Quantitative protein sensing with germanium THz-antennas manufactured using CMOS processes

The development of a CMOS manufactured THz sensing platform could enable the integration of state-of-the-art sensing principles with the mixed signal electronics ecosystem in small footprint, low-cost devices. To this aim, in this work we demonstrate a label-free protein sensing platform using highly doped germanium plasmonic antennas realized on Si and SOI substrates and operating in the THz range of the electromagnetic spectrum. The antenna response to different concentrations of BSA shows in both cases a linear response with saturation above 20 mg/mL. Ge antennas on SOI substrates feature a two-fold sensitivity as compared to conventional Si substrates, reaching a value of 6 GHz/(mg/mL), which is four-fold what reported using metal-based metamaterials. We believe that this result could pave the way to a low-cost lab-on-a-chip biosensing platform

Silicon-Based Terahertz Circuits and Systems

The Terahertz frequency range, often referred to as the `Terahertz' gap, lies wedged between microwave at the lower end and infrared at the higher end of the spectrum, occupying frequencies between 0.3-3.0 THz. For a long time, applications in THz frequencies had been limited to astronomy and chemical sciences, but with advancement in THz technology in recent years, it has shown great promise in a wide range of applications ranging from disease diagnostics, non-invasive early skin cancer detection, label-free DNA sequencing to security screening for concealed weapons and contraband detection, global environmental monitoring, nondestructive quality control and ultra-fast wireless communication. Up until recently, the terahertz frequency range has been mostly addressed by high mobility compound III-V processes, expensive nonlinear optics, or cryogenically cooled quantum cascade lasers. A low cost, room temperature alternative can enable the development of such a wide array of applications, not currently accessible due to cost and size limitations. In this thesis, we will discuss our approach towards development of integrated terahertz technology in silicon-based processes. In the spirit of academic research, we will address frequencies close to 0.3 THz as 'Terahertz'. In this thesis, we address both fronts of integrated THz systems in silicon: THz power generation, radiation and transmitter systems, and THz signal detection and receiver systems. THz power generation in silicon-based integrated circuit technology is challenging due to lower carrier mobility, lower cut-o frequencies compared to compound III-V processes, lower breakdown voltages and lossy passives. Radiation from silicon chip is also challenging due to lossy substrates and high dielectric constant of silicon. In this work, we propose novel ways of combining circuit and electromagnetic techniques in a holistic design approach, which can overcome limitations of conventional block-by-block or partitioned design methodology, in order to generate high-frequency signals above the classical definition of cut-off frequencies (ƒt/ƒmax). We demonstrate this design philosophy in an active electromagnetic structure, which we call Distributed Active Radiator. It is inspired by an Inverse Maxwellian approach, where instead of using classical circuit and electromagnetic blocks to generate and radiate THz frequencies, we formulate surface (metal) currents in silicon chip for a desired THz field prole and develop active means of controlling different harmonic currents to perform signal generation, frequency multiplication, radiation and lossless filtering, simultaneously in a compact footprint. By removing the articial boundaries between circuits, electromagnetics and antenna, we open ourselves to a broader design space. This enabled us to demonstrate the rst 1 mW Eective-isotropic-radiated-power(EIRP) THz (0.29 THz) source in CMOS with total radiated power being three orders of magnitude more than previously demonstrated. We also proposed a near-field synchronization mechanism, which is a scalable method of realizing large arrays of synchronized autonomous radiating sources in silicon. We also demonstrate the first THz CMOS array with digitally controlled beam-scanning in 2D space with radiated output EIRP of nearly 10 mW at 0.28 THz. On the receiver side, we use a similar electronics and electromagnetics co-design approach to realize a 4x4 pixel integrated silicon Terahertz camera demonstrating to the best of our knowledge, the most sensitive silicon THz detector array without using post-processing, silicon lens or high-resistivity substrate options (NEP &lt; 10 pW &#8730; Hz at 0.26 THz). We put the 16 pixel silicon THz camera together with the CMOS DAR THz power generation arrays and demonstrated, for the first time, an all silicon THz imaging system with a CMOS source.</p

A New Silicon-Based Dielectric Waveguide Technology for Millimeter-Wave/Terahertz Devices and Integrated Systems

