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Offers : 48

Dispersion characterization of active glass waveguides

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offer n° IMEPLaHC-10292019-PHOTO

                                                      Master thesis -Master Recherche / PFE
                                                                             (5 to 6 month)
                                                     Dispersion characterization of active glass waveguides

IMEP-LaHC is working on integrated optics since a few decades and is one of the leading laboratories in the field of photonics on glass. A current objective of the team “PHOTO” of this institute is to develop mode-locked lasers using the glass photonics platform. Mode-locking can be obtained by different methods; the one we have selected uses a fast saturable absorber to form solitons in an optical cavity.

The method to produce those soliton is well known theoretically and requires balancing two effects that occur during the propagation of an optical pulse in the waveguide. The first one is dispersion that comes from both the material and the waveguide. The second effect is a non-linear phenomenon called “self phase modulation (SPM)”. Both phenomena need to be precisely characterized for a given technology in order to build an efficient mode-locked laser cavity. The present internship will focus on the precise measurement of the group dispersion of our waveguides.

Dispersion can be measured using an unbalanced Mach-Zehnder (MZ) interferometer whose arms are fabricated with the waveguides to be characterized [1]. A mask containing unbalanced MZ interferometers is already available at the laboratory, the rest is up to the intern !

The internship will be organized as follows:

  • Bibliographic study concerning the context (mode-locked lasers architectures, …) and the core subject (dispersion measurement in integrated waveguides)
  • Using the provided photolithography mask, fabricate MZ devices using the clean room facilities of the laboratory.
  •  Characterize the different MZ present on the chip (transmission spectrum).
  • Analyze the measured spectra, compare to theory and choose which device is best suited for measuring dispersion.

This internship thus requires a student with an inclination for experimental work (fabrication and characterization). Some knowledge about integrated optics and an experience with clean room environment will be appreciated.

This Master’s subject thesis is a preliminary work for a future PhD subject on the same topic, but could also lead to a PhD thesis on another subject within the PHOTO team of IMEP LaHC.

[1] Dulkeith, Eric, et al. “Group index and group velocity dispersion in silicon-on-insulator photonic wires.” Optics Express 14.9 (2006): 3853-3863.

Advisors:
Jean-Emmanuel BROQUIN,  broquin@minatec.grenoble-inp.fr
Lionel BASTARD,  lionel.bastard@grenoble-inp.fr

  • Keywords : Engineering science, Engineering science, Electronics and microelectronics - Optoelectronics, FMNT, IMEP-LaHc
  • Laboratory : FMNT / IMEP-LaHc
  • CEA code : IMEPLaHC-10292019-PHOTO
  • Contact : lionel.bastard@grenoble-inp.fr

Micro-heaters for integrated laser tuning

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offer n° IMEPLaHC-10282019-PHOTO

                                                           Master thesis – Master Recherche / PFE
                                                                               (5 to 6 month)

                                                              Micro-heaters for integrated laser tuning

IMEP-LaHC is working on integrated optics since a few decades and is one of the leading laboratories in the field of photonics on glass. A current objective of the team “PHOTO” of this institute is to fabricate carriers of GHz to THz frequencies for future telecommunication systems and THz spectroscopy. The carrier signal is produced by the interaction on a rapid photodetector of two integrated optics lasers fabricated on the same substrate.

Such a device has already been demonstrated in a previous PhD thesis carried out at IMEP-LaHC [1]. The GHz or THz frequency is fixed by the design of the laser cavities and cannot be modified once the device has been fabricated. This internship is dedicated to obtaining a variable-frequency output by varying the temperature of one of the lasers. This temperature variation will be achieved by integrating a micro-heater on the device.

There are two parts to this internship:

  1. The first task is to use the existing literature and Comsol simulations to design the thin metallic layer which will constitute the micro-heater. Simulations will also be used to predict the temperature increase on the waveguide and the tunability of the produced carrier that can be expected.
  2. The second task is to fabricate the micro-heaters in a clean-room environment. Electrical and optical characterizations of the fabricated heaters will then be carried out by the intern and compared with the expected behavior of the device.

This internship thus requires a student with an inclination for both simulations and experimental work. Some knowledge about integrated optics and an experience with clean room environment will be appreciated.

This Master’s subject thesis is a preliminary work for a future PhD subject on the same topic, but could also lead to a PhD thesis on another subject within the PHOTO team of IMEP LaHC.

