  In this article we have shown that the atomic states can be engineered by
tunning the coupling Rabi frequency for a system with $\mathcal{N}$-type
configuration. Electromagnetically induced transparency (EIT),
Electromagnetically induced absorption (EIA) and Autler-Townes (AT) splitting
has been observed experimentally in a four level $\mathcal{N}$-type atomic
vapor of $^{85}Rb$ atoms in the hyperfine levels of $D_2$ transition. It has
been shown that the response of the atomic medium can be tunned from highly
transparent to highly absorptive in our case. The evolution of the atomic
states from the dark state |D> to the non-coupled state |NC> has been studied
with the partial dressed state approach which makes the backbone of the
modification of the atomic response. In addition, transient solutions in the
time domain and steady state solution in the frequency domain has been studied.
The population dynamics and the coherence contribution in each case has been
analyzed by the time dependent solutions. The experimentally observed steady
line-shape profiles has been supported by the steady state solution of
optical-Bloch equations considering the Maxwell Boltzmann velocity
distributions of the atoms. It has been observed that the crossover between the
EIT and the AT splitting has been replaced by the interference contribution of
the EIA in this $\mathcal{N}$-type system.
