No abstract

The metal nanoparticle (MNP) can lead to significant reshaping of spectral features in the three level Λ system. For this a master equation is derived with the Born-Markov approximation, but in place of bare states, it's the dressed states transitions which are coupled to reservoir. This master equation gives many new interesting terms which are not present in traditionally derived master equations. The dressed state-reservoir coupling results in sampling of Local density of states (LDOS) by the dressed state transitions causing asymmetricity in the spectrum.

We use biorthogonal basis consisting of the ‘right’ and ‘left’ eigenvectors of the effective non-Hermitian Hamiltonian of a three-level Λ system driven by a bi-chromatic field, and resolve the probe absorption spectrum into components corresponding to the decaying dressed states of the system. It is observed that the spectrum primarily consists of three components and two of them undergo dramatic changes when the control field Rabi frequency is changed from the low to high field regime. Based on the symmetry properties of a combination of these components, a parameter internal to the dynamics of the system is defined and is used to distinguish between electromagnetically induced transparency (EIT) and Autler-Townes (AT) splitting, and the threshold for transition between them in an objective manner. The formulation is further extended to the resonance fluorescence spectrum on the probe transition in the EIT and AT regimes.