| Since the first laser being made in60s last century, people have observed series of new phenomena by using high-intensity and good-monochromaticity laser coupled with materials, such as optical rectification, SHG, stimulated Raman scattering, self-focusing effect, etc. In order to have a deep understanding of these interesting phenomena, the nonlinear optical theory was built.With the development of the nonlinear optics, people has been applying the research results into all kinds of regions. For examples, using nonlinear effect to form soliton in fiber; using XPM and SPM to make all-optics switch; making optical memory with faster reading speed and higher fidelity. All of these will have great impact on the quantum calculation and quantum communication in the future. Base on the rich and important application value of nonlinear optics, more and more people has started to research the enhancement and modification of the interacting between laser and materials. Nowadays with the developed science and technology, people have started doing the nonlinearity research in the level of quantum.Based on the work about elelctromagnetically induced transparency and enhancement and modification of the nonlinearity in our group, this article made a theoretical and experiment research about the self-Kerr nonlinearity in an N-type four level atom. By using density matrix method, the article shows the change of self-Kerr nonlinear n2with the modification of the switching field which can be well explained by dressed-state theory; experimentally, by using of an optical resonant cavity, we measure n2in the position of resonance in hot Rb atoms. The experimental result shows that with the unidirectional increase of the switching field power, we can get two obvious change of n2in the position of resonance, which corresponds well with the theoretical results. This research can provide more innovative ideas in making soliton and SPM, which are very important in fiber communication and all-optics switch. |
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