Advances in Terahertz Source Technologies

"During the past several decades, tremendous progress has been made in terahertz (THz) science and technology. There is a continuing need to have terahertz waves ready for practical applications. Terahertz photonic and electronic devices are being readied to be employed in application systems such as communication links, satellite communications, radar, surveillance, hard/soft material heating, biomedical treatment, and biomedical diagnostics. This book focuses on the advances in terahertz source technologies both from photonics and electronics (solid-state and vacuum-state) points of view. Written in a noncomplicated language, the book will be useful for a broad spectrum of readers, including advanced undergraduate- and graduate-level students in electronics and photonics, researchers in various disciplines in physics, chemistry, biology, astronomy, and electrical engineering, system engineers in various industrial sectors, general readers, and those who are interested in the interaction between electromagnetic waves and matters and in the effects of electromagnetic waves on matters"-- Provided by publisher Cover Half Title Title Page Copyright Page Table of Contents Preface Part I: THz Photonic Sources Chapter 1: THz Optical Parametric Generators and Oscillators 1.1: Injection-Seeded THz-Wave Parametric Generation Pumped by Subnanosecond Near-Infrared Pulses 1.2: Highly Efficient THz-Wave Parametric Wavelength Conversion between Near-Infrared Light and THz Waves 1.3: Multi-Wavelength THz Parametric Generator 1.4: Rapidly Wavelength-Switchable THz Parametric Generator 1.5: Backward THz-Wave Parametric Oscillation Chapter 2: Terahertz Wave Emission with Photoconductive Antennas 2.1: Operation Principles of Photoconductive Antennas 2.2: Design Considerations of Photoconductive Antennas 2.2.1: Photoconductive Material 2.2.2: Antenna Structure 2.2.3: Pump Laser 2.2.4: Sub-bandgap excitation of LT-GaAs-based Photoconductive antennas 2.3: Plasmonics-Enhanced Photoconductive Antennas 2.3.1: PCAs Based on Plasmonic Light Concentrators 2.3.2: PCAs Based on Plasmonic Contact Electrodes 2.3.3: PCAs Based on Plasmonic Nanoantenna Arrays 2.3.4: PCAs Based on Plasmonic Nanocavities 2.4: Conclusion and Outlook Chapter 3: Optical Rectification–Based Sources 3.1: Phase Matching, Velocity Matching, Tilted Pulse Front 3.2: Semiconductor-Based Sources 3.2.1: Contact Grating 3.2.2: Multiphoton Absorption 3.3: Organic Crystal-Based Sources 3.4: Lithium Niobate–Based Sources 3.4.1: Limitations of TPF 3.4.2: New Designs 3.5: Dispersion of Refractive Index, Absorption and Nonlinear Coefficient 3.6: Models for THz Generation 3.7: Summary Chapter 4: Method of Terahertz Liquid Photonics 4.1: Background 4.2: Liquid for THz Source 4.3: THz Wave Emission under Single-Color Optical Excitation in a Thin Water Film 4.4: THz Wave Emission under the Excitation of Asymmetric Optical Fields 4.5: THz Emission from Waterlines 4.6: Summary of Results of THz Wave Generation from Liquid Water 4.6.1: Key Observations 4.6.2: Other Confirmations 4.7: THz Wave Generation from Liquid Metal 4.8: THz Wave Generation from Liquids with Nanoparticles 4.9: THz Wave Emission from Liquid Nitrogen 4.10: Density Singularity of Water at 4°C 4.11: Molecular Orientation and Alignment 4.12: Magnetic Fluids 4.13: Future Perspective 4.14: Summary Chapter 5: Photomixing THz Sources 5.1: Generation of CW THz Radiation Using Photomixing 5.1.1: Devices for Photomixing THz Sources and THz Radiation Powers 5.1.2: Generation of THz Radiation Using Superposed Two Single-Mode Laser Beams (Two-Beam