The interaction of strong low-area pulses with two-level systems shows absorption line narrowing and hole burning within the homogeneous linewidth as a result of nonlinear wave mixing. The wave mixing results from the two-level electronic saturation nonlinearity and occurs, depending on the sign of the pulse area, as a strong absorption enhancement or gain at the transition frequency of the two-level system for resonant excitation.
© 2002 Optical Society of America
J. Förstner, A. Knorr, M. Lindberg, and S. W. Koch, "Line narrowing and hole burning within the homogeneous linewidth: a new wave-mixing effect in two-level systems," Opt. Lett. 27, 1830-1832 (2002)