Figure 1.  OSU ODMR light path schematic. From right to left, antenna radiates microwave frequency signal, piezo stage allows for scanning, x-y stage for rough movement, objective to focus laser and collect fluorescence, electromagnetic coil to induce Zeeman splitting, dichroic mirror to reflect laser and pass fluorescence, variable neutral filter density filter to control laser intensity, laser to optically pump sample, 550nm long pass filter to reduce background laser, confocal for higher resolution, spectrometer to collect fluorescence,  EM-CCD for imaging NV centers, and SPAD to measure intensity/ quantum parameters.

Figure 2.  Scanning fluorescence image of NV rich diamond (left). Fluorescence Spectrum of NV Center in Diamond (right). Black line demonstrates fluorescence collected without confocal system in place. The blue line shows fluorescence  spectrum within a confocal volume.

Figure 3. ODMR Spectrum with Lorentzian Fit and B= 0. Microwave frequency was swept in 0.1 GHz increments and relative intensity was measured using integration of the fluorescence spectrum. Peak located at 2.868 GHz (Top left). High Resolution ODMR Spectrum of single NV center with B > 0 applied.  Zeeman splitting is observed. Peaks observed at 2864 MHz and 2877 MHz. 20 points per increment (Top right). ODMR Spectrum with B > 0 aligned approximately to [111] NV ensemble crystal axis. Four-fold splitting is observed, corresponding to 4 crystal axis directions. Further splitting is degenerate and not observable (bottom).