Compact solid-state sources of terahertz (THz) radiation are being sought for sensing, imaging, and spectroscopy applications across the physical and biological sciences. We demonstrate that coherent continuous-wave THz radiation of sizable power can be extracted from intrinsic Josephson junctions in the layered high-temperature superconductor Bi2Sr2CaCu2O8. In analogy to a laser cavity, the excitation of an electromagnetic cavity resonance inside the sample generates a macroscopic coherent state in which a large number of junctions are synchronized to oscillate in phase. The emission power is found to increase as the square of the number of junctions reaching values of 0.5 microwatt at frequencies up to 0.85 THz, and persists up to ∼50 kelvin. These results should stimulate the development of superconducting compact sources of THz radiation.

http://absimage.aps.org/image/MAR08/MWS_MAR08-2007-004672.pdf

Emission of Coherent THz-Radiation from Superconductors.

The field of terahertz integrated technology has undergone significant development in the past ten years. This has included work on different substrate technologies such as III–V semiconductors and silicon, work on field-effect transistor devices and heterojunction bipolar devices, and work on both fully electronic and hybrid electronic–photonic systems. While approaches in electronic and photonics can often seem distinct, techniques have blended in the terahertz frequency range and many emerging systems can be classified as photonics-inspired or hybrid. Here, we review the development of terahertz integrated electronic and hybrid electronic–photonic systems, examining, in particular, advances that deliver important functionalities for applications in communication, sensing and imaging. Many of the advances in integrated systems have emerged, not from improvements in single devices, but rather from new architectures that are multifunctional and reconfigurable and break the trade-offs of classical approaches to electronic system design. We thus focus on these approaches to capture the diversity of techniques and methodologies in the field. This Review Article examines the development of terahertz integrated electronic and hybrid electronic–photonic systems, considering, in particular, advances that deliver important functionalities for applications in communication, sensing and imaging.

Terahertz integrated electronic and hybrid electronic–photonic systems

Terahertz (THz) science and technology have greatly progressed over the past two decades to a point where the THz region of the electromagnetic spectrum is now a mature research area with many fundamental and practical applications. Furthermore, THz imaging is positioned to play a key role in many industrial applications, as THz technology is steadily shifting from university-grade instrumentation to commercial systems. In this context, the objective of this review is to discuss recent advances in THz imaging with an emphasis on the modalities that could enable real-time high-resolution imaging. To this end, we first discuss several key imaging modalities developed over the years: THz transmission, reflection, and conductivity imaging; THz pulsed imaging; THz computed tomography; and THz near-field imaging. Then, we discuss several enabling technologies for real-time THz imaging within the time-domain spectroscopy paradigm: fast optical delay lines, photoconductive antenna arrays, and electro-optic sampling with cameras. Next, we discuss the advances in THz cameras, particularly THz thermal cameras and THz field-effect transistor cameras. Finally, we overview the most recent techniques that enable fast THz imaging with single-pixel detectors: mechanical beam-steering, compressive sensing, spectral encoding, and fast Fourier optics. We believe that this critical and comprehensive review of enabling hardware, instrumentation, algorithms, and potential applications in real-time high-resolution THz imaging can serve a diverse community of fundamental and applied scientists.

Toward real-time terahertz imaging

The field of terahertz science and technology has been an active and thriving research area for several decades. However, the field has recently experienced an inflection point, as several exciting breakthroughs have enabled new opportunities for both fundamental and applied research. These events are reshaping the field, and will impact research directions for years to come. In this Perspective article, I discuss a few important examples: the development of methods to access nonlinear optical effects in the terahertz range; methods to probe nanoscale phenomena; and, the growing likelihood that terahertz technologies will be a critical player in future wireless networks. Here, a few examples of research in each of these areas are discussed, followed by some speculation about where these exciting breakthroughs may lead in the near future.

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Perspective: Terahertz science and technology

Add this article to private library Remove from private library Submit corrections to this record View record in the new ADS The book presents an introductory treatment of digital and analog communication systems with emphasis on digital systems. Attention is given to the following topics: systems and signal analysis, random signal theory, information and channel capacity, baseband data transmission, analog signal transmission, noise in analog communication systems, digital carrier modulation schemes, error control coding, and the digital transmission of analog signals. Bibtex entry for this abstract Preferred format for this abstract

