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Acoustic modulation of light emission centres in hexagonal boron nitride


Light emission centres in solids are promising candidates for applications in quantum information processing due to their capability of acting as single photon sources. One of the challenges related to these kinds of quantum light sources is to find mechanisms for the efficient control of their optoelectronic properties. Here, we show that surface acoustic waves can modulate the optical properties of light emission centres in hexagonal boron nitride. These results have been published as a Featured Article in Applied Physics Letters.

Figure 1. (a) Luminescence spectra of a light emitter for increasing SAW powers. (b) Amplitude of the spectral modulation with respect to the strain generated by the SAW. The solid lines in both panels are fittings according to the theoretical model.

In this work, we have analysed the optical behaviour of two kinds of h-BN samples, namely commercial multi-layer flakes and few-layer-films grown by molecular beam epitaxy. After deposition at the surface of a strong piezoelectric substrate, we generated surface acoustic waves (SAWs) by applying radio frequency signals to interdigital transducers patterned on the substrate. We show that the oscillating tensile and compressive strain of the SAW can modulate periodically the light emission wavelength of defect centres contained in the flakes, resulting in a broadening of their emission line, see Fig. 1(a). From the linear dependence of the modulation amplitude with respect to the strain applied by the SAW, cf. Fig. 1(b), we estimate a deformation potential of about 40 meV per % of strain.

Due to the relatively low number of layers typically present in these h-BN samples, the light emission centres can experience energy and intensity fluctuations due to their interaction with nearby charge traps present at the interfaces or other kinds of shallow impurities. In our work, we also show that the dynamic piezoelectric field of the SAW could contribute to the stabilization of the optical properties of the light centres in the epitaxial few-layer-thick films by controlling the ionization state of the nearby charge traps.

Author: F. Iikawa , A. Hernández-Mínguez , I. Aharonovich , S. Nakhaie , Y.-T. Liou , J. M. J. Lopes , P. V. Santos
Title: Acoustically modulated optical emission of hexagonal boron nitride layers
Source: Appl. Phys. Lett. , 114 , 171104 ( 2019 )
DOI: 10.1063/1.5093299