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Sujet de stage / Master 2 Internship

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Irradiation effects in ZnGeP2 crystals

Contact: BOIZOT Bruno, , bruno.boizot@polytechnique.edu, +33 1 69 33 45 22
Summary:
ZnGeP2 crystals have good properties in the IR domain. However, synthesis point defects limit this property by absorption processes. The goal of this M2 training period is therefore is to study the nature of the defects responsible and to modify their structure using irradiation.
Possibility of continuation in PhD: Oui
Deadline for application:04/04/2019

Full description:
Infrared laser sources are based on non-linear optics: a pump laser (1 or 2 µm) is converted into tunable ~3 – 12 µm laser emissions thanks to a single crystal with appropriate properties. Beyond 4µm, conventional oxide crystals are no longer usable that's why non-oxide compounds are studied: ZnGeP2 (ZGP) is one of the best. Nevertheless, optical quality must be improved to increase the laser yield. Different kinds of defects can appear during the growth process: twinning, index inhomogeneity, point defects, ...
Some point defects as ion vacancies are responsible of the residual absorbance at 2 µm (the pumping wavelength). Recent tests on the SIRIUS electron irradiation facility at the Ecole Polytechnique showed that, at a certain irradiation level around 1017 e.cm-2, this absorption decreases drastically. A complete study has to be undertaken completed with defects characterization using Electron Paramagnetic Resonance (EPR) spectroscopy. The goal is therefore to identify the nature of the defect responsible of the absorbance at 2 µm and the mecanisms at atomic level leading to the property improvement observed in the irradiated samples.
Technics/methods used during the internship:
Electron paramagnetic resonance Crystal synthesis Irradiation at SIRIUS facility

Laboratory
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