Alberto Grau – 30.04.2026
Non-suspended silicon optomechanical cavity as a mass sensor for nanoparticles detection
On April 30th, our colleague Alberto Grau presented his latest work on using optomechanical cavities for nanoparticle detection. Traditionally, for these sensors to be ultra-sensitive, the nanoparticle must be positioned exactly at the point of maximum light confinement—a condition that is nearly impossible to control in real-world settings. Alberto’s research demonstrates that, by using functionalized photonic crystal cavities, it is possible to accurately detect gold particles even when they are not located at the center of the sensor. A summary of the work is included below:
“Optical cavities are powerful tools for nanoparticle detection, though their sensitivity typically depends on precise particle placement within maximum field confinement regions. In this work, we demonstrate the detection of gold nanospheres using a silicon photonic crystal nanobeam cavity, even when particles are located in weak-coupling regions such as the cavity sidewalls. Experimental characterization shows significant variations in the optical response, supported by numerical simulations. These findings confirm the robustness of optical cavities as nanoparticle sensors, even in non-ideal placement scenarios.”
Josep Martínez – 26.03.2026
On-Chip Chiroptical Sensor based on Directional
Deflection of Light: A Stern-Gerlach Integrated Optical Analog
On March 26th, our colleague Josep Martínez presented an innovative proposal aimed at overcoming the current limitations of chiroptical sensors in integrated circuits. Traditionally, detecting chirality (the ‘handedness’ of molecules) requires the use of circularly polarized light, which is notoriously difficult to generate efficiently on-chip. Josep’s proposal draws inspiration from the famous Stern-Gerlach experiment of quantum physics, enabling the discrimination of chiral substances using conventional linear light by observing the physical deflection of the light beam toward either side of the sensor. A summary of the presented work is included below:
“Traditional chiroptical techniques for detecting the chirality of matter often require circularly-polarized light, which is challenging to implement in integrated photonic platforms. This work proposes an alternative inspired by the Stern–Gerlach experiment, where a chiral sample is illuminated by a linearly polarized beam. Enantio-discrimination is achieved through a spatially resolved scheme using optical antennas: the interaction with the sample induces a transverse deflection of the beam toward a specific side depending on its chirality. This on-chip platform enables compact implementations of chiral sensing, spectroscopy, and optical computing without the need for complex chiral light excitation.”
Prof. Dr. Carlos Alonso Ramos – 29.01.2026
Silicon photonics harnessing periodic nanostructures and AI
On January 29th, we had the pleasure of hosting Prof. Dr. Carlos Alonso Ramos, a researcher from the Silicon Photonics Team at the Center for Nanoscience and Nanotechnology (C2N, Université Paris-Saclay), at the UPV School of Telecommunications (ETSIT).
Since 2020, Professor Alonso has led the Silicon Photonics team at C2N, which is comprised of 30 members. He has published over 100 articles in scientific journals and has supervised 14 doctoral theses. His research focuses on exploring emerging physical phenomena for the fabrication of high-performance photonic circuits. The team he leads pioneered the development of AI-based integrated Fourier transform spectrometers and the generation of high-visibility photon pairs in silicon.
This is a summary of his latest work:
“In this session, I will present our latest results on the use of periodic nanostructures for exploiting Kerr and Brillouin nonlinearities. Additionally, I will explain how artificial intelligence can be used to improve the robustness of complex photonic circuits against fabrication imperfections and variations of experimental conditions.”
Prof. Dr. Sergei Tretyakov – 21.01.2026
All-angle scanning and superdirective reflectarrays
On January 21st, we had the privilege of hosting Prof. Dr. Sergei Tretyakov from Aalto University (Finland) at the UPV School of Telecommunications (ETSIT). Professor Tretyakov is a pioneer in the study of metamaterials for microwave applications and has become one of the most influential researchers in the field of electromagnetic metasurfaces in recent years. He has authored over 350 articles in international journals and 5 books, most notably “Analytical Modeling in Applied Electromagnetics” and “Electromagnetic waves in chiral and bi-isotropic media.”
During his visit, he delivered a seminar in the ETSIT assembly hall regarding his latest research:
“This is about our recent work on optimizing array element coupling using connectors behind the ground plane. We show that we can get perfect anomalous reflection even for λ/2-spaced arrays, while in our earlier works, we needed to optimize evanescent waves using subwavelength spacing.”
Luis Manuel Máñez – 04.12.2025
Strong mode coupling in Bianisotropic Metasurfaces
Metasurfaces have been widely analyzed through homogenization methods, which take advantage of the fact that meta-atoms are much smaller than the wavelength, allowing their electromagnetic behaviour to be modelled as a set of effective parameters for the constitutive relations. These techniques work well at microwave frequencies but encounter difficulties in the optical range, where the meta-atoms become comparable to the resonant wavelength, and the confinement of modes is weaker.
At optical frequencies, the coupled-mode theory has gained recognition as a robust phenomenological framework for capturing resonant effects in photonic systems. In this study, we investigate the relationship between the temporal coupled-mode theory (TCMT) and bianisotropic homogenization approaches. By examining how mode coupling strength is related to bianisotropic material parameters, we uncover a direct link between resonant interactions and the scattering properties of metasurfaces.
Based on the proposed theory, we design metasurfaces supporting quasi-bound states in the continuum (q-BICs), which exhibit giant bianisotropic effects at optical frequencies. We emphasize the analysis of strong mode coupling in metasurfaces supporting q-BICs using both FEM simulations and theory.
