Influence of non-local radiation transport on the gain of a He-Ne ring laser

Abstract

Summary form only given. Ring laser gyros are widely used inertial sensors in aeronautic applications due to their superior sensitivity and reliability. Today, the improvement of such a device involves a clear understanding of the physical mechanisms of various processes occurring inside the cavity viz. from the low-pressure He-Ne DC discharge to the laser amplification. In this context, a modeling of the behavior of a He-Ne ring laser gyro has been performed. Our modeling is divided into three parts. The first is a one dimension model of the positive column of the DC discharge in the fluid approximation. Then, a 0-D collisional radiative model (CRM), treating most of the excited states of the He-Ne mixture, is employed to calculate the population inversion of the He-Ne laser. Finally, the laser amplification is determined with a two-level Maxwell-Bloch treatment. This global model shows partial agreement with experimental data for the laser power in different configurations of the laser cavity length, discharge length and current, indicating that additional physical processes have to be included, in particular while considering the CRM model. In this context, we have analyzed the influence of radial transport on the CRM. First the non-local transport of the resonant lines has been determined, using a numerical model based on a Monte-Carlo treatment of the radiation trapping. It takes into account the partial frequency redistribution, the neon isotopic structure and the high collisional broadening in the presence of Helium. This non-local radiation transport, together with transport diffusion of metastable or quasi-metastable states, has been included into a full 1-D CRM. We will present at the conference our results of parametric studies performed with this model, which allows to identify the relative influence of non-local transport and diffusion on the radial profile of He and Ne excited states. Finally, the influence of the radiation transport on the radial and frequency profiles of the laser gain at low and strong saturation will be analyzed.