Harnessing optical micro-combs for microwave photonics

In the past decade, optical frequency combs generated by high-Q micro-resonators, or micro-combs, which feature compact device footprints, high energy efficiency, and high-repetition-rates in broad optical bandwidths, have led to a revolution in a wide range of fields including metrology, mode-locked lasers, telecommunications, RF photonics, spectroscopy, sensing, and quantum optics. Among these, an application that has attracted great interest is the use of micro-combs for RF photonics, where they offer enhanced functionalities as well as reduced size and power consumption over other approaches. This article reviews the recent advances in this emerging field. We provide an overview of the main achievements that have been obtained to date, and highlight the strong potential of micro-combs for RF photonics applications. We also discuss some of the open challenges and limitations that need to be met for practical applications.Comment: 32 Pages, 13 Figures, 172 Reference

UWB Signal Generation and Modulation Based on Photonic Approaches

Demands for efficient and reliable wireless communications between computers, mobile phones, and other portable electronic devices in short distances are increasing very fast. Ultra-wideband impulse radio is one of the promising techniques, which has gained much research interests in recent years. It covers a wide scope of applications in short-reach wireless communications. Conventionally, the low-bandwidth electronics can process the UWB signals very well. More recently, microwave photonics has enabled a new paradigm for developing UWB techniques in photonic domain. The photonic approaches offer much higher bandwidth and seamless compatibility with optical fiber networks, which allow for scaling the UWB technology to more advanced application scenarios. This chapter is included because photonic approaches have become a unique and effective technique in microwave signal processing. We do not attempt to offer a comprehensive review of UWB photonics, but rather to introduce the typical photonic solutions for UWB signal generation, modulation, transmission, down conversion, and so on

Single-Beam Coherent Raman Spectroscopy and Microscopy via Spectral Notch Shaping

Raman spectroscopy is one of the key techniques in the study of vibrational modes and molecular structures. In Coherent Anti-Stokes Raman Scattering (CARS) spectroscopy, a molecular vibrational spectrum is resolved via the third-order nonlinear interaction of pump, Stokes and probe photons, typically using a complex experimental setup with multiple beams and laser sources. Although CARS has become a widespread technique for label-free chemical imaging and detection of contaminants, its multi-source, multi-beam experimental implementation is challenging. In this work we present a simple and easily implementable scheme for performing single-beam CARS spectroscopy and microscopy using a single femtosecond pulse, shaped by a tunable narrowband notch filter. As a substitute for multiple sources, the single broadband pulse simultaneously provides the pump, Stokes and probe photons, exciting a broad band of vibrational levels. High spectroscopic resolution is obtained by utilizing a tunable spectral notch, shaped with a resonant photonic crystal slab filter, as a narrowband, time-delayed probe. Using this scheme the entire vibrational spectrum can be resolved in a single-shot multiplexed measurement, circumventing the need for a multi-source configuration or a complex pulse-shaping apparatus. We demonstrate high-resolution single-beam micro-spectroscopy and vibrational imaging of various samples in the 300cm^{-1}-1000cm^{-1} spectral range

New opportunities for 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 developments of ultra-small and high-bandwidth electro-optic modulators, frequency synthesizers with the lowest noise, 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 multi-functionality and reconfigurability similar to their electronic counterparts. 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 in the intersection of integrated microwave photonics with other fields including quantum and neuromorphic photonics

スパースアレイ・レーダにおける信号処理技術

Tohoku University佐藤源之課

Ultra Wideband

Ultra wideband (UWB) has advanced and merged as a technology, and many more people are aware of the potential for this exciting technology. The current UWB field is changing rapidly with new techniques and ideas where several issues are involved in developing the systems. Among UWB system design, the UWB RF transceiver and UWB antenna are the key components. Recently, a considerable amount of researches has been devoted to the development of the UWB RF transceiver and antenna for its enabling high data transmission rates and low power consumption. Our book attempts to present current and emerging trends in-research and development of UWB systems as well as future expectations

Predicting movements of onsite workers and mobile equipment for enhancing construction site safety

Tens of thousands of time-loss injuries and deaths are annually reported from the construction sector, and a high percentage of them are due to the workers being struck by mobile equipment on sites. In order to address this site safety issue, it is necessary to provide proactive warning systems. One critical part in such systems is to locate the current positions of onsite workers and mobile equipment and also predict their future positions to prevent immediate collisions. This paper proposes novel Kalman filters for predicting the movements of the workers and mobile equipment on the construction sites. The filters take the positions of the equipment and workers estimated from multiple video cameras as input, and output the corresponding predictions on their future positions. Moreover, the filters could adjust their predictions based on the worker or equipment's previous movements. The effectiveness of the filters has been tested with real site videos and the results show the high prediction accuracy of the filters