Integrated optical phased arrays can be used for beam shaping and steering with a small footprint, lightweight, high mechanical stability, low price, and high-yield, benefiting from the mature CMOS-compatible fabrication. This paper reviews the development of integrated optical phased arrays in recent years. The principles, building blocks, and configurations of integrated optical phased arrays for beam forming and steering are presented. Various material platforms can be used to build integrated optical phased arrays, e.g., silicon photonics platforms, III/V platforms, and III–V/silicon hybrid platforms. Integrated optical phased arrays can be implemented in the visible, near-infrared, and mid-infrared spectral ranges. The main performance parameters, such as field of view, beamwidth, sidelobe suppression, modulation speed, power consumption, scalability, and so on, are discussed in detail. Some of the typical applications of integrated optical phased arrays, such as free-space communication, light detection and ranging, imaging, and biological sensing, are shown, with future perspectives provided at the end.

We have designed and fabricated a shallow-etched grating on gallium arsenide nanomembranes for efficient chip-to-fiber coupling in quantum photonic integrated circuits. Experimental results show that the grating provides a fiber-coupling efficiency of >60%, a greatly suppressed back reflection of 43 nm. Highly efficient single-photon collection from embedded indium arsenide quantum dots to an optical fiber was realized with the designed grating, showing an average six-fold increase in the photon count compared to commonly used circular gratings, offering an efficient interface for on-chip quantum information processing.

The active routing of photons using rapid reconfigurable integrated circuits is a key functionality for quantum-information processing. Typical waveguide-based optical switches rely on the modulation of the refractive index, producing a modest variation of the phase of the optical fields. Mechanical motion of nanophotonic structures, on the contrary, can be tailored to produce a much larger effect, without introducing loss or emitter decoherence and operating at a speed matching the quantum memory storage time of the on-chip quantum emitter. Here we demonstrate a compact and low-loss nano-opto-electromechanical single-photon router, based on two coupled waveguides whose distance is adjusted on demand by an external voltage. We show controllable two-port routing of single photons emitted from quantum dots embedded in the same chip. We report a maximum splitting ratio $>23\mathrm{dB}$, insertion loss of 0.67 dB, and sub-microsecond response time. The device is an essential building block for constructing advanced quantum photonic architectures on-chip, towards, e.g., coherent multi-photon sources, deterministic photon–photon quantum gates, quantum-repeater nodes, or scalable quantum networks.

This paper presents a transverse mode suppression theory and its experimental verification through aluminum nitride Lamb wave resonators (LWRs) operating at 142 MHz. An effective 2-D approximation model of the LWR is proposed, based on which the origin of transverse modes in LWR is investigated. The displacement distribution, resonant frequencies, and electromechanical coupling coefficients (k ² _t ) of the main mode and its auxiliary transverse modes are obtained. A spurious mode suppression theory in terms of the expression of k ² _t in the 2-D model is proposed. Three kinds of electrodes are designed to suppress the transverse mode adjacent to the main mode, including a novel interdigital transducer gap technique that is reported for the first time. With the applicable geometries, these methods reduce the spurious response from 11.8 to <;0.5 dB, without significantly affecting the figure of merit of the resonator.

Epitaxial quantum dots formed by III–V compound semiconductors are excellent sources of non-classical photons, creating single photons and entangled multi-photon states on demand. Their semiconductor nature allows for a straightforward combination with mature integrated photonic technologies, leading to novel functional devices at the single-photon level. Integrating a quantum dot into a carefully engineered photonic cavity enables control of the radiative decay rate using the Purcell effect and the realization of photon–photon nonlinear gates. In this review, we introduce the basis of epitaxial quantum dots and discuss their applications as non-classical light sources. We highlight two interfaces—one between flying photons and the quantum-dot dipole, and the other between the photons and the spin. We summarize the recent development of integrated photonics and reconfigurable devices that have been combined with quantum dots or are suitable for hybrid integration. Finally, we provide an outlook of employing quantum-dot platforms for practical applications in large-scale quantum computation and the quantum Internet.

Optical microcavity sensors using intensity detection open up the possibility to realize fully integrated high-performance sensing devices, which are significant for both fundamental study of molecular interaction and rapid disease diagnosis. Although the performance of microresonator-based sensors has been studied focusing on the resonance-tracking method, the situation can be much different for intensity-detection sensors. Here we conducted a systematically investigation on the noises sources in intensity detection scheme and their influences on key performance parameters, e.g., signal-to-noise ratio (SNR), limit-of-detection (LOD), and detection range, for various sensors configurations. Especially, the trade-off between SNR and LOD is identified and theoretically analyzed. With experiment noises taken into consideration, our work aims to provide design guidelines for integrated microresonator sensors with optimized performance.