Suppression of spectral diffusion by anti-Stokes excitation of quantum emitters in hexagonal boron nitride

Abstract

Solid-state quantum emitters are garnering a lot of attention due to their role in scalable quantum photonics. A notable majority of these emitters, however, exhibit spectral diffusion due to local, fluctuating electromagnetic fields. In this work, we demonstrate efficient Anti-Stokes (AS) excitation of quantum emitters in hexagonal boron nitride (hBN), and show that the process results in the suppression of a specific mechanism responsible for spectral diffusion of the emitters. We also demonstrate an all-optical gating scheme that exploits Stokes and Anti-Stokes excitation to manipulate spectral diffusion so as to switch and lock the emission energy of the photon source. In this scheme, reversible spectral jumps are deliberately enabled by pumping the emitter with high energy (Stokes) excitation; AS excitation is then used to lock the system into a fixed state characterized by a fixed emission energy. Our results provide important insights into the photophysical properties of quantum emitters in hBN, and introduce a new strategy for controlling the emission wavelength of quantum emitters.

Bottom‐Up Synthesis of Hexagonal Boron Nitride Nanoparticles with Intensity‐Stabilized Quantum Emitters

“…As such, the decrease in the linewidths of ZPLs from the coated nanoparticles suggests that there was a considerable reduction in spectral diffusion from these emitters. [ 46,52 ] From these results, we hypothesize that the silica‐coating film acts as a passivating layer that neutralizes the surface states such as dangling bonds, functional groups, surface point defects, etc. Such a passivating effect, in turn, reduces the spontaneous Stark effects caused by the optical cycling of these surface states, as illustrated in Figure 3e.…”

“…To enable better visualization of the effect, we overlaid the histograms taken from the pristine and coated emitters (Figure 3d). While the intensity counts of the pristine emitters display a bi‐ or multi‐modal distribution of (fluorescence) states, [ 14,29,33,51,52 ] only a single peak is observed for the coated emitters.…”

Advances in quantum light emission from 2D materials

“…However, using different substrates such as Al 2 O 3 [33] or GaInP [34,35] has improved the quality and reduced the random spectral fluctuations of quantum emitters in both insulating [~45 μeV full width at half-maximum (FWHM) with nonresonant excitation] and semiconducting (70 μeV FWHM with nonresonant excitation) 2D materials. While resonant excitation was used to stabilize the ZPL for few tens of seconds [36], anti-Stokes excitation of quantum emitters in hBN was also used to suppress the spectral wandering [37]. Improving material quality [38] and/ or active electrical [39][40][41] or strain-based feedback can further help to minimize unwanted spectral wandering.…”

Optical quantum technologies with hexagonal boron nitride single photon sources

“…To date a record tuning of quantum emission around 65 meV 124 and higher rate of emission enhancement (around 6 to 15 fold) owing to coupling with photonic crystal cavities from silicon nitride (Si 3 N 4 ) 121 and Al nano-antenna 122 was perceived. However the quantum emitters in hBN experience spectral diffusion at cryogenic temperatures, Resonant and antistokes 154 excitation technique found to overcome the complication due to spectral diffusion.…”