Photomixing) 5.1.3: Generation of THz Radiation by Photomixing Using a Dual-Mode Laser 5.1.4: Generation of THz Radiation by Photomixing Using a Multimode Laser 5.2: Photomixing THz Sources Combined with Coherent Detection 5.2.1: Coherent Detection System Using Superposed Two Single-Mode Laser Beams 5.2.2: Cross-Correlation Spectroscopic System (CCS) 5.3: Stable CW THz Wave Generation and Detection Using Laser Chaos 5.3.1: Laser Chaos 5.3.1.1: Time evolution of variables 5.3.1.2: Classification of lasers 5.3.1.3: Effects of delayed feedback 5.3.2: Application of Laser Chaos to Generation of THz Radiations 5.3.2.1: Merits of LDs as an irradiation source for THz radiation generation 5.3.2.2: Optical spectra of laser chaos 5.3.2.3: Generated THz waves 5.3.2.4: Simple stabilization mechanism 5.3.2.5: Stability of optical beats in laser chaos 5.3.3: Further Challenges Chapter 6: Spintronic THz Emitters 6.1: Introduction 6.2: Spin-to-Charge Conversion Mechanism Responsible for THz Radiation 6.3: Experimental Detection of THz Emission 6.4: Strategies to Engineer Intensity and Bandwidth of THz Signal 6.4.1: Material Dependence 6.4.2: Thickness Dependence 6.4.3: Wavelength Dependence 6.4.4: Interface Dependence 6.4.5: Stack Geometry Dependence 6.5: Future Perspectives of THz STEs 6.6: Conclusion Chapter 7: Terahertz Frequency Comb 7.1: Introduction 7.2: Coherent Link of Frequency Using Frequency Comb 7.3: THz-Comb-Referenced Spectrum Analyzer 7.4: Optical-Comb-Referenced Frequency Synthesizer 7.5: Dual-THz-Comb Spectroscopy 7.6: Conclusions and Future Trends Part II: THz Solid-State Electronic Sources Chapter 8: High-Efficiency THz Oscillators 8.1: Introduction 8.1.1: Fundamental Oscillators 8.1.2: Harmonic Oscillators 8.2: Challenges 8.3: Design and Optimization Flow 8.4: Design Example 8.4.1: Optimization Target 8.4.2: Core Transistor Optimization 8.4.3: Transformer-Based Impedance Optimization 8.5: Conclusion Chapter 9: Resonant Tunneling Diode (RTD) THz Sources 9.1: Introduction 9.2: Characteristics of RTD Oscillators 9.2.1: Structure and Oscillation Principle 9.2.2: Toward High-Frequency and High-Power Oscillation 9.2.3: Functionality 9.3: Applications of RTD Oscillators 9.3.1: Wireless Communication 9.3.2: Imaging and Radar 9.3.3: Analytics 9.4: Summary Chapter 10: Plasmon-Based THz Oscillators 10.1: Introduction 10.2: Theory 10.2.1: Hydrodynamics of 2D Plasmons 10.2.2: Dyakonov–Shur Doppler-Shift-Type Instability 10.2.3: Ryzhii–Satou–Shur Electron-Transit-Type Instability 10.2.4: Cherenkov Plasmonic-Boom-Type Instability 10.2.5: Coupling between Plasmons and Photons 10.3: Experiments 10.3.1: AlGaN/GaN Single-Gate HEMT 10.3.2: InGaAs/InAlAs/InP Dual-Grating-Gate HEMT 10.3.3: Graphene-Channel Dual-Grating-Gate FET 10.4: Future Subjects and Prospects 10.5: Conclusion Chapter 11: Beamforming THz Transmitters 11.1: Introduction 11.2: THz Phase Shifters 11.2.1: Reflective-Type Phase Shifters (RTPS) 11.2.2: Switched-Type Phase Shifters (STPS) 11.2.3: Vector-Sum Phase Shifters (VSPS) 11.3: Integrated Beamforming THz Transmitters 11.3.1: 280 GHz CMOS Beamforming Array on Distributed Active Radiators 11.3.2: 320 GHz BiCMOS Beamforming Transmitter 11.3.3: 370–410 GHz CMOS Beamforming Transmitter Chapter 12: Solid-State THz Power Amplifiers 12.1: Introduction 12.2: THz Power Amplifier Fundamentals 12.2.1: Unit Cell Design 12.2.2: Power Combining Techniques 12.2.3: Power Supply Oscillations and Heat Effect 12.2.4: Technology Considerations 12.3: Design Examples 12.3.1: 140 GHz Power Amplifier 12.3.1.1: Unit cell design 12.3.1.2: Combiner design 12.3.1.3: Measurement results 12.3.2: 210 GHz Power