The discovery of two-dimensional (2D) materials has gained worldwide attention owing to their extraordinary optical, electrical, and mechanical properties. Due to their atomic layer thicknesses, the emerging 2D materials have great advantages of enhanced interaction strength, broad operating bandwidth, and ultralow power consumption for optoelectromechanical coupling. The van der Waals (vdW) epitaxy or multidimensional integration of 2D material family provides a promising platform for on-chip advanced nano-optoelectromechanical systems (NOEMS). Here, we provide a comprehensive review on the nanomechanical properties of 2D materials and the recent advances of 2D-materials-integrated nano-electromechanical systems (NEMS) and nano-optomechanical systems (NOMS). By utilizing active nanophotonics and optoelectronics as the interface, 2D active NOEMS and their coupling effects are particularly highlighted at the 2D atomic scale. Finally, we share our viewpoints on the future perspectives and key challenges of scalable 2D-materials-integrated active NOEMS for on-chip miniaturized, lightweight, and multifunctional integration applications.

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Novel physical concepts that originate from quantum mechanics, such as non‐Hermitian systems (dealing mostly with PT and anti‐PT symmetry) and bound states in the continuum (BICs), have attracted great interest in the optics and photonics community. To date, BICs and anti‐PT symmetry seem to be two independent topics. Here, a parallel cascaded‐resonator system is proposed for the first time to achieve BICs and anti‐PT symmetry simultaneously. It is found that the requirements for the Fabry–Pérot BIC and anti‐PT symmetry can both be satisfied when the phase shift between any two adjacent resonators is an integer multiple of π. The cascaded‐resonator systems consisting of different numbers of resonators are further analyzed and their robustness to fabrication imperfections is demonstrated. The proposed structure can readily be realized on an integrated photonic platform, and can enable many applications that benefit from the advantages of both BICs and anti‐PT symmetry, such as optical delay and storage, all‐optical nonlinear processing, high‐sensitivity sensing, and chiral mode switching.

Parity-time (PT) symmetry, an interesting concept originally introduced in quantum mechanics, has been extended to many other branches of physics. Besides its demonstrations in optics and electronics, the study of PT-symmetric mechanics is growing rapidly. To date, most PT-symmetric mechanical systems have relatively large size and low operating frequency, which limits their applications in high-speed sensing and signal processing. Here, we propose a PT-symmetric mechanical system with gain/loss provided by the cavity optomechanical effect, which can overcome those limitations. We theoretically analyze and numerically simulate the optical control of PT-symmetric optomechanical systems that consist of two or more mechanical resonators. We find the property of unidirectional reflection in these systems, which may pave the way for the study of topological acoustics and phononic signal processing.

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