This paper presents on-wafer S-parameter characterisation of resonant-tunnelling diodes between 0.5 THz and 1.1 THz. Diodes with a peak current density of 532 kA/cm$^{2}$ and a clear negative differential region have been fabricated. An on-chip Multi-Thru-Reflect-Line calibration kit was developed and utilised to achieve accurate S-parameter measurements up to 1.1 THz.

We report status and current results of the preliminary reliability study on 300 GHz InP heterostructure barrier varactor diode multipliers and 1200 GHz GaAs Schottky diode mixers. Both types of diodes are monolithically integrated with circuits and were processed on 3 InP and GaAs wafers respectively using established III-V processing. We will present results on thermal step-stress tests up to 300oC, indicating the operational temperature limitations of the devices. Also, the analysis of the accelerated lifetime testing (1000h) will be discussed.

We report on the developments in this two-yearEuropean Space Agency funded project that aims at performing a preliminary reliability study of 300 GHz InP heterostructure barrier varactor diode multipliers and 1.2 THz GaAs Schottky diode mixers. Fabrication of the monolithically integrated circuits will be done on 3” wafers usingestablished III-V processing. The reliability tests that will be performed include thermal and electrical step-stress studies, as well as shock, humidity and accelerated lifetime tests. We will present results and analysis of these experiments.

We present results on coupled microstrip resonators at W-band, albeit scalable up in frequency, that can be utilized as highly sensitive detectors. By incorporating tunable varactor circuits, we will explore the possibility of resolving spectral features, i.e qualitative analysis of a materials frequency response.

There is a high demand for compact, room-temperature sources operating at millimeter-wave and terahertz (THz) frequencies for space instruments and terrestrial applications. This part of the electromagnetic spectrum is by far the least explored because of the difficulty of generating energy at these frequencies. Continuous-wave oscillators based on either electronics or photonics are limited in output power for fundamental reasons. Varistor and varactor frequency multipliers have shown outstanding performance in terms of output power, but further technical development will be essential to solve the lack of efficient and compact terahertz sources. In this paper, we present the status of heterostructure barrier varactor (HBV) diode frequency multipliers. The performance and prospects for THz applications in which HBV diode technology can offer advantages over conventional solutions are discussed. For instance, such a device can be easily scaled by increasing the number of barriers to produce and handle higher power. The inherent symmetry confines the power generation to odd harmonics, thereby simplifying the design of high-order frequency multipliers. For example, high-power triplers (x 3), quintuplers (x 5), nonlinear transmission lines (NLTLs) and grid multipliers utilizing HBV diodes are presented. Overall, HBV technology is a natural stepping stone from highpower microwave amplifiers to higher frequencies and can both simplify and improve the performance of terahertz sources.

This paper presents a compact varactor grid frequency doubler encapsulated in a waveguide environment, thus providing single mode (H-10) waveguide connection at both input and output. Schottky diodes are used as varactors in this 128-element grid frequency doubler. By packaging the grid and its embedding network together with a stepped waveguide taper on the output, a module measuring 9 mm x 19 mm by 19 mm is created. A peak output power of 0.25 W is produced at 183 GHz with 1.32 W of input power and a corresponding conversion efficiency of 19%. The peak conversion efficiency is 23% at 183 GHz with 666 mW of input power.

Studies of biological and artificial membrane systems, such as niosomes, currently rely on the use of fluorescent tags, which can influence the system under investigation. For this reason, the development of label-free, non-invasive detection techniques is of great interest. We demonstrate an open-volume label-free millimeter-wave sensing platform based on a coplanar waveguide, developed for identification and characterization of niosome constituents. A design based on a λ/2-line resonator was used and on-wafer measurements of transmission and reflection parameters were performed up to 110 GHz. Our sensor was able to clearly distinguish between common niosome constituents, non-ionic surfactants Tween 20 and Span 80, measuring a resonance shift of 3 GHz between them. The complex permittivities of the molecular compounds have been extracted. Our results indicate insignificant frequency dependence in the investigated frequency range (3 GHz – 110 GHz). Values of permittivity around 3.0 + 0.7i and 2.2 + 0.4i were obtained for Tween 20 and Span 80, respectively.

