Publications by authors named "David Jegouso"

6 Publications

  • Page 1 of 1

Birefringence phase-matched direct third-harmonic generation in a ridge optical waveguide based on a KTiOPO single crystal.

Opt Express 2021 Jul;29(14):22266-22274

Birefringence phase-matched third-harmonic generation at 1594 nm is performed for the first time in a KTiOPO single crystal micrometric ridge waveguide. The energy conversion efficiency reaches 3.4% for a pump energy as low as 2 µJ over a pulse duration of 15 ps at a repetition rate of 10 Hz. Strong agreements between theory and experiments for both phase-matching and conversion efficiency is obtained, which let us envision future triple photon generation quantum experiments.
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http://dx.doi.org/10.1364/OE.432636DOI Listing
July 2021

In-Plane Magnetic Domains and Néel-like Domain Walls in Thin Flakes of the Room Temperature CrTe Van der Waals Ferromagnet.

ACS Appl Mater Interfaces 2020 Jul 25;12(27):30702-30710. Epub 2020 Jun 25.

Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut NEEL, 38000 Grenoble, France.

The recent discovery of magnetic van der Waals (vdW) materials triggered a wealth of investigations in materials science and now offers genuinely new prospects for both fundamental and applied research. Although the catalog of vdW ferromagnets is rapidly expanding, most of them have a Curie temperature below 300 K, a notable disadvantage for potential applications. Combining element-selective X-ray magnetic imaging and magnetic force microscopy, we resolve at room temperature the magnetic domains and domain walls in micron-sized flakes of the CrTe vdW ferromagnet. Flux-closure magnetic patterns suggesting an in-plane six-fold symmetry are observed. Upon annealing the material above its Curie point (315 K), the magnetic domains disappear. By cooling back the sample, a different magnetic domain distribution is obtained, indicating material stability and lack of magnetic memory upon thermal cycling. The domain walls presumably have Néel texture, are preferentially oriented along directions separated by 120°, and have a width of several tens of nanometers. Besides microscopic mapping of magnetic domains and domain walls, the coercivity of the material is found to be of a few millitesla only, showing that the CrTe compound is magnetically soft. The coercivity is found to increase as the volume of the material decreases.
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http://dx.doi.org/10.1021/acsami.0c07017DOI Listing
July 2020

Entangled-photon decision maker.

Sci Rep 2019 08 22;9(1):12229. Epub 2019 Aug 22.

Université Grenoble Alpes, CNRS, Institut Néel, 38042, Grenoble, France.

The competitive multi-armed bandit (CMAB) problem is related to social issues such as maximizing total social benefits while preserving equality among individuals by overcoming conflicts between individual decisions, which could seriously decrease social benefits. The study described herein provides experimental evidence that entangled photons physically resolve the CMAB in the 2-arms 2-players case, maximizing the social rewards while ensuring equality. Moreover, we demonstrated that deception, or outperforming the other player by receiving a greater reward, cannot be accomplished in a polarization-entangled-photon-based system, while deception is achievable in systems based on classical polarization-correlated photons with fixed polarizations. Besides, random polarization-correlated photons have been studied numerically and shown to ensure equality between players and deception prevention as well, although the CMAB maximum performance is reduced as compared with entangled photon experiments. Autonomous alignment schemes for polarization bases were also experimentally demonstrated based only on decision conflict information observed by an individual without communications between players. This study paves a way for collective decision making in uncertain dynamically changing environments based on entangled quantum states, a crucial step toward utilizing quantum systems for intelligent functionalities.
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http://dx.doi.org/10.1038/s41598-019-48647-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6706396PMC
August 2019

Phase-matching directions, refined Sellmeier equations, and second-order nonlinear coefficient of the infrared Langatate crystal La₃Ga(5.5)Ta(0.5)O₁₄.

Opt Lett 2014 Jul;39(13):4033-6

We directly measured phase-matching directions of second harmonic, sum, and difference frequency generations in the Langatate La₃Ga(5.5)Ta(0.5)O₁₄ (LGT) uniaxial crystal. The simultaneous fit of the data enabled us to refine the Sellmeier equations of the ordinary and extraordinary principal refractive indices over the entire transparency range of the crystal, and to calculate the phase-matching curves and efficiencies of LGT for infrared optical parametric generation.
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http://dx.doi.org/10.1364/OL.39.004033DOI Listing
July 2014

Dual-wavelength source from 5%MgO:PPLN cylinders for the characterization of nonlinear infrared crystals.

Opt Express 2013 Nov;21(23):28886-91

We conceived a unique fully parametric source based on two independent cylindrical OPOs simultaneously pumped by the same Nd:YAG laser. Each OPO delivers more than 2 mJ and is continuously tunable between 1.41 µm and 4.3 µm. This source is of particular interest for the study of the generation of infrared parametric light in nonlinear crystals. It was validated by performing difference frequency generation experiments in CdSe crystals with output in the range 8 - 10 µm.
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http://dx.doi.org/10.1364/OE.21.028886DOI Listing
November 2013

Widely tunable optical parametric oscillator in a 5 mm thick 5% MgO:PPLN partial cylinder.

Opt Lett 2013 Mar;38(6):860-2

Institut Néel Centre National de la Recherche Scientifique-Université Joseph Fourier, Grenoble, France.

A 5 mm thick and 38 mm long 5% MgO-doped periodically poled lithium niobate (MgO:PPLN) cylinder with a grating period of 28 μm has been engineered as a partial cylinder with an angular aperture of 45°. An optical parametric oscillator based on this crystal and pumped at 1.064 μm is reported. The output energy is comparable to that generated in the same kind of sample cut as a slab, but the wavelength tunability from 1.41 to 4.3 μm is much broader and continuous.
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http://dx.doi.org/10.1364/OL.38.000860DOI Listing
March 2013
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