Photon-Pair Recombination via Sum-Frequency Generation by Chirped, Aperiodically Poled LiNb Waveguide

In the past couple of decades, the use of quantum states of light has been gaining interest in different disciplines from telecommunications to imaging and sensing due to its non-classical features that allow to exceed classical limitations. A quantum enhancement in fluorescence microscopy has been explored in a recent study, whereby, time-frequency-entangled photon pairs generated through spontaneous parametric down conversion (SPDC) process were used to demonstrate linear absorption rates in standard fluorophores by the virtue of entangled two-photon absorption (ETPA) [1]. Meanwhile, a prior study on sum-frequency generation (SFG) with down-converted photon pairs has demonstrated that the rate of photon pair recombination is linearly proportional to the down-converted bandwidth [2]. In other words, as the bandwidth of the down-converted photon pairs increases, it reduces the temporal separation between the photons, which in turn, increases the probability for up-conversion via SFG.