Abstract- Color centers in diamond offer excellent potential for nano-photonic devices that will enhance our understanding of light-matter interactions in room temperature. In this work we report a successful demonstration of engineering bright, nanometer scale diamond membranes and subsequent fabrication of optical cavities. We show coupling of emitters to microdisk cavities and photonic crystal cavities sculpted of the single crystal diamond membrane.   

Single emitters in diamond, such as the silicon-vacancy (SiV) or the nitrogen vacancy (NV) are promising solid state qubits for realization of quantum communications and nanophotonics applications¹. In recent years there has been great progress in engineering and characterizing these defects in ultra pure diamond crystals. However, the challenge of effectively incorporating the emitters into practical photonic structures and devices remains outstanding.

Sculpting optical structures from diamond is often challenging as diamond cannot be readily engineered to have sacrificial layers. Top down approaches to fabricate diamond nanowires by reactive ion etching (RIE) has been demonstrated and the fabrication of diamond photonic crystal cavities has been attempted using a focused ion beam approach. However, the extensive ion damage of the Ga+ ion beam largely interfered with the diamond luminescence. Recently, due to the dramatic improvement in diamond synthesis, thin diamond membranes became commercially available. Using such a membrane, the first diamond microring resonator with a tenfold increase in the radiative decay time was recently engineered ².

In this work we report a successful demonstration of engineering bright, nanometer scale diamond membranes and subsequent fabrication of optical cavities. In our approach, 1.7 mm thick diamond membranes were generated by forming a sacrificial layer using ion implantation, followed by thermal annealing. These membranes then served as templates for the epitaxial overgrowth of ~ 300 nm of diamond using a microwave chemical vapor deposition (CVD) technique. Remarkably, the regrown films alone reveal the presence of optically active defects, such as SiV or NV centers, as well as good electron spin coherence of the NV. Furthermore, the grown material shows excellent structural characteristics, as was confirmed by Raman spectroscopy.

Microdisk cavities with diameters of 1.5 – 3.5 mm were subsequently formed from the regrown single crystal diamond membranes. Whispering gallery modes (WGMs) with quality factors of ~ 3000 were experimentally measured from the diamond cavities using micro-photoluminescence spectroscopy. Spectral overlap of WGMs with the ZPL of SiV centers was observed and lifetime reduction of the coupled emitter – cavity system was measured ^3-4.

To summarize, we presented a comprehensive technique to fabricate optical cavities from single crystal diamond. Developing such a process is critical towards engineering quantum photonic networks in diamond. The demonstration of coupling between color centers in diamond and a single crystal diamond cavity is a crucial step towards “all-diamond” integrated nano-photonic networks. 

References

1. I. Aharonovich, A. D. Greentree, and S. Prawer, Nat. Photon. 5, 397, (2011).

2. A. Faraon, P. Barclay, C. Santori, K. Fu, and R. Beausoleil, Nature Photon. 5, 301, (2011).

3. J. C. Lee, I. Aharonovich, A. P. Magyar, F. Rol, E. L. Hu arXiv:1111.6852

4. I. Aharonovich, J. C. Lee, A. P. Magyar, B. B. Buckley, C. G. Yale, D. D. Awschalom, and E. L. Hu, Adv. Mater in press, DOI 10.1002/adma.201103932

Acknowledgements The financial support from DARPA, QuEST and AFOSR is gratefully acknowledged.