Tailoring a nanofiber for enhanced photon emission and coupling efficiency from single quantum emitters.
We present a novel approach to enhance the spontaneous emission rate of single quantum emitters in an optical nanofiber-based cavity by introducing a narrow air-filled groove into the cavity. Our results show that the Purcell factor for single quantum emitters inside the groove of the nanofiber-based cavity can be at least six times greater than for such an emitter on the fiber surface when using an optimized cavity mode and groove width. Moreover, the coupling efficiency of single quantum emitters into the guided mode of this nanofiber-based cavity can reach up to ∼80% with only 35 cavity-grating periods. This new system has the potential to act as an all-fiber platform to realize efficient coupling of photons from single emitters into an optical fiber for quantum information applications.
Direct optical excitation of an NV center via a nanofiber Bragg-cavity: a theoretical simulation.
Direct optical excitation of a nitrogen-vacancy (NV) center in nanodiamond by light via a nanofiber is of interest for all-fiber-integrated quantum applications. However, the background light induced by the excitation light via the nanofiber is problematic as it has the same optical wavelength as the emission light from the NV center. In this paper, we propose using a nanofiber Bragg cavity to address this problem. We numerically simulate and estimate the electric field of a nanodiamond induced by excitation light applied from an objective lens on a confocal microscope system, a nanofiber, and nanofiber Bragg-cavities (NFBCs). We estimate that by using a nanofiber, the optical excitation intensity can be decreased by roughly a factor of 10 compared to using an objective lens, while for an NFBC with a grating number of 240 (120 for one side) on a nanofiber the optical excitation intensity can be significantly decreased by roughly a factor of 100. This reduction of optical excitation intensity will make it possible to distinguish the fluorescence of the NV center from the background light.
Integrated two-beam antenna array featuring dual-circular polarization
A concept of an integrated antenna array featuring two independent beams and dual circular polarization has been described. The antenna array consists of two radiating elements which are excited at two orthogonally placed feeding ports with the use of four appropriately connected 3-dB/90° directional couplers. Therefore, such an array generates two symmetrically located beams having right-handed circular polarization (RHCP) and identical two beams having left-handed circular polarization (LHCP). The presented concept has been verified by the design and measurements of an antenna array operating at 2.4 GHz frequency range.