Terahertz Time Domain Spectroscopy In The Agricultural And Materials In The Application Of Basic Research

Terahertz (THz, 1THz=1012Hz) radiation with a frequency range of 0.1THz~10THz, sandwiched between microwave and infrared, belongs to far infrared region. In recent years, rapid progress in ultrafast laser technology provides a steady and available source for terahertz pulses generation, which greatly promotes the development of THz spectroscopy technique. THz time-domain spectroscopy (THz-TDS) is a powerful tool developed in 1990s for spectroscopy measurement. This technique can record the amplitude of the wave by electro-optical or photoconductive sampling. After fast Fourier transform, the amplitude and phase of the THz pulse wave can be obtained, then the refractive index and absorption coefficient of the material in THz frequency region can be extracted.In this paper, THz Time-Domain Spectroscopy technique is applied to study the agricultural and material samples.Firstly, we have studied the THz spectrum of some samples in agriculture at room temperature, including corn leaf, amylose, amylopectin, amino acid and melamine. The results show that the THz spectrums of four different maize leaves are similar. There is no characteristic absorption peak observed, and the absorption strengthens gradually with the frequency increasing. The absorption spectrums of amylose and amylopectin show that there is only overall absorption, which is similar with corn leaf. Compared the two results, the refractive index and absorption coefficient of amylose is bigger than amylopectin. The results of amino acid and melamine indicate that their absorption of THz wave is very small, the absorption coefficients are close to zero in 0.2THz~1.7THz frequency range.Secondly, we have measured several ferroelectric materials and GaAs semiconductor, their optical constants are given in this paper. Compared the results of samples with different composition ratio or manufacturing parameters. And according to the experimental results, materials'possible applications in THz radiation are given. Our experimental work may provide useful reference value for the future research and applications of those materials in THz radiation.