Ultra-slow soliton pairs in four-level inverted Y-system via electromagnetically induced transparency

摘要

Using the Schrodinger Maxwell equations, we theoretically investigate the propagation properties of probe and mixing fields in a lifetime-broadened inverted-Y type cold atomic medium. This system is driven by two strong control (pumping and coupling) fields. The results reveal that the probe (or mixing) field consists of two modes with different group velocity and absorption. Under slowly varying envelope approximation, we discuss the propagation equation of the probe (or mixing) field, which includes the high-order nonlinear term. The solutions show that optical solitons pairs can be generated in the cold atom medium with ultra-slow group velocities.