Amplifier 12.3.3: 270 GHz Power Amplifier 12.3.4: 600 GHz Power Amplifier 12.3.4.1: Unit gain stage 12.3.4.2: Differential gain block 12.3.4.3: Measurement results Chapter 13: Terahertz Silicon On-Chip Antenna 13.1: Introduction 13.2: Si IC Technologies for on-Chip Antenna 13.3: Topside Radiating Antenna with Frontside Ground 13.3.1: Antenna Structure and Design Considerations 13.3.2: Design Examples 13.3.2.1: On-chip patch antenna 13.3.2.2: Slot antenna 13.3.2.3: Antenna with AMC 13.4: Topside Radiating Antenna with Backside Ground 13.4.1: Antenna Structure and Design Considerations 13.4.2: Design Examples 13.4.2.1: Slot-ring antenna 13.4.2.2: Dipole antenna 13.4.2.3: Patch antenna with DGS 13.4.2.4: Comb-shaped dipole with chip-integrated dielectric resonator 13.5: Backside Radiating on-Chip Antenna 13.5.1: Antenna Structure and Design Considerations 13.5.2: Design Examples 13.5.2.1: Backside radiating antenna with a lens 13.5.2.2: Backside radiating antenna without lens 13.6: Design Rules Related to Antenna Design Chapter 14: Package Technologies for THz Devices 14.1: Introduction 14.2: Issues in Package at THz Frequencies 14.2.1: Packaging Materials 14.2.2: Interconnections 14.2.3: Signal Interfaces 14.3: Metallic Waveguide Packages 14.4: LTCC Packages at THz Frequencies 14.5: Concept of Quasi-Optical THz Package Chapter 15: Semiconductor Technologies for THz Applications 15.1: Si CMOS Technology 15.1.1: Device Operation 15.1.2: Structural Variations 15.1.2.1: SOI MOSFET 15.1.2.2: FinFET and GAA FET 15.1.3: Performance Trend 15.2: SiGe HBT Technology 15.2.1: Device Operation 15.2.2: Performance Trend 15.3: III–V HEMT Technology 15.3.1: Device Operation 15.3.2: Performance Trend 15.4: III–V HBT Technology 15.4.1: Device Operation 15.4.2: Performance Trend Part III: THz Vacuum Electronic Sources Chapter 16: Development and Applications of THz Gyrotrons 16.1: Introduction 16.2: Development of THz Gyrotrons 16.3: THz Gyrotrons: New Concepts, Challenges, and Trends in Their Development 16.4: Some of the Most Prominent Applications of THz Gyrotrons 16.4.1: Controlled Thermonuclear Fusion 16.4.2: Materials Treatment 16.4.3: Advanced Spectroscopic Techniques 16.4.3.1: DNP-NMR spectroscopy 16.4.3.2: ESR spectroscopy 16.4.3.3: XDMR spectroscopy 16.4.3.4: Measuring the energy levels of positronium 16.4.3.5: Radioacoustic spectroscopy using gyrotron radiation 16.4.4: Plasma Physics and Localized Gas Discharges 16.4.5: Electron Cyclotron Resonance Ion Sources 16.4.6: Applications in Bioscience and Material Science Areas 16.5: Conclusions and Outlook Chapter 17: Extended-Interaction Klystrons 17.1: EIK Cavity 17.2: Beam-Wave Interaction in EIK 17.3: Gain 17.4: RF Power 17.5: Sheet-Beam EIKs 17.6: THz EIKs 17.7: Conclusions Chapter 18: THz Oscillators Based on Cherenkov, Smith–Purcell and Hybrid Radiation Effects 18.1: Introduction 18.2: Theory of Cherenkov and Smith–Purcell/Diffraction Radiation Effects 18.3: Principles of THz BWO Design and Challenges for Efficient Generation in the THz Range. The Clinotron Effect 18.3.1: Principle of the Clinotron 18.4: Mode Transformation in Oversized Circuits in the THz Range 18.4.1: Simulation and Experimental Results 18.5: Principles for Design of the THz Diffraction Radiation Oscillator 18.6: Excitation of THz Self-Oscillations in Resonant Systems Supporting Hybrid Bulk-Surface Modes: Cavity with Bieriodic Grating and Electromagnetic Mode Interaction 18.6.1: Feedback by the Backward Radiating Harmonic 18.6.2: Radiation Angle Is Normal to the Grating 18.6.3: Regime of Grazing Radiation Angle 18.6.4: Experimental Results 18.7: Conclusion Chapter 