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Author: Amir Ali Tavallaee
Publisher:
ISBN:
Category :
Languages : en
Pages : 146
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Book Description
Terahertz quantum-cascade (QC) lasers operating at 0.6 − 5 THz (λ ∼ 60 − 500 μm) are poised to become the dominant solid-state sources of continuous-wave (cw) far-infrared radiation enabling applications in terahertz spectroscopy, imaging, and sensing. QC-lasers are the longest wavelength semiconductor laser sources in which terahertz gain is obtained from electronic intersubband radiative transitions in GaAs/AlGaAs heterostructure quantum wells. Since their invention in 2001, rapid development has enabled demonstration of cw powers greater than 100 mW. However, challenges still remain in the areas of operating temperature, laser efficiency and power, and beam quality to name a few. The highest-temperature operation of terahertz quantum-cascade lasers (200 K pulsed, 117 K cw) depends on the use of a low-loss "metal-metal" waveguide where the active gain material is sandwiched between two metal cladding layers; a technique similar, in concept, to microstrip transmission line technology at microwave frequencies. Due to the subwavelength transverse dimensions of the metal-metal waveguide, however, obtaining a directive beam pattern and efficient out-coupling of THz power is non-trivial. This thesis reports the demonstration of a one-dimensional waveguide for terahertz quantum-cascade lasers that acts as a leaky-wave antenna and tailors laser radiation in one dimension to a directional beam. This scheme adapts microwave transmission-line metamaterial concepts to a planar structure realized in terahertz metal-metal waveguide technology and is fundamentally different from distributed feedback/photonic crystal structures that work based on Bragg scattering of propagating modes. The leaky-wave metamaterial antenna operates based on a propagating mode with an effective phase index smaller than unity such that it radiates in the surface direction via a leaky-wave mechanism. Surface emission (∼ 40◦ from broadside) with a single directive beam (FWHM ∼ 15◦) at 2.74 THz was demonstrated from terahertz QC-lasers with leaky-wave coupler antennas which exhibited slope efficiencies ∼ 4 times greater than conventional Fabry-Perot metal-metal waveguides. Using this technique the first demonstration of beam scanning for a terahertz QC-laser was reported (from 35◦ − 60◦) as the emission frequency varied from 2.65 − 2.81 THz. Towards the bigger goal of realizing an active terahertz metamaterial to ultimately develop "zero-index" terahertz quantum-cascade lasers immune to spatial hole burning, or "negative-index" metamaterials for superresolution terahertz imaging, a composite right-/left-handed transmission-line metamaterial based upon subwavelength metal waveguide loaded with terahertz QC material was demonstrated. Due to the addition of distributed series capacitors (realized by introducing gaps in top metallization) and shunt inductors (realized by operating in the higher-order lateral mode of the waveguide), the transmission-line metamaterial exhibits left-handed (backward waves or negative index) leaky-wave propagation from 2.3 − 2.45 THz in addition to the conventional right-handed leaky-wave behavior (from 2.6 − 3.0 THz).
Author: Amir Ali Tavallaee
Publisher:
ISBN:
Category :
Languages : en
Pages : 146
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Book Description
Terahertz quantum-cascade (QC) lasers operating at 0.6 − 5 THz (λ ∼ 60 − 500 μm) are poised to become the dominant solid-state sources of continuous-wave (cw) far-infrared radiation enabling applications in terahertz spectroscopy, imaging, and sensing. QC-lasers are the longest wavelength semiconductor laser sources in which terahertz gain is obtained from electronic intersubband radiative transitions in GaAs/AlGaAs heterostructure quantum wells. Since their invention in 2001, rapid development has enabled demonstration of cw powers greater than 100 mW. However, challenges still remain in the areas of operating temperature, laser efficiency and power, and beam quality to name a few. The highest-temperature operation of terahertz quantum-cascade lasers (200 K pulsed, 117 K cw) depends on the use of a low-loss "metal-metal" waveguide where the active gain material is sandwiched between two metal cladding layers; a technique similar, in concept, to microstrip transmission line technology at microwave frequencies. Due to the subwavelength transverse dimensions of the metal-metal waveguide, however, obtaining a directive beam pattern and efficient out-coupling of THz power is non-trivial. This thesis reports the demonstration of a one-dimensional waveguide for terahertz quantum-cascade lasers that acts as a leaky-wave antenna and tailors laser radiation in one dimension to a directional beam. This scheme adapts microwave transmission-line metamaterial concepts to a planar structure realized in terahertz metal-metal waveguide technology and is fundamentally different from distributed feedback/photonic crystal structures that work based on Bragg scattering of propagating modes. The leaky-wave metamaterial antenna operates based on a propagating mode with an effective phase index smaller than unity such that it radiates in the surface direction via a leaky-wave mechanism. Surface emission (∼ 40◦ from broadside) with a single directive beam (FWHM ∼ 15◦) at 2.74 THz was demonstrated from terahertz QC-lasers with leaky-wave coupler antennas which exhibited slope efficiencies ∼ 4 times greater than conventional Fabry-Perot metal-metal waveguides. Using this technique the first