Large-scale photonic switches are essential devices for energy-and cost-efficient optical communication networks in cloud and data-intensive computing. Silicon photonics is an attractive platform for high-density photonic integrated circuits with low manufacturing costs through the leveraging of existing advanced complementary metal-oxidesemiconductor processes. Many optical components such as lasers, modulators, splitters, and photodetectors have been successfully integrated on silicon; however, the quest for large-scale silicon photonic switches has remained elusive. Previous silicon photonic switches made of cascaded 1 × 2 or 2 × 2 building blocks have a limited port count (≤8 × 8) or excessive optical losses (>15 dB). Here, we present a 64 × 64 digital silicon photonic switch with a low on-chip insertion loss (3.7 dB) and broadband operation (300 nm). The measured switching time is 0.91 μs, and the extinction ratio is larger than 60 dB. The matrix switch with 4096 microelectromechanical-systems-actuated vertical adiabatic couplers has been integrated on a 8.6 mm × 8.6 mm chip. To our knowledge this is the largest monolithic switch, and the largest silicon photonic integrated circuit, reported to date. The passive matrix architecture of our switch is fundamentally more scalable than that of multistage switches.

Integrated photonics will play a key role in quantum systems as they grow from few-qubit prototypes to tens of thousands of qubits. The underlying optical quantum technologies can only be realized through the integration of these components onto quantum photonic integrated circuits (QPICs) with accompanying electronics. In the last decade, remarkable advances in quantum photonic integration have enabled table-top experiments to be scaled down to prototype chips with improvements in efficiency, robustness, and key performance metrics. These advances have enabled integrated quantum photonic technologies combining up to 650 optical and electrical components onto a single chip that are capable of programmable quantum information processing, chip-to-chip networking, hybrid quantum system integration, and high-speed communications. In this roadmap article, we highlight the status, current and future challenges, and emerging technologies in several key research areas in integrated quantum photonics, including photonic platforms, quantum and classical light sources, quantum frequency conversion, integrated detectors, and applications in computing, communications, and sensing. With advances in materials, photonic design architectures, fabrication and integration processes, packaging, and testing and benchmarking, in the next decade we can expect a transition from single- and few-function prototypes to large-scale integration of multi-functional and reconfigurable devices that will have a transformative impact on quantum information science and engineering.

Fast optical circuit switches (OCSs) with high port count offer reconfigurable bandwidth in optical networks and have the potential to significantly increase the performance and efficiency of modern datacenters. In this paper, we report on a new type of integrated OCS that combines silicon photonics with MEMS actuation. The switch is built on a 50 × 50 passive crossbar network with very low optical loss (0.04 dB/crossing). Efficient switching is achieved by a pair of directional couplers with moving waveguides and an actuation voltage of 14 V. 2500 MEMS-actuated directional coupler switches have been integrated with the crossbar network to form a strictly nonblocking 50 × 50 OCS on a 9 mm × 9 mm chip. The measured switching time is 2.5 μs, and the extinction ratio is 26 dB. To our knowledge, this is the largest silicon photonic switch reported to date. The switch architecture is highly scalable because the light travels through only one active switching element, regardless of the size of the switch.

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Photonic integrated circuits have seen a dramatic increase in complexity over the past decades. This development has been spurred by recent applications in datacenter communications and enabled by the availability of standardized mature technology platforms. Mechanical movement of wave-guiding structures at the micro-and nanoscale provides unique opportunities to further enhance functionality and to reduce power consumption in photonic integrated circuits. We here demonstrate integration of MEMS-enabled components in a simplified silicon photonics process based on IMEC's Standard iSiPP50G Silicon Photonics Platform and a custom release process.