19: Folded Waveguide Traveling Wave Tube 19.1: Introduction 19.2: Theory and Algorithm 19.2.1: High-Frequency Characteristics 19.2.2: Theory of Beam-Wave Interaction 19.3: Improvement of High-Frequency Structure 19.3.1: Ridge/Groove-Loaded FW SWS 19.3.2: Metamaterial Structure Loaded FW SWS 19.3.3: Nonuniform-Unit FW SWS 19.3.4: Resonant Cavity Loaded FW-TWT 19.3.5: High-Order Harmonic Amplifier FWSWS 19.3.6: Multibeam/Sheet-Beam FW SWS 19.4: Electron Optical System 19.5: Fabrication Technology 19.5.1: EDM 19.5.2: CNC 19.5.3: DRIE 19.5.4: LIGA 19.5.5: Other Technologies 19.6: Performance of FW-TWT 19.7: Conclusion Chapter 20: Vacuum Nanoelectronics and Electron Emission Physics 20.1: Background 20.2: Emission Equations 20.2.1: Thermal Emission 20.2.2: Photoemission 20.2.3: Tunneling Emission 20.2.4: Gamow and Shape Factors 20.2.5: Field Emission 20.2.6: Beyond the Simple Models 20.3: Heating Effects in Field Emission 20.3.1: Simple Model 20.3.2: Heating of Wires and Nanotubes 20.4: Time Factors 20.4.1: Tunneling Time 20.4.2: Transit Time 20.5: Quadratic Barriers 20.6: Space Charge 20.6.1: Non-Planar Image Charge 20.6.2: Conical Emitters 20.6.3: Depletion Barrier 20.6.4: Shape Factors Including Image Charge 20.7: Concluding Remarks Chapter 21: Terahertz Free-Electron Laser 21.1: Historical Introduction 21.2: Theory 21.2.1: The Basis 21.2.1.1: Considerations about efficiency 21.2.2: Waveguide Operation and Dispersion Relations 21.3: The Source Survey 21.3.1: Undulator Based FELs 21.3.1.1: The ENEA THz Compact-FEL 21.3.1.2: Coherent spontaneous emission and energy-phase correlation 21.3.2: Cerenkov, Smith–Purcell and Other Devices 21.4: Gimmicks: Novel Schemes 21.4.1: Tailoring THz Radiation Properties 21.4.2: Techniques to Optimize FEL Performance in the THz Range 21.4.2.1: Wide-band emission 21.4.2.2: Buncher-emitter scheme Chapter 22: Cathode Technologies for Terahertz Source 22.1: Introduction 22.2: Emission Physics of Cathode 22.2.1: Fermi Level 22.2.2: Vacuum Level 22.2.3: Work Function 22.3: Classifications of Emission Mechanism 22.3.1: Thermionic Emission 22.3.2: Evolution of Thermionic Cathode 22.3.2.1: Modern dispenser cathode 22.4: Thermionic Cathode for Terahertz Devices 22.4.1: CPD Cathode 22.4.2: Nanoparticle-Based Cathode 22.5: Field Emitter Cathode for Terahertz Devices 22.5.1: Field Emission Theory 22.5.1.1: Calculation of supply function and transmission coefficient 22.6: Conclusions and Future Prospects Chapter 23: Microfabrication Technologies 23.1: Introduction 23.1.1: Purpose/Objectives 23.1.2: The State of Microfabrication Techniques 23.1.3: Scope of Chapter, Scales 23.2: Microfabrication Materials 23.2.1: Copper 23.2.1.1: Electronic grade oxygen-free copper 23.2.1.2: Cupronickel 23.2.1.3: Glidcop ® 23.2.1.4: Elkonite ® 23.2.2: Silver 23.2.3: Aluminum 23.2.4: Other Alloys 23.2.5: Lossy and Dielectric Materials 23.3: Machines and Techniques 23.3.1: Subtractive Methods 23.3.2: Additive Methods 23.3.2.1: Direct AM 23.3.2.2: Indirect AM 23.3.2.3: Inverse AM 23.3.3: Hybrid Manufacturing 23.3.4: Multi-Material Manufacturing 23.3.4.1: Micro-CNC 23.3.4.2: Electron beam AM 23.3.4.3: Laser powder bed fusion (L-PBF) 23.3.4.4: Binder jetting 23.3.4.5: Electrical discharge machining 23.3.4.6: Laser ablative machining (subtractive) 23.3.4.7: Lithography 23.3.4.8: Deep reactive ion etching 23.3.4.9: 3D photopolymer printing 23.3.5: Surface Treatments 23.4: Joining/Brazing 23.4.1: Brazing 23.4.2: Diffusion Bonding 23.4.3: Transient Liquid Phase Bonding 23.4.4: Laser welding 23.5: Recommendations and Application to THz Devices 23.6: Discussion, Conclusion, and Outlook Index