Ultra Wideband Signals and Systems in Communication Engineering

Resonance conditions for a substrate-superstrate printed antenna geometry which allow for large antenna gain are presented. Asymptotic formulas for gain, beamwidth, and bandwidth are given, and the bandwidth limitation of the method is discussed. The method is extended to produce narrow patterns about the horizon, and directive patterns at two different angles.

Gain enhancement methods for printed circuit antennas

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

A new class of planar optics has emerged using subwavelength gratings with a large refractive index contrast, herein referred to as high-contrast gratings (HCGs). This seemingly simple structure lends itself to extraordinary properties, which can be designed top-down based on intuitive guidelines. The HCG is a single layer of high-index material that can be as thin as 15% of one wavelength. It can be designed to reflect or transmit nearly completely and with specific optical phase over a broad spectral range and/or various incident beam angles. We present a simple theory providing an intuitive phase selection rule to explain the extraordinary features. Our analytical results agree well not only with numerical simulations but also experimental data. The HCG has made easy fabrication of surface-normal optical devices possible, including vertical-cavity surface-emitting lasers (VCSELs), tunable VCSELs, and tunable filters. HCGs can be designed to result in high-quality-factor (Q) resonators with surface-normal output, which is promising for wafer-scale lasers and optical sensors. Spatially chirped HCGs are shown to be excellent focusing reflectors and lenses with very high numerical apertures. This field has seen rapid advances in experimental demonstrations and theoretical results. We provide an overview of the underlying new physics and the latest results of devices.

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High-contrast gratings for integrated optoelectronics

A vertical-cavity surface emitting laser (VCSEL) was invented 30 years ago. A lot of unique features can be expected, such as low-power consumption, wafer-level testing, small packaging capability, and so on. The market of VCSELs has been growing up rapidly in recent years, and they are now key devices in local area networks using multimode optical fibers. Also, long wavelength VCSELs are currently attracting much interest for use in single-mode fiber metropolitan area and wide area network applications. In addition, a VCSEL-based disruptive technology enables various consumer applications such as a laser mouse and laser printers. In this paper, the recent advance of VCSEL photonics will be reviewed, which include the wavelength extension of single-mode VCSELs and their wavelength integration/control. Also, this paper explores the potential and challenges for new functions of VCSELs toward optical signal processing

https://cnst.nctu.edu.tw/mbe08/abstract/6-13.30-14.00-koyama.pdf

Recent Advances of VCSEL Photonics

A dual-loop nonlinear optoelectronic oscillator with an inbuilt ultra-wideband (UWB) band pass filter is proposed to generate chaotic-UWB signals for the first time. To avoid the spectrum-overlay-induced interference between UWB signals and the other existing narrow band signals, a microwave photonics filter is built up in the loops to filter out the corresponding frequency components. In the experiment, the chaotic-UWB signals with a frequency notch response located at 7.5 GHz, 5 GHz, or simultaneous 7.5 and 5 GHz are generated as the time delay difference between the two loops is set at 133, 200, or 400 ps, respectively. The peak sidelobe levels of the autocorrelation traces are as low as -33.7 dB at least, which implies that the generated UWB signals could be applied in random UWB radar directly.

Spectral Sculpting of Chaotic-UWB Signals Using a Dual-Loop Optoelectronic Oscillator

A multi-period-delayed feedback (MPDF) photonic circuit constructed by a Sagnac ring and two coupled rings was designed. By coupling a distributed feedback (DFB) laser diode (LD) with the MPDF, a narrow linewidth semiconductor laser was demonstrated. The linewidth of the DFB-LD with MPDF was narrowed to be around 2 kHz, which is reduced by three orders of magnitude, and the linewidth reduction capability could be maintained when the wavelength of the DFB-LD was tuned in a range wider than 3 nm. The laser frequency stability can also be improved using the proposed technique, and the frequency fluctuation was reduced for nearly 8 times in comparison with the DFB-LD.

Narrow linewidth semiconductor laser with a multi-period-delayed feedback photonic circuit.

A fast-switching single passband microwave photonic finite impulse response filter (MPF) using an incoherent broadband optical source (BOS) and an integrated spectrum shaper is proposed and experimentally demonstrated. The key component of our proposed MPF is the silica-on-silicon integrated spectrum shaper, which is used to slice the spectrum of the BOS. The performance of the integrated spectrum shaper is measured in terms of time delay, power consistency, and switching speed. A number of spectral shapes with the free spectrum range from 1.88 to 0.058 nm can be flexibly switched by changing the driving voltage of the optical switches. With the dispersion compensating fiber as dispersion medium, a fast-switching MPF with the switching speed up to 1.4-KHz is demonstrated in a wide tunable range from 1 to 12 GHz and the sidelobe suppression is up to 35 dB, which shows a great agreement with the theoretical result.

Fast-Switching Microwave Photonic Filter Using an Integrated Spectrum Shaper

This Review reviews semiconductor lasers with an emphasis on high-speed information technologies. Semiconductor lasers are classified based on their applications in optical communications. Different types of semiconductor lasers are discussed in terms of principle, history, advantages, and limitations.

Semiconductor lasers for high-speed information technologies (Invited Paper)

Compared with microelectronic packaging, optoelectronic packaging as a new packaging type has been developed rapidly and it will play an essential role in optical communication.In this paper, we try to summarize the development history, research status, technology issues and future prospects, and hope to provide a meaningful reference.

https://iopscience.iop.org/article/10.1088/1674-4926/36/10/101001/pdf

Ninghua Zhu

Papers

Spectral Sculpting of Chaotic-UWB Signals Using a Dual-Loop Optoelectronic Oscillator

Narrow linewidth semiconductor laser with a multi-period-delayed feedback photonic circuit.

Fast-Switching Microwave Photonic Filter Using an Integrated Spectrum Shaper

Semiconductor lasers for high-speed information technologies (Invited Paper)

Packaging investigation of optoelectronic devices