Steady-state emission from a laser with a dynamic distributed feedback

Equations describing steady-state emission from a distributed-feedback (DFB) laser with a dynamic population grating are derived and solved numerically for a three-level active medium with various amounts of detuning of the Bragg frequency from the center of the gain profile at arbitrary pumping rates. An analysis of possible methods of numerical solution of these equations is made and the corresponding experimental conditions are identified. It is shown that in constructing an algorithm for solving such equations it is necessary to allow for the history of the process by which steady-state emission has been attained. A quantitative difference is established between the selectivities of a DFB structure under linear and nonlinear conditions and this difference is attributed to the influence of a self-induced grating of the efficiency of operation of a DFB laser. A study is made of the dependence of the output intensity on the pump power and on the detuning of the emission frequency from the Bragg frequency and from the center of the gain profile of the active medium.