Digital and analog communication systems

This paper presents a fully integrated direct-conversion quadrature transmitter and receiver chipset at 240 GHz. It is implemented in a 0.13- $\mu{\hbox{m}}$ SiGe bipolar-CMOS technology. A wideband frequency multiplier ( $\times$ 16) based local-oscillator (LO) signal source and a wideband on-chip antenna designed to be used with an external replaceable silicon lens makes this chipset suited for applications requiring fixed and tunable LO. The chipset is packaged in a low-cost FR4 printed circuit board resulting in a complete solution with compact form-factor. At 236 GHz, the effective-isotropic-radiated-power is 21.86 dBm and the minimum single-sideband noise figure is 15 dB. The usable RF bandwidth for this chipset is 65 GHz and the 6-dB bandwidth is 17 GHz. At the system level, we demonstrate a high data-rate communication system where an external modem is operated in its two IF-bandwidth modes (250 MHz and 1 GHz). For the quadrature phase-shift keying modulation scheme, the measured data rate is 2.73 Gb/s (modem 1-GHz IF) with bit-error rate of ${\hbox{10}}^{-9}$ for a 15-cm link. The estimated data rate over the 17-GHz RF bandwidth is, hence, 23.025 Gb/s. Also, higher order modulation schemes like 16 quadrature amplitude modulation (QAM) with a data rate of 0.677 Gb/s and 64-QAM with a data rate of 1.0154 Gb/s (modem 250-MHz IF) is demonstrated. A second application demonstrator is presented where the wide tunable RF bandwidth of the chipset is used for material characterization. It is used to characterize an FR4 material (DE104) over the 215–260-GHz range.

A Fully Integrated 240-GHz Direct-Conversion Quadrature Transmitter and Receiver Chipset in SiGe Technology

The design and measurement of active multiple-feed on-chip antennas realized in a SiGe seven metal layer backend process are presented for millimeter-wave applications. To prevent the excitation of surface waves, the principle of an integrated lens antenna (ILA) is used. In-antenna power-combining is realized by using a novel concept in which the outputs of two or more parallel differential amplifiers are directly combined in the radiating element itself. The proof-of-concept is shown by characterizing the antennas directly without the amplifiers being connected and by using adequate feeding networks capable of demonstrating high ILA bandwidths. Further, the power-splitting is realized through distributed transformer circuits, which offer high bandwidths at low losses. Different antennas are evaluated in order to attain reflection coefficients better than -10 dB over the entire frequency band of 200-320 GHz. Finally, the power-combining capabilities of such antennas are demonstrated by connecting a four-feed differential antenna to four single stage cascode amplifiers in parallel.

Active Multiple Feed On-Chip Antennas With Efficient In-Antenna Power Combining Operating at 200–320 GHz

This paper presents a 430 GHz source implemented in a 0.13-µm SiGe BiCMOS technology with f T /f max of 300 GHz/450 GHz. The source comprises a fundamental differential Colpitts cascode oscillator at 215 GHz driving a balanced common-collector doubler that utilizes inductive 2nd-harmonic feedback at the emitter output in order to boost the generated 2nd-harmonic current. The doubler is co-designed with a lens-coupled on-chip circular slot antenna providing the appropriate input impedance to the doubler output. In combination with a 3-mm diameter silicon-lens, the total peak radiated power is −6.3 dBm at a power dissipation of 165 mW. To the authors knowledge, the presented source shows the highest reported power for any silicon-based single-element radiator beyond 350 GHz.

A lens-integrated 430 GHz SiGe HBT source with up to −6.3 dBm radiated power

Despite its several applications, terahertz (THz) radiation has posed a particular challenge for hardware design. Several expensive and bulky laser or III-V semiconductor based solutions have been employed for THz systems. However, over the last decade, there has been a tremendous research into the design of THz integrated circuits in commercial silicon CMOS and SiGe HBT BiCMOS process technologies. Silicon based systems primarily benefit from the mixed signal integration capabilities of the technology, which enable a new set of possibilities and applications in the THz domain. In this paper, we review the current status of THz integrated circuits. We discuss trends in silicon based THz sources and receivers, as well as different THz on-chip systems that have been reported so far for different application areas.

Current Status of Terahertz Integrated Circuits - From Components to Systems

A low noise amplifier (LNA) design for 230GHz applications in an advanced SiGe heterojunction bipolar transistor technology is presented. The circuit consists of a four-stage pseudo-differential cascode topology. It was implemented in a commercially available SiGe BiCMOS technology with fT/fmax of 300/450GHz. By employing positive feedback for unilateralization the small-signal gain is increased, enabling circuit operation in high frequency bands and improved efficiency. The amplifier has measured 22.5dB gain at 233GHz with a 3dB bandwidth of 10GHz and a simulated noise figure of 12.5dB. The low noise amplifier draws only 17mA from a 4V supply.

Stefan Malz

Papers

A Fully Integrated 240-GHz Direct-Conversion Quadrature Transmitter and Receiver Chipset in SiGe Technology

Active Multiple Feed On-Chip Antennas With Efficient In-Antenna Power Combining Operating at 200–320 GHz

A lens-integrated 430 GHz SiGe HBT source with up to −6.3 dBm radiated power

Current Status of Terahertz Integrated Circuits - From Components to Systems

A 233-GHz low noise amplifier with 22.5dB gain in 0.13μm SiGe