Terahertz generation mechanism in nano-grating electrode photomixers on Fe-doped InGaAsP

We report the generation mechanism associated with nano-grating electrode photomixers fabricated on Fe-doped InGaAsP substrates. Two different emitter designs incorporating nano-gratings coupled to the same broadband antenna were characterized in a continuous-wave terahertz (THz) frequency system employing telecommunications wavelength lasers for generation and coherent detection. The current-voltage characteristics and THz emission bandwidth of the emitters is compared for different bias polarities and optical polarisations. The THz output from the emitters is also mapped as a function of the position of the laser excitation spot for both continuous-wave and pulsed excitation. This mapping, together with full-wave simulations of the structures, confirms the generation mechanism to be due to an enhanced optical electric field at the grating tips resulting in increased optical absorption, coinciding with a concentration of the electrostatic field

Photonic-Enabled Microwave and Terahertz Communication Systems

Abstract: An optical heterodyne technique for generating millimetre-wave and THz carriers with high spectral purity and low phase noise is described, for application to Gb/s wireless communications systems. Progress on key integrated optical components is reported. Introduction Microwave photonics research [1] has found applications in areas as diverse as electronic warfare and medical imaging, and the development of wireless-over-fibre systems for distribution of cellular radio and other wireless signals within large buildings and other areas where coverage from conventional hill-top sites is poor, has proved to be of considerable commercial importance, with sales of systems reaching some $250 m annually. Now, with wireless local area networks (LANs) ubiquitous and demand for higher wireless transmission rates using IEEE 802.16 and similar standards growing, new potential applications for photonics in wireless communications are emerging, to generate, modulate and detect signals at higher carrier frequencies (>60 GHz) that can support Gb/s data rate

The 2017 Terahertz Science and Technology Roadmap

Science and technologies based on terahertz frequency electromagnetic radiation (100GHz-30THz) have developed rapidly over the last 30 years. For most of the 20th century, terahertz radiation, then referred to as sub-millimeter wave or far-infrared radiation, was mainly utilized by astronomers and some spectroscopists. Following the development of laser based terahertz time-domain spectroscopy in the 1980s and 1990s the field of THz science and technology expanded rapidly, to the extent that it now touches many areas from fundamental science to “real world” applications. For example THz radiation is being used to optimize materials for new solar cells, and may also be a key technology for the next generation of airport security scanners. While the field was emerging it was possible to keep track of all new developments, however now the field has grown so much that it is increasingly difficult to follow the diverse range of new discoveries and applications that are appearing. At this point in time, when the field of THz science and technology is moving from an emerging to a more established and interdisciplinary field, it is apt to present a roadmap to help identify the breadth and future directions of the field. The aim of this roadmap is to present a snapshot of the present state of THz science and technology in 2016, and provide an opinion on the challenges and opportunities that the future holds. To be able to achieve this aim, we have invited a group of international experts to write 17 sections that cover most of the key areas of THz Science and Technology. We hope that The 2016 Roadmap on THz Science and Technology will prove to be a useful resource by providing a wide ranging introduction to the capabilities of THz radiation for those outside or just entering the field as well as providing perspective and breadth for those who are well established. We also feel that this review should serve as a useful guide for government and funding agencies

10 Gb/s noise suppression using an ion implanted waveguide saturable absorber

Noise suppression of 3dB per pass is demonstrated using a top-implanted passive InGaAsP/InGaAsP multiple quantum well ridge waveguide saturable absorber. The contrast ratio and recovery time are 3dB and ∼16ps respectively. © 2006 Optical Society of America

10-Gb/s All-Optical 2R Regeneration Using an MQW Fabry-Perot Saturable Absorber and a Nonlinear Fiber

An all-optical 2R regenerator that consists of an ion implanted InGaAsP multiple-quantum-well saturable absorber, a nonlinear fiber, and an optical filter is presented. Error-free 10-Gb/s transmission over 7000 km of standard fiber with an amplifier spacing of 80 km is demonstrated in a recirculating loop experiment.</p

10-Gb/s All-Optical 2R Regeneration Using an MQW Fabry-Perot Saturable Absorber and a Nonlinear Fiber

An all-optical 2R regenerator that consists of an ion implanted InGaAsP multiple-quantum-well saturable absorber, a nonlinear fiber, and an optical filter is presented. Error-free 10-Gb/s transmission over 7000 km of standard fiber with an amplifier spacing of 80 km is demonstrated in a recirculating loop experiment.</p

Neck Muscle and Head/Neck Kinematic Responses While Bracing Against the Steering Wheel During Front and Rear Impacts

Drivers often react to an impending collision by bracing against the steering wheel. The goal of the present study was to quantify the effect of bracing on neck muscle activity and head/torso kinematics during low-speed front and rear impacts. Eleven seated subjects (3F, 8 M) experienced multiple sled impacts (Delta v = 0.77 m/s; a(peak) = 19.9 m/s(2), Delta t = 65.5 ms) with their hands on the steering wheel in two conditions: relaxed and braced against the steering wheel. Electromyographic activity in eight neck muscles (sternohyoid, sternocleidomastoid, splenius capitis, semispinalis capitis, semispinalis cervicis, multifidus, levator scapulae, and trapezius) was recorded unilaterally with indwelling electrodes and normalized by maximum voluntary contraction (MVC) levels. Head and torso kinematics (linear acceleration, angular velocity, angular rotation, and retraction) were measured with sensors and motion tracking. Muscle and kinematic variables were compared between the relaxed and braced conditions using linear mixed models. We found that pre-impact bracing generated only small increases in the pre-impact muscle activity (&lt; 5% MVC) when compared to the relaxed condition. Pre-impact bracing did not increase peak neck muscle responses during the impacts; instead it reduced peak trapezius and multifidus muscle activity by about half during front impacts. Bracing led to widespread changes in the peak amplitude and timing of the torso and head kinematics that were not consistent with a simple stiffening of the head/neck/torso system. Instead pre-impact bracing served to couple the torso more rigidly to the seat while not necessarily coupling the head more rigidly to the torso