The efficiency of collecting photons from optically active defect centres in bulk diamond is greatly reduced by refraction and reflection at the diamond-air interface. We report on the fabrication and measurement of a geometrical solution to the problem; integrated solid immersion lenses (SILs) etched directly into the surface of diamond. An increase of a factor of 10 was observed in the saturated count-rate from a single negatively charged nitrogen-vacancy (NV − ) within a 5 µm diameter SIL compared with NV − s under a planar surface in the same crystal. A factor of 3 reduction in background emission was also observed due to the reduced excitation volume with a SIL present. Such a system is potentially scalable and easily adaptable to other defect centres in bulk diamond.The ability to address single defect centres in diamond using confocal microscopy allows optical access to these single 'atom like' systems trapped within a macro-scale solid. The negatively charged nitrogenvacancy centre (NV − ) is of particular interest for applications such as single photon generation [1,2], nanoscale magnetometery [3], and fundamental investigations of spin interactions and entanglement at room temperature [4][5][6]. Other defect centres that exhibit single photon emission have also been identified (e.g. the nickel-related 'NE8' [7], the silicon-vacancy [8], and chromium related centres [9]), but the search continues for other defect centres with spin properties like those of the NV − centre [10]. The high refractive index of diamond causes refraction of the emitted light at the diamond-air interface, reducing the possible angular collection of a microscope objective. Thus the NV − photon collection efficiency is severely reduced. This is a problem regardless of the application, or of the particular defect centre of interest. Here we report on the fabrication and measurement of hemispherical integrated solid immersion lenses (SILs) etched directly into the surface of diamond. These structures eliminate surface refraction, thus increasing the numerical aperture (NA) of the microscope system. This allows a substantial increase in the resolution and background rejection of our system, along with a strong enhancement in NV − photon collection efficiency. Moreover, this geometrical solution can easily be applied to other defect centres in bulk diamond which emit at different wavelengths [11].The photon collection efficiency from NV − centres in diamond has previously been improved by using NV − centres located within nanocrystals small enough that the centres effectively emit into free space [2,12], or nanophotonic structures such as nanowires which guide emission towards collection [13]. Photon collection is increased by a factor of up to about 5 in the former case and 10 in the latter. However with the NV − centres positioned so close to the surface, local strain, impurities and other surface effects have been shown to degrade the stability, and spin coherence time of the NV − centre [14,15], so a solution which improves the p...

The mechanical properties of various chemical vapor deposition diamond structures compared to the ideal single crystal App. Phys. Rev. 2012, 3 (2012 The mechanical properties of various chemical vapor deposition diamond structures compared to the ideal single crystal J. Appl. Phys. 111, 051101 (2012) Bias-enhanced nucleation and growth processes for improving the electron field emission properties of diamond films J. Appl. Phys. 111, 053701 (2012) Direct visualization and characterization of chemical bonding and phase composition of grain boundaries in polycrystalline diamond films by transmission electron microscopy and high resolution electron energy loss spectroscopy Appl. Phys. Lett. 99, 201907 (2011) Impurity impact ionization avalanche in p-type diamond Appl. Phys. Lett. 99, 202105 (2011) Additional information on Appl. Phys. Lett. We describe a technique for fabricating micro-and nanostructures incorporating fluorescent defects in diamond with a positional accuracy better than hundreds of nanometers. Using confocal fluorescence microscopy and focused ion beam etching, we initially locate a suitable defect with respect to registration marks on the diamond surface then etch a structure using these coordinates. We demonstrate the technique by etching an 8 m diameter hemisphere positioned with single negatively charged nitrogen-vacancy defect lies at its origin. Direct comparison of the fluorescence photon count rate before and after fabrication shows an eightfold increase due to the presence of the hemisphere.

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