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.

We demonstrate a polarization rotator-splitter (PRS) design on standard 220 nm silicon-on-insulator (SOI) wafers with all rib waveguides and 2 μm silicon dioxide (SiO2) claddings. The design is fully compatible with the imec iSiPP50G silicon photonics platform. We show TM0-TE0 converting loss < 0.5 dB and all polarization crosstalk < -10 dB in the wavelength range of 1500- 1600 nm.

A wideband polarization rotator-splitter based on imec iSiPP50G silicon photonics platform

Programmable optical chips are a key technology for integrated microwave photonics. They enable flexible and stable signal processing operations on miniaturized chips with ultimate control precision and potential for low-cost fabrication. Integrated microwave photonic filters are an important function for photonic-assisted RF front-ends which opens a path to overcome the bandwidth limitation of the current digital electronics. Programmable optical chips enable such filters with high function flexibility, continuous tunability, and sharp frequency selectivity, which facilitate innovations of a wide range of new applications. Here, we review the recent works in this area that pave the path towards realizing microwave photonic filters with DSP-level flexibility, MHz-level frequency selectivity, and very importantly, full function integration on a chip scale.

Programmable optical chips for integrated microwave photonics RF filters

Microwave photonics (MWP) merges optical components and subsystems with RF engineering. As an emerging technology, it enables realization of complex RF functionalities beyond the capability of the current all-electronics systems. In the investigations of the recent decades, the advantages of MWP systems such as large instantaneous bandwidth, RF frequency transparency, flexible tunability and reconfigurability, and less susceptibility to electromagnetic interference, have been harnessed to realize various RF functionalities. Among them, the well-known include signal generation, signal transmission and distribution, signal processing, control, signal measurement and analysis. This technology opens new perspectives for information and communication systems and networks, and it also creates possibilities for new RF applications in both niche and consumer markets. From the industrial perspective, however, the success of MWP solutions, with respect to the conventional all-electronics solutions, is believed to be determined by the progress of photonic integration, where the optical components and subsystems are incorporated in photonic integrated circuits (PICs) [1]. Compared to the MWP systems constructed using discrete optical components, the PIC-based MWP systems, or termed as integrated microwave photonics (IMWP), feature higher robustness and compactness, smaller SWaP, and most importantly, the potential of large reduction on system cost.

Integrated microwave photonic signal processors in TriPleX TM waveguide

Reconfigurable multichannel optical filters (MOFs) with a high resolution are key devices for high-spectral-efficiency multi-carrier optical transmission systems. However, very few on-chip MOFs reported so far can meet the demands of high spectral resolution, device complexity, and scalable input/output ports. Here, we present a 10 GHz-bandwidth self-configurable silicon MOF using a resonator-assisted discrete-Fourier-transform interferometer. With the help of ultra-low-loss silicon photonic waveguides and low-phase-error Mach–Zehnder switches, the present chip features a low excess loss, low power consumption, high port-count scalability, and sub-GHz spectral resolution. In particular, the present MOF is capable of performing some specific filtering responses with, e.g., near-rectangular or sinc shapes. Furthermore, an efficient self-configuring approach is also developed for the present chip to be programmable, so that different spectral responses can be achieved as desired by automatically optimizing the settings of all the tuning elements, showing great potential for high-capacity optical communication networks. 

Self-Configuring GHz-Scale Multichannel Silicon Photonic Filter Using a Resonator-Assisted Discrete-Fourier-Transform Interferometer

A method of transmitting digital information over an optical channel (132) includes mapping (106, 108) input digital information bits to first and second complex-valued symbol sets A complex rotation (110, 112) is applied to each symbol of the first and second complex-valued symbol sets In-phase (I) and quadrature (Q) components of a first polarisation state of an optical carrier (122) are modulated with the real parts of the first and second complex-valued symbol sets respectively, while in-phase (I) and quadrature(Q) components of a second polarisation state of the optical carrier are modulated with the imaginary parts of the first and second complex-valued symbol sets respectively

Leimeng Zhuang

Papers

A wideband polarization rotator-splitter based on imec iSiPP50G silicon photonics platform

Programmable optical chips for integrated microwave photonics RF filters

Integrated microwave photonic signal processors in TriPleX TM waveguide

Self-Configuring GHz-Scale Multichannel Silicon Photonic Filter Using a Resonator-Assisted Discrete-Fourier-Transform Interferometer

Method and system for polarisation division multiplexed optical transmission