We have periodically (25ms on - 25ms off) illuminated lysozyme crystals with 0.4 THz radiation and simultaneously monitored their X-ray diffraction intensity in order to study non-thermal structural changes in the protein. In this work we analyze the X-ray scaled and unmerged diffraction intensity observations using a multivariate Bayesian model in order to improve the accuracy of the intensity estimates. The diffraction intensity pairs of the illuminated and non-illuminated state show a predominantly positive correlation. The correlation decreases with increasing resolution suggesting that finer slicing and faster sampling of the rocking curve may further improve the accuracy and effect size of structure factor amplitude differences, making the interpretation of structural changes more straightforward. The improved analysis retains the most important structural features described previously (in helix 3) and provide addition details about the B-factor changes close to the substrate binding site.

This paper presents a high-power 240-290 GHz wave-guide enclosed two-dimensional (2-D) grid heterostructure barrier varactor (HBV) frequency multiplier. A 35 mW of output power is produced at 247 GHz with an input power of 900 mW. The operational bandwidth is tunable within a 50 GHz span by the use of an input tuner able to adjust the input matching of the 2-D grid HBV frequency multiplier. Tuning is achieved by moving a suspended dielectric slab in the input waveguide.

Whether long-range quantum coherent states could exist in biological systems, and beyond low-temperature regimes where quantum physics is known to be applicable, has been the subject to debate for decades. It was proposed by Fröhlich that vibrational modes within protein molecules can order and condense into a lowest-frequency vibrational mode in a process similar to Bose-Einstein condensation, and thus that macroscopic coherence could potentially be observed in biological systems. Despite the prediction of these so-called Fröhlich condensates almost five decades ago, experimental evidence thereof has been lacking. Here, we present the first experimental observation of Fröhlich condensation in a protein structure. To that end, and to overcome the challenges associated with probing low-frequency molecular vibrations in proteins (which has hampered understanding of their role in proteins' function), we combined terahertz techniques with a highly sensitive X-ray crystallographic method to visualize low-frequency vibrational modes in the protein structure of hen-egg white lysozyme. We found that 0.4 THz electromagnetic radiation induces non-thermal changes in electron density. In particular, we observed a local increase of electron density in a long α-helix motif consistent with a subtle longitudinal compression of the helix. These observed electron density changes occur at a low absorption rate indicating that thermalization of terahertz photons happens on a micro- to milli-second time scale, which is much slower than the expected nanosecond time scale due to damping of delocalized low frequency vibrations. Our analyses show that the micro- to milli-second lifetime of the vibration can only be explained by Fröhlich condensation, a phenomenon predicted almost half a century ago, yet never experimentally confirmed.

Compact heterodyne receivers operating in the terahertz range are needed for earth observation instruments, space science missions (e.g. ESA’s “Jupiter icy moons explorer - JUICE”) and in the millimeter wave region for ground-based applications such as security scanners. Existing terahertz heterodyne receivers are usually bulky due to complex hybrid integration and there is a strong need for a terahertz monolithic integration circuit (“TMIC”) platform that allows for higher circuit functionality, ease of assembly, and low loss at terahertz frequencies. Moreover, this part of the electromagnetic spectrum, where optical and microwave techniques meet, call for an integration scheme that can support both active THz electronics & photonics. A possible solution is heterogeneous integration of THz devices (III-V, graphene) on a silicon carrier, which also allows for advanced micromaching of passive components and interconnects such as waveguides and antennas. This talk provides an overview of research on integrated diode circuits for terahertz applications. Progress on heterogeneous integration of HBV multipliers and Schottky diode mixers on silicon substrates (SOI) will be presented.

We present an overview of research on integrated diode circuits for terahertz applications carried out at Chalmers University of Technology. This includes progress on heterogeneous integration of heterostructure barrier varactor multipliers on silicon substrates. The described technology uses silicon-on-insulator (SOI) substrates, for which accurate and well-defined substrate thickness for the microstrip circuitry is obtained.

We present a silicon integrated Heterostructure Barrier Varactor (HBV) frequency quintupler ( ×5) operating between 440 GHz and 490 GHz. By epitaxial transfer of InP-based HBV material structure onto silicon-on-insulator (SOI), a uniform and accurate thickness (20 μm) of the frequency quintupler chip is achieved. In a single stage this device delivers 2.8 mW of output power at 474 GHz, when pumped with 400 mW at 94.75 GHz, corresponding to conversion efficiency of 0.75%. The present device exhibits a 3-dB bandwidth of 4%.