Terahertz Spatial Intensity Measurement And Imaging Technologies Based On Frequency Comb

Terahertz electromagnetic radiation is in the frequency spectrum between microwave and infrared,it is a bridge between electronics and photonics,and has important applications in the fields of biomedicine and safety inspection.The concept of terahertz frequency comb was first proposed by Japanese researchers,and it has shown good accuracy and accuracy in terahertz frequency measurement.The research on terahertz spatial radiation intensity through frequency comb started relatively late.In this paper,electro-optical crystals and photoconductive antennas were used to generate terahertz frequency comb,and the distribution of terahertz spatial radiation intensity was studied.The main research contents of this paper are as follows:(1)The basic knowledge of optical frequency comb and terahertz frequency comb is studied theoretically,the method of generating beat frequency signal is analyzed,and the process of generating beat frequency signal when terahertz frequency comb interacts with terahertz source is deduced.(2)A terahertz spatial radiation intensity measurement system based on electro-optical sampling was established.The femtosecond laser output center wavelength was 800 nm,and the electro-optical crystal ZnTe was excited to generate terahertz frequency comb.A terahertz space radiation intensity measurement system based on the photoconductive antenna was built.The femtosecond laser output center wavelength was 1550 nm,and the photoconductive antenna was excited to generate terahertz frequency comb.(3)Five different photoconductive antennas were used as terahertz sources to generate terahertz radiation.Four of them are 100 GHz and one is 300 GHz.Two systems were used to measure the spatial radiation intensity of the five terahertz sources.Experiments with different detection distances were designed for the same terahertz source.The detection distance refers to the distance between the terahertz source and the electro-optic crystal ZnTe or the photoconductive day.The above experiments can reveal the evolution characteristics of terahertz radiation generated by five antennas in space transmission.(4)Based on the terahertz frequency comb measurement technology,the terahertz imaging system is further studied,and the terahertz imaging system based on electro-optical sampling and photoconductive antenna is established.The photoelectric crystal ZnTe and the photoconductive antenna were used as the detector,and two different photoconductive antennas were used to generate terahertz radiation as the imaging light source.