Broadband Biphoton Generation and Polarization Splitting in a Monolithic AlGaAs Chip

The ability to combine various advanced functionalities on a single chip is a key issue for both classical and quantum photonic-based technologies. On-chip generation and handling of orthogonally polarized photon pairs, one of the most used resources in quantum information protocols, is a central challenge for the development of scalable quantum photonics circuits; in particular, the management of spectrally broadband biphoton states, an asset attracting growing attention for its capability to convey large-scale quantum information in a single spatial mode, is missing. Here, we demonstrate a monolithic AlGaAs chip, including the generation of broadband orthogonally polarized photon pairs and their polarization splitting; 85% of the pairs are deterministically separated by the chip over a 60 nm bandwidth. The quality of the two-photon interference at the chip output is assessed via a Hong–Ou–Mandel experiment displaying a raw visibility of 75.5% over the same bandwidth. These results, obtained for the first time at room temperature and telecom wavelength, in a platform combining strong confinement, high second-order nonlinearity, electro-optic effect, and direct bandgap, confirm the validity of our approach and represent a significant step toward miniaturized and easy-to-handle photonic devices working in the broadband regime for quantum information processing.