wherein
the nonlinear optical crystal is magnesium-oxide doped lithium niobate crystal with congruent composition.

6. The terahertz-wave generation method of claim 5 , wherein
the laser damage threshold is 5.6 GW/cm 2 .

7. The terahertz-wave generation method of claim 5 , wherein
the photorefractive effect occurrence threshold is 52 kW/cm 2 .

8. The terahertz-wave generation method of claim 1 , wherein
the nonlinear optical crystal is lithium niobate crystal with stoichiometric composition.

9. The terahertz-wave generation method of claim 8 , wherein
the laser damage threshold is 14 GW/cm 2 .

10. The terahertz-wave generation method of claim 8 , wherein
the photorefractive effect occurrence threshold is 2 MW/cm 2 .

11. A terahertz-wave generation apparatus, comprising:
a pump light source configured to output pump light having a pulse width of 10 ps or more, the pulse width of 1 ns or less, and a repetition frequency of 1 kHz or more;
a nonlinear optical crystal capable of generating a terahertz wave by optical parametric effect;
a first optical system configured to guide the pump light output by the pump light source to the nonlinear optical crystal; and
a controller configured to control at least one of the pump light source and the first optical system so that a peak excited power density is equal to or greater than a predetermined terahertz-wave lasing threshold and equal to or less than a predetermined laser damage threshold, and an average excited power density is equal to or less than a predetermined photorefractive effect occurrence threshold, wherein
the terahertz-wave generation apparatus is configured to generate the terahertz wave in a direction satisfying a non-collinear phase-matching condition by making the pump light incident on the nonlinear optical crystal.

12. The terahertz-wave generation apparatus of claim 11 , wherein
the controller is configured to control at least one of the peak excited power density and the average excited power density by controlling the pump light source to change power of the pump light.

13. The terahertz-wave generation apparatus of claim 11 , wherein
the first optical system includes a pump light amplification system configured to amplify the pump light, and
the controller is configured to control at least one of the peak excited power density and the average excited power density by changing an amplification factor of the pump light amplified by the pump light amplification system.

14. The terahertz-wave generation apparatus of claim 11 , wherein
the first optical system includes a lens system capable of changing a focal position, and
the controller is configured to control at least one of the peak excited power density and the average excited power density by controlling the lens system.

15. The terahertz-wave generation apparatus of claim 11 , further comprising
a second optical system configured to inject seed light in a generation direction of idler light generated by making the pump light incident on the nonlinear optical crystal, wherein
the controller is configured to control at least one of the peak excited power density and the average excited power density by change power of the seed light.

16. The terahertz-wave generation apparatus of claim 11 , wherein
the terahertz-wave lasing threshold is 500 MW/cm 2 .

17. The terahertz-wave generation apparatus of claim 11 , wherein
the nonlinear optical crystal is magnesium-oxide doped lithium niobate crystal with congruent composition.

18. The terahertz-wave generation apparatus of claim 17 , wherein
the laser damage threshold is 5.6 GW/cm 2 .

19. The terahertz-wave generation apparatus of claim 17 , wherein
the photorefractive effect occurrence threshold is 52 kW/cm 2 .

20. The terahertz-wave generation apparatus of claim 11 , wherein
the nonlinear optical crystal is lithium niobate crystal with stoichiometric composition.

21. The terahertz-wave generation apparatus of claim 20 , wherein
the laser damage threshold is 14 GW/cm 2 .

22. The terahertz-wave generation device of claim 20 , wherein
the photorefractive effect occurrence threshold is 2 MW/cm 2 .

Assignees

• Topcon Corp
• Riken

Inventors

• Moriguchi Yoshikiyo
• Minamide Hiroaki

Classifications

• G02F1/39

  for parametric generation or amplification of light, infrared or ultraviolet waves · CPC title

• G02F1/3534

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

• H01S3/10

  Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating · CPC title

• G02F2/002 Primary

  using optical mixing · CPC title

• G02F2203/13

  involving THZ radiation · CPC title