Plot the transmission and phase shift of probe beam.
EIT(electromagnetically induced transparency) is achieved in a three-level system (|g1>, |g2>, |e>) when the coupling laser (drives |g2> to |e> transition) and the probe laser(drives |g1> to |e> transition) have the same detuning.
Vary the parameters and observe the effects. Note that when delta_p = delta_c, there is a peak in transmission.