Nonlinear properties of electromagnetically induced transparency in rubidium vapor

Nonlinear properties of electromagnetically induced transparency (EIT) with respect to a weak probe light are studied. We observe EIT in a rubidium vapor, measure the slow light group velocity and the EIT resonance width, and find that those parameters show a strong dependence on the probe power. We theoretically study the influence of the EIT probe dependence on the performance of the EIT-based optical delay lines and magnetometers.