Theoretical solution to second-harmonic generation of ultrashort laser pulse

Abstract

We propose a theoretical method called the broadband nonlinear coupled wave theory (BNCWT) to evaluate the second harmonic generation (SHG) process of ultrashort laser pulse transporting in nonlinear media. Because of the broadband nature of the pulse laser, all the relevant second-order nonlinear interactions for different frequency components are considered in the analysis and simulation, including sum-frequency generation (SFG) and SHG. The SHG of an ultrashort pulse can be regarded as a series of self-SFG and self-SHG processes for different frequency components, and their mutual coupling. The solution of the problem traces back to the solution of a set of nonlinear coupled wave equations satisfied by all frequency components involved within the laser pulse. Numerical simulations show great consistency with experimental results, indicating that the proposed BNCWT is instructive and efficient and can have great practical value for experimental prediction.