Entangled-photon generation in nano-to-bulk crossover regime.

We have theoretically investigated the generation of entangled photons from biexcitons in a semiconductor film with a thickness in the nano-to-bulk crossover regime. In contrast with the cases of quantum dots and bulk materials, we can highly control the generated state of entangled photons through the design of a peculiar energy structure of exciton-photon coupled modes in the thickness range between nanometers and micrometers. Owing to the enhancement of the radiative decay rate of excitons (exciton superradiance), the statistical accuracy of generated photons can be increased beyond the trade-off problem with signal intensity. By implementing an optical cavity structure in the strong-coupling regime, the generation efficiency can be enhanced while maintaining the high statistical accuracy.