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Haute Ecole d'Ingénierie

Détection de la cavitation

Pedroni, François ; Münch-Alligné, Cécile (Dir.)

Mémoire de bachelor : Haute Ecole d'Ingénierie, 2019.

La mise en place d’une nouvelle veine d’essai sur le banc de test hydraulique de la HES-SO Valais a pour but d’étudier le phénomène de la cavitation. Pour cette étude un profil de type NACA0015 a été monté dans la veine. En faisant varier un certain nombre de paramètres comme la vitesse du fluide, le niveau de pression dans la veine, l’incidence du profil NACA, le jeu de...

Université de Neuchâtel

Compact laser sources from the extreme ultraviolet to the mid-infrared spectral range

Merceron, Loïc P. J. M. ; Südmeyer, Thomas (Dir.)

Thèse de doctorat : Université de Neuchâtel, 2019.

Lasers have revolutionized the way we live and work in so many ways and have become a major part of our lives. We use them in telecommunications, medical care, material processing, data storage and printing, just to name a few. Lasers have proved to be important tools and are a major subject of research in science, continuously developed further and finding new uses. Pushed by the need to...

Université de Fribourg

Topological effects of a vorticity filament on the coherent backscattering cone

Aubry, Geoffroy J. ; Roux, Philippe

In: Physical Review Letters, 2019, vol. 123, no. 3, p. 035503

In this Letter, we report on the effects of a vorticity filament on the coherent backscattering cone. Using ultrasonic waves in a strongly reverberating cavity, we experimentally show that the discrete number of loops of acoustic paths around a pointlike vortex located at the center of the cavity drives the cancellation and the potential rebirth of the coherent backscattering enhancement. The...

Université de Neuchâtel

New frontiers of ultrafast thin-disk laser oscillators for applications in metrology and the generation of THz and XUV radiation

Modsching, Norbert Paul ; Südmeyer, Thomas (Dir.)

Thèse de doctorat : Université de Neuchâtel, 2019.

Ultrafast laser systems find application as versatile tool in industry and science. Ultrafast laser systems based on Ti:sapphire – the workhorse in ultrafast science – operate typically at kHz repetition rates and benefit from the available broad gain bandwidth for the direct generation of sub 100-fs pulse durations. However, thermal effects in the gain medium due to a high quantum defect...

Université de Neuchâtel

Rubidium vapour-cell frequency standards : metrology of optical and microwave frequency references

Moreno, William ; Mileti, Gaetano (Dir.)

Thèse de doctorat : Université de Neuchâtel, 2019.

This thesis concerns the development, study, and optimisation of compact and high-performance frequency references based on rubidium (Rb) vapour cells1. More specially, two Rb vapour-cell frequency references are studied: an optical-frequency reference at 1.5 μm and a double-resonance pulsed optically pumped (POP) atomic clock. The use of vapour cells allows compact frequency...

Université de Neuchâtel

Impact of microwave-field inhomogeneity in an alkali vapour cell using Ramsey double-resonance spectroscopy

Moreno, William ; Pellaton, Matthieu ; Affolderbach, Christoph ; Almat, Nil ; Gruet, Florian ; Mileti, Gaetano

In: Quantum Electronics, 2019, vol. 49, no. 3, p. 293-297

We numerically and experimentally evaluate the impact of the inhomogeneity of the microwave field in the cavity used to perform double-resonance (DR) Ramsey spectroscopy in a buffer gas alkali vapour cell. The Ramsey spectrum is numerically simulated using a simple theoretical model and taking into account the field distribution in a magnetron-type microwave resonator. An experimental evaluation...

Université de Neuchâtel

Semiconductor disk laser-based frequency combs

Jornod, Nayara ; Südmeyer, Thomas (Dir.)

Thèse de doctorat : Université de Neuchâtel, 2018.

This thesis studies the first self-referenced frequency combs based on modelocked semiconductor disk lasers (SDLs). The generation of stabilized frequency combs based on ultrafast lasers has been a significant breakthrough for many applications in various fields of physics, spectroscopy and metrology. Optical frequency combs can serve as a frequency ruler that provides a direct and...

Université de Neuchâtel

Measurement of the linewidth enhancement factor of singlemode room temperature continuous wave quantum cascade lasers

Aellen, Thierry ; Aebi, Philipp (Dir.)

Thèse de doctorat : Université de Neuchâtel, 2008.

The invention of the laser source in 1960 has led to a wide range of applications showing a widespread impact in every aspect of our today life, including for example hospital, factory or simply at home. In particular, recent developments originating from the compact, highly efficient and common semiconductor lasers that are simply supplied by an electrical current. The diode coherent light...