| 1. |
- Jensen, Maja, 1978, et al.
(författare)
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High-resolution macromolecular crystallography at the FemtoMAX beamline with time-over-threshold photon detection
- 2021
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Ingår i: Journal of Synchrotron Radiation. - 1600-5775 .- 0909-0495. ; 28, s. 64-70
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Tidskriftsartikel (refereegranskat)abstract
- Protein dynamics contribute to protein function on different time scales. Ultrafast X-ray diffraction snapshots can visualize the location and amplitude of atom displacements after perturbation. Since amplitudes of ultrafast motions are small, high-quality X-ray diffraction data is necessary for detection. Diffraction from bovine trypsin crystals using single femtosecond X-ray pulses was recorded at FemtoMAX, which is a versatile beamline of the MAX IV synchrotron. The time-over-threshold detection made it possible that single photons are distinguishable even under short-pulse low-repetition-rate conditions. The diffraction data quality from FemtoMAX beamline enables atomic resolution investigation of protein structures. This evaluation is based on the shape of the Wilson plot, cumulative intensity distribution compared with theoretical distribution, I/σ, Rmerge /Rmeas and CC1/2 statistics versus resolution. The FemtoMAX beamline provides an interesting alternative to X-ray free-electron lasers when studying reversible processes in protein crystals.
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| 2. |
- Cabello Sánchez, Juan, 1992, et al.
(författare)
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A Capacitive-Gap Coupled Terahertz Planar-Goubau-Line Power Divider
- 2023
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Ingår i: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 13:6, s. 698-703
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Tidskriftsartikel (refereegranskat)abstract
- The planar Goubau line is a single-conductor waveguide with a low attenuation constant at terahertz frequencies compared to other planar waveguides. However, its single-conductor nature complicates the design of circuit elements compared to multi-conductor waveguides, especially when impedance transformation is needed, like in the case of power dividers. In this paper, we present a power divider for a planar Goubau line based on capacitive-gap coupled lines, providing a matched input port. A 900-GHz equal power divider was fabricated on a suspended silicon membrane and was characterized with a Vector Network Analyzer and terahertz probes between 0.5 THz and 1.1 THz. Simulations and measurements are in good agreement, the measured input return loss is lower than 15dB at the design frequency, and the average coupler loss is estimated to be lower than 1 dB when de-embedding the feeding lines.
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| 3. |
- Cabello Sánchez, Juan, 1992, et al.
(författare)
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A Corrugated Planar-Goubau-Line Termination for Terahertz Waves
- 2023
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Ingår i: IEEE Microwave and Wireless Technology Letters. - 2771-957X .- 2771-9588. ; 33:6, s. 643-646
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Tidskriftsartikel (refereegranskat)abstract
- The planar Goubau line is a promising low-loss metal waveguide for terahertz applications. To enable advanced circuits and multi-port measurements based on planar Goubau lines, there is a strong need for broadband impedance-matched loads, which can be used to absorb the energy and minimize standing waves in a system. In this work, we propose a termination for planar Goubau lines based on an exponentially-tapered corrugated line, gradually increasing conductor losses while maintaining small reflections. The corrugation density is high enough to increase conductor losses without requiring an auxiliary low-conductivity material. A 400-µm long planar Goubau line load was fabricated on a 10-µm thick silicon substrate suspended in the air. Simulations of the load show excellent agreement with calibrated reflection measurements in the frequency range 0.5 THz – 1.1 THz. Above the cut-off frequency of around 580 GHz, the measured reflections are less than -19 dB, below the noise floor of the characterization setup.
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| 4. |
- Cabello Sánchez, Juan, 1992, et al.
(författare)
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Capacitively-coupled resonators for terahertz planar-Goubau-line filters
- 2023
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Ingår i: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 13:1, s. 58-66
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Tidskriftsartikel (refereegranskat)abstract
- Low-loss planar Goubau lines show promising potential for terahertz applications. However, a single-wire waveguide exhibits less design freedom than standard multi-conductor lines, which is a significant constraint for realizing standard components. Existing filters for planar Goubau line lack clear design procedures preventing the synthesis of an arbitrary filter response. In this work, we present a design for a bandpass/bandstop filter for planar Goubau line by periodically loading the line with capacitively-coupled ?∕2 resonators, which can be easily tuned by changing their electrical length. The filter’s working principle is explained by a proposed transmission-line model. We designed and fabricated a passband filter centered at 0.9 THz on a 10-?m silicon-membrane substrate and compared measurement results between 0.5 THz and 1.1 THz to electromagnetic simulations, showing excellent agreement in both ?11 and ?21. The measured passband has an insertion loss of 7 dB and a 3-dB bandwidth of 31%. Overall, the proposed filter design has good performance while having a simple design procedure.
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| 5. |
- Cabello Sanchez, Juan, 1992, et al.
(författare)
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Design, fabrication and S-parameter characterization of a planar Goubau line from 0.75 THz to 1.1 THz for near-field on-wafer biosensing
- 2017
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Ingår i: 8th International THz-Bio Workshop.
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Konferensbidrag (refereegranskat)abstract
- We present the design, fabrication and characterization of a Planar Goubau Line (PGL) from 0.75 THz to 1.1 THz intended for on-wafer near-field characterization of biological samples. A design method of the transition between the Coplanar Waveguide (CPW) and the PGL was developed for minimising reflections. In order to minimize losses and the propagation of substrate modes, the structures were fabricated on a 30 μm benzocyclobutene (BCB) substrate on top of a high resistive silicon that acts as mechanical support. The structures were characterized with on-wafer S-parameter measurements from 0.75 to 1.1 THz using Vector Network Analyser.
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| 6. |
- Cabello Sánchez, Juan, 1992, et al.
(författare)
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Multiline TRL Calibration Standards for S-parameter Measurement of Planar Goubau Lines from 0.75 THz to 1.1 THz
- 2018
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Ingår i: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. ; 2018-June, s. 879-882
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Konferensbidrag (refereegranskat)abstract
- We present a multiline Thru-Reflect-Line (TRL) calibration standard for Planar Goubau Line (PGL) which allows setting the calibration plane along the PGL and thus removing the effect of the embedding structure. This opens the possibility of characterizing PGL-circuits. The presented structures were used for calibrating S-parameters measurements between 0.75 THz and 1.1 THz to characterize a 1 mm long and 10 µm wide PGL. The line shows negligible dispersion with an effective relative permittivity of 2.0 and an attenuation constant lower than 0.35 Np/mm (0.65 dB/λ).
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| 7. |
- Cabello Sánchez, Juan, 1992, et al.
(författare)
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On-Chip Characterization of High-Loss Liquids Between 750 and 1100 GHz
- 2021
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Ingår i: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 11:1, s. 113-116
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Tidskriftsartikel (refereegranskat)abstract
- Terahertz spectroscopy is a promising tool for analyzing the picosecond dynamics of biomolecules, which is influenced by surrounding water molecules. However, water causes extreme losses to terahertz signals, preventing sensitive measurements at this frequency range. Here, we present sensitive on-chip terahertz spectroscopy of highly lossy aqueous solutions using a vector network analyzer, contact probes, and a coplanar waveguide with a 0.1 mm wide microfluidic channel. The complex permittivities of various deionized water/isopropyl alcohol concentration are extracted from a known reference measurement across the frequency range 750–1100 GHz and agrees well with literature data. The results prove the presented method as a highsensitive approach for on-chip terahertz spectroscopy of high-loss liquids, capable of resolving the permittivity of water.
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| 8. |
- Cabello Sánchez, Juan, 1992
(författare)
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On-chip terahertz characterisation of liquids
- 2020
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Spectroscopy at terahertz frequencies can be used in a wide range of applications including radio-astronomy, pharmaceutical manufacturing control, and the study of processes in molecular biology. Biomolecular samples should preferably be studied in their native environment, water, however, water poses extreme attenuation for THz-frequency waves, deteriorating or even impeding analysis using these waves. The most common THz spectroscopy method, time-domain spectroscopy, can measure water samples using free-space measurements, lacks sensitivity when trying to measure on a chip environment. To exploit the advantages that chip measurements offer, such as integration and cost, this thesis works on developing on-chip THz spectroscopy of aqueous samples using a frequency-domain approach, with vector network analysers. Vector network analysers exhibit a higher dynamic range than time-domain spectroscopy systems, making them a promising alternative for sensitive THz measurements. For maximising the sensitivity of the measurements, the losses must be minimised. One important source of losses at THz frequencies are conductor and radiation loss. In this thesis, two planar waveguides were designed, coplanar waveguide and planar Goubau line, minimising their losses at THz frequencies by avoiding the coupling to other parasitic modes, obtaining attenuation constants as low as 0.85 Np/mm for coplanar waveguide and 0.33 Np/mm for planar Goubau line. Additionally, planar Goubau line calibration structures were developed for setting the measurement plane along this planar waveguide. Finally, coplanar waveguides were integrated with microfluidic channels to perform spectroscopy measurements of water samples, showing good performances as THz sensors of high-loss liquids. This thesis is a first step towards a sensitive and miniaturised system for measuring the electrical properties of high-loss liquids, which could shed light on the fundamental biomolecular processes in the picosecond time-scale.
