Stimulated Raman Adiabatic Passage in a Dense Medium

Abstract

We have considered a coherent population transfer to a higher excited singlet state (S2) of molecules with anomalous fluorescence in molecular assemblies (e.g., a dense medium). A direct excitation to S2 requires light in the UV region. Because of this, the transition is conveniently realized by a two-step (two-photon) process: S0→S1→S2, where transitions S0→S1 and S1→S2 correspond to the optical region. We have shown that efficient stimulated Raman adiabatic passage (STIRAP) in the ladder configuration can be realized in this case, using suitably chirped pulses, to compensate a change of the two-photon transition frequency in time, induced by the pulses themselves, due to near dipole-dipole interactions. We have provided a reduced state formulation of the optical control process. Chirping the “pump” pulse that excites transition S0→S1 is nonequivalent to chirping the “Stokes” pulse that excites transition S1→S2, with respect to the population of the intermediate state (S1) in the pulse nonadiabatic regime. We have also shown that with suitably chirped pulses, efficient STIRAP still persists even for a rather large decay of the intermediate state.

Nonlinear organic plasmonics: Applications to optical control of Coulomb blocking in nanojunctions

“…This idea was proposed in studies of a two-state system in relation to Rabi oscillations in inter-subband transitions in quantum wells 21 and for obtaining efficient stimulated Raman adiabatic passage in molecules in a dense medium. 19 Let us suppose that we use suitably chirped pulses compensating the "local field" detuning pDn that enables us to keep the value of x 21 À pDnðtÞ À xðtÞ Dx as a constant. In that case, one can obtain an integral equation for non-equilibrium population difference D 0 ðDx; tÞ.…”

Study of Electron-Vibrational Interaction in Molecular Aggregates Using Mean-Field Theory: From Exciton Absorption and Luminescence to Exciton-Polariton Dispersion in Nanofibers

“…where b m (α) = ρ m,21 (α, t), 28,38 and averaging in the density matrix is carry out with respect to the vibrational subsystem of the m-th molecule. Let us write the equation for the expectation value of b k corresponding to operator equation (11).…”

“…where b m (α) = ρ m,21 (α, t), 28,38 and averaging in the density matrix is carry out with respect to the vibrational subsystem of the m-th molecule.…”

“…The complete density matrix averaged over the stochastic process, which modulates the molecule energy levels, is obtained by integration of ρ m , ij (α, t ) over α, ⟨ρ m ⟩ ij ( t ) = ∫ρ m , ij (α, t ) dα, where quantities ⟨ρ m ⟩ jj ( t ) are the normalized populations of the corresponding electronic states: ⟨ρ m ⟩ jj ( t ) ≡ n m , j , n m ,1 + n m ,2 = 1. Combining eqs and (), one can introduce the expectation value of b k where ⟨ b m (α)⟩ = ρ m ,21 (α, t ), , and averaging in the density matrix is performed with respect to the vibrational subsystem of the m th molecule.…”

Mean-field electron-vibrational theory of collective effects in photonic organic materials. Long-range Frenkel exciton polaritons in nanofibers of organic dye

“…where nk1 = b k b † k , and nk2 = b † k b k is the exciton population operator. Considering an assembly of identical molecules, one can write b k = ρ 21 (α, t) 29 if averaging in Eq. ( 5) is carried out using density matrix ρ (α, t).…”