A repository & source of cutting edge news about emerging terahertz technology, it's commercialization & innovations in THz devices, quality & process control, medical diagnostics, security, astronomy, communications, applications in graphene, metamaterials, CMOS, compressive sensing, 3d printing, and the Internet of Nanothings. NOTHING POSTED IS INVESTMENT ADVICE! REPOSTED COPYRIGHT IS FOR EDUCATIONAL USE.
The sensitive detection of terahertz (THz)-wave radiation from compact sources at room temperature is crucial for real-world THz-wave applications. Here, we demonstrate the nonlinear optical detection of THz-wave radiation from continuous-wave (CW) resonant tunneling diodes (RTDs) at 0.58, 0.78, and 1.14 THz. The up-conversion process in a MgO:LiNbO3 crystal under the noncollinear phase-matching condition offers efficient wavelength conversion from a THz wave to a near-infrared (NIR) wave that is detected using a commercial NIR photodetector. The minimum detection limit of CW THz-wave power is as low as 5 nW at 1.14 THz, corresponding to 2-aJ energy and 2.7 × 103 photons within the time window of a 0.31-ns pump pulse. Our results show that the input frequency and power of RTD devices can be calibrated by measuring the output wavelength and energy of up-converted waves, respectively. This optical detection technique for compact electronic THz-wave sources will open up a new opportunity for the realization of real-world THz-wave applications.
The capability of synchrotron radiation to produce ultrabright emission has attracted considerable interest over the last half a century. To date, magnetic undulators with a period of several centimetres are commonly used for wiggling relativistic electrons in a modulated field. Here, we propose a novel compact undulator with a period down to the submillimetre level based on a spontaneous electric field that is driven by a femtosecond laser. Both the guided energetic electrons and the gyrotron-like undulator are spontaneously produced by irradiating a thin metallic wire with an intense laser pulse. An intense radial electric field instantaneously created on the wire can guide the electrons' helical motion along the wire and induce periodic THz emission. We have demonstrated that this scheme can produce intense THz sources with a conversion efficiency of 1% that are frequency-tunable by adjusting the diameter of the wire. Amplified emission of THz radiation by more than tenfold has been observed.
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High-resolution optical backscatter reflectometry (OBR) has become a valuable tool in the design, test and diagnostics of fiber components, photonic integrated circuits (PICs) and short fiber networks. In much the same way standard OTDR is used for system-level test, high-resolution OBR can locate and identify issues (bends, breaks, bad splices, defects, interfaces, etc.) in components and short networks with sub-millimeter resolution long before they become problems.
Luna will be hosting a webinar, “See What You’re Missing: Improve Optical Component, PIC & Short Network Design Using High Resolution Backscatter Reflectometry,” that will review multiple applications of high-resolution OBR and demonstrate how OBR can help improve product quality and reduce cost and time to market. Examples will range from assessing the performance and quality of silicon photonics designs to trouble-shooting short fiber networks like those found in data centers and avionics applications.
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Mass spectrometry is a chemical analysis and detection tool that has been around for 130 years. In that time there have been so many tweaks and improvements that observers have become a bit blasé about the next big leap in its development.
But the latest improvement out of the Georgia Institute of Technology may be the biggest yet for the venerable old analytical tool. In research described Nature Nanotechnology, the Georgia Tech researchers have managed to make mass spectrometry more sensitive than ever before, more portable, cheaper and even safer. All of these advancements were accomplished by replacing the direct current power source typically used as power source with triboelectric nanogenerators (TENGs). You can see a demonstration of the technology at work in the video below.
While the researchers concede the mechanism by which the enhancement takes place demands more investigation, they believe the unique aspects of the TENG output—oscillating high voltage and controlled current—should enable improvements in the ionization process, increasing the voltage applied without damaging samples.
The so-called TENGs were developed at Georgia Tech back in 2012 and Zhong Lin Wang and his colleagues at Georgia Tech have been improving the technology and expanding its applications ever since. TENGs essentially harvest static electricity from friction. The TENG devices consist of two different materials that are rubbed together. In this way, materials that tend to give off electrons, such as glass or nylon, will donate them to materials that tend to absorb them, such as silicon or teflon. By converting mechanical energy from friction to electricity the TENGs can power small electronic devices.
Applied to mass spectrometry, the TENGs replace the direct current power source for generating the ions. This takes the advantage of a fixed input charge in each cycle of the operation of the TENG regardless of the current or voltage, allowing the mass spectrometer to analyze the smallest possible sample at the highest possible sensitivity.
“The sensitivity has been increased to being able to detect down to 100 molecules,” said Wang in an e-mail interview with IEEE Spectrum. “This is the highest ever.”
Wang also points out how efficient the TENG power source is in using samples. In mass spectrometry, a sample is ionized and the ions are sorted according to their mass-to-charge ratio. But with DC voltages, the number of generated ions does not depend on the applied voltage in a straightforward fashion. As a result, controlling the number of charges used in the ionization of neutral species is usually impossible. The fixed number of charges provided by TENGs offer unprecedented control over ion generation. This makes it very efficient in how it uses the sample.
“The key here is that the total charge delivered in each cycle is entirely controlled and constant regardless of the speed at which the TENG is triggered,” said Wang in a press release.
Facundo Fernández, a professor in Georgia Tech’s School of Chemistry and Biochemistry, added: “Our discovery is basically a new and very controlled way of putting charge onto molecules. We know exactly how much charge we produce using these nanogenerators, allowing us to reach sensitivity levels that are unheard of – at the zeptomole scale (10-21th part of a mole or about 600 molecules). We can measure down to literally hundreds of molecules without tagging.”
The Georgia Tech team has measured the TENGs generating as much as 6000 and 8000 volts as a mass spectrometry ionizer. Standard ionizers normally operate at less than 1500 volts.
“Because the voltage from these nanogenerators is high, we believe that the size of the sample droplets can be much smaller than with the conventional way of making ions,” Fernández said. “That increases the ion generation efficiency. We are operating in a completely different electrospray regime, and it could completely change the way this technology is used.”
By eliminating the often high-voltage power supplies, mass spectrometry could become more portable, leading the researchers to speculate that they could be used in extreme and harsh environments since they would become a durable self-contained unit.
While dramatically improving sensitivity, portability and adding a bit of safety by replacing the high-voltage power supplies, the TENGs also enable the deposition of ions onto surfaces, including non-conducting ones. This becomes possible because the TENGs are creating an oscillating ionization that produces a sequence of alternating positive and negative charges, resulting in a net neutral surface.
Wang added: “This opens a new field for applying TENG in portable and mobile instruments with high performance. The next phase of research is to optimize the performance of the system so that it can be used for sophisticated analytical chemistry and biochemistry.”
We experimentally demonstrated that nonlinear filament interaction could spectrally modulate terahertz (THz) radiation generated from asymmetric two-color filaments. It was the spatial plasma density modulation in plasma channels that induced the THz spectral modulation. As a result of optical manipulation of electron density in the filamentary plasma gratings, the proportion of high-frequency THz spectra increased, while that of low-frequency THz spectra decreased, indicating that the increase of free electron density in the filamentary plasma grating brought about THz frequency upshifts.
Suzana Domingues, Daniele Perenzoni, Matteo Perenzoni, David Stoppa,
https://link.springer.com/article/10.1007/s10762-017-0372-3 In this paper, a switched-capacitor readout circuit topology integrated with a THz antenna and field-effect transistor detector is analyzed, designed, and fabricated in a 0.13-μm standard CMOS technology. The main objective is to perform amplification and filtering of the signal, as well as subtraction of background in case of modulated source, in order to avoid the need for an external lock-in amplifier, in a compact implementation. A maximum responsivity of 139.7 kV/W, and a corresponding minimum NEP of 2.2 nW/√Hz, was obtained with a two-stage readout circuit at 1 kHz modulation frequency. The presented switched-capacitor circuit is suitable for implementation in pixel arrays due to its compact size and power consumption (0.014 mm2 and 36 μW).
Researchers at the NUP/UPNA-Public University of Navarre have designed two types of sensors whose innovative technologies obtain information on the water status of a vineyard. The work has been developed by a NUP/UPNA multidisciplinary team in collaboration with various Navarrese companies.
The first of these sensors does not require contact with the plant, and works by capturing information in the terahertz range. "These devices transmit a terahertz signal and measure what proportion of the signal is returned by the trunk of the vine," explained Gonzaga Santesteban-García, lecturer in the Department of Agricultural Production and leader of theresearch project. "It involves reflectance technology without any contact with the plant. That way, we can check the plant's water status. It is a technique that has not been used before for this purpose." The results of this development have been published in the journalsFrontiers in Plant Scienceand theJournal of Infrared, Millimeter and Terahertz Waves.
The sensor design is simple because high bandwidth is not needed; it uses planar technology, which allows a high degree of miniaturization and thus considerably cuts the cost per unit, since many of its chips can be obtained commercially at a low price.
