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David Grojo

Publications and source records attributed to David Grojo.

4 recordsLinked to original sources
arXiv2023

Femtosecond laser induced creation of G and W-centers in silicon-on-insulator substrates

The creation of fluorescent defects in silicon is a key stepping stone towards assuring the integration perspectives of quantum photonic devices into existing technologies. Here we demonstrate the creation, by femtosecond laser annealing, of W and G-centers in commercial silicon on insulator (SOI) previously implanted with 12C+ ions. Their quality is comparable to that found for the same emitters obtained with conventional implant processes; as quantified by the photoluminescence radiative lifetime, the broadening of their zero-phonon line (ZPL) and the evolution of these quantities with temperature. In addition to this, we show that both defects can be created without carbon implantation and that we can erase the G-centers by annealing while enhancing the W-centers' emission. These demonstrations are relevant to the deterministic and operando generation of quantum emitters in silicon.

physics.optics↗
arXiv2022

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 $\mu$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-$\mu$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↗
arXiv2022

Transmission laser welding of similar and dissimilar semiconductor materials

Laser micro-welding is an advanced manufacturing method today applied in various domains. However, important physical limitations have prevented so far to demonstrate its applicability in silicon and other technology-essential semiconductors. Concentrating on circumventing the optical limits on the deliverable energy density at interfaces between narrow-gap materials with intense infrared light, we make the first feasibility demonstration of transmission laser welding between silicon workpieces using nanosecond laser pulses. We obtain a shear joining strength of 32$\pm$10 MPa which compares very favorably to the complex process alternatives. Supported by experiments repeated on different material combinations including gallium arsenide, we confirm that this remarkable performance level is achievable for similar and dissimilar semiconductors. The demonstrations rely on a small footprint fiber laser, an aspect that holds great promises for the advent of a high-efficiency flexible process beneficial for important technology developments including lab-on-a-chip and hybrid semiconductor systems.

physics.app-ph↗