Technologies for efficient generation and fast scanning of narrow free‐space laser beams find major applications in three‐dimensional (3D) imaging and mapping, like Lidar for remote sensing and navigation, and secure free‐space optical communications. The ultimate goal for such a system is to reduce its size, weight, and power consumption, so that it can be mounted on, e.g. drones and autonomous cars. Moreover, beam scanning should ideally be done at video frame rates, something that is beyond the capabilities of current opto‐mechanical systems. Photonic integrated circuit (PIC) technology holds the promise of achieving low‐cost, compact, robust and energy‐efficient complex optical systems. PICs integrate, for example, lasers, modulators, detectors, and filters on a single piece of semiconductor, typically silicon or indium phosphide, much like electronic integrated circuits. This technology is maturing fast, driven by high‐bandwidth communications applications, and mature fabrication facilities. State‐of‐the‐art commercial PICs integrate hundreds of elements, and the integration of thousands of elements has been shown in the laboratory. Over the last few years, there has been a considerable research effort to integrate beam steering systems on a PIC, and various beam steering demonstrators based on optical phased arrays have been realized. Arrays of up to thousands of coherent emitters, including their phase and amplitude control, have been integrated, and various applications have been explored. In this review paper, I will present an overview of the state of the art of this technology and its opportunities, illustrated by recent breakthroughs.

A unique and novel platform that combines III-V and silicon photonic components with ultra-low loss silicon nitride waveguides for monolithic integration of novel photonic circuits is presented. Successful (proof-of-principle) integration of eight hybrid III-V/silicon photodetectors and an arrayed waveguide grating is shown. The InGaAs photodiodes in this platform had average fiber-coupled responsivity of 0.36 A/W at 1550 nm, 30 GHz electrical bandwidth, and operated up to 50 Gb/s. The AWG had an insertion loss of 0.85 dB and adjacent-channel cross-talk less than -38 dB.

In this article, the potential of photonic integrated circuits (PICs) for modern gas sensing applications is discussed. Optical detection systems can be found at the high-end of the currently available gas detectors, and PIC-based optical spectroscopic devices promise a significant reduction in size and cost. The performance of such devices is reviewed here. This discussion is not limited to one semiconductor platform, but includes several available platforms operating from the visible wavelength range up to the long wavelength infrared. The different platforms are evaluated regarding their capabilities in creating a fully integrated spectroscopic setup, including light source, interaction cell and detection unit. Advanced spectroscopy methods are assessed regarding their PIC compatibility. Based on the comparison of PICs with state-of-the-art bulk optical devices, it can be concluded that they can fill the application space of compact and low cost optical gas sensors.

We present the design methodology and experimental characterization of compact out-of-plane focusing grating couplers for integration with magnetoresistive random access memory technology. Focusing grating couplers have recently found attention as layer-couplers for photonic-electronic integration. The components we demonstrate are designed for a wavelength of 1550 nm, fabricated in a standard 220 nm SOI photonic platform and optimized given the fabrication restrictions for standard 193-nm UV lithography. For the first time, we extend the design based on the phase matching condition to a two-dimensional (2-D) grating design with two optical input ports. We further present the experimental characterization of the focusing behaviour by spatially probing the emitted beam with a tapered-and-lensed fiber and demonstrate the polarization controlling capabilities of the 2-D FGCs.

We introduce a hybrid plasmonic-photonic device for on-chip all-optical switching and reading of ferrimagnet bits with perpendicular magnetic anisotropy in a racetrack spintronic memory, coupled onto an indium phosphide waveguide. The device comprises V-shaped gold plasmonic nanoantennas coupled with a photonic crystal cavity, which enables switching and reading of the magnetic state of nanoscale bits by enhancing the absorbed energy density and polar magneto-optical Kerr effect locally. Using a finite-difference time-domain method, we show that our device can switch and read targeted bits down to 100 nm in the presence of oppositely magnetized background regions in the racetrack with widths up to 120 nm, clearly outperforming a bare photonic waveguide. Our hybrid device provides the missing link between integrated photonics and nanoscale spintronics by tackling the challenges of nonlinear absorption in the waveguide, weak magneto-optics, and size mismatch, leading to the development of ultrafast and energy-efficient advanced on-chip applications.