Opt. Lett. 37, 2853–2855 (2012)

Electrically induced transparency is a promising optical scheme for a variety of applications in parallel optical computing and quantum information processing. Now, Lu Zhao and co-workers from Tsinghua University and Beijing Normal University in China have investigated two-dimensional quadratic phase shift and image reconstruction in an ultracold atomic gas in the microkelvin temperature regime. The researchers considered enhanced cross-phase modulation in a four-level N-type electrically induced transparency system. They tuned a pattern-bearing weak probe field and a strong coupling field to the two different transition wavelengths in the atomic gas. By adiabatically switching off the coupling field, they coherently mapped the probe carrying the diffraction pattern to the atomic spin coherence, which was determined by the Rabi frequency of the strong coupling field. They then retrieved the intensity profile, which is proportional to the square of the Rabi frequency, by sending a signal field to the atomic gas. Because the signal field was red-detuned from the transition frequency of the atomic gas, the cross-phase modulation dominated the nonlinear absorption, which allowed the researchers to reconstruct the stored image in the far-field.