Diamond is a cherished material not only for its beauty but also other properties like its hardness, thermal conductivity and transparency from UV to far IR wavelengths. Diamond has a point defect, the nitrogen-vacancy (NV) center, which has a long electron spin coherence time. The NV defect can be located, manipulated and read out optically . These properties make NVs excellent candidates for optically detected spin magnetometry and quantum computing. An integrated photonics platform in diamond would be beneficial for the development of NV-based devices, in which NV centers are optically linked for long-range quantum entanglement due to the integration and stability provided by monolithic optical waveguides.
In this work, we have applied high repetition rate femtosecond laser writing to fabricate buried 3D optical waveguides in diamond . By engineering the geometry of the type II waveguide, we have obtained single mode guiding from visible to the infrared wavelengths . Photoluminescence characterization revealed that the NV properties were preserved within the waveguide. We have also been able to create single NV centers on demand in ultrapure diamond using a single pulse from a femtosecond laser followed by a thermal treatment of the sample. With these building blocks in place, we have fabricated a photonic integrated device containing optical waveguides coupled to NV centers deterministically placed within the waveguide. The single NVs were excited and their emission collected by the optical waveguides, allowing easy interfacing to standard optical fibers for a compelling integrated quantum photonics platform .
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