Nitrogen-vacancy (NV) centers in millimeter-scale diamond samples were produced by irradiation and subsequent annealing under varied conditions. The optical and spin relaxation properties of these samples were characterized using confocal microscopy, visible and infrared absorption, and optically detected magnetic resonance. The sample with the highest NV concentration, approximately 16 ppm (2.8 × 10 18 cm −3 ), was prepared with no observable traces of neutrally-charged vacancy defects. The eective transverse spin-relaxation time for this sample was T * 2 = 118(48) ns, predominately limited by residual paramagnetic nitrogen which was determined to have a concentration of 49(7) ppm. Under ideal conditions, the shot-noise limited sensitivity is projected to be ∼ 150 fT/ √ Hz for a 100 µm-scale magnetometer based on this sample. Other samples with NV concentrations from .007 to 12 ppm and eective relaxation times ranging from 27 to over 291 ns were prepared and characterized.

We demonstrate coupling of the zero-phonon line of individual nitrogen-vacancy centers and the modes of microring resonators fabricated in single-crystal diamond. A zero-phonon line enhancement exceeding ten-fold is estimated from lifetime measurements at cryogenic temperatures. The devices are fabricated using standard semiconductor techniques and off-the-shelf materials, thus enabling integrated diamond photonics.Integrated quantum photonic technologies are key for future applications in quantum information [1, 2], ultralow-power opto-electronics [3], and sensing [4]. As individual quantum bits, nitrogen-vacancy (NV) centers in diamond are among the most attractive solid-state systems identified to date, owing to their long-lived electron and nuclear spin coherence, and capability for individual optical initialization, readout and information storage [5][6][7][8][9]. The major outstanding problem is interconnecting many NVs for large-scale computation. One of the most promising approaches is to couple them to optical resonators, that enhance the zero-phonon line (ZPL) emission, and can be further interconnected in a photonic network [10][11][12].

A technique is demonstrated which efficiently transfers light between a tapered standard single-mode optical fiber and a high-Q, ultra-small mode volume, silicon photonic crystal resonant cavity. Cavity mode quality factors of 4.7x10(4) are measured, and a total fiber-to-cavity coupling efficiency of 44% is demonstrated. Using this efficient cavity input and output channel, the steady-state nonlinear absorption and dispersion of the photonic crystal cavity is studied. Optical bistability is observed for fiber input powers as low as 250 microW, corresponding to a dropped power of 100 microW and 3 fJ of stored cavity energy. A high-density effective free-carrier lifetime for these silicon photonic crystal resonators of ~ 0.5 ns is also estimated from power dependent loss and dispersion measurements.

The optical transition linewidth and emission polarization of single nitrogen-vacancy (NV) centers are measured from 5 K to room temperature. Interexcited state population relaxation is shown to broaden the zero-phonon line and both the relaxation and linewidth are found to follow a T(5) dependence for T < 100 K. This dependence indicates that the dynamic Jahn-Teller effect is the dominant dephasing mechanism for the NV optical transitions at low temperatures.