demonstration of beam scanning for a terahertz QC-laser was reported (from 35◦ − 60◦) as the emission frequency varied from 2.65 − 2.81 THz. Towards the bigger goal of realizing an active terahertz metamaterial to ultimately develop "zero-index" terahertz quantum-cascade lasers immune to spatial hole burning, or "negative-index" metamaterials for superresolution terahertz imaging, a composite right-/left-handed transmission-line metamaterial based upon subwavelength metal waveguide loaded with terahertz QC material was demonstrated. Due to the addition of distributed series capacitors (realized by introducing gaps in top metallization) and shunt inductors (realized by operating in the higher-order lateral mode of the waveguide), the transmission-line metamaterial exhibits left-handed (backward waves or negative index) leaky-wave propagation from 2.3 − 2.45 THz in addition to the conventional right-handed leaky-wave behavior (from 2.6 − 3.0 THz).
Author: Christopher Curwen
Publisher:
ISBN:
Category :
Languages : en
Pages : 96
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Book Description
Terahertz quantum cascade lasers are compact, coherent sources of THz power that have drawn considerable attention in the past 10-15 years for their potential use in THz applications such as spectroscopy and imaging. One of the key developments required to further the usefulness of THz QCLs is robust, broadband tenability. In this work, I describe a new technique for tuning THz QCLs by incorporation MEMS fixed-fixed and fixed-free cantilever beams into a THz transmission line metamaterial resonant cavity. An analytic model for such THz transmission line metamaterials is demonstrated using transmission line theory and is supported by 2-D and 3-D finite element simulations. Proposed processes for fabricating tunable THz transmission line metamaterials are outlined and current progress on actual fabrication and device testing is reported.
Author: Philip Wing-Chun Hon
Publisher:
ISBN:
Category :
Languages : en
Pages : 199
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Book Description
Generation and detection of microwave radiation is done with electronic systems where the underyling processes involve oscillating free charges (such as on an antenna or within a transistor or diode). On the higher energy side of the spectrum, generation and detection of near infrared and visible radiation is achieved via quantum transitions with emission wavelengths that are dictated by the material. Solutions moving up towards the THz regime using microwave based solutions are limited by carrier transit time and RC time-constant limitations. Techniques and solutions moving down toward the THz regime using photonic techniques have emission wavelengths naturally limited by the band gap of the material. However, THz quantum-cascade (QC) lasers, which are an extension of photonic concepts to lower energies, have artificially engineered energy levels and hence emission wavelengths. THz QC-lasers have been demonstrated to operate at frequencies between 1.2 and 5.0 THz and the best high-temperature operation is based upon the metal-metal (MM) waveguide configuration, in which the multiple-quantum well active region is sandwiched between two metal cladding layers, typically separated by 2-10 [mu]m. Soon after the demonstration of MM waveguide QC-lasers, it was recognized that the beam pattern from a conventional cleaved-facet Fabry Pérot (FP) ridge cavity produced a highly divergent beam pattern, characterized by concentric rings in the far field. This thesis presents work on a new approach to tailor the beam pattern of THz MM waveguide QC-devices. Namely, dispersion engineering using metamaterials based on the composite right/left-handed (CRLH) transmission line formalism is adapted to the MM waveguide configuration to realize an entirely new class of devices. Dispersion, radiative loss, and radiation patterns are presented for many newly designed 1-D and 2-D THz QC transmission line metamaterial designs. The first ever active 1-D THz QC transmisison line metamaterial is experimentally characterized and its radiation pattern and polarization closely match theoretical and full-wave finite element method (FEM) simulated predictions. Proven microwave techniques such as circuit, antenna cavity modeling and array factor theory are used to understand the radiative properties of conventional THz QC-lasers. We predict far-field beam patterns and polarizations, approximate cavity quality factors, and associate these properties with individual surfaces or structures of the device. The analysis technique is also applied to the project's 1-D and 2-D THz CRLH QC-devices yielding qualitative agreement with experiments. The first THz design, analysis and experimental verification of a metasur face comprised of an array of passive THz QC transmission lines is presented. By using the cavity model, array factor, circuit and electromagnetic theory a surface impedance model is developed to characterize the metasurface. The surface impedance model reveals waveguide mode dependent radiative coupling with the light line and capacitve/inductive surface impedance. Polarization dependent angle-resolved Fourier transform infrared reflection spectroscopy measurements match the model and full-wave FEM predictions, further assisting the understanding of such devices. To address the broader goal of a directive and scalable THz QC-device, thefeasibility of a 2-D metamaterial inspired QC-laser and an active reflectarray is considered. Finally, preliminary work on a technology enabling active metasurface reflector for a QC vertical external cavity surface emitting laser is discussed.
