D. Grojo
Aix-Marseille University
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Publication
Featured researches published by D. Grojo.
Nanoscale Research Letters | 2010
Av Kabashin; Ph Delaporte; A. Pereira; D. Grojo; R. Torres; Th Sarnet; M. Sentis
An overview of pulsed laser-assisted methods for nanofabrication, which are currently developed in our Institute (LP3), is presented. The methods compass a variety of possibilities for material nanostructuring offered by laser–matter interactions and imply either the nanostructuring of the laser-illuminated surface itself, as in cases of direct laser ablation or laser plasma-assisted treatment of semiconductors to form light-absorbing and light-emitting nano-architectures, as well as periodic nanoarrays, or laser-assisted production of nanoclusters and their controlled growth in gaseous or liquid medium to form nanostructured films or colloidal nanoparticles. Nanomaterials synthesized by laser-assisted methods have a variety of unique properties, not reproducible by any other route, and are of importance for photovoltaics, optoelectronics, biological sensing, imaging and therapeutics.
Optics Letters | 2014
D. Grojo; Nicolas Sandeau; Luca Boarino; Catalin Constantinescu; Natascia De Leo; Michele Laus; Katia Sparnacci
It is accepted so far that the formation of photonic nanojets requires the use of large dielectric spheres (several wavelengths in diameter). Here we show both numerically and experimentally that similar effects can be obtained with properly engineered sub-wavelength core-shell colloids. The design of the spheres is strongly inspired by a far-field approach for the generation of Bessel beams.
Journal of Applied Physics | 2015
D. Grojo; Alexandros Mouskeftaras; P. Delaporte; Shuting Lei
We produce and characterize high-angle femtosecond Bessel beams at 1300-nm wavelength leading to nonlinearly ionized plasma micro-channels in both glass and silicon. With microjoule pulse energy, we demonstrate controlled through-modifications in 150-μm glass substrates. In silicon, strong two-photon absorption leads to larger damages at the front surface but also a clamping of the intensity inside the bulk at a level of ≈4 × 1011 W cm−2 which is below the threshold for volume and rear surface modification. We show that the intensity clamping is associated with a strong degradation of the Bessel-like profile. The observations highlight that the inherent limitation to ultrafast energy deposition inside semiconductors with Gaussian focusing [Mouskeftaras et al., Appl. Phys. Lett. 105, 191103 (2014)] applies also for high-angle Bessel beams.
Applied Physics Letters | 2014
Alexandros Mouskeftaras; Andrei Rode; R. Clady; M. Sentis; O. Utéza; D. Grojo
This research has received financial support from the French National Research Agency (ANR 2010-JCJC-913- 01), the French Carnot Star Institute (Via-LASER), and the CNRS PICS Program No. 45052. A.R. is grateful for partial support by the Australian Research Council’s (Discovery Project DP 120102980) and by the Air Force Office of Scientific Research (USA, Grant No. FA 9550-12-1-0482).
Journal of Applied Physics | 2011
I. B. Bogatyrev; D. Grojo; P. Delaporte; S. Leyder; M. Sentis; W. Marine; Tatiana Itina
We present a theoretical model, which describes local energy deposition inside IR-transparent silicon and gallium arsenide with focused 1.3-μm wavelength femtosecond laser pulses. Our work relies on the ionization rate equation and two temperature model (TTM), as we simulate the non-linear propagation of focused femtosecond light pulses by using a 3D finite difference time domain method. We find a strong absorption dependence on the initial free electron density (doping concentration) that evidences the role of avalanche ionization. Despite an influence of Kerr-type self-focusing at intensity required for non-linear absorption, we show the laser energy deposition remains confined when the focus position is moved down to 1-mm below the surface. Our simulation results are in agreement with the degree of control observed in a simple model experiment.