The second of the sensors is based on a totally different principle. In this case, the aim was to use magnetoelastic sensors to detect the changes that take place throughout the day and night in the size of the trunk or branches of the vine. Gonzaga-Santiesteban explained that sensors of this type offer two advantages over the classical dendrometers used by some wineries. "Firstly, this is a different technology enabling costs to be reduced and, secondly, we have made it more flexible so that these devices can be fitted not only to the trunk, as until now, but also to different parts of the vine, such as, for example, the cluster," he added. The results of this development have also been partially published in the journal IEEE Transactions on Magnetics.
Mechanically flexible 3D terahertz photonic crystals (3D-TPCs) are created by the direct-writing technology with a composite ink system composed of polydimethylsiloxane (PDMS) and barium titanate (BaTiO3) nanoparticles. The direct-writing technology allows an easy creation of complex 3D structures with designed geometry, while the refractive indices of the composite ink can be modulated by varying the content of BaTiO3 nanoparticles. Thus, 3D-TPCs with different terahertz properties are obtained by the direct-writing technology. More interestingly, these 3D-TPCs demonstrate a unique tunable terahertz property under external force field due to their mechanical flexibility from the PDMS matrix of the composite ink. Thus, their terahertz property is responsive to external force fields reversibly, which can find novel applications in terahertz technology and other related technological applications
A terahertz (THz) wire-grid polarizer with metallic bridges on a quartz substrate was simulated, fabricated, and tested. The device functions as a wide-band polarizer to incident THz radiation. In addition, the metallic bridges permit the device to function as a transparent electrode when a DC bias is applied to it. Three design variations of the polarizer with bridges and a polarizer without bridges were studied. Results show the devices with bridges have average 𝑠-polarization transmittance of less than −3dB and average extinction ratios of approximately 40 dB across a frequency range of 220–990 GHz and thus are comparable to a polarizer without bridges.
Abstract: In the span of electromagnetic wave band from microwave to X-rays, the biological tissue-light interaction at the terahertz (THz) wavelength band (λ ~ 3mm – 30um) is particularly unique for two reasons. First, the THz band retains a large dielectric constant for water from the microwave region while having shorter wavelengths for imaging applications with < 1mm resolution. Second, scattering from typical soft tissue structures (cells, collagen matrix, etc.) is largely mitigated in the THz band, unlike in higher-frequency bands (IR band and up). Using this balance of properties, our study applies THz sensing to study diseases and conditions that compromise our body’s ability to balance water in tissues.
This study focuses on developing a new medical imaging technology using terahertz (THz) frequency wave for precise tissue water content measurement and imaging of cornea, which is a critical refractive and protective component of the eye. In ophthalmology, most corneal disorders such as Fuchs’ endothelial dystrophy (corneal hydration mal-regulation), keratoconus (irregularly shaped cornea), and pseudophakic bullous keratopathy (corneal graft rejection) result in corneal edema, leading to chronic vision impairment if left untreated. Reliable corneal tissue water content (CTWC) measurement can help with early diagnosis and intervention for corneal diseases and provide a better understanding of the formation, progression of corneal disorders.
This study developed a novel terahertz (THz) remote-sensing technique that measures absolute CTWC and have potential to be practically implemented in the clinical setting. The presentation will discuss development of a novel ophthalmic THz imaging system for completely non-contact, all normal incidence imaging of corneal surface. The imaging system employs wavelength independent quasioptical design that achieves 1.4 mm spatial resolution at 650GHz. THz corneal hydration sensing capability with this imager is demonstrated in in vivo rabbit model, showing onset of the acute corneal edema from endothelial damage, in the first THz imagery of living cornea ever captured. The imaging system is currently used in the initial clinical trial for healthy and diseased cornea of patients with corneal graft and corneal dystrophies.
Biography:Shijun Sung is a doctoral student working with Prof. Warren Grundfest on the development of terahertz (THz) imaging and sensing method for applications in medical imaging. Shijun completed his B.S., M.S. in Electrical Engineering at UCLA. His doctoral research focuses on novel quasioptical imaging system development for diagnostic imaging of corneal dystrophies.
Terahertz (THz) spectra of DNA nucleobase crystals were experimentally studied by terahertz time domain spectroscopy (THz-TDS), Fourier transform infrared spectroscopy (FTIR), and computationally studied by the generalized energy-based fragmentation approach under periodic boundary conditions (denoted as PBC-GEBF). We analyzed the vibrational spectra of solid-state DNA nucleobases and assigned the corresponding vibrational modes to the main peaks in the experimental spectra with the PBC-GEBF results. The computational results were verified to be in good accordance with the experimental data. Harmonic vibrational frequency results revealed that all the vibrational modes belong to collective vibrational modes, which involve complicated mixtures of inter- and intramolecular displacements, somewhere in the vicinity of 0.5–9 THz
