We evidence experimentally the convective and absolute instabilities in an optical system. In our system, the presence of noise and spatial non-uniformities (as in most of the ``real systems'') add additional complexities. First... more
We evidence experimentally the convective and absolute instabilities in an optical system. In our system, the presence of noise and spatial non-uniformities (as in most of the ``real systems'') add additional complexities. First we derive analytical expressions of both thresholds for the ideal noiseless and spatially uniform situation. Then numerical simulations allow to determine signatures of those instabilities. The corresponding
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We analyze the narrowband terahertz emission process occurring from electron bunches passing in a bending magnet, after a laser-induced sinusoidal modulation has been performed. In particular, we focus on experimental tunability curves,... more
We analyze the narrowband terahertz emission process occurring from electron bunches passing in a bending magnet, after a laