Color centers in diamond needles for all-optical sensing

This study explores the luminescence properties of color centers in single-crystal diamond needles synthesized via chemical vapor deposition and their potential for all-optical sensing applications. The theoretical part is dedicated to the fundamentals of quantum sensing for different modalities, with the focus on all-optical approaches using diamond color centers. Current achievements and limitations are reviewed, and it is proposed to expand the diamond-based sensing platform by investigating color centers beyond the well-studied NV⁻ and SiV⁻ defects. The methodological part introduces a pipeline developed in this work for estimating the concentrations of NV charge states through spectral decomposition based on non-negative matrix factorization. Another section addresses the influence of gas composition during chemical vapor deposition growth, specifically the methane content in hydrogen-based mixtures, on the formation and optical properties of color centers. This part results in the identification of methane concentration windows that can be used to control NV charge state incorporation in single-crystal diamond needles. The experimental part focuses on all-optical thermometry and magnetometry using 389 nm and 468 nm color centers. The results demonstrate the feasibility of these less-explored centers for quantum sensing through characteristic optical signatures, thereby highlighting their potential as promising alternatives or extensions for future diamond-based quantum sensing technologies.