Controlling electromagnetically induced transparency by the laser phase

Continuous wave (CW) laser light propagation through the medium of double-Λatoms is theoretically and experimentally investigated. The propagation of light through an optical thick double-Φmedium is non-trivial, because the phase is changed in the course of propagation, which leads to the dramatic change of the absorption and refraction. The amplification of one laser wave in expense of the others and frequency generation enhanced by quantum interference in such a medium is possible. The phase dependent electromagnetically induced transparency is reported.