Author: Saroj Rout
Publisher: Springer
ISBN: 3319522191
Category : Technology & Engineering
Languages : en
Pages : 126
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Book Description
This book covers the theoretical background, experimental methods and implementation details to engineer for communication and imaging application, terahertz devices using metamaterials, in mainstream semiconductor foundry processes. This book will provide engineers and physicists an authoritative reference to construct such devices with minimal background. The authors describe the design and construction of electromagnetic (EM) devices for terahertz frequencies (108-1010 cycles/sec) using artificial materials that are a fraction of the wavelength of the incident EM wave, resulting in an effective electric and magnetic properties (permittivity and permeability) that are unavailable in natural materials.
Author: Ho-Jin Song
Publisher: CRC Press
ISBN: 9814613096
Category : Science
Languages : en
Pages : 606
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Book Description
Terahertz waves, which lie in the frequency range of 0.1-10 THz, have long been investigated in a few limited fields, such as astronomy, because of a lack of devices for their generation and detection. Several technical breakthroughs made over the last couple of decades now allow us to radiate and detect terahertz waves more easily, which has trigg
Author: Sudipta Das
Publisher: Springer Nature
ISBN: 981194105X
Category : Science
Languages : en
Pages : 304
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Book Description
This book is aimed to bring the emerging application aspects of THz technology and various modules used for its successful realization. It gathers scientific technological novelties and advancements already developed or under development in the academic and research communities. This book focuses on recent advances, different research issues in terahertz technology and would also seek out theoretical, methodological, well-established and validated empirical work dealing with these different topics. In particular, this textbook covers design considerations and current trends of THz antennas and antenna arrays to deal with the transmission and reception of THz EM waves. It also presents a discussion on metamaterial structures, meta-surfaces, and absorbers to be used for some kind of sensing and detection applications. Furthermore, it reports on THz wireless communication aspects, 6G network issues and challenges, advantages and disadvantages, generation and detection of THz waves, Signal and Communication Processing for THz communication, reconfigurable low-noise amplifier (LNA) design, III-Nitride HEMTs for THz Applications, photonic crystal fiber for sensing applications, THz Design Variable Estimation by Deep Optimization, and THz Imaging issues. Once the readers finish studying this book then they will learn about the importance of THz technology, advancement in the field, applications, THz modules like antennas, MIMO and DRAs, communication aspects, LNAs, generation of THz waves, etc and future scope. It also leads to enhancement in their knowledge in THz technology, gives a platform to future technology and novel applications realization.
