The tutorial will take place in Davis Hall 101 at UB North Campus or on Zoom link below.
Tutorial Session, Chair: Vladimir Mitin
Sessions and presenters are:
1:00 pm – 2:00 pm
Tutorial – 1
Michael Shur, Rensselaer Polytechnic Institute
Counterintuitive Physics of Terahertz Electronics.
Abstract: In typical electronic layers formed at semiconductor heterointerfaces, electron-electron collisions are so frequent that electrons form a two-dimensional viscous electronic fluid. (This is contrary to a popular belief that they form a two-dimensional electron gas.) The viscosity of this fluid in graphene at cryogenic temperatures is hundreds of times higher than the viscosity of honey. In conventional semiconductors at room temperature, viscosity is similar to glycerin viscosity – still very important, but not necessarily dominant. The electron transport in electronic (or hole) fluid was collision-dominated in most of the last century field effect transistors operating at room temperature. It is collision-dominated in modern Thin Film Transistors, but in more advanced transistors (such as MOSFETs used in iPhone 15 pro) the electron transport is ballistic or quasi-ballistic. Ballistic or quasi-ballistic electronic fluid supports the waves of electron density – called plasma waves that could resonate with impinging terahertz (THz) radiation and become unstable (amplifying or even generating THz radiation). At high intensities of impinging THz radiation, plasma waves get transformed into shock waves. Even more interesting is the physics of “plasmonic crystals” combining properties of a fluid and crystal. I will discuss “plasmonic boom” instabilities, the instabilities controlled by boundary conditions, and transit time instabilities in plasmonic crystals. These instabilities provide the mechanisms for generating sub-THz and THz radiation for 6G communications and multiple other applications of THz electronics. I will also present predictions and the first measured data on Tesla-range DC magnetic fields generated in circular plasmonic crystals by circularly polarized THz radiation, and explain recently observed switching from decay to transparency to amplification in graphene plasmonic crystals.
2:00 pm – 3:00 pm
Tutorial – 2
Taiichi Otsuji, Tohoku University
Plasmonic Terahertz Devices Using Graphene-Based 2D Materials
Abstract: Graphene has attracted considerable attention due to its massless and gapless energy spectrum. This lecture reviews recent advances in the research of plasmonic terahertz (THz) devices using graphene-based two-dimensional (2D) materials, particularly highlighting the THz sources and detectors for use in future 6G/7G THz wireless communications systems. Carrier-injection pumping of graphene can enable negative-dynamic conductivity in the terahertz (THz) range leading to new types of THz lasers. We developed a prototype of a graphene channel laser transistor, demonstrating broadband amplified spontaneous emission from 1 to 7.6 THz and weak single-mode lasing at 5.2 THz at 100K. To increase the operating temperature and lasing radiation intensity, we introduced a physics of the current-driven instability in graphene Dirac plasmons (GDPs), succeeding in tunable resonant THz amplification with the maximal gain of 9% at room temperature. The obtained gain was far beyond the well-known landmark level of the quantum mechanical limit of 2.3% when photons directly interact with electrons without excitation of graphene plasmons. A discovery of a new instability mechanisms of GDPs called Coulomb-drag instability as well as Zener-Klein-tunneling instability will also be introduced thanks to the strong viscous Dirac fermions of graphene carriers. In terms of THz detection, recently we experimentally demonstrated 100-Gbit/s-class fast and sensitive THz detection in a graphene-channel transistor utilizing current-driven plasmonic, photothermoelectric, and a new type of so-called three-dimensional rectification mechanisms. In the final part, future trends and prospects including graphene-based van der Waals heterostructures as well as active control of the parity and time-reversal symmetry are also addressed.
3:00 pm – 3:15 pm: Coffee Break
3:15 pm – 4:15 pm
Tutorial – 3
Andrei Sergeev, U.S. Army Research Laboratory
Counting of THz Photons based on Nanoscale Electron Heating
Abstract: Superconducting single-photon detectors (SSPDs) offer unprecedented sensitivity at THz wavelengths that contain information critical for the prediction of climate change and understanding of the origin of the Universe. SSPDs are the tool of choice for future Deep Space Optical Communications (Deep Space Network), Space-Ground Communications (Space-Ground Sensor Network), and medical imaging. SSPDs can be used to provide high-speed and energy-efficient transfer of big data from multiple sensors established at various network platforms, they also open new possibilities in LiDAR (Light Detection and Ranging) and 3D imaging (Depth imaging) to enhance sensing characteristics, including range, data acquisition duration, depth resolution, and illumination power. Current superconducting detectors are based on well-explored conventional superconductors. These materials provide good sensing performance, but the potential for further improvements has been exhausted. For breakthroughs in sensor performance and sensing capabilities, we must explore novel superconducting materials and novel sensing concepts. For this, we can leverage recent advances in photonics and atomic-layer-by-layer molecular beam epitaxy synthesis of high-Tc cuprate superconductors. Cuprate heterostructures (CHS) may offer high and tunable transition temperature, ultra-small electron heat capacity, ultrafast phonon heat removal, slow electron-phonon cooling, intense electron heating, low intrinsic noise, and strong coupling to the radiation, fast and reconfigurable out-diffusion electron cooling, and high scalability. CHSs present an excellent opportunity for developing next-generation SSPDs and enhancing active 3D imaging, including range, data acquisition duration, depth resolution, and illumination power. This talk will discuss electron heating in nanoscale superconductors, control of electron-phonon coupling by nanoscale disorder, material properties of traditional superconducting films and cuprate heterostructures, and optimal design of SSPDs for various applications. I will also present a history of R&D devoted to THz SSPDs, in particular innovative research at UB under the guidance of Professor Vladimir Mitin. Finally, I will discuss characteristics of current devices and evaluate performance of potential devices based on superconducting heterostructures.
https://buffalo.zoom.us/j/93565601922?pwd=QzVkMGNKT1hyM0hSdzBkMzhXeURVZz09
Room: 101, Bldg: Davis Hall, State University of NY at Buffalo, Amherst, New York, United States, 14260, Virtual: https://events.vtools.ieee.org/m/419860
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