Elliptical faceted diamond nanowire for higher coupling with bidirectional tunable

For a variety of applications in quatum communication and sensing, Nitrogen Vacancy (NV -) centres with negatively charged inside diamonds must be connected to optical systems. An adiabatic photon channeling from a highly effective mode index to a lowered effective mode index, or vice versa is necessary to achieve efficient power transfer from an optical fibre to on-chip photonic devices. To achieve this, there is a major issue in dealing with photonics structures. Here, we report a combined structure of elliptically-faceted (ELFA) diamond nanowire with NV-centres and optical nanofiber, exhibiting tunable bidirectional coupling with improved efficiency. Coupling efficiency oscillation with modulation contrast value shows diabatic to adiabatic transition, corresponding to smaller to longer values of etched length. Our estimates show a coupling efficiency of 85% with directional tunability.