Terahertz Radiation Of Ferromagnetic Thin Films And Applications In Thin Film Materials

In this paper,the properties of terahertz radiation from Fe/Pt heterostructure films with femtosecond laser irradiation were studied.The terahertz signal is modulated by external magnetic field.Finally,the optical parameters?electrical conductivity?of topological insulator Bi₂Se₃ thin film were extracted with pure optical means by using the interaction between terahertz signal and the material.This thesis studies the following problems:?1?The correlation between the terahertz polarization direction of Fe/Pt sample and the polarization direction of incident laser was investigated,and it was found that the terahertz signal strength was proportional to the intensity of excited light.It does not support the optical rectification effect of terahertz radiation.?2?According to the difference between electric dipole radiation and magnetic dipole radiation,the magnetic moment of the sample is controlled by introducing an external magnetic field.The polarity of terahertz signal was changed by changing the direction of excitation light irradiating Fe/Pt films.The demagnetization signal and terahertz signal were measured synchronously and the waveform relationship was explored.Finally,we showed that the electric dipole radiation should play a dominant role in the terahertz radiation mechanism of Fe/Pt films.?3?We measured terahertz radiation and MOKE of Fe/Pt films,an amazing coincidence relation was found.We can use magnets to regulate terahertz signals.?4?The electrical conductivity of the topological insulator Bi₂Se₃ was extracted by terahertz signal,also the influence of pump light was explored.