Development of an entangled photon source at 1550nm

Entangled photon pairs play a key role in various technological applications, such as quantum communications, quantum optical computing, and quantum sensing, while also providing insights into the fundamental properties of entanglement in bipartite systems. This thesis focuses on designing, developing, and realizing a pulsed polarization-entangled photon-pair source operating at a wavelength of 1550 nm. The photons are generated through the collinear and degenerate type-II spontaneous parametric down-conversion (SPDC) process within a periodically poled potassium titanyl phosphate (PPKTP) crystal, with a Sagnac interferometer ensuring high-quality entanglement. The source has been implemented on the optical table and meticulously examined to enhance performance through a fine characterization of the optical elements while accounting for the constraints imposed by the system geometry. After the realization of the source, the focus shifted to the optimization of its performance in terms of brightness, heralding ratio, and visibility of the generated entangled states, which heavily depend on the specific optical setup configuration. To achieve this, a theoretical model of the collinear SPDC process is extended and then employed to estimate the impact of the lenses used to focus the pump beam within the crystal and to collect the 1550nm photons on the brightness and heralding ratio. Simulation results are compared with experimental data from four selected source configurations to validate the theoretical predictions.