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.

Integrated microwave photonics

This paper reviews the recent advances in the field of radio frequency signal processing using photonic devices and subsystems or microwave photonic (MWP) signal processing. We focus our attention on the results reported during the last six years, as previous work has been adequately addressed in previous review papers. After a brief introduction to the basic concepts involved in MWP signal processing, we focus our attention on the most significant advances reported by different research groups in overcoming their main limitation factors. Recent advances in the emergent topic of integrated MWP signal processors are also covered and the novel approaches toward the evaluation of the main figures of merit are discussed. New proposed applications and future directions of work are also considered.

Microwave Photonic Signal Processing

Integrated microwave photonics, an emerging technology combining radio frequency (RF) engineering and integrated photonics, has great potential to be adopted for wideband analog processing applications. However, it has been a challenge to provide photonic integrated circuits with equal levels of function flexibility as compared with their electronic counterparts. Here, we introduce a disruptive approach to tackle this need, which is analogous to an electronic field-programmable gate array. We use a grid of tunable Mach–Zehnder couplers interconnected in a two-dimensional mesh network, each working as a photonic processing unit. Such a device is able to be programmed into many different circuit topologies and thereby provide a diversity of functions. This paper provides, to the best of our knowledge, the first ever demonstration of this concept and shows that a programmable chip with a free spectral range of 14 GHz enables RF filters featuring continuous, over-two-octave frequency coverage, i.e., 1.6–6 GHz, and variable passband shaping ranging from a 55 dB extinction notch filter to a 1.6 GHz bandwidth flat-top filter.

https://ris.utwente.nl/ws/files/6955872/optica-2-10-854.pdf

Programmable photonic signal processor chip for radiofrequency applications

Highly selective and reconfigurable microwave filters are of great importance in radio-frequency signal processing. Microwave photonic (MWP) filters are of particular interest, as they offer flexible reconfiguration and an order of magnitude higher frequency tuning range than electronic filters. However, all MWP filters to date have been limited by trade-offs between key parameters such as tuning range, resolution, and suppression. This problem is exacerbated in the case of integrated MWP filters, blocking the path to compact, high-performance filters. Here we show the first chip-based MWP bandstop filter with ultrahigh suppression, high resolution in the megahertz range, and 0–30 GHz frequency tuning. This record performance was achieved using an ultralow Brillouin gain from a compact photonic chip and a novel approach of optical resonance-assisted RF signal cancellation. The results point to new ways of creating energy-efficient and reconfigurable integrated MWP signal processors for wireless communications and defence applications.

Low-power, chip-based stimulated Brillouin scattering microwave photonic filter with ultrahigh selectivity

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.

/pdf/integrated-microwave-photonics-1p1bt2cwny.pdf

The flexibility of microwave photonics provides advantages over electronic circuitry, yet the lack of integrated chip-scale devices limits its practical application. This study presents microwave filters based on photonic crystal waveguides with controllable delays as a step towards intregable circuits.

/pdf/integrable-microwave-filter-based-on-a-photonic-crystal-22603ilmg2.pdf

Integrable microwave filter based on a photonic crystal delay line

We have designed and fabricated a photonic crystal filter intended for demultiplexing in wavelength division domain. This device is single-mode, the total insertion losses are about 12dB and the channel isolation can exceed 25dB. Non return to zero signal at 40Gb/s have been successfully filtered with no penalty in the bit error rate analysis. The device is cascadable to form a multi-channel demultiplexer and can be tuned through an integrated, low power temperature controller.

https://hal.archives-ouvertes.fr/hal-00720241/document

40 Gb/s wavelength division demultiplexing with a PhC filter

We review the properties of photonic crystals in III–V materials from the prospective of light-matter interaction enhanced by “slow-light”. We discuss some key functions, namely the generation of a time delay and the nonlinear conversion. Compared to optical fibers, the typical scales, dispersion and nonlinear lengths are reduced to the mm range, thereby opening the possibility of on-chip all optical processing. That has been enabled by the minimisation of linear and nonlinear losses.

Slow light devices in III–V photonic crystals: state of the art and open issues

We demonstrate 20 μW second harmonic generation in a photonic crystal waveguide. The collected signal has been used for optical performance monitoring of the chromatic dispersion and optical signal to noise ratio of a 42.5 Gb/s Return to Zero signal all over the C-band.

/pdf/efficient-second-harmonic-generation-in-photonic-crystal-4wgfsd4iy8.pdf

S. Xavier

Papers

Integrable microwave filter based on a photonic crystal delay line

40 Gb/s wavelength division demultiplexing with a PhC filter

Slow light devices in III–V photonic crystals: state of the art and open issues

Efficient second harmonic generation in photonic crystal waveguides for optical performance monitoring in the full C-band at 42.5 Gb/s