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| 9. |
- Cabello Sánchez, Juan, 1992
(författare)
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Planar-Goubau-line components for terahertz applications
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Terahertz-wave technology has a broad range of applications, including radio astronomy, telecommunications, security, medical applications, pharmaceutical quality control, and biological sensing. However, the sources, detectors, and components are less efficient at this frequency band due to parasitic effects and increased total losses, which hinder the performance of terahertz systems. A common platform for terahertz systems is planar technology, which offers good integration, ease of fabrication, and low cost. However, it also suffers from high losses, which must be minimised to keep the system's performance. A pivotal choice to reduce losses is using power-efficient waveguides, and single-conductor waveguides have shown promisingly high power efficiencies compared to multi-conductor planar waveguides. The planar Goubau line (PGL) is a planar single-conductor waveguide consisting of a metal strip on top of a dielectric substrate which propagates a quasi-transverse magnetic surface wave, similarly to Sommerfeld's wire and the Goubau line, a conducting wire coated with a dielectric layer. Some limitations of the PGL, which complicate the design of components, are the lack of a ground plane and the weak dependence of impedance with the metal strip width of the line. This thesis presents the development of PGL technology and components for terahertz frequencies. It developed design strategies to maximise the power efficiency, using electrically-thin substrates, which drastically drop radiation losses compared to thick substrates. The first PGL calibration standards were developed, which de-embeds the transition needed to excite the propagation mode and sets the calibration plane along the line, allowing the direct characterisation of PGL components. This work also presents several PGL components with a straightforward design procedure, including a stopband filter based on capacitively-coupled λ/2 resonators, an impedance-matched load based on an exponentially-tapered corrugated line, and a power divider based on capacitive-gap coupled lines to a standing wave in the input port. Finally, the PGL was integrated with a microfluidic channel to measure changes in the complex refractive index of a high-loss aqueous sample (water/isopropyl alcohol) as the first step toward a biological sensor.
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| 10. |
- Cabello Sánchez, Juan, 1992, et al.
(författare)
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Terahertz Planar Goubau Line Components on Thin Suspended Silicon Substrate
- 2022
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Ingår i: International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz. - 2162-2027 .- 2162-2035. ; August
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Konferensbidrag (refereegranskat)abstract
- The planar Goubau line is a low-loss planar single-conductor waveguide that holds promise for terahertz applications, where power efficiency is crucial. We present three circuit elements for planar Goubau line: a stopband filter, a matching load, and a power divider, which have been fabricated in a high-resistivity silicon membrane. Simulation results are presented for the matching load and the power divider. The filter’s performance is validated by comparing measurement results with simulations, showing good agreement.
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| 11. |
- Cabello Sánchez, Juan, 1992, et al.
(författare)
-
Transmission Loss in Coplanar Waveguide and Planar Goubau Line between 0.75 THz and 1.1 THz
- 2018
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Ingår i: International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz. - 2162-2027 .- 2162-2035. ; 2018-September, s. 1-2
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Konferensbidrag (refereegranskat)abstract
- In many cases, metallic planar waveguides are required in the design of integrated circuits. However, at terahertz frequencies, metallic planar waveguides present high losses, which make necessary the use more efficient waveguides to avoid power limitations. In this work, the attenuation constant of two popular planar waveguides for terahertz frequencies, Coplanar Waveguide (CPW) and Planar Goubau Line (PGL), are compared between 0.75 THz and 1.1 THz. To measure the PGL, its transition is deembeded using a multiline Thru-Reflect-Line calibration standard. Measurement results show a lower attenuation constant across the band for a PGL (0.13 mm-1 < α < 0.39 mm-1) than for a CPW (0.68 mm-1 < α < 0.99 mm-1) when an ultra-thin substrate is used suspended in air, which greatly reduces the substrate mode coupling from the PGL. These results put the PGL as a less lossy metallic planar waveguide for terahertz applications.
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| 12. |
- Masyukov, Maxim, et al.
(författare)
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A calibration-free method to assess the quality of standards for THz on-wafer measurements
- 2022
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Ingår i: International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz. - 2162-2027 .- 2162-2035. ; 2022-August
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Konferensbidrag (refereegranskat)abstract
- A method to assess the quality of the calibration standards has been developed and tested. The actual response of the tested transmission lines for LRRM-16 calibration approach has been simulated in HFSS environment, fabricated, and tested with on-wafer measurement setup. The method for quality assessment is based on the properties of similar matrices, that compares traces and determinants of the S-parameters products for fabricated and simulated structures.
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