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Reference : UPR10-MICPEF-011
Workplace : VALBONNE
Date of publication : Thursday, September 26, 2019
Scientific Responsible name : Patrice GENEVET et Jesus ZUNIGA PEREZ
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 2 December 2019
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
This thesis is devoted to the design, realization and characterization of new optical devices based on the introduction of two-dimensional elements, metasurfaces. These elements are composed of resonant optical diffusers of subwavelength size. These are generally positioned along an interface in a suitable pattern and at a distance also subwavelength. The presence of these diffusers introduces abrupt local changes of phase, which opens the way to a new mastery of the direction of propagation of the electromagnetic field.
In this thesis, we propose to realize metasurfaces on laser devices such as "vertical cavity surface emitting laser (VCSEL)" or "edge emitter" which have the property of emitting laser light, thus coherent and with a length of very specific wave, by the surface or by the slice. We propose to use the metasurface concept to control the direction of light emitted by this kind of devices and to influence their characteristics. This approach will effectively enable us to achieve new types of lasers, by controlling their collimation (technical word indicating that the light emitted does not spread in all directions but on the contrary remains confined in a beam of some mm diameter at propagation), either by directly influencing the laser process. Indeed, two physical processes make it possible to obtain a coherent light emission characteristic of the laser beams. The first approach, based on a population inversion is used in most devices.The second is based on a process of condensation of quantum states (mid-photons mid-excitons) also called polaritons. Due to their hybrid nature, the polariton condensation mechanisms are strongly influenced by the dispersion of the laser cavity. Since metasurfaces make it possible to modify and control the optical properties of a laser cavity, they will enable us to design innovative laser devices, based on the effects of novel condensations.
These new types of components have a number of applications. Knowing, for example, that VCSEL sources are today the most used laser sources in modern opto-electronic components, the candidate will have the opportunity to work in relation with manufacturers in order to promote and exploit their advances in the laboratory.
The Research Center for Heteroepitaxy and its Applications (CRHEA - UPR10) is a CNRS research laboratory specializing in the epitaxy of large bandgap semiconductor materials such as III nitride materials (GaN, AlN), zinc oxide (ZnO), silicon carbide (SiC) and their micro- and nanofabrication in a clean room. CRHEA also studies 2D materials such as graphene, or boron nitride.
The main areas covered by the CRHEA concern the energy transition, the communications of the future, the environment and health. CRHEA also conducts fundamental studies in nanoscience and crystal growth.
High energy bandgap materials are key elements for power electronics, ultra-high frequency electronics, LED-based lighting and new generations of micro-displays. CRHEA visible and ultraviolet light sources have multiple applications for lighting, biophotonics and water purification. CRHEA also develops components in the THz domain, photonic circuits, advanced optical components based on metasurfaces, spintronic applications, sensors and is involved in the development of quantum technologies.
The laboratory has eight molecular beam epitaxy growth reactors and six vapor phase growth reactors. It also has tools for structural characterization of materials and a clean room for micro and nanofabrication.
The combination of top-down and bottom-up approaches makes it possible to exploit all the possibilities offered by nanostructures and this is the strength of the Nanotechnologies team, which uses GaN and ZnO as materials of choice. Our interests range from basic materials science, including MBE and MOCVD growth to new materials (eg ZnMnO, rare earth nitrides and oxynitrides), to the development of more complex nanophotonic systems. These include metasurfaces, which allow the manufacture of ultrathin-ultralight optoelectronic components such as metal lenses, optical microcavities. These are the ideal playground for testing effects in quantum electrodynamics and obtaining Bose-Einstein condensates in a semiconductor environment. Finally, a nanophotonic platform based on GaN nanowires is able to stimulate biological cells with unprecedented spatial resolution. Moreover, the manipulation of the spin of carriers and / or excitons within these photonic structures, thanks to our magnetic materials, opens the possibility of coupling spin and photons in an electrically addressable interface.
Constraints and risks
The candidate will perform optical experiments using pulsed lasers (class 3B). He will use CRHEA's cleanroom equipment for the production of nanostructured components, including metal deposition, plasma etching, and other uses of chemicals.
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