Synchronisation des modes lasers par modulation d'amplitude: analyse linéaire dans le domaine spectral

Abstract

A theoretical study of homogeneous gain laser mode-locking by means of loss modulation is presented in this paper. A linear and causal mathematical formulation is used to describe the interaction between the laser field and the homogeneous medium. The frequency spectrum generated by the laser field is shown to satisfy a difference equation whose order is fixed by the Fourier expansion of the modulation function. Three types of solutions have been found to this equation: a family of uncoupled solutions called supermodes, a single solution, and a continuum of solutions. Unstable laser emission associated with a detuned modulation frequency is attributed to the onset of a continuum of solutions. A frequency filter with a small bandwidth suppresses such a continuum. As a result, the laser field quickly converges towards a stable profile over a broad band of modulation frequencies. [Translated by the journal]