Electromagnetically Induced Transparency

The energy lost by the radiation field through absorption is taken up by the atoms when they are excited from the lower to the upper state. As the radiation field intensity is progressively increased, a point is reached where the excitation absorption process begins to dominate the random decay processes that establish the status quo. There is an important conclusion that we can reach in this particular type of experiment. This is that a coherently trapped population is set up in the ground states so that no population transfer takes place to the excited state. The initial experiments were carried out in strontium vapour with pulsed lasers providing the radiation fields, and involved auto-ionising transitions in a lambda arrangement. The simple 3 state model, when solved numerically, provides considerable insight into the origins of electromagnetically induced transparency in both cascade, lambda and vee schemes.