Numerical Splitting Schemes for Solving the Ginzburg–Landau Equation with Saturated Gain and Cubic Mode Locked

The general characteristics of an optical signal as a result of generation in a resonator can be described using a dynamic model based on the complex cubic Ginzburg–Landau equation, which takes into account the saturated gain and dissipative terms responsible for the distributed action of various intracavity devices. The paper proposes two new effective modifications of the split-step Fourier method for a numerical solution to equations of this type. The first algorithm is based on the application of a new way of separating physical processes affecting the optical signal during propagation in a fiber, which made it possible to express the action of both nonlinear and dispersive spatial steps by explicit analytical expressions. The second proposed method enabled significant improvement in the accuracy of calculations due to including energy evolution in the coefficients of the equation. Numerical experiments have shown that the new schemes can produce the second order of approximation with respect to the evolutionary variable in contrast to the classical scheme that provides only the first order of approximation.