Ultrabright single-photon emission from germanium-vacancy zero-phonon lines: deterministic emitter-waveguide interfacing at plasmonic hot spots

Abstract

Striving for nanometer-sized solid-state single-photon sources, we investigate atomlike quantum emitters based on single germanium vacancy (GeV) centers isolated in crystalline nanodiamonds (NDs). Cryogenic characterization indicated symmetry-protected and bright (> 10 6 counts/s with off-resonance excitation) zero-phonon optical transitions with up to 6-fold enhancement in energy splitting of their ground states as compared to that found for GeV centers in bulk diamonds (i.e., up to 870 GHz in highly strained NDs vs 150 GHz in bulk). Utilizing lithographic alignment techniques, we demonstrate an integrated nanophotonic platform for deterministic interfacing plasmonic waveguides with isolated GeV centers in NDs that enables 10-fold enhancement of singlephoton decay rates along with the emission direction control by judiciously designing and positioning a Bragg reflector. This approach allows one to realize the unidirectional emission from single-photon dipolar sources introducing a novel method that is alternative to the propagation-direction-dependent techniques based on chiral interactions or topological protection. The developed plasmon-based nanophotonic platform opens thereby new perspectives for quantum nanophotonics in general and for realizing entanglement between single photons and spin qubits, in particular.

Mono-crystalline gold platelets: a high-quality platform for surface plasmon polaritons

“…Alternatively, chemically grown colloidal gold platelets [3,5,4,6] with atomically smooth surfaces were synthesized and have proven their superiority in terms of stronger plasmonic resonances [7,8] and longer propagation in plasmonic circuits [8]. These gold platelets have enabled fascinating new explorations of fundamental plasmonic properties revealed by photoemission electron microscopy [9,10] and improved plasmonic device performances such as for novel light generation applications [11] and quantum light guiding [12]. Other mono-crystalline gold structures such as gold tappers demonstrated improved nanofocusing properties and second harmonic generation under pulsed illumination [13].…”

Design and Numerical Verification of Four States Polarization-independent Grating Coupler Using a Double-Layer Approach for a Single-photon Source based on HPW

“…The following simulations are based on an operation wavelength (λ) of 700 nm. This λ is widely used as a general emission λ for the QEs embedded inside a DLSPP or HPW waveguides [3,16]. Besides, an HSQ layer with an optimum thickness of 20 nm is deposited above the first GC layer to act as a separator between the two GCs layers [23].…”

Design And Numerical Verification of Four States Polarization-Independent Grating Coupler Using A Double-Layer Approach For A Single-Photon Source Based On HPW

“…Moreover, a polarization-independent GC is needed in on-chip photonic circuits that its operations rely on the polarization state of the propagated light inside the photonic waveguide. For example, in [3], the emission of the quantum emitter (QE) embedded in the dielectric-loaded surface plasmon polariton (DLSPP) could be processed to produce a different polarization than the waveguide's output emission polarization.…”