arXiv subjects

Fernando Agulló-Rueda

Publications and source records attributed to Fernando Agulló-Rueda.

2 recordsLinked to original sources

arXiv2026

Laser fabrication of vibrating microcavities on silicon: Formation dynamics and frequency tunability

Laser processing of silicon has long since become a standard method for wafer dicing, surface texturing, re-crystallization after ion implantation, as well as surface amorphization, to name a few examples. Here, we introduce a novel concept, the fabrication of vibrating microcavities in a commercial platform, Si wafers covered by a thick SiO2 layer, acting as a membrane. We demonstrate that by exposing our material system to single ultrashort laser pulses above the evaporation threshold of Si, a controlled delamination of the cover layer without fracture can be achieved, leading to the formation of a microcavity accompanied by a surface bulging up to 1.5 micrometer. The formation dynamics of the microcavities has been investigated by time-resolved optical probe techniques. Ultrafast pump-probe microscopy resolves the initial stages of substrate melting, the onset of layer expansion followed by relaxation. Real-time reflectivity measurements with nanosecond resolution resolve the long lived, highly complex oscillation process of the membrane, extending over tens of microseconds. The formed cavities can be re-excited at low fluence without damage or degradation, featuring vibrations at single frequencies with high Q factors. The frequencies can be tuned continuously from 8 MHz up to 19 MHz by adjusting the fabrication fluence. A simple classical model is found to well describe the behavior of the membranes. Our results pave the way for applications in micro- and nanooptics and acoustics, in great part due to the commercial availability of the Si-SiO2 platform and the simplicity of the fabrication method. An extension to the field of microelectromechanical system (MEMS) of this technology is proposed.

physics.optics↗

arXiv2026

Antimony for broadband nanophotonics across the ultraviolet, visible and infrared

Semimetal elemental antimony (Sb) nanostructures show great potential for applications where nanophotonic properties play a key role, such as phase-change optical memories, non-linear optical elements, photothermal therapy agents, photodetectors and photocatalysts. However, designing advanced Sb-based photonic devices critically requires an accurate and reliable knowledge of the optical response of bulk and nanoscale Sb. Herein, we report for the first time a fully consistent and accurately measured dielectric function for Sb nanoscale films in a wide spectral range from the ultraviolet to the far infrared (4 - 0.04 eV, i.e. ~ 0.3 - 30 $μ$m), surpassing previous reports that explored a limited spectral range. It is found that the Sb spectral response is driven exclusively by giant interband transitions in the visible up to mid infrared (4 - 0.4 eV, i.e. ~ 0.3 - 3 $μ$m), and that their contribution dominates over that of free carriers down to 0.12 eV (i.e. ~ 10 $μ$m). Such spectral response enables Sb nanostructures to display spectrally selective and tunable nanophotonic resonances. First, we showcase interband plasmonic resonances in the visible-to-near infrared for Sb nanogratings. Second, we report giant refractive index dielectric resonances in the mid infrared for nanostructured Sb/dielectric/metal resonant cavities. These findings open a pathway to optimized planar Sb nanoscale designs enabling a tailored light-matter interaction, which will be useful for integrated data, telecom, medical, optoelectronic and energy conversion devices operating in a broad spectral range.

physics.optics↗