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Jolly A.,Institute Doptique Daquitaine | Jolly A.,CEA Cesta | Gokhan F.S.,Hasan Kalyoncu University | Jolly J.-C.,University of Notre Dame | And 2 more authors.
Applied Physics B: Lasers and Optics | Year: 2015

We demonstrate the effectiveness of silicon phase masks to implement spatially resolved, multispectral imaging capabilities in the range of terahertz frequencies, using a standard setup of basic interest for time-domain spectrometry with a single-cell source and a single-cell detector. Our principle primarily aims at the development of robust and inexpensive systems. It consists of appropriate space-to-time encoding, in order to ensure single-scan triggering and then take advantage of rapid and self-consistent measurements in the two-dimensional space. The process enables very efficient discrimination giving access to a relevant spatial resolution in the analysis of small size, planar assemblies made of inhomogeneous materials. Benchmark results are provided to validate the concept, thanks to prototyping phase masks with 2 × 2 pixels, prior evidencing actual performance limitations in the case of 3 × 3 pixels. Due to the frequency bandwidth of 0.1–1.5 THz in our setup and to the available operating conditions, currently acceptable pixel resolutions lie in the range of 3–4 mm. Numerical modeling by means of finite elements helps to discuss these numbers and to investigate the relevant theoretical issues, figuring the main propagation issues in connection with a sub-picosecond seed pulse throughout various masks. This involves diffraction and trailing edge effects when crossing the mask together with residual, parasitic reflections. Finally, we give a consistent prospective for improved performance, via realistic updates regarding the architecture of the setup and complementary post-processing. Further values for the attainable spatial resolution then range from 5 × 5 to 6 × 6 pixels. © 2015, Springer-Verlag Berlin Heidelberg.

Schembri F.,CNRS Laboratory of Future | Schembri F.,Institute dOptique dAquitaine | Bodiguel H.,CNRS Laboratory of Future | Colin A.,CNRS Laboratory of Future
Soft Matter | Year: 2015

We report the development and analysis of a velocimetry technique based on the short time displacement of molecular tracers, tagged thanks to photobleaching. We use confocal microscopy to achieve a good resolution transverse to the observation field in the direction of the velocity gradient. The intensity profiles are fitted by an approximate analytical model which accounts for hydrodynamic dispersion, and allow access to the local velocity. The method is validated using pressure driven flow in microfluidic slits having a thickness of a few tens of micrometers. We discuss the main drawbacks of this technique which is an overestimation of the velocity close to the walls due to the combination of molecular diffusion and shear. We demonstrate that this error, limited to a near wall region of a few micrometers thick, could be controlled by limiting the diffusion of fluorophore molecules or minimizing the bleaching time. The presented technique could be combined with standard particle imaging velocimetry to access velocity differences and allow particle trajectory analysis in microflows of suspensions. This journal is © The Royal Society of Chemistry.

Lozan O.,French National Center for Scientific Research | Perrin M.,French National Center for Scientific Research | Ea-Kim B.,CNRS Charles Fabry Laboratory | Rampnoux J.M.,French National Center for Scientific Research | And 2 more authors.
Physical Review Letters | Year: 2014

In this Letter, we study the heat dissipated at metal surfaces by the electromagnetic field scattered by isolated subwavelength apertures in metal screens. In contrast to the common belief that the intensity of waves created by local sources should decrease with the distance from the sources, we reveal that the dissipated heat at the surface remains constant over a broad spatial interval. This behavior that occurs for noble metals at near infrared wavelengths is observed with nonintrusive thermoreflectance measurements and is explained with an analytical model, which underlines the intricate role played by quasicylindrical waves in the phenomenon. Additionally, we show that, by monitoring the phase of the quasicylindrical waves, the total heat dissipated at the metal surface can be rendered substantially smaller than the heat dissipated by the launched plasmon. This interesting property offers an alternative to amplification for overcoming the loss issue in miniaturized plasmonic devices. © 2014 American Physical Society.

Nguyen M.,French National Center for Scientific Research | Loumena C.,Institute dOptique dAquitaine | Bussiere A.,Institute dOptique dAquitaine | Kling R.,Institute dOptique dAquitaine | And 2 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2016

Processing of helicopter engines faster, better and more reliably is the triptych which binds LOMA, ALPhANOV and TURBOMECA. In current production machines, flash lamp pumped lasers are employed to drill thousands of cooling holes with specific geometries and diameters to ensure a homogeneous air flow over the surface. However we aim to enhance the production process. Therefore, the three partners started an initiative to identify and overcome the shortcomings of the current process, where the laser source is a key element for improvement. In this paper, we report on the latest developments in multi-pulse drilling using an IPG fiber laser. The latter delivers, at a tunable repetition rate (from single shot up to 2 kHz), laser pulses whose width and peak power are adjustable in between 0.2 - 10 ms and 0 - 12 kW respectively. We have focused our work on drilling of thick sheets of metal alloys with different geometries and different processing strategies. We will show that using such laser system it is possible to decrease the processing time while limiting the heat affected zones and collateral effects. Finally, the impact of the different physical processes in play during the drilling on the geometry of the holes will be discussed. © 2016 SPIE.

Lott G.,Electro Scientific Industries Inc. | Falletto N.,Electro Scientific Industries Inc. | Falletto N.,EOlite Systems Inc. | Devilder P.-J.,EOlite Systems Inc. | Kling R.,Institute dOptique dAquitaine
Journal of Laser Applications | Year: 2016

The ability to rapidly and precisely generate high-quality features with small dimensions in sapphire is paramount for broadening its appeal and expanding its utilization for consumer electronics applications. Intrinsic properties of sapphire, including high scratch resistance, make it an attractive option for these purposes, but the ability to machine fine features in sapphire substrates with common mechanical and laser-based methods has proved elusive to this point. In this study, we present results from a series of systematic trials to determine the optimum laser processing parameters for drilling 400 μm diameter holes with no cracks or chips and <5° taper in 430 μm thick sapphire wafers with a 0.8 ps 1030 nm source. Holes are drilled at repetition rates from 21 to 1042 kHz, overlaps from 70% to 98%, and translation of the beam waist through the sample at rates from 10 to 200 μm/s. We present qualitative and quantitative results generated from laser scanning microscopy demonstrating that holes with <5° taper and no cracks or chips can be drilled at repetition rates of 260 kHz with 90% and 95% overlap and 521 kHz with 95% overlap. We find that the optimum processing parameters for drilling holes with <5° taper correlates well with the conditions necessary for avoiding chipping, cracking, and back-side damage rings. Holes with <5° taper can be drilled in as short as 4-6 s per holes, and holes with <2° taper can be drilled in 10-12 s per hole. © 2016 Laser Institute of America.

Jolly A.,Institute dOptique dAquitaine | Jolly A.,CEA Cesta | Gokhan F.S.,Hasan Kalyoncu University | Bello R.,Institute dOptique dAquitaine | Dupriez P.,Institute dOptique dAquitaine
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

We present a comprehensive experimental study of the technique of Longitudinal Mode Filling (LMF) applied to the reduction of Stimulated Brillouin Scattering (SBS), in Ytterbium Doped Fibre Amplifiers (YDFA) at the wavelength of 1064 nm. Pulse durations and Mode Field Diameters (MFD) lie in the ranges of 10 - 100 ns and 10 - 35 μm, respectively. Input pulse-shaping is implemented by means of direct current modulation in multimode Laser-Diode seeds. This evidences a number of interests in the development of robust and low cost Master Oscillator Power Amplifiers (MOPA). Highly energetic, but properly shaped, nanosecond pulses may be produced this way without any need of additional electro-optical means for in-line phase and amplitude modulation. Seeds consist of Distributed Feed- Back (DFB) and Fibre Bragg Gratings (FBG) with different fibre lengths. We demonstrate the benefit of LMF with properly controlled mode spacing, in combination with chirp effects due to fast current transients in the semiconductors, in order to deal with SBS thresholds in the range of a few to some hundred μJ. The variations of the SBS threshold are discussed versus the number of longitudinal modes, the operating conditions of the selected seed and pulse-shaping conditions. © 2015 SPIE.

Refregier Ph.,École Centrale Marseille | Wasik V.,École Centrale Marseille | Vynck K.,ESPCI ParisTech | Vynck K.,Institute DOptique DAquitaine | Carminati R.,ESPCI ParisTech
Optics Letters | Year: 2014

The theory of the intrinsic coherence, originally developed for 2D fields, is generalized in order to analyze coherence properties of light with a polarization that can fluctuate in three dimensions. Several notions, such as the concept of mean-square coherence and the capacity to describe irreversible behaviors, are demonstrated and illustrated with the example of light in 3D disordered media with frozen and nonfrozen disorders. © 2014 Optical Society of America.

Zoubir A.,Institute Doptique Daquitaine | Dupriez P.,Institute Doptique Daquitaine
European Physical Journal: Special Topics | Year: 2015

The concept of massively parallel coherent fiber lasers holds great promise to generate enormous laser peak power in order to produce highly energetic particle beams. Such technology is expected to provide a route to practical particle colliders or to proton generation for medical applications. Such concept is based on the phasing of thousands of fiber amplifiers each emitting mJ level pulses, in which optical fibers are key components. In this paper, we present important technological building blocks based on optical fibers, which could pave the way for efficient, compact and cost-effective components to address the technological challenges ahead. © 2015, EDP Sciences and Springer.

Berisset M.,Institute dOptique dAquitaine | Lebrun L.,Institute dOptique dAquitaine | Faucon M.,Institute dOptique dAquitaine | Kling R.,Institute dOptique dAquitaine | And 2 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2016

We demonstrated herein a new type of cladding light strippers suitable for high power systems. By precisely micro-machining the surface of the fiber we create CLS with efficiencies as high as 97 % for large NA, multi-mode, cladding light (NA = 0.3), and 70 % for single-mode, low NA, light. The NA of the cladding light is reduced from 0.3 down to 0.08. The CLS exhibit a 1°C/stripped-Watt temperature elevation making them very suitable for high power applications. This fabrication method is simple and reliable. We have tested different texturization geometries on several different fibers: 20/400 from Nufern, KAGOME, and LMA 10 and LMA 15 fibers (results not shown herein) and we observed good efficiencies and temperature elevation behavior for all of them. Finally, large scale production of CLS with this method is possible since the time necessary to prepare on CLS is very small, in the order of few seconds. © 2016 SPIE.

Aguergaray C.,Institute dOptique dAquitaine
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2016

We demonstrate herein a PM-fiber based cavity design capable of supporting many different pulse dynamics, such as soliton propagation or dissipative solitons in a dispersion managed cavity. By changing the dispersion of the fiber Bragg grating of the cavity we modify the net cavity dispersion, and thus stimulate various pulse dynamics. In particular we demonstrate the first net normal cavity, all-PM, all-fiber, dipersion managed cavity operating the in the 2μm range. Furthermore, we also demonstrate an all-fiber all-PM MOPA system capable of delivering up to 6 W of average power at 16 MHz by direct amplification of 70 ps long narrowband pulses. The amplifier stages are not fully saturated and are currently limited by the pump power available. © 2016 SPIE.

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