Coplanar waveguide | EPFL Graph Search

Coplanar waveguide is a type of electrical planar transmission line which can be fabricated using printed circuit board technology, and is used to convey microwave-frequency signals. On a smaller scale, coplanar waveguide transmission lines are also built into monolithic microwave integrated circuits. Conventional coplanar waveguide (CPW) consists of a single conducting track printed onto a dielectric substrate, together with a pair of return conductors, one to either side of the track. All three conductors are on the same side of the substrate, and hence are coplanar. The return conductors are separated from the central track by a small gap, which has an unvarying width along the length of the line. Away from the central conductor, the return conductors usually extend to an indefinite but large distance, so that each is notionally a semi-infinite plane. Conductor-backed coplanar waveguide (CBCPW), also known as coplanar waveguide with ground (CPWG), is a common variant which has

Optical-Microwave Pump-Probe Studies of Electronic Properties in Novel Materials

András Bojtor, Karoly Holczer, Sándor Kollarics, Bence Gábor Márkus, Ferenc Simon

Combined microwave-optical pump-probe methods are emerging to study the quantum state of spin qubit centers and the charge dynamics in semiconductors. A major hindrance is the limited bandwidth of microwave irradiation/detection circuitry which can be overcome with the use of broadband coplanar waveguides (CPWs). The development and performance characterization of two spectrometers is presented as follows: an optically detected magnetic resonance spectrometer (ODMR) and a microwave-detected photoconductivity measurement. In the first method, light serves as detection and microwaves excite the investigated medium, whereas in the second, the roles are interchanged. The performance is demonstrated by measuring ODMR maps on the nitrogen-vacancy (NV) center in diamond and time-resolved photoconductivity in p-doped silicon. The results demonstrate both an efficient coupling of the microwave irradiation to the samples as well as an excellent sensitivity for minute changes in sample conductivity.

WILEY-V C H VERLAG GMBH2020

Development of a contactless capacitive immunosensor

Brice Perruche

In the present work, a label-free, contactless and capacitive immunosensor is developed using impedance spectroscopy, in the aim to perform low-cost immunoassays. Chapter 1 puts this work in perspective with some existing techniques, while a presentation of impedance theory used in this work is carried out in chapter 2. In Chapter 3, numerical simulations using a commercial finite element method software is carried out. The response of coplanar and face-to-face designs using an insulating layer is studied with respect to a frequency ranging from 100 Hz to 10 MHz . Two levels of capacitance were observed across the frequency range : the low frequency capacitance created by the insulating layer and the high frequency capacitance created by the solution. These capacitances depend on parameters like the solution conductivity, the distance between the electrodes, the electrodes width or the insulating layer thickness. A dimensionless parameter is defined to evaluate the quality of the geometry at high frequencies. Microchips using a coplanar design are developed in Chapter 4. They are composed of two silver electrodes drilled in a PET sheet by laser photoablation. The design of both holder and of the microchips is optimized to increase as much as possible the signal-to-noise ratio. Bovine Serum Albumin is detected by a variation of the channel conductivity. Chapter 5 introduces the design of a sensor using electrodes made of a mass market aluminium foil. The study of the frequency response of the electrodes led to the creation of a discrete analytical model. The electrodes are then mounted into a holder using a face-to-face or coplanar design. The system is characterized through the variation of several geometrical parameters (height of fluid in the reservoir, electrode surface area, solution conductivity, ...). The coplanar design is also optimized to be able to work in a holder equipped with a fluidic channel. Finally, the ability of the aluminium electrodes based sensor to monitor an adsorption is studied in Chapter 6. The resonance is used to detect the adsorption of proteins like BSA on the electrodes using coplanar and face-to-face designs. The adsorption is found to follow a Langmuir isotherm and an adsorption equilibrium constant is extracted. The second adsorbate layer is detected using a coplanar design, enabling the achievement of a immunoassay.

EPFL2011

Stress-state manipulation in fused silica via femtosecond laser irradiation

Yves Bellouard, Ya Cheng, Philippe Gillet, Charles Michel Henri Pépin

Controlling the stress in glass after laser exposure is of prime importance not only for photonics applications, but also for preserving the mechanical integrity of glass components in general. The sub-surface exposure of fused silica to femtosecond laser pulses can induce a permanent and localized modification to the glass structure. In this work, we present evidence that femtosecond laser exposure can be used to continuously tailor the stress in the material, from a tensile to compressive state, as the laser pulse energy is changed. In addition, we demonstrate that this effect can not only be obtained while transitioning between different laser-induced microstructures, but also at low pulse energy, in the laser exposure regime particularly relevant for fabricating waveguides. These results demonstrate that femtosecond laser exposure is a versatile tool for fully controlling the stress landscape in a volume of silica, opening up new technological opportunities, like for instance, direct write stress-free waveguides, direct-write stress-induced birefringence state or mechanically reinforced parts, by locally preloading it. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License.

Optical Soc Amer2016

Development of a contactless capacitive immunosensor

Brice Perruche

EPFL2011