Method for improving terahertz wave generation efficiency and transmissivity

Abstract

The invention discloses a method for improving terahertz wave generation efficiency and transmissivity. The method comprises the following steps: obtaining an angle of inclination; obtaining a function expression of the amount of inclination according to the angle of inclination and a grating dispersion equation; obtaining the front surface grating ruling density of lithium niobate crystals according to the Littrow incidence condition, a grating equation and the function expression of the amount of inclination; modeling the grating by a modal method to obtain the grooving width and depth according to the relations between the minus one order diffraction efficiency of the grating and the filling factor and grooving depth of the grating; carving grating structures on the planes of incidence of the lithium niobate crystals by a micro-nano machining method in the machining tolerance range according to the front surface grating ruling density and the grooving width and depth; adding micro right-angle pyramid structures on the incidence interfaces of the lithium niobate crystals through micro-nano machining; and ensuring a pumped laser to emit pump light at specific incidence angles on the front surfaces of the lithium niobate crystals and generate terahertz waves on the emergence interfaces, wherein the grating ruling is parallel to the light axes of the lithium niobate crystals. The method has the beneficial effects of simplifying the components and shortening the light paths.

Description

technical field [0001] The invention relates to the technical field of ultrafast terahertz wave generation, in particular to a method for improving terahertz wave generation efficiency and transmittance. Background technique [0002] Optical rectification of ultrashort light pulses in nonlinear media is an important method for optically generating ultrafast terahertz waves. The traditional optical rectification technology is to select a suitable femtosecond laser and a matching nonlinear crystal, and use the characteristic that the pumping light and the transmission path of the terahertz wave are completely consistent to perform collinear phase matching to generate and radiate the terahertz wave. [0003] In order to improve the conversion efficiency of pump light to terahertz waves, it is necessary to select a nonlinear medium with a larger effective nonlinear coefficient as the emitter, and use a pump light pulse with a higher peak power to excite the crystal. However, in ...

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Problems solved by technology

[0006] In the prior art, due to the use of dispersive elements such as gratings, the optical path is relatively complex and the structure is relatively large, and due to the use of a single lens or a telescope-type focusing system, the pulse intensity wavefront of the pumping light will be distorted when it is transmitted into the crystal, affecting The efficiency of generating terahertz waves; due to the high refractive index of lithium niobate crystals, the Fresnel reflection loss of terahertz waves generated in the crystal at the exit end face is relatively large, and the output efficiency is low

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