Rare Earth‐Diamond Hybrid Structures for Optical Quantum Technologies

Abstract Diamond containing nitrogen‐vacancy centers (NV⁻) is one of the most investigated materials for quantum technologies, because of this system's exceptional spin properties. Although the NV⁻ optical transition is very bright, it suffers from spectral diffusion and weak zero‐phonon line, and is in the visible range. This limits integration into quantum photonic structures and interfacing with optical fiber networks. In contrast, rare earth (RE) ions exhibit extremely narrow and stable optical transitions, including erbium's 1.5 µm telecom wavelength. Combining RE with NV⁻ properties through short‐range interactions is however challenging as RE do not readily enter the diamond lattice. In this work, a thin‐film‐based architecture in which RE and NV⁻ centers can interact while preserving their unique properties is introduced. Thin films of Er³⁺:Y₂O₃ are grown by chemical vapor deposition on diamond substrates with well‐crystallized and highly textured structures. An extensive spectroscopic study of Er³⁺ transitions at room and low temperatures further reveals that photoluminescence spectra and decays are close to bulk materials. It is also shown that Y₂O₃ thin film deposition has no detrimental effects on NV⁻ optical and spin properties. RE thin films deposited on diamond can thus be suitable for building hybrid materials for new functionalities in quantum sensing, communication, and processing.