Spectrum modulation method for air plasma generated terahertz wave and light path system

Abstract

The invention relates to a modulation method for air plasma generated terahertz wave; the method comprises the steps of first, designing a lens phase diagram that is a phase distribution diagram of lens phase factors; second, loading the lens phase diagram to a light path system for air plasma generated terahertz wave so as to generate plasma filaments and to irradiate terahertz wave; the step of designing the lens phase diagram in the first step includes: a, adjusting phase distribution of the lens phase diagram, and using the light path system for air plasma generated terahertz wave to generate terahertz wave; b, studying relationship between the spectrum of the generated terahertz wave and the form of generated plasmas; c, setting the spectrum of terahertz wave expectedly to be generated, calculating spacing of two plasmas that generate the terahertz wave; d, calculating equivalent focal length f1 of the lens phase diagram; e, designing the lens phase diagram. The method according to the embodiments of the invention is simple to perform, dynamic modulation is provided for the spectrum of terahertz wave, and energy utilization rate is increased.

Description

technical field [0001] The invention relates to the field of optics, in particular to a spectrum modulation method and an optical path system for generating terahertz waves by air plasma. Background technique [0002] Since the vibration and rotational energy levels of many polar macromolecules fall within the terahertz spectrum range, terahertz waves can be used for spectrum measurement and identification of substances. Different substances have different spectrum distributions, commonly known as the “fingerprint” of substances. Therefore, terahertz waves are widely used in the fields of security detection, detection and identification of biopharmaceuticals, drugs and explosives. [0003] The method of ionizing air to induce plasma to generate terahertz waves is that when high-energy ultrashort laser pulses are focused in the air, the air at the focal point will be ionized to form plasma, and then radiate terahertz waves. This method has the least terahertz loss, which mak...

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Problems solved by technology

[0006] The purpose of the present invention is to overcome the problems of poor modulation effect on terahertz spectrum, low energy utilization rate of pump light, and complex optical path system in the prior art.

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