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.

/pdf/high-contrast-gratings-for-integrated-optoelectronics-3ykfc99oae.pdf

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

In this letter, the power spectrum of a cooled distributed feedback laser module is measured using the self-heterodyne technique. Periodical oscillation peaks have been observed in the measurement. Further investigation shows that the additional modulation signal is coupled from the thermal electric cooler (TEC) controller to the laser driver, and then applied to the laser diode. The additional modulation can be eliminated by properly isolating the laser driving source from the TEC controller.

Analysis of the Additional Modulation of Semiconductor Lasers Using Optical Heterodyne Techniques

As a paradigmatic microwave photonic resonant system that is capable of producing high-quality self-sustained microwave oscillations, the optoelectronic oscillator (OEO) has been intensively investigated in recent years, and a diversity of new insights and breakthroughs have been proposed and demonstrated. In this perspective, we discuss the recent progress, opportunities, and challenges of OEOs. Specifically, an overview of different OEO schemes for single-frequency and complex microwave signal generation is provided. Emerging advances in integrated OEO and applications of OEO are briefly reviewed. We also discuss the remaining challenges and opportunities in this field.

https://aip.scitation.org/doi/pdf/10.1063/5.0134289

Perspectives on optoelectronic oscillators

A simple edge-triggered and chirp-free ultra-wideband (UWB) monocycle pulse shaper was proposed and demonstrated utilizing a nonlinearly operated polarization-to-intensity converter, which mainly consists of a polarization modulator (PolM), two polarization controllers (PCs), and a time-delay device. As static phase shift of the incident light φ0=π, a 500-MHz monocycle pulse sequence with 10-dB bandwidth of 10 GHz and fractional bandwidth of 133% was obtained while a 250-MHz electrical quasi-square-wave was applied on the PolM. In addition, polarity switch of the UWB monocycle pulse can be realized by adjusting the bias voltage of the PolM or controlling the PC.

Edge-Triggered Ultra-Wideband Pulse Shaper Using Polarization-to-Intensity Conversion

We review the recent progress of photonic generation of millimeter wave (MMW)-ultra-wideband (UWB) signals. To fully satisfy the standard defined by the Federal Communications Commission (FCC), the baseband signal (background signal) and the residual local oscillator (LO) signal should be well controlled. We discuss several schemes in this work for generating background-free MMW-UWB signals that are fully compliant with the FCC requirement.

Photonic generation of background-free millimeter-wave ultra-wideband signals (Invited Paper)

A novel photonics-assisted unconventional double-sideband sub-carrier modulation is proposed for dual-polarization UDWDM-PON with direct detection. High spectral-efficiency is achieved by removing the band-limited electrical mixing components.

Ninghua Zhu

Papers

Analysis of the Additional Modulation of Semiconductor Lasers Using Optical Heterodyne Techniques

Perspectives on optoelectronic oscillators

Edge-Triggered Ultra-Wideband Pulse Shaper Using Polarization-to-Intensity Conversion

Photonic generation of background-free millimeter-wave ultra-wideband signals (Invited Paper)

Photonics-assisted microwave mixing and direct detection for dual-polarization and SCM based UDWDM-PON