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.

/pdf/neuromorphic-photonic-networks-using-silicon-photonic-weight-3o4fn6wx4m.pdf

Neuromorphic photonic networks using silicon photonic weight banks.

This letter presents an alternative approach to achieve a high-bandwidth RF splitter functionality based on a microwave photonic system. The proposed approach has an arbitrary amplitude and a phase offset between the two outputs. In addition, it features a simple system architecture and easy tuning mechanism. In the experimental demonstration, an instantaneous RF band from 5 to 20 GHz was shown.

Photonic High-Bandwidth RF Splitter With Arbitrary Amplitude and Phase Offset

Currently an integrated photonic beamformer for electronically-steered Ku-band phased array antenna (PAA) systems for satellite communications is being developed, targeting continuous reception of the full DVB-S band (10.7- 12.75 GHz), squint-free and seamless beam steering, and polarization agility. The use of an integrated photonic beamformer enables an antenna system with multi-gigahertz instantaneous bandwidth, compact form factor, light weight, and large beam scanning range, which are challenging requirements for beamformers using only electronics-based RF technologies. An important aspect tackled in this paper is to reduce the system cost such that it is commercially suitable for civil purposes in mobile satellite communications, particularly in aeronautic/avionic satellite communications, where low profile and light weight are essential requirements for the antenna system.

Development of a broadband integrated optical beamformer for Ku-Band Phased Array Antennas

This work presents an integrated microwave photonics splitter with reconfigurable amplitude, phase, and delay offsets. The core components for this function are a dual-parallel Mach–Zehnder modulator, a deinterleaver, and tunable delay lines, all implemented using photonic integrated circuits. Using a demonstrator with an optical free spectral range of 25 GHz, we show experimentally the RF splitting function over two continuous bands, i.e., 0.9–11.6 GHz and 13.4–20 GHz. This result promises a deployable solution for creating wideband, reconfigurable RF splitters in integrated forms.

Integrated microwave photonic splitter with reconfigurable amplitude, phase, and delay offsets

Hybrid integration of III–V and ferroelectric materials is being broadly adopted to enhance functionalities in silicon photonic integrated circuits (PICs). Bonding and transfer printing have been the popular approaches for integration of III–V gain media with silicon PICs. Similar approaches are also being considered for ferroelectrics to enable larger RF modulation bandwidths, higher linearity, lower optical loss integrated optical modulators on chip. In this paper, we review existing integration strategies of III–V materials and present a route towards hybrid integration of both III–V and ferroelectrics on the same chip. We show that adiabatic transformation of the optical mode between hybrid ferroelectric and silicon sections enables efficient transfer of optical modal energies for maximum overlap of the optical mode with the ferroelectric media, similar to approaches adopted to maximize optical overlap with the gain section, thereby reducing lasing thresholds for hybrid III–V integration with silicon PICs. Preliminary designs are presented to enable a foundry compatible hybrid integration route of diverse functionalities on silicon PICs.

Hybrid material integration in silicon photonic integrated circuits

Integrated optical beam forming networks (OBFNs) offer many advantages for phased array applications. ORR-based true-time-delay units can be cascaded in a binary tree topology and tuned for continuously-adjustable broadband time delay. Nonetheless, with large number of antenna elements, the OBFN may become very complex. A novel idea is proposed to exploit the frequency periodicity of the ORRs and the WDM technique to achieve multiple-signal-paths on a single beamformer, thus reducing complexity and costs. The use of high index contrast waveguides in Si-compatible technology further reduces chip footprint and allows the use of integrated OBFNs for large arrays and multi-beam applications.

/pdf/multiwavelength-optical-beam-forming-network-with-ring-419d2i0854.pdf

Leimeng Zhuang

Papers

Photonic High-Bandwidth RF Splitter With Arbitrary Amplitude and Phase Offset

Development of a broadband integrated optical beamformer for Ku-Band Phased Array Antennas

Integrated microwave photonic splitter with reconfigurable amplitude, phase, and delay offsets

Hybrid material integration in silicon photonic integrated circuits

Multiwavelength optical beam forming network with ring resonator-based binary-tree architecture for broadband phased array antenna systems