  Color centers in diamond are promising candidates for quantum nanosensing
applications. The efficient collection of the optical signal is the key to
achieving high sensitivity and resolution, but it is limited by the collection
optics. Embedding the color centers in diamond microstructures can help to
enhance the collection efficiency, but often require challenging fabrication
and integration. Here we investigate the photoluminescence (PL) of
silicon-vacancy (SiV) centers in commercially available atomic force microscope
(AFM) diamond pyramid (DP) tips. We find that the DP geometry efficiently
channels PL emitted at the DP apex towards the base, where we experimentally
demonstrate an enhanced PL collection of up to 8 times higher compared to other
directions. Our experimental observations are in good agreement with numerical
simulations using a finite-difference time-domain (FDTD) method. Our results
indicate that AFM tips could be an economical, efficient and straightforward
way of implementing color-center-based nanosensing as they provide enhanced
sensitivity and easy integration with existing AFM platforms.