Author: Hua Wang
Publisher: Academic Press
ISBN: 0124095224
Category : Technology & Engineering
Languages : en
Pages : 578
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Book Description
RF and mm-Wave Power Generation in Silicon presents the challenges and solutions of designing power amplifiers at RF and mm-Wave frequencies in a silicon-based process technology. It covers practical power amplifier design methodologies, energy- and spectrum-efficient power amplifier design examples in the RF frequency for cellular and wireless connectivity applications, and power amplifier and power generation designs for enabling new communication and sensing applications in the mm-Wave and THz frequencies. With this book you will learn: - Power amplifier design fundamentals and methodologies - Latest advances in silicon-based RF power amplifier architectures and designs and their integration in wireless communication systems - State-of-the-art mm-Wave/THz power amplifier and power generation circuits and systems in silicon - Extensive coverage from fundamentals to advanced design topics, focusing on various layers of abstraction: from device modeling and circuit design strategy to advanced digital and mixed-signal architectures for highly efficient and linear power amplifiers - New architectures for power amplifiers in the cellar and wireless connectivity covering detailed design methodologies and state-of-the-art performances - Detailed design techniques, trade-off analysis and design examples for efficiency enhancement at power back-off and linear amplification for spectrally-efficient non-constant envelope modulations - Extensive coverage of mm-Wave power-generation techniques from the early days of the 60 GHz research to current state-of the-art reconfigurable, digital mm-Wave PA architectures - Detailed analysis of power generation challenges in the higher mm-Wave and THz frequencies and novel technical solutions for a wide range for potential applications, including ultrafast wireless communication to sensing, imaging and spectroscopy - Contributions from the world-class experts from both academia and industry
Author: Richard A. Klemm
Publisher: Oxford University Press
ISBN: 0199593310
Category : Science
Languages : en
Pages : 574
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Book Description
This book provides a comparison of the different chemical structures, normal state properties, and simplest superconducting properties of all known classes of layered superconductors. It introduces the three phenomenological models used to describe such systems, and will guide young researchers hoping to produce a room-temperature superconductor.
Author: D Saeedkia
Publisher: Elsevier
ISBN: 0857096494
Category : Technology & Engineering
Languages : en
Pages : 684
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Book Description
The recent development of easy-to-use sources and detectors of terahertz radiation has enabled growth in applications of terahertz (Thz) imaging and sensing. This vastly adaptable technology offers great potential across a wide range of areas, and the Handbook of terahertz technology for imaging, sensing and communications explores the fundamental principles, important developments and key applications emerging in this exciting field.Part one provides an authoritative introduction to the fundamentals of terahertz technology for imaging, sensing and communications. The generation, detection and emission of waves are discussed alongside fundamental aspects of surface plasmon polaritons, terahertz near-field imaging and sensing, room temperature terahertz detectors and terahertz wireless communications. Part two goes on to discuss recent progress and such novel techniques in terahertz technology as terahertz bio-sensing, array imagers, and resonant field enhancement of terahertz waves. Fiber-coupled time-domain spectroscopy systems (THz-TDS), terahertz photomixer systems, terahertz nanotechnology, frequency metrology and semiconductor material development for terahertz applications are all reviewed. Finally, applications of terahertz technology are explored in part three, including applications in tomographic imaging and material spectroscopy, art conservation, and the aerospace, wood products, semiconductor and pharmaceutical industries.With its distinguished editor and international team of expert contributors, the Handbook of terahertz technology for imaging, sensing and communications is an authoritative guide to the field for laser engineers, manufacturers of sensing devices and imaging equipment, security companies, the military, professionals working in process monitoring, and academics interested in this field. - Examines techniques for the generation and detection of terahertz waves - Discusses material development for terahertz applications - Explores applications in tomographic imaging, art conservation and the pharmaceutical and aerospace industries
Author: Ricardo Marqués
Publisher: John Wiley & Sons
ISBN: 1118211561
Category : Technology & Engineering
Languages : en
Pages : 274
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Book Description
The first general textbook to offer a complete overview of metamaterial theory and its microwave applications Metamaterials with Negative Parameters represents the only unified treatment of metamaterials available in one convenient book. Devoted mainly to metamaterials that can be characterized by a negative effective permittivity and/or permeability, the book includes a wide overview of the most important topics, scientific fundamentals, and technical applications of metamaterials. Chapter coverage includes: the electrodynamics of left-handed media, synthesis of bulk metamaterials, synthesis of metamaterials in planar technology, microwave applications of metamaterial concepts, and advanced and related topics, including SRR- and CSRR-based admittance surfaces, magneto- and electro-inductive waves, and sub-diffraction imaging devices. A list of problems and references is included at the end of each chapter, and a bibliography offers a complete, up-to-daterepresentation of the current state of the art in metamaterials. Geared toward students and professionals alike, Metamaterials with Negative Parameters is an ideal textbook for postgraduate courses and also serves as a valuable introductory reference for scientists and RF/microwave engineers.
