Study On Physical Mechanism Of Three - Wave Mixing Process

Three-wave mixing (TWM) is a basic concept in nonlinear optics. It is similar to two-level atomic system under undepleted pump approximation. For TWM, the general form of coupling-wave equation is substituted for classical Hamiltonian structure. In this thesis, we use a new method to study the Rabi oscillation of the atom transition process in the two-level system based on the dressed state representation and explain the physical mechanisms about the oscillation of sum-frequency light. Considering the quasi-phase matching, energy conversion of sum-frequency process is also similar to Landau-Zener tunneling (LZT) process of two-level system. By using the asymptotic solution and analytical solution of LZT, the energy-transfer mechanism of sum-frequency processes is analyzed in detail. In addition, the general form of the steady-state and adiabatic conditions of TWM process are given by using the adiabatic theory of nonlinear quantum systems. And we discuss the problem of energy conversion between the light fields under adiabatic conditions of TWM process. In a word, the energy-transfer mechanism of parametric processes is revealed based on similarities between the macroscopic quantum phenomena and quantum physical phenomena. The main contents of the following five parts:1. The coupling-wave equation of TWM process is given. And we introduce the original model and basic theory of LZT process.2. Under undepleted pump approximation, the sum-frequency process is discussed by using the method studied the Rabi oscillation of two-level atom system in the dressed state representation, A new perspective which explains the physical mechanisms of oscillation about sum-frequency light is given. For the linear chirp, energy tunneling problem is discussed by using the theory of LZT process. We also discussed the influence of chirp coefficient on the frequency conversion of sum-frequency process. And broadband frequency can be obtained by tuning chirp coefficient.3. Three wave coupling equations are solved directly. We give the definition and solution of steady-state, and discuss the energy conversion of optical field in steady-state system. In addition, the general form of coupling-wave equation is substituted for classical Hamiltonian structure. And the steady-state solution are given again by classical mechanic, it is consistent with previous result.4. Solved the problem of three-wave coupling process by the adiabatic theory of the nonlinear system and given the definition of adiabatic conditions. The adiabatic condition is met under smaller chirp coefficient and large the intensity of light. So the most value of energy conversion can be achieved in TWM process. In addition, conversion efficiency and spectral width is obtained in the TWM process.