Wave propagation and group velocity

Microwave photonics (MWP) is an emerging field in which radio frequency (RF) signals are generated, distributed, processed and analyzed using the strength of photonic techniques. It is a technology that enables various functionalities which are not feasible to achieve only in the microwave domain. A particular aspect that recently gains significant interests is the use of photonic integrated circuit (PIC) technology in the MWP field for enhanced functionalities and robustness as well as the reduction of size, weight, cost and power consumption. This article reviews the recent advances in this emerging field which is dubbed as integrated microwave photonics. Key integrated MWP technologies are reviewed and the prospective of the field is discussed.

Integrated microwave photonics

Recent advances in photonic integration have propelled microwave photonic technologies to new heights. The ability to interface hybrid material platforms to enhance light–matter interactions has led to the development of ultra-small and high-bandwidth electro-optic modulators, low-noise frequency synthesizers and chip signal processors with orders-of-magnitude enhanced spectral resolution. On the other hand, the maturity of high-volume semiconductor processing has finally enabled the complete integration of light sources, modulators and detectors in a single microwave photonic processor chip and has ushered the creation of a complex signal processor with multifunctionality and reconfigurability similar to electronic devices. Here, we review these recent advances and discuss the impact of these new frontiers for short- and long-term applications in communications and information processing. We also take a look at the future perspectives at the intersection of integrated microwave photonics and other fields including quantum and neuromorphic photonics. This Review discusses recent advances of microwave photonic technologies and their applications in communications and information processing, as well as their potential implementations in quantum and neuromorphic photonics.

The growing maturity of integrated photonic technology makes it possible to build increasingly large and complex photonic circuits on the surface of a chip. Today, most of these circuits are designed for a specific application, but the increase in complexity has introduced a generation of photonic circuits that can be programmed using software for a wide variety of functions through a mesh of on-chip waveguides, tunable beam couplers and optical phase shifters. Here we discuss the state of this emerging technology, including recent developments in photonic building blocks and circuit architectures, as well as electronic control and programming strategies. We cover possible applications in linear matrix operations, quantum information processing and microwave photonics, and examine how these generic chips can accelerate the development of future photonic circuits by providing a higher-level platform for prototyping novel optical functionalities without the need for custom chip fabrication. The current state of programmable photonic integrated circuits is discussed, including recent developments in their building blocks, circuit architectures, electronic control and programming strategies, as well as different application spaces.

https://biblio.ugent.be/publication/8677857/file/8677861.pdf

Programmable photonic circuits.

Photonic systems for high-performance information processing have attracted renewed interest. Neuromorphic silicon photonics has the potential to integrate processing functions that vastly exceed the capabilities of electronics. We report first observations of a recurrent silicon photonic neural network, in which connections are configured by microring weight banks. A mathematical isomorphism between the silicon photonic circuit and a continuous neural network model is demonstrated through dynamical bifurcation analysis. Exploiting this isomorphism, a simulated 24-node silicon photonic neural network is programmed using “neural compiler” to solve a differential system emulation task. A 294-fold acceleration against a conventional benchmark is predicted. We also propose and derive power consumption analysis for modulator-class neurons that, as opposed to laser-class neurons, are compatible with silicon photonic platforms. At increased scale, Neuromorphic silicon photonics could access new regimes of ultrafast information processing for radio, control, and scientific computing.

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Neuromorphic photonic networks using silicon photonic weight banks.

Nyquist wavelength division (de)multiplexing (N-WDM) is a highly promising technique for next-generation high-speed elastic networks. In N-WDM, Nyquist filtering is an essential function that governs the channel spectral efficiency. However, most Nyquist filter implementations to date require either expensive, power-hungry digital electronics or complex arrangements of bulky optical components, hindering their adoption for important functions such as Nyquist channel shaping and reconfigurable optical add-drop multiplexers (ROADMs) for Nyquist super-channels. Here, we present a distinctive solution with low-cost, power-efficient, and simple-device natures, which is an on-chip optical Nyquist-filtering (de)interleaver featuring sub-GHz resolution and a near-rectangular passband with 8% transition band. This unprecedented performance is provided by a simple photonic integrated circuit comprising a two-ring-resonator-assisted Mach-Zehnder interferometer, which features high circuit compactness using high-index-contrast Si3N4 waveguide, while showing sub-picosecond optical delay accuracy enabling full C-band coverage with more than 160 effective free spectral ranges of 25 GHz across a bandwidth over 4 THz. Such devices show clear potential for chip-scale realization of N-WDM transceivers and ROADMs.

Full-C-band, sub-GHz-resolution Nyquist-filtering (de)interleaver in photonic integrated circuit

We study pulse transmission across a single optical ring-resonator circuit theoretically The theory is supported by experimental measurements From the study, we discuss intuitively the fulfillment of the causality rules in negative delay phenomenon, which occurs when the circuit possesses a negative group velocity

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Pulse Transmission across a Single Optical Ring-Resonator with Negative Group Velocity: Theory and Experiment

We demonstrate the all-optical generation of a 3.8-THz wide superchannel, using a photonic-chip-based filter for sub-channel definition. The photonic chip is able to shape and aggregate 304× NRZ-32-QAM sub-channels, carrying 10-Gbd data, with an effective data-rate of 24.79 Tb/s.

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Photonic-Chip-Enabled 25 Tb/s Optical Superchannel using Cyclic Spectra

Optische bundelvormer voor breedbandige phased array antennes

Both long haul and short distance network interconnects for conventional data networks and intra-/interchip data links continue to scale in complexity and bandwidth. This has signalled the emergence of the optical interconnect, with silicon photonics being the leading candidate due to its unique combination of low fabrication costs and performance enhancements. Electronic-photonic integration compatibility with CMOS technology, makes integrated photonic circuits more appealing. Hence, it is very critical to make the fabrication of integrated photonic devices as foundry compatible as possible to fully utilize CMOS foundry capabilities. We have proposed a fabrication method for thin film lithium niobate (LN)-based electro-optic modulators which has excellent compatibility with silicon photonic foundry processes and minimizes the back end of the line processes. This paves the way for large scale production of the hybrid Silicon-lithium niobate devices.

Leimeng Zhuang

Papers

Full-C-band, sub-GHz-resolution Nyquist-filtering (de)interleaver in photonic integrated circuit

Pulse Transmission across a Single Optical Ring-Resonator with Negative Group Velocity: Theory and Experiment

Photonic-Chip-Enabled 25 Tb/s Optical Superchannel using Cyclic Spectra

Optische bundelvormer voor breedbandige phased array antennes

Foundry-compatible thin-film lithium niobate electro-optic modulators