Abstract
Photonic bound states in the continuum (BICs) have recently been studied in various systems and have found wide applications in sensors, lasers, and filters. Applying BICs in photonic integrated circuits enables low-loss light guidance and routing in low-refractive-index waveguides on high-refractive-index substrates, which opens a new avenue for integrated photonics with functional single-crystal materials. Here, we demonstrate high-quality integrated lithium niobate microcavities inside which the photonic BIC modes circulate and further modulate these BIC modes acousto-optically by using piezoelectrically actuated surface acoustic waves at microwave frequencies. With a high acousto-optic modulation frequency, the acousto-optic coupling is well situated in the resolved-sideband regime. This leads to coherent coupling between microwave and optical photons, which is exhibited by the observed electro-acousto-optically induced transparency and absorption. Therefore, our devices serve as a paradigm for manipulating and controlling photonic BICs on a chip, which will enable many other applications of photonic BICs in the areas of microwave photonics and quantum information processing.
Highlights
The concept of “bound states in the continuum” (BICs) was first proposed by von Neumann and Wigner[1] in 1929 with mathematical construction of a three-dimensional potential that can support perfectly confined states in a continuous band
We demonstrated a high-quality photonic microcavity based on the BIC mechanism, which is integrated with an Surface acoustic waves (SAWs) interdigital transducer (IDT) monolithically on a thin-film LiNbO3-on-insulator platform
We demonstrated for the first time acousto-optic modulation of the photonic BIC mode with modulation frequencies beyond 4 GHz
Summary
The concept of “bound states in the continuum” (BICs) was first proposed by von Neumann and Wigner[1] in 1929 with mathematical construction of a three-dimensional potential that can support perfectly confined states in a continuous band. The light guided by the low-refractive-index waveguide can be confined to a region of the high-refractive-index substrate below the Acousto-optics, such as Brillouin scattering, involves the study of phonon–photon interactions based on changes in the refractive index of a medium due to the presence of acoustic waves in that medium. It has found wide applications in various areas, such as nonreciprocal light transmission[30], modulation[31], frequency shifting[32,33], and signal processing[34,35]. SAWs can be used to achieve strong acousto–optic interactions in
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