| The linear and nonlinear optical effect of the magnetic material originated in the response to the magnetic field. The study for it can start from the dynamic magnetization, then obtain the linear and nonlinear susceptibilities, find the resonant frequency ranges. On these basises, the linear and nonlinear properties of the magnetic materials can be investigated further. The resonant frequencies of the typical antiferromagnetic materials are situated in terahertz frequency range, which can be used THz signal conditioning. It is practical significance to study the nonlinearity of AF through the theory and experiments. However, the AF nonlinearity is very weak, which need much stronger light density to illuminate it. Now, according to the existing technology it is hard to meet this requirement. On the basis of the existing light source it will be a very meaningful topic to find the effective ways to improve the nonlinear effect. Now the second harmonic generation(SHG), Sum-frequency and Difference-frequency technologies is a common tool to achieve the frequency conversion and also a method to produce a new light source. In this work, the second nonlinear theory of AF is established, a method to enhance the sum-and difference-frequencies conversion is discussed. The AF nonlinearity mentioned results from the magnetic dipole-dipole interaction between electromagnetic waves and AF dynamic magnetizations, which are different from the theory of the traditional nonlinear topics.The main methods, process and results are as follows:1. The Sum-frequency and Difference-frequency susceptibilities are obtained from the dynamics equations of magnetization in a uniaxial AF with two sublattices. We obtain the nonlinear susceptibilities in the style of explicit function in the presence of external magnetic field, which make a solid theoretical foundation for discussing the nonlinear effects of AF.2. Magnetic optical effects of one-and two-dimension ferromagnetic material/metal are discussed. The ferromagnetic material is chosed bismuth iron garnet(BIG), and the noble metal is Ag. The Faraday rotation effect of the onedimensional BIG/Ag magnetic photonic crystal is discussed. Compared with the BIG film, the maximum of Farady rotation is about 356 times. And the Kerr rotation effects also is discussed for the two-dimesional BIG/Ag magnetic photonic crystal structure since the improvement of Farady rotation is modified weakly. The results show that the maximum Kerr rotation angle is raised 3 orders of magnitude.3. We investigate some methods to increase the Sum-frequency of an AF film for a fixed input power. The AF systems include: the AF film and dielectrics/AF/dielectrics and dielectrics/AF/Ag. It is analyzed for the Sumfrequency excitation mechanism of AF and the effect of the structure on the enhancement of Sum-frequency. We found that the Sum-frequency outputs depend sensitively on the dielectrics and the incident angles. The output of dielectrics/AF/Ag can be enhanced about ten times of that of the single film. Meanwhile, we realize that Sum-frequency is controlled by the magnetic field.4. The Difference-frequency effects of Si O2/Mn F2/Ag and Zn F2/Mn F2/Ag are discussed. It is found that the Difference-frequency outputs of dielectrics/AF/Ag are about one order by the single AF film. Also, when the magnetic field is increased, the Difference-frequency outputs of Zn F2/Mn F2/Ag are enhanced almost two orders. The Difference-frequency conversion is higher than Sum-frequency conversion at the fixed incident energy. |
PDF Full Text Request