We present a unified analytical framework for resonant optical tunnelling in planar three-layer photonic systems embedded in a transparent dielectric medium. Using a generalized Fresnel-coefficient approach, we derive compact expressions for the transmission and show that resonant tunnelling occurs in two fundamentally different regimes, determined by the nature of the waves supported in the core layer. When the core supports propagating harmonic waves, resonances obey the conventional Fabry–Perot phase condition. By contrast, when the core supports evanescent or damped waves, resonant tunnelling arises from an amplitude-matching condition governed by the magnitude of the composite reflection coefficient. These two regimes lead to qualitatively different transmission characteristics and distinct tunnelling behaviour. Transparent systems, including ideal metals, are analysed first in order to isolate the underlying physical mechanisms. Absorption is then incorporated, showing the transition from unitary resonant tunnelling to attenuated optical tunnelling in realistic plasmonic structures. Angular–spectral transmission maps illustrate the general features of each configuration and show that resonant tunnelling may occur even when the tunnelling layer is several wavelengths thick. The results provide a consistent physical interpretation of resonant tunnelling across dielectric and metal–dielectric multilayer systems.

The traditional method for characterizing optical thin films consists in calculating the proportion of light that is reflected and transmitted by the film. In this work, we present an alternative procedure based on the analysis of electromagnetic fields and energy flow within the film. Using our approach, we provide a unified description of a plethora of phenomena in three-layered structures, including frustrated total internal reflection, dielectric waveguiding, or surface plasmon resonance. Our approach highlights the distinguishing features of evanescent and damped waves in opposition to travelling waves, particularly those concerning the propagation of energy. The theoretical framework proposed here contributes to explicitly visualize the intrinsic difference between propagation in thin films and thicker media, providing physical insight into energy transport through them.

Frustrated total internal reflection (FTIR) is analyzed from a novel perspective. Unlike similar works, the angle of incidence is used here as the experimental variable instead of the film thickness through which light tunnels. This method makes it possible to visualize not only the phenomenon of FTIR but also the resonance processes that occur for angles of incidence below the critical angle. An affordable straightforward experiment appropriate for undergraduates is presented. The experiment involves measuring the reflection and transmission of light through a pair of prisms separated by an air or water layer, and the results are in fair agreement with theory.

In this work, we study the contributions that different molecular blocks have in the wavelength-dependence of the refractive index in ionic liquids. The ionic liquids chosen for this work are combinations of the bis(trifluoromethylsulfonyl)imide anion with cations based on four different heterocycles with different extents of charge delocalization. The analysis is performed in terms of the experimental electronic polarizability, which is obtained by combining measurements of refractive index curves and densities via the Lorentz-Lorenz equation. Exploiting the additivity of electronic polarizability in ionic liquids, the contribution of the anion and the heterocycles of the cations is separated from that of the alkyl chains. Our results show important differences in these contributions, revealing a key influence of the charge delocalization in the cationic rings on the behavior of the refractive index dispersion. The understanding of how different parts of ionic liquids affect their refractive index dependence on wavelength would allow to gain precise control of this magnitude, enabling the development of customized optical materials for diverse applications in photonics and sensing technologies.

This work models light transmission through metal-dielectric-metal microcavities supporting Coupled Surface Plasmons (CSP). An extended Fabry-Perot formula reveals two plasmonic resonances that merge beyond a critical cavity thickness. Remarkably, transmittance at these resonances remains high and nearly constant for thicknesses exceeding the light's penetration depth. Results at a 1 mu m wavelength show over 10% transmittance up to 3.5 mu m, offering new insights for photonic device design

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Coupled surface plasmons arise in the surfaces of a dielectric layer between two metallic media when a dim wave propagating in the dielectric generates resonant free charge oscillations at the interfaces. Here, we consider surface plasmon resonance in a Fabry-Perot type cavity with plane metallic mirrors and an inner dielectric medium, optically less dense than the outer surrounding dielectric medium. The experimentally observed transmission as a function of both the angle of incidence of light and the wavelength is well modelled by an elementary transmittance function from which resonance conditions are obtained both in the Fabry-Perot and Surface-Plasmon regime.

The Fresnel formalism of transmission and reflection of coherent waves on the abrupt interface between two different optical media is revisited and extended to study optical phenomena concerning guided waves. Using the Fresnel formalism, the propagation of light through different sequences of parallel layers of constant refractive index is analysed, revealing that, in all cases, the solutions corresponding to waveguiding share major features. In the analysis, aiming to connect waveguiding with coherent optical scattering, the possibility of the system having a resonance is examined, and it is shown that guided modes always emerge as singular solutions of the associated coherent scattering configuration. Invariably, the resonance condition that must be satisfied to obtain waveguiding corresponds to the pole of the associated total reflection and transmission coefficients. Even more, the fulfilment of the requirements to meet the resonance condition is a clear indication of the possibility of waveguiding.

Spreading optics and photonics arises as a pivotal duty for researchers in the field, aiming to inspire new generations of students to pursue a scientific career. Furthermore, essential abilities for researchers such as explaining science to an audience or approaching abstract concepts in a visual manner can be easily learnt whilst performing science fostering activities. With these ideas in mind, USCOPTICA Student Chapter and Santiago USC YM Sections were born. Bachelor and Master students and early-stage researchers collaborate in our group, performing diverse outreach sessions, comprising hands-on scientific workshops in schools and science diffusion events, roundtables raising awareness on social issues in Academia and cycles of conferences in collaboration with other student groups. The following abstract aims to share with the scientific community our major activities in the last two years.

In this paper, we discuss a demonstration we have been performing for years with students from different levels, from physics students from our university to high school students in some talks aimed at encouraging them to study science. It provides visualization of Brewster’s angle in an ingenious way using a “loaded” liquid crystal display (LCD) monitor lacking its front polarizing filter. The demonstration is based on observing the hidden image of this loaded LCD reflected in a transparent plate. In some way, we deal with a reverse version of what happens when a vampire faces a mirror and sees no reflected image of himself.

Uncertainties of refractive and group index in dispersion measurement by spectrally resolved white light interferometry are deeply analyzed. First, the contribution to uncertainty of the different parameters affecting both indices is identified. Afterwards, results are presented for a 1.5 mm thick fused silica sample over a broad spectral range, from 400 to 1000 nm, and the effects that mostly deteriorate the measurement accuracy are established. Finally, the different contributions are quadratically combined to determine the total uncertainty of the two indices.

In this contribution we show how, in times of pandemic, outreach activities driven by social networks can be a successful alternative to face-to-face events. Designing each activity to properly suit the host platform ensures success.

This contribution reports the organization and celebration after the Covid-19 pandemic of a singular scientific conference focused on early-career researchers from the Spanish universities of Santiago de Compostela and Salamanca: the “I Northwest Meeting of Young Researchers in Optics (I NW MYRO)”.

Since the advent of the COVID-19 pandemic, face-to-face outreach has been gradually replaced by dissemination through social networks. However, the use of social networks for outreaching is not easy since there is an important risk of biasing the communication by converting it into an exclusively one-way channel. In this contribution, we explain how a transmedia perspective can transform a regular activity, as a photo contest for the International Day of Light 2021, into an interactive, comprehensive and functional event in Twitter, Instagram and Twitch.