For a generic semiclassical laser dynamics in the complex Ginzburg-Landau form, we develop a Bogoliubov approach for the computation of the laser emission linewidth. Our method provides a unifying perspective of the treatments by Henry and Petermann: both broadening mechanisms are ascribed to the nonorthogonality of the Bogoliubov modes, which live in a space with doubled degrees of freedom. As an example of application, the method allows one to study the interplay of drive dissipation, interactions, and spatial inhomogeneity typical of polariton condensates. The traditional theory of the Henry and Petermann factors is found to fail dramatically in the presence of sizable optical nonlinearities stemming from polariton-polariton interactions. Even in a strong confining potential, the intrinsically multimode nature of the density fluctuations has to be included in order to quantitatively describe phase diffusion in the manner of Henry.

• Received 16 November 2021
• Accepted 15 February 2022

DOI:https://doi.org/10.1103/PhysRevA.105.023527