Quantum interference in a lambda system driven by non-overlapping pulses with the same carrier frequency

This article describes quantum interference in a lambda system driven by two identical pulses that are each sufficiently broadband to drive both dipole-allowed transitions. The first pulse drives the system into a quantum superposition, making the effect of the second pulse depend critically on its optical phase and resulting in Ramsey-like fringes. This method, using just two pulses of the same carrier frequency, is conceptually simpler than in previous Raman–Ramsey studies, which use pump and Stokes pulses in each of two spatially separated regions. The goal here is not efficient population transfer, but to investigate narrow features resulting from quantum interference. I first explore these effects for low-inversion, which illustrates many key features using an easy-to-visualize model. I then use Schrödinger’s equation in a semiclassical model to extend the results to arbitrary inversion. Informative quantum interference features remain when using this simplified scheme. © 2010 Optical Society of America OCIS codes: 020.1670, 190.5650, 300.6450.