On-chip terahertz characterisation of liquids
Licentiate thesis, 2020

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.

terahertz spectroscopy

dielectric permittivity



isopropyl alcohol (IPA)

coplanar waveguides (CPW)


vector network analyzers (VNA)

Through-Reflect-Line (TRL) calibration

planar Goubau line

on-wafer measurements

microfluidic channels

material properties

scattering parameters

Kollektorn, MC2 Department, Kemivägen 9 floor 4, 41296 Gothenburg, Sweden
Opponent: Dr. Vessen Vassilev, Microwave Electronics Laboratory, Chalmers University of Technology, Sweden


Juan Cabello Sánchez

Chalmers, Microtechnology and Nanoscience (MC2), Terahertz and Millimetre Wave Laboratory

Multiline TRL Calibration Standards for S-parameter Measurement of Planar Goubau Lines from 0.75 THz to 1.1 THz

IEEE MTT-S International Microwave Symposium Digest,; (2018)p. 879-882

Paper in proceedings

Transmission Loss in Coplanar Waveguide and Planar Goubau Line between 0.75 THz and 1.1 THz

International Conference on Infrared, Millimeter, and Terahertz Waves,; (2018)p. 1-2

Paper in proceedings

On-Chip Characterization of High-Loss Liquids between 750 GHz and 1100 GHz

IEEE Transactions on Terahertz Science and Technology,; Vol. 11(2021)p. 113-116

Journal article

Analysis biological processes

Swedish Research Council (VR), 2016-01-01 -- 2019-12-31.

Areas of Advance

Information and Communication Technology


Kollberg Laboratory

Nanofabrication Laboratory

Subject Categories

Medical Laboratory and Measurements Technologies

Other Physics Topics

Other Electrical Engineering, Electronic Engineering, Information Engineering


Chalmers University of Technology

Kollektorn, MC2 Department, Kemivägen 9 floor 4, 41296 Gothenburg, Sweden


Opponent: Dr. Vessen Vassilev, Microwave Electronics Laboratory, Chalmers University of Technology, Sweden

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