Seminars

This work focuses on the development of an elegant technique designed to improve the conventional surface plasmon resonance (SPR)-based sensor. These sensors are used widely throughout research and commercial industries such as (bio)sensing and medical testing. A surface plasmon can be formed by incident light coupling to the surface-air interface of a noble metal thin film. The resultant coherent excitation of surface-bound electrons interacts with the reflected light in a destructive manner, thereby reducing the reflected light intensity. As this process is highly dependent on the refractive indices of the component materials, the narrow resonance conditions can be harnessed for use as a sensing technique.
Here, advances in the conventional sensor design allow the direct and rapid heating via a modulated current. The current through a microscale constriction in the thin film locally Joule heats the sensor. The temperature cycles enable homodyne detection by taking advantage of the temperature-dependence of the refractive indices causing a modulated reflected light intensity. This method enhances discrimination and detectability of the conventional SPR sensor. A detailed characterisation of the technique is aided by complete in-house design and manufacturing processes. The characterisations include investigations into the phase dependence and incident beam spot position, as well as microscopy in optical, atomic force (AFM), scanning electron (SEM), and even scanning Joule expansion (SJEM). The investigations are supported by Fresnel equations analysis and multiphysics simulations. The resultant understanding of the system culminates in the improved detection of self-assembled sub-monolayer adsorbates directly on the sensor surface.

In the last decade, significant progress has been made on the question of the nature and energetics of particles accelerated in SNRs and PWNe by combining the gamma-ray observations provided by the Fermi-LAT at GeV and Cherenkov telescopes at TeV. However, in order to explain the Galactic cosmic-ray spectrum, Galactic accelerators should be able to generate particles up to PeV (10^15 eV) energies, and this evidence has been so far lacking. Water Cherenkov detectors, in particular LHAASO, have provided a transformational view on the gamma-ray sky at 100 TeV, giving new insights on the nature of Galactic PeVatrons. This seminar will discuss the different ways our community is defining PeVatron sources, where we expect to find them, and how our focus has gradually shifted from SNRs to PWNe as plausible PeV accelerators. An overview of the recent GeV and multi-TeV measurements motivating this shift will be presented, followed by a discussion of the advancements that will be made with the next generation Cherenkov Telescope Array Observatory (CTAO) in particular on particle acceleration in supernovae.