Much of the interest in diamond stems from the unique combination of optical and spin properties exhibited by nitrogen-vacancy (NV) color centers. The electronic spin state of single NV centers can be initialized and read out optically. These NV centers can be manipulated using combinations of optical transitions, as well as with microwaves. Remarkably, this latter approach is possible even at room temperature thanks to their long spin coherence time. These properties have spurred considerable activity in creating quantum optical devices that incorporate NV centers, with the ultimate goal of performing quantum information processing. In this special issue, Schroeder et al. review the latest developments in this rapidly advancing field, and Gould et al. report on a promising approach for creating integrated quantum optical devices from diamond. Diamond NV center spins can also be used for measuring magnetic fields thanks to Zeeman and related effects. Gupta et al. report on a clever signal processing method for improving the magnetic field measurement sensitivity achievable with NV centers, while Aman et al. examine the performance of nanodiamond based NV center magnetometry and Dmitriev et al. study resolving vector components of magnetic fields with NV centers.

Despite this remarkable success of diamond NV center based photonics, there is much to be learned about the optical properties of diamond impurities and color centers. Here Yelisseyev et al. and Pimenov et al. present studies of the emission from color centers and the role of physical processes used to create them.

Diamond’s well-appreciated physical properties are also beneficial for optical applications, including laser development. Its hardness is accompanied by a large Raman shift, and its large electronic bandgap results in a massive transparency window. The large thermal conductivity of diamond also allows operation at high powers without suffering from heating. In combination, these properties provide a route toward creating optically pumped lasers operating over a wide range of wavelengths. Here Jasbeer et al. report on the effects of stress on the threshold of bulk diamond Raman lasers, and Feigel et al. present the design of a fully on-chip diamond Raman laser that can operate from ultraviolet to short wavelength infrared wavelengths.

We hope that this collection of articles provides readers with a useful status update on the field of diamond photonics and that it spurs future research in this exciting field.