Energy-time-entangled two-photon molecular absorption

Nonlinear spectroscopy and microscopy techniques are ubiquitous in a wide range of applications across physics biology. However, these usually rely on high-powered pulsed laser systems. A promising alternative is to exploit entangled two-photon absorption (ETPA), which can lead tens orders magnitude lower incident fluxes than conventional schemes. the role different degrees freedom ETPA was unclear following recent experimental studies, when compared earlier theoretical works. Here, we first demonstrate linear dependence rate with photon-pair rate, clear signature ETPA, estimate values for concentration-dependent cross section Rhodamine 6G. We then investigate energy-time entanglement polarization fluorescence strong signal interphoton delay that reflects coherence time wave packet.