[1] N. Arab, “Optique intégrée sur verre pour la génération de fréquences radio”, PhD Thesis at Grenoble-INP, http://www.theses.fr/2018GREAT102

Advisors:
Lionel BASTARD lionel.bastard@grenoble-inp.fr
Julien POETTE julien.poette@grenoble-inp.fr

  • Keywords : Engineering science, Engineering science, Electronics and microelectronics - Optoelectronics, FMNT, IMEP-LaHc
  • Laboratory : FMNT / IMEP-LaHc
  • CEA code : IMEPLaHC-10282019-PHOTO
  • Contact : lionel.bastard@grenoble-inp.fr

Micromagnetic study of a voltage controlled skyrmion chirality switch

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offer n° 191022-9

Skyrmions in thin films are spin textures across which the magnetization follows a cycloid with a unique sense of rotation, known as chirality. These specific magnetic patterns can be stabilized in various kinds of materials, and particularly in ultrathin trilayers with no inversion symmetry (e.g. heavy metal/ferromagnet/oxide) exhibiting simultaneously an interfacial interaction called Dzyaloshinskii-Moriya (DMI) and a strong perpendicular magnetic anisotropy (PMA). Since they are ideally topological solitons, skyrmions are currently attracting considerable interest both for the underlying physics and for their applicative potential. Their ability to be set in motion by electrical current opens the way to imagine them as dense storage data bits or magnetic logic operations. Furthermore, the possibility to tune magnetic interfacial properties by a gate voltage enables low power control of spintronic devices and provides a versatile, local and dynamic degree of freedom that can be implemented in innovative designs.

In this context, in collaboration with Institut Néel, we have recently shown that a gate voltage can not only switch skyrmions on and off but also tune the interface properties (PMA and DMI). The new mechanism leading to DMI revealed by our experiments allows expecting a control of DMI sign, which would lead to an inversion of the skyrmion’s chirality.

In this internship, we target to study by micromagnetic simulations the possibility to change DMI sign and to demonstrate voltage controlled skyrmion chirality switch. This breakthrough would open new possibilities for skyrmion manipulation, as a change of chirality would invert the direction of current-induced motion. It will also open new and rich physics on the dynamical control of the topology of these solitons.

  • Keywords : Mathematics - Numerical analysis - Simulation, spintronics, IRIG, SPINTEC
  • Laboratory : IRIG / SPINTEC
  • CEA code : 191022-9
  • Contact : liliana.buda@cea.fr

Theoretical studies of spin-orbit phenomena at interfaces comprising magnetic and nonmagnetic materials in a view of memory devices

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offer n° 191022-8

This internship project aims on unveiling microscopic mechanisms of spin-orbit phenomena including perpendicular magnetic anisotropy in order to help optimizing spin-based memory applications and provide the scientific underpinnings of next generation energy efficient, ultrafast and ultrasmall spintronic devices.

  • Keywords : spintronics, Theoretical Physics, IRIG, SPINTEC
  • Laboratory : IRIG / SPINTEC
  • CEA code : 191022-8
  • Contact : mair.chshiev@cea.fr

Modeling of spin Hall induced domain wall dynamics in core-shell nanowires

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offer n° 191022-7

Recent progress in domain wall nucleation and its control in nanostructures with tubular shape [see Figure 1] makes them fascinating objects for fundamental research as well as for data storage advanced technologies. In these systems the interplay between magnetization and 3D properties results in novel physical phenomena such as unconventional spin textures, additional energy terms due to curvature or spin wave non-reciprocity. Three-dimensional spintronics exploits the interaction of magnetization with spin polarized currents in such cylindrical objects in view of designing the 3D building blocks for magnetic storage devices. The advancements of experimental techniques in this field in our laboratory offer new challenges for theory and modeling. To simulate non-trivial 3D magnetic textures and the impact of current on its dynamics in cylindrical geometries we have developed the multipurpose micromagnetic finite element C++ software [1] jointly in Spintec and Néel Institute. Our software is permanently enlarged with new physics to accompany experimental development. This internship is an excellent opportunity to get familiar with finite element modeling and contribute to the development of the multi-physics software for spintronics.

  • Keywords : Mathematics - Numerical analysis - Simulation, spintronics, IRIG, SPINTEC
  • Laboratory : IRIG / SPINTEC
  • CEA code : 191022-7
  • Contact : daria.gusakova@cea.fr
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