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

Fully characterization of an active optical filter based on an equivalent-phase-shifted DFB-SOA

Dual-pattern communication system using DBR laser in the intensity-modulation and direct-detection system

We report a simple and novel scheme to achieve the reconfigurable frequency mixing based on a filter-free photonic microwave in-phase/quadrature (I/Q) modulator. With proper photodetection configuration, four microwave frequency mixing functions are expediently reconfigured in our system: single-ended mixing, balanced mixing, I/Q mixing and image-reject mixing. The employed crucial optical modulator is a dual-polarization dual-parallel Mach–Zehnder modulator (DPol-DPMZM) driven by in-phase and quadrature intermediate frequency (IF) and local oscillator (LO) signals. The generation and switching of frequency down- and up-conversion and different mixing functions depend on the main direct current (DC) biases of the two sub-DPMZMs, instead of using additional optical hybrid, wavelength division multiplexer (WDM) or two pairs of cascaded polarization controller (PC) and polarization beam splitter (PBS) in previous reports. Our demonstrated experiment shows that the reconfigurable frequency mixer has high mixing spur suppression, frequency tunability, and image rejection ratio (IRR) of over 35 dB. The proposed simple and multifunctional structure may bring a broad potential application in radar and communication systems.

Filter-Free Photonic Microwave I/Q Modulator for Reconfigurable Frequency Mixing

In this paper, recent progresses on all-optical signal processing based on semiconductor lasers under lasing conditions are reviewed, such as integrator and differentiator.

Ninghua Zhu

Papers

Fully characterization of an active optical filter based on an equivalent-phase-shifted DFB-SOA

Dual-pattern communication system using DBR laser in the intensity-modulation and direct-detection system

Filter-Free Photonic Microwave I/Q Modulator for Reconfigurable Frequency Mixing

All-optical signal processing based on semiconductor lasers under lasing condition

Multiband Chirp Microwave Signals Generator With Multiple Chirp Rates Based on Photonic Approach