Optical non-linearity in an attractive Rydberg gas
Jonathan D. Pritchard, A. Gauguet, Kevin J. Weatherill, Charles S. Adams
Abstract
We use the technique of electro-magnetically induced transparency (EIT) to probe the effect of attractive dipole-dipole interactions in a hi ghly excited Rydberg gas. The transient character of the EIT response is investigated by rapidly scanning the probe laser through resonance. We characterize the resulting cooperative optical non-linearity as a function of probe strength, density and scan direction. For the 58D5/2 Rydberg state, an atom density of 1.6 � 10 10 cm 3 and a positive frequency scan we measure a third-order non-linearity of � (3) = 5 � 10 7 m 2 V 2 . For the reverse scan we observe a second order non-linearity of � (2) = 5 � 10 6 mV 1 . The contrasting behaviour can be explained in terms of motional effects and resonant excitation of Rydberg pairs.