Linewidth evaluation of gain-guided VCSEL's

An electromagnetic model of Vertical Cavity Surface Emitting Lasers (VCSEL's) based on semiconductor compounds is developed to study the threshold conditions, the mode field distributions and the noise properties, in particular the linewidth. The model relies on the solution of Maxwell equations by using an expansion in plane waves. The main purpose is the description of the optical field confinement due to the gain mechanism induced by carrier injection. This strongly influences the noise properties and gives rise, in the case of a waveguide device, to the Petermann factor. The solution of the problem is based on an integral equation of the Fredholm type whose eigenvalues are related to the threshold operating conditions and whose eigenvectors give the field distributions. The noise characteristics are analyzed by introducing a Langevin source term in the integral equation.