In recent decades, the millimeter-Wave (mmWave)/THz band has attracted great attention in the research community. The Terahertz frequency band runs from approximately 300 GHz to 3 THz, an incredible 2700 GHz of bandwidth. The Terahertz frequency range has traditionally been considered as the RF "no man's land", between electronic and optical technologies. Many efforts have been made to extend existing active and passive devices to take advantage of these higher frequencies. The development of a universal technology for integrating various functionalities in the THz region is the ultimate goal of many researchers. The primary focus of this research is to develop a novel silicon waveguide-based technology for implementing various structures and devices in the mmWave and THz range of frequencies. The structures introduced in this study are designed based on High Resistivity Silicon (HRS). Two technologies are developed and investigated at the Centre for Intelligent Antenna and Radio Systems (CIARS): Silicon-On-Glass (SOG) and Silicon Image Guide (SIG) technologies. The proposed technologies provide a low-cost, highly efficient, and integratable platform for realization a variety of mmWave/THz systems suitable for various applications such as sensing, communication, and imaging. A comprehensive study is conducted for functionality and error analysis of the proposed technologies. Also, a vast range of passive structures such as bends, dividers, and couplers are designed, fabricated and successfully tested with desired performance at the mmWave range of frequencies. Additionally, three types of dielectric waveguide antennas are designed and optimized: parasitic tapered antenna, groove grating antenna, and strip grating antenna. Another focus of this thesis is to investigate the behavior of resonance structures, operating based on Whispering Gallery Modes (WGMs). The WG mode is a special type of high order mode of a circular shaped resonator, and offers very unique properties, which make it very suitable for sensing applications. In this research, an efficient algorithm is developed for analyzing the WGM resonators. Then, the proposed HRS platforms are used for implementing various WGM resonance configurations. The introduced WGM structures are employed for two major applications: DNA sensing and resonance tuning. The results for DNA testing are quite impressive in being able to distinguish between different kinds of DNA. To demonstrate the usefulness of the developed HRS structures, a number of complex systems including, a Butler matrix network, a finger-shaped phase shifter, and tunable WGM resonance structures are designed, optimized, and realized in this report. As part of this research, a novel Microwave-Photonic idea is proposed for sensing purposes. The core of the system is based on the WGM resonance structures implemented on the HRS platforms. The proposed system is tested and promising results are achieved.4 month

Terahertz (THz) Waveguiding Architecture Featuring Doubly-Corrugated Spoofed Surface Plasmon Polariton (DC-SSPP): Theory and Applications in Micro-Electronics and Sensing

Terahertz (10^12 Hz) has long been considered a missing link between microwave and optical IR spectra. This frequency range has attracted enormous research attentions in recent years, with ever-growing anticipation for its applications in remote sensing, molecular spectroscopy, signal processing and next-generation high-speed electronics. However, its development has been seriously hindered by the lack of waveguiding and manipulating architectures that could support the propagation of THz radiations without excessive signal distortion and power loss. Facing this challenge, this work exploits the spoofed surface plasmon polariton (SSPP) mode of the THz oscillation and introduces the doubly corrugated SSPP (DC-SSPP) architecture to support sub-wavelength, low-dispersion THz transmission. DC-SSPP displays unique bandgap structure, which can be effectively modulated via structural and material variables. These unequaled properties make DC-SSPP the ideal solution to support not only signal transmission but also THz sensing and THz-electronics applications. In this thesis, theoretical analysis is carried out to thoroughly characterize the THz propagation, field distribution and transmission band structures in the novel architecture. Via numerical approximation and finite element simulations, design variations of the DC-SSPP are further studied and optimized to fulfill application-specific requirements. We demonstrate effective DNA sensing by adopting the Mach-Zehnder interferometer (MZI) or waveguide-cavity-waveguide insertions, which showed detectability with minuscule sample size even in the aqueous environment. We manifest high-speed analog-to-digital conversion via a combination of MZI DC-SSPP with nonlinear, partial-coupling detector arrays. Full characterization of the proposed ADC is carried out where high operation speed, small signal distortion, and great output linearity is shown. Also included in this work is a detailed review of the THz emitters and detectors, which are indispensable constituents of the THz system discussed herein. The future of the DC-SSPP in building THz bio-computing and THz digital circuits, considered as the next step of this research work, is also explored and demonstrated with the novel concept of directed logic network.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/137130/1/xuzhao_1.pd

Characterization of Optimized Si-MOSFETs for Terahertz Detection

Research into components needed to utilize the THz region of the electromagnetic spectrum has recently gained more attention due to advances in semiconductor technology and materials science. These advances have led to the desire of create CMOS focal plane arrays (FPA) for THz imaging in a range of applications such as astronomy, security, earth science, industry, and communications. Si-MOSFETs are being investigated as the sensing node in THz FPAs due to their ability to detect THz and their ease of integration into the CMOS process facilitating the fabrication of large format arrays. To investigate the performance of devices fabricated at a commercial foundry, a test chip containing MOSFETs with appropriately sized dipole bowtie antennae were fabricated using a 0.35 micron CMOS process. A number of fabrication parameters were varied including both MOSFET geometry and antenna design to investigate optimizing detection for the 200 GHz atmospheric window. To test these devices an experimental low noise setup comprising of a lock-in amplifier, low noise current pre-amplifier, and various low noise techniques has been assembled. Different biasing conditions and temperature were used to analyze the mechanisms of detection and find the best operating parameters. The devices that implemented a 2 µm source extension, and antennae attached to the source and gate region yielded the largest response to 200 GHz incident radiation. The peak THz response varied little between room temperature and when cooled to 130K. Responsivities as high as 4.5 mA/W were measured and NEP as low as 6 nW/√Hz were achieved at room temperature. These results show agreement with other works regarding THz response to temperature and different biasing conditions

Science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems

We present the science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems, targeting an evolution in technology, that might lead to impacts and benefits reaching into most areas of society. This roadmap was developed within the framework of the European Graphene Flagship and outlines the main targets and research areas as best understood at the start of this ambitious project. We provide an overview of the key aspects of graphene and related materials (GRMs), ranging from fundamental research challenges to a variety of applications in a large number of sectors, highlighting the steps necessary to take GRMs from a state of raw potential to a point where they might revolutionize multiple industries. We also define an extensive list of acronyms in an effort to standardize the nomenclature in this emerging field.Peer ReviewedPostprint (published version