Abstract

We have measured the absorption of a weak, stochastic field in the presence of a strong, degenerate stochastic pump that saturates the 3S_1/2(F = 2, m_f=2) → 3P_3/2(F = 3, m_f = 3) transition in atomic sodium. The probe is a time delayed replica of the pump field, and the net field obeys non-Markovian phase diffusing statistics. The absorption (gain) of the probe field was measured as a function of the time delay. We use cw lasers and impose phase diffusing statistics (δ-correlated frequency fluctuations) with a system of electro-optics. The time delay is provided by lengths of optical fiber. Our results agree well with a recent theory for atomic response to non-Markovian fields, valid for arbitrary strengths and bandwidths of the pump field and a weak time delayed probe. For both pump and probe fields resonant with the transition, we observe maximum gain for a probe time delay of approximately 0.8 lifetimes of the upper state (γ⁻¹).

© 1992 Optical Society of America