Nearly Resonant Gain Grating Effect In An Atomic Medium

Many novel and interesting atomic coherence effects have been discovered.Among them,electromagnetically induced transparency(EIT)has greatly promoted the development of quantum science research and technology.EIT effect has the characteristics of weak absorption and strong dispersion,which can be combined with nonlinear optical media to effectively enhance the nonlinear effect of the media.The EIT effect opens up a new way to study the interaction between light and atoms.In this paper,nearly resonant gain grating(NRGG)is studied.This effect has important researches and applications value for the design and control of all-optical devices.The research contents of this paper mainly include the following three points:1.The wave equation and the polarizability in nonlinear media are introduced,the real and imaginary parts of the polarizability in nonlinear media are deduced,and the physical meaning of the corresponding real and imaginary parts is explained.2.The electromagnetically induced amplitude grating is studied theoretically in the ?-type three-level atomic system,and the phase grating effect of electromagnetically induced is discussed in the N-type and tripod-type cold four-level atomic system respectively.The results show that the zero-order diffraction light is dispersed to the higher-order directions under the action of phase modulation of N-type and tripod-type electromagnetic induced phase grating,so as to improve the higher-order diffraction efficiency.3.The near resonance gain grating effect in N-type four-level cold atom system is introduced.The theoretical analysis with analytical solution shows that the modulated field can amplify the energy of the probe field by about 4times in the case of only amplitude modulation,and the energy is mainly distributed in the zero-order diffraction direction.With the addition of phase modulation,the coupling field plays an important role in the distribution of diffracted light and transfers more energy to the higher-order diffraction directions.Therefore,the grating with high gain,strong diffraction ability and controllable threshold is obtained,which has a wider application prospect in new photonic devices and laser technologies such as all-optical switch and quantum all-optical control.