HAL Portal IOGS (nstitut d'Optique Graduate School)
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Impact of a tilted coverslip on two-photon and STED microscopy
No full textInternational audienceThe advent of super-resolution microscopy has opened up new avenues to unveil brain structures with unprecedented spatial resolution in the living state. Yet, its application to live animals remains a genuine challenge. Getting optical access to the brain in vivo requires the use of a ‘cranial window’, whose mounting greatly influences image quality. Indeed, the coverslip used for the cranial window should lie as orthogonal as possible to the optical axis of the objective, or else significant optical aberrations occur. In this work, we assess the effect of the tilt angle of the coverslip on STED and two-photon microscopy, in particular, image brightness and spatial resolution. We then propose an approach to measure and reduce the tilt using a simple device added to the microscope, which can ensure orthogonality with a precision of 0.07°
Temperature Effect on the Radioluminescence of Differently doped Silica-based Optical Fibres
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Comparative analysis of optical and numerical models for reflectance and color prediction of monolithic dental resin composites with varying thicknesses
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Switching Off your Device Does Not Protect Against Fault Attacks
No full textInternational audiencePhysical attacks, and among them fault injection attacks, are a significant threat to the security of embedded systems. Among the means of fault injection, laser has the significant advantage of being extremely spatially accurate. Numerous state-of-the-art studies have investigated the use of lasers to inject faults into a target at run-time. However, the high precision of laser fault injection comes with requirements on the knowledge of the implementation and exact execution time of the victim code. The main contribution of this work is the demonstration on experimental basis that it is also possible to perform laser fault injection on an unpowered device. Specifically, we targeted the Flash non-volatile memory of a 32-bit microcontroller. The advantage of this new attack path is that it does not require any synchronisation between the victim and the attacker. We provide an experimental characterization of this phenomenon with a description of the fault model from the physical level up to the software level. Finally, we applied these results to carry out a persistent fault analysis on a 128-bit AES with a particularly realistic attacker model which reinforces the interest of the PFA
Avancements de la compréhension de la synthèse et de la croissance desnanoparticules par ablation laser et décharge par étincelle.
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In situ monitoring of thin alumina passive film growth by surface plasmon resonance (SPR) during an electrochemical process
No full textInternational audienceAbstract This article presents a sensing technique to characterize the growth of an alumina passive film on an aluminum micro structured layer in situ. The technique uses surface plasmon resonance (SPR) on aluminum coated gratings with spectroscopic measurements during electrochemical polarization in 0.02M Na 2 SO 4 . The structure of the sensor was first simulated and then fabricated by photolithography. The grating was then replicated by nanoimprint (NIL) in Sol–Gel before pure aluminum layer was deposited by RF magnetron sputtering to produce the samples used in this study. Coupled plasmonic and electrochemical measurements confirmed the feasibility of in situ characterization (thickness) of alumina passive film on aluminum-based gratings in neutral aqueous media. Combining both measurements with an appropriated SPR spectrum fitting lead to alumina thickness monitoring within a few nanometers’ accuracy. The objectives and challenges of this study are to better characterize the alumina growth during electrochemical process combining in situ electrochemical process and SPR spectra in order to determine thin passive layer characteristics
Femtosecond laser upscaling strategy and biological validation for dental screws with improved osteogenic performance
No full textOsseointegration is one of the key conditions for long term successful dental implantation. To this end, titanium alloys undergo plethora of surface treatments able to sustain osteogenic differentiation. For these surface treatments, femtosecond laser (FSL) can generate precise and reproducible surface patterns on titanium, avoiding thermal damage and chemical pollution. We recently identify that laser-induced periodic surface structure (LIPSS) with radial orientation, generated on model (flat) titanium surface, has a high osteogenic potential. However, nano-texturing is time consuming. In the present study, we aimed to reduce the texturing time of radial LIPSS, as well as processing of large commercially available dental screws by ways of laser beam engineering. Our objectives were to maintain at least osteogenic properties demonstrated on model surfaces by adjusting laser beam diameters and to demonstrate maintenance of performance with a dental screw texturing process not exceeding 1 minute.We first textured model surfaces with radial LIPSS by laser beams of different diameters, with surface impacts of 24µm, 80µm or 180µm, named as R24, R80 or R180 respectively. Osteogenic performance of human mesenchymal stem cells (hMSCs) were compared; seeded on polished control surfaces and textured surfaces and subjected to osteogenic evaluation by cell/matrix imaging, qRT-PCR and mineral deposition quantification. All textured surfaces showed greater osteogenic potential than the control surfaces, with significantly higher efficacy on R180 surface. Therefore, R180 pattern with large beam impacts was chosen for texturing on a dental screw and its osteogenic activity was compared to that of a non-textured screw. Interestingly, R180 required only 40 seconds to be textured on whole screws, on which it preserved a high osteogenic potential. Thus, by using FSL technology, we have improved the osteogenic potential of a topographic pattern while optimizing and scaling up its processing time on a medical device
A Lightweight Non-Oscillatory Delay-Sensor for Remote Power Analysis
No full textInternational audienceTraditionally, there have been two main obstacles for practical power analysis attacks: the adversary needed physical access to the device, and they had to use sophisticated sensing equipment to obtain the samples. However, it is now known that an attacker may leverage remote access to the platform and internal sensors to perform power analysis attacks. Internal sensors are circuits created from components native to the device, for example the reconfigurable fabric in some heterogeneous SoCs. Now, the main drawbacks of these sensors are their large sizes and that they require precise placement to improve their fidelity. This facilitates their detection. In this paper, we describe a novel internal sensor created from an 8-bit multiplier. This circuit can be implemented with just two LUT6 and four CARRY4 in AMD-Xilinx FPGAs. It can produce up to 200 MSpS. Furthermore, no precise placement nor special hardware description are required in its implementation. To validate our claims, we have recovered the full key of an unprotected implementation of AES-128 clocked at 100 MHz with under 3e4 encryption traces
Mixed-field Radiation Monitoring and Beam Characterisation Through Silicon Diode Detectors
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Beyond the Microscale: Advances in Surface Nanopatterning by Laser-Driven Self-Organization
No full textInternational audienceDesigning complex local properties that seamlessly integrate efficientfunctions into processed materials presents a formidable challenge. Apromising solution has emerged in the form of ultrafast laser-surfacestructuring. Through time-controlled polarization ultrafast irradiation at thepicosecond timescale, spontaneous self-organization of surfaces can beinduced. The thermal gradient length scale unfolds on the micro- andnanoscale, instigating thermoconvection that leads to structured surfacesupon quenching. Convective instabilities dynamically shape intricate yetself-regulated periodic relief structures. The ability to achieve laser-inducedself-organization in both surface dimensions holds immense scientificimportance, as it unlocks the potential to create uniform periodic 2D patternsby harnessing the inherent regulation of nonlinear dynamics processes influids. This comprehensive review explores recent advances in understandingand leveraging ultrafast laser-induced self-organization for precise patterningacross versatile scales and applications. The insights herein hold the potentialto drive significant advancements in nanoscale manufacturing through 2Dlaser-induced periodic surface structures