Reference : UMR9001-XAVCHE-002
Workplace : PALAISEAU
Date of publication : Friday, July 29, 2022
Scientific Responsible name : Xavier Checoury
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 November 2022
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
PhD title: On-chip free electron lasers
Free electron lasers (FEL) are very large physics instruments that use relativistic electrons as a gain medium. The wavelength is not fixed by a physical material property of an atomic, molecular or semiconductor excitation, as in usual lasers, but by the designed geometry of the laser cavity and by the speed of electrons. Both can be tuned on demand offering an exceptional versatility. Indeed, such lasers can emit powerful radiations from the X-rays to the terahertz wavelength.
During this PhD thesis, we aim at bringing the wavelength versatility of macroscopic FEL to integrated optics by developing an on-chip free electron laser, that would be a world first, as only incoherent sources have been realized so far [1,2]. These lasers will rely on stimulated Cherenkov emission generated inside a periodic dielectric structure, that is traversed by an electron flow generated on the same chip by an integrated electron gun. Thanks to an original design of both the cavity and the electron gun, the integrated FELs are expected to work at voltage as low as 200 V and at a moderate vacuum, in the mbar range, providing a low cost, CMOS compatible and energy efficient FEL functioning in extreme environments involving high temperature and exposure to various radiations.
The structures for enabling on-chip light generation typically comprise a periodic structure, making it possible to achieve the required phase matching for Cherenkov emission. Among them, photonic crystals (PhC), whose dielectric constant is periodic in two (2D) directions of space, are particularly attractive since they are known to be particularly effective for highly confining light in waveguides or micro-cavities with high quality factor, of the order of a few millions [3-4].
The PhD student will participate in developing the models, in designing, simulating and characterizing the photonic structures. The PhD student will also be in charge of the fabrication processes and their optimization in the C2N clean room. Finally, characterization with electron beams will take place in collaboration with our partners in the framework of the OFELIA project funded by the French national research agency. Our partners in this project are the LPS (Orsay), the Institute of Light and Matter (Lyon) and also Thales R&T (Palaiseau).
To apply, a very good knowledge of electromagnetism is necessary as well as some experience with electromagnetic simulation (FDTD for instance). A basic knowledge of the characterization of optoelectronics components and of clean room processing is a plus. These aptitudes, as well as the interest and motivation for the subject, must be attested by the CV and developed in a convincing cover letter.
 F. Liu, Nature Phot. 11, 289 (2017).  C. Roques-Carmes, Nature comm. 10, 3176 (2019).  Z. Han, Optics Comm. 283, 4387–4391 (2010).  T. Asano, Opt. Express 25, 1769 (2017).
The thesis will take place at the Center de Nanosciences et de Nanotechnologies - C2N (CNRS/Université Paris-Saclay), a flagship laboratory for research in Nanosciences and Nanotechnologies and equipped with one of the largest academic clean rooms in France.
The student will join the QD team of the C2N photonics department, specialized in nanophotonics: https://www.qdgroup.universite-paris-saclay.fr/index.html.
The thesis will take place within the framework of the OFELIA project funded by the ANR in close collaboration with our partners: The Solid State Physics Laboratory (LPS), Thales R&T, located a few hundred meters from the C2N as well as the Institut Lumière Matière (ILM) in Lyon. The student will have to interact during the project with all of these partners for the characterizations of the laser.
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