Method for imaging of samples by using polarization controllable terahertz waves

Abstract

The invention discloses a method for imaging of samples by using polarization controllable terahertz waves, comprising the following steps: when the polarization state of terahertz waves is linear polarization, the polarization direction is adjusted to a horizontal direction, an image of horizontal terahertz waves formed after interacting with the tested samples is measured; the polarization direction is adjusted to a vertical direction, an image of vertical terahertz waves formed after interacting with the tested samples is measured. Two images of terahertz waves are analyzed, because the reception signal is strong, the image of horizontal terahertz waves can reflect the intensity changes after interacting with the samples; and the image of vertical terahertz waves can reflect the minutechanges of the polarization of terahertz waves caused by samples.

Description

technical field [0001] The invention relates to the field of terahertz wave imaging, in particular to a method for imaging a sample by using polarization-controllable terahertz waves. Background technique [0002] Due to its unique properties such as transient, low energy and coherence, terahertz radiation has great scientific research value and broad application prospects in satellite communication, nondestructive testing, and military radar. Terahertz polarization measurement, terahertz communication, biomedical imaging, military target recognition, chemical composition analysis, and the production of terahertz filters all require precise control of the polarization direction of terahertz waves. [0003] By studying the polarization direction of the terahertz radiation generated by the excitation of the air plasma by the dual-frequency laser, the relative phase between the fundamental wave and the second harmonic in the four-wave mixing can be changed to control the polari...

AI Technical Summary

Problems solved by technology

[0004] In the imaging technology using the electro-optic sampling detection method, the current imaging method is characterized by only detecting the component of the terahertz electric field vector in one direction, which makes it difficult for some imaging results to be truly interpreted, resulting in the obtained sample image information more limited

For example, the reduction of the amplitude of the electric field intensity of the sample signal relative to the reference signal is generally understood to be caused by the absorption and scattering of the terahertz radiation by the sample, but in fact, the rotation of the terahertz electric field vector will also cause this decrease in detection intensity

Therefore, the current imaging method cannot consider the birefringence characteristics of the sample for terahertz waves, and, in addition to the birefringence effect, reflection after oblique incidence and multiple scattering may cause changes in the direction of the terahertz electric field

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