Nonlinear optics in TiO2 nanoscale waveguides

Abstract

We propose polycrystalline anatase TiO2 nanoscale waveguides as a platform for efficient, on-chip generation of triplet photons via third-order spontaneous parametric down-conversion (TOSPDC). TiO2 has a high nonlinear index of refraction (0:16 × 1018 m2/W at 1565 nm), a wide transparency window (absorption edge at 400 nm) and negligible two-photon absorption above 800 nm, making it an advantageous material for integrated photonics. Efficient generation of threephoton entanglement on an integrated platform is necessary for many experiments in quantum optics, with applications in quantum metrology and communication. We couple simulations to experiments to determine and confirm optimal waveguide geometries for meeting TOSPDC phase-matching constraints and maximizing the efficiency of triplet-photon generation in TiO2 nanoscale devices.