Past colloquia and seminars


High Refractive Index nanosystems: a versatile alternative to plasmonics

General public Colloquium / Congress / Forum

Optical antennas transform light from freely propagating waves into highly localized excitations that interact strongly with matter. In particular, plasmonic nanostructures acting as nanoantennas have been employed to obtain strong light-matter interactions at deep subwavelength size scales. However, its ohmic losses lead to temperature increase in the
nanoantenna and its surroundings. This effect is well known and some applications take advantage of it, such as photothermal imaging, drug delivery, some biosensing techniques or cancer therapy. In the case of other applications, it is detrimental as it strongly limits the power that can be delivered to a hot spot before the particle reshapes or melts, affecting its nanoscale lighting or the emission properties of targets near the nanoantennas. Another limitation of metals is the difficulty to generate optical magnetic response. Recently, the use of low-loss resonators made of high permittivity dielectric materials (non-plasmonic), has shown as an effective alternative to Plasmonic ones in applications like sensing (including enantiomers), spectroscopy (SERS or SEF), design of light emitting devices aimed at integrated photonics or optical nano circuits where tuning the light propagation direction would be beneficial to improve its performance.

In the first part of the talk I will review and highlight the properties and strengths of plasmonic nanoantennas, paying special attention at recent results in novel nanoheaters capable of deliver heat asymmetrically, something desired in photothermal cancer therapies or drug delivery. In the second part of the talk, I will discuss its weaknesses for certain applications, and pay special attention to non-plasmonic nanoantennas, as a novel way to compensate for those weaknesses. These novel nanoantennas, apart from producing both, large near field enhancement and good scattering efficiencies, offer interesting optical properties, like the possibility of exciting nanoscale displacement currents that can lead to magnetic response, allowing the tuning of the amplitude and phase difference of electric and magnetic resonances independently. This opens a new path to enhance and guide light by just conveniently designing the shape and size of the nanostructures.

When? 20.03.2024 16:50
Where? PER 08 0.51
Chemin du Musée 3
1700 Fribourg
speaker Prof. Pablo Albella
Universidad de Cantabria
Invited by group Acuna
Contact Prof. Guillermo Acuna
Chemin du Musée 3
1700 Fribourg