Enhanced Exciton Coherence Time and Correlation with Probability of Absorption of Classical and Entangled Light in Quantum-Confined Systems

The study of dephasing time in a material by using time-resolved two-photon near-field scanning optical microscope (NSOM) with classical light has been of great interest due to its many applications. If a material shows longer coherence time between molecules and excitation pulse,it can contain information about the material for a longer time. On the contrary, the use of quantum light for studying the molecular structure has also been of great interest in many applications. In this study, a correlation between quantum coherence of the material and the probability of absorbing classical and quantum light has been shown. The dephasing time in rhodamine-B (Rh-B) chromophores doped in polystyrene nanospheres (PS-Rh) and bare Rh-B chromophores has been observed using time-resolved two-photon NSOM at room temperature. It has been observed that the quantum coherence on a single PS bead doped with Rh-B chromophores has a longer lifetime compared to the bare Rh-B chromophores. A possible reason for longer coherence time in PS-Rh nanospheres could be the isolation of Rh-B chromophores inside the PS nanospheres, which removes the heterogeneity and local environment effects and increases the interference between the laser pulse and superposition state. The interaction of these PS-Rh nanospheres and Rh-B chromophores with classical and entangled light has also been investigated using classical and entangled two-photon absorption spectroscopies, and the cross-sections have been calculated. It was observed that doped PS-Rh nanospheres show higher nonlinear optical properties than the Rh-B chromophores. In this study, it has been shown that, in addition to the transition dipole moment and detuning energy, classical and entangled two-photon cross-sections are also being affected by the quantum coherence.