Abstract
Luminescent defects in hexagonal boron nitride (h-BN) have recently emerged as a promising platform for non-classical light emission. On-chip solutions, however, require techniques for controllable in-situ manipulation of quantum light. Here, we demonstrate the dynamic spectral and temporal tuning of the optical emission from h-BN via moving acousto-mechanical modulation induced by stimulated phonons. When perturbed by the propagating acoustic phonon, the optically probed radiative h-BN defects are periodically strained and their sharp emission lines are modulated by the deformation potential coupling. This results in an acoustically driven spectral tuning within a 2.5-meV bandwidth. Our findings, supported by first-principles theoretical calculations, reveal exceptionally high elasto-optic coupling in h-BN of ~50 meV/%. Temporal control of the emitted photons is achieved by combining the acoustically mediated fine-spectral tuning with spectral detection filtering. This study opens the door to the use of sound for scalable integration of h-BN emitters in nanophotonic and quantum information technologies.
Highlights
Luminescent defects in hexagonal boron nitride (h-BN) have recently emerged as a promising platform for non-classical light emission
The surface acoustic waves (SAWs) are electrically excited by applying an radio frequency (RF) voltage to interdigital transducers (IDTs) designed to operate at frequency fSAW ~293 MHz at room temperature
To produce single-photon emitters (SPEs), the hexagonal boron nitride (hBN) powder was thermally expanded resulting in layers with lateral dimensions of ~200–300 nm and thickness of ~3–5 nm, which were mechanically dispersed onto the SAW propagation path (Fig. 1)
Summary
Luminescent defects in hexagonal boron nitride (h-BN) have recently emerged as a promising platform for non-classical light emission. 6,7,9 suggest that this wide span of the emission wavelengths may result from inhomogeneous broadening of several defect species or can likely originate from defects belonging to the same atomistic model coupled to the fluctuating local lattice strain and/or dielectric environments Whatever its origin, such large spectral inhomogeneity has shown to be detrimental to developing identical single-photon sources, as well as for other applications in nanophotonics and quantum information processing that rely on a strict and well-defined emission energy. From the optical response of the emitting states to the moving mechanical vibration, we estimate the absolute deformation potential and the strain-induced tuning coefficient for h-BN to be ~5 eV and ~50 meV/%, respectively These values, which are substantiated by theoretical analysis, exceed by an order of magnitude the previous experimental findings obtained under externally applied static strain[6], thereby evidencing high elasto-optic coupling in h-BN. These functionalities are beneficial for the deployment of h-BN defect centers in quantum and integrated photonic applications
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