arXiv subjects

Mario Garcia-Lechuga

Publications and source records attributed to Mario Garcia-Lechuga.

5 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

Scaling the Wavelength to Optimize Ultrafast Laser Processing of Bandgap Materials

The spectral characteristics of ultrashort laser pulses offer unique possibilities to control interactions in space and time as well as the subsequent material responses. In particular, selecting the wavelength predefines the fundamental mechanisms governing laser-matter interaction, and thus, how energy is deposited. This Chapter provides an overview on how the essential physical effects in ultrafast laser-matter interaction scale with the wavelength, and the consequences for bandgap material processing applications. First, we recall the main spectral properties of bandgap materials and discuss the important question of the expected processing resolutions depending on wavelength. Then, recent studies on the impact of the wavelength in ultrafast laser-dielectric interaction are presented. Finally, we present how the latest developments in infrared ultrafast laser sources can be advantageously utilized to internally process narrow-gap materials despite challenges related to increased nonlinearities.

physics.optics↗

arXiv2026

Hybrid Femtosecond Laser and Ion-Implantation Processing for Controlled, Deep, High-Efficiency Ablation in Fused Silica

Femtosecond laser modification of fused silica enables precise surface tailoring for the fabrication of micro-optical components such as microlenses and diffractive elements. However, the process is governed by laser-matter interactions where the local fluence determines the processing depth, often limiting control over feature geometry and efficiency. Here, we present a hybrid approach combining localized Au implantation (1.8 MeV Au2+ ions) into SiO2 samples with femtosecond laser irradiation (250 fs), effectively tuning the laser-matter interaction and resulting morphology. At both 515 nm and 1030 nm irradiation wavelengths, single-shot femtosecond pulses produce cylindrical craters with sharp edges and flat-bottom profiles. Independently of the fluence, these craters exhibit a constant depth of 550 nm, corresponding to the region of maximum Au concentration. The effect manifests already at moderate fluence (app. 4 J/sq.cm) and yields high ablation efficiency, up to 15 cubic micrometers per microjoule. The hybrid method also works effectively at lower implantation doses that preserve the excellent transmission of fused silica, offering a promising pathway for the high-quality fabrication of flat optical components such as binary phase masks, phase lenses, or fused-silica micromolds.

physics.optics↗

arXiv2023

Wavelength-independent performance of femtosecond laser dielectric ablation spanning over three octaves

Ultrafast laser breakdown of wide bandgap dielectrics is today a key for major technologies ranging from 3D material processing in optical materials to nanosurgery. However, a contradiction persists between the strongly nonlinear character of energy absorption and the robustness of processes to the changes of the bandgap/wavelength ratio depending on applications. While various materials and bandgaps have been studied, we concentrate here the investigations on the spectral domain with experiments performed with wavelength drivers varied from deep-ultraviolet (258 nm) to mid-infrared (3.5 $μ$m). The measured fluence thresholds for single shot ablation in dielectrics using 200-fs pulses exhibit a plateau extending from the visible domain up to 3.5-$μ$m wavelength. This is accompanied, after ablation crater analysis, by a remarkable invariance of the observed ablation precision and efficiency. Only at the shortest tested wavelength of 258 nm, a twofold decrease of the ablation threshold and significant changes of the machining depths are detected. This defines a lower spectral limit of the wavelength-independence of the ablation process. By comparison with simulations, avalanche ionization coefficients are extracted and compared with those predicted with the Drude model. This must be beneficial to improve predictive models and process engineering developments exploiting the new high-power ultrafast laser technologies emitting in various spectral domains.

physics.optics↗

arXiv2014

Transient Newton rings in dielectrics upon fs laser ablation

We report the appearance of transient Newton rings in dielectrics (sapphire and lead-oxide glass) during ablation with single fs laser pulses. Employing femtosecond microscopy with 800 nm excitation and 400 nm illumination, we observe a characteristic ring pattern that dynamically changes for increasing delay times between pump and probe pulse. Such transient Newton rings have been previously observed in metals and semiconductors at fluences above the ablation threshold and were related to optical interference of the probe beam reflected at the front surface of the ablating layer and at the interface of the non-ablating substrate. Yet, it had been generally assumed that this phenomenon cannot be (and has not been) observed in dielectrics due to the different ablation mechanism and optical properties of dielectrics. The fact that we are able to observe them has important consequences for the comprehension of the ablation mechanisms in dielectrics and provides a new method for investigating these mechanisms in more detail.

physics.optics↗