Optics Letters | 2016
Maxime Chambonneau; Qingfeng Li; Margaux Chanal; N. Sanner; D. Grojo
Direct three-dimensional (3D) laser writing of waveguides is highly advanced in a wide range of bandgap materials, but has no equivalent in silicon so far. We show that nanosecond laser single-pass irradiation is capable of producing channel micro-modifications deep into crystalline silicon. With an appropriate shot overlap, a relative change of the refractive index exceeding 10-3 is obtained without apparent nonuniformity at the micrometer scale. Despite the remaining challenge of propagation losses, we show that the created structures form, to the best of our knowledge, the first laser-written waveguides in the bulk of monolithic silicon samples. This paves the way toward the capability of producing 3D architectures for the rapidly growing field of silicon photonics.
International Journal of Nanotechnology | 2012
Av Kabashin; Thierry Sarnet; D. Grojo; Ph. Delaporte; L. Charmasson; P. Blandin; R. Torres; T.J–Y. Derrien; M. Sentis
We present an overview of laser methods for nanostructuring of surfaces that are in the focus of ongoing research activities of our Institute (LP3). The methods imply the removal of material by laser radiation to provide either spontaneous nanostructuring of laser–illuminated surface or its controlled nano–modification. Here, the desired relief or architecture is achieved through a proper selection of radiation characteristics (pulse duration and wavelength) and parameters of environment (pressure of ambient gas, etc.). Examples of formed nano–architectures include penguin–like structures of black Si with enhanced light absorption in the visible, semiconductor (Si, Ge, ZnO, etc.) quantum dot nanostructures with UV/visible fluorescence, as well as periodic plasmonic nanoarrays. Exhibiting a series of unique properties, these structures are of importance for photovoltaics, optoelectronics and biological sensing applications.
Applied Physics Letters | 2016
Alexandros Mouskeftaras; Margaux Chanal; Maxime Chambonneau; R. Clady; O. Utéza; D. Grojo
Carrier kinetics in the density range of N = 10(17) - 10(20) cm(-3) is investigated inside the bulk of crystalline silicon. Most conventional experimental techniques used to study carrier mobility are indirect and lack sensitivity because of charging effects and recombination on the surface. An all optical technique is used to overcome these obstacles. By focusing 1.3-mu m femtosecond laser pulses in the volume, we inject an initial free-carrier population by two-photon absorption. Then, we use pump-and-probe infrared microscopy as a tool to obtain simultaneous measurements of the carrier diffusion and recombination dynamics in a microscale region deep inside the material. The rate equation model is used to simulate our experimental results. We report a constant ambipolar diffusion coefficient D-a of 2.5 cm(2) s(-1) and an effective carrier lifetime tau(eff) of 2.5 ns at room temperature. A discussion on our findings at these high-injection levels is presented
Physical Review E | 2017
Jörg Hermann; D. Grojo; E. Axente; Christoph Gerhard; Miloš Burger; V. Craciun
Laboratory plasmas inherently exhibit temperature and density gradients leading to complex investigations. We show that plasmas generated by laser ablation can constitute a robust exception to this. Supported by emission features not observed with other sources, we achieve plasmas of various compositions which are both uniform and in local thermodynamic equilibrium. These properties characterize an ideal radiation source opening multiple perspectives in plasma spectroscopy. The finding also constitutes a breakthrough in the analytical field as fast analyses of complex materials become possible.
Journal of Applied Physics | 2015
Guang Yang; Marc Dussauze; Vincent Rodriguez; Frédéric Adamietz; Nicolas Marquestaut; K.L.N. Deepak; D. Grojo; O. Utéza; P. Delaporte; Thierry Cardinal; Evelyne Fargin
Micro-structured second harmonic generation responses have been achieved on borophosphate niobium glasses by thermal poling using micro-patterned silicon substrates. The poling imprinting process has created sub-micrometer sized patterns of both surface relief and second order optical responses on the anode glass surface. Field enhancement effects within the micro structured electrode are believed to govern the charge density on the glass surface during the process and thus amplitudes of both implemented electric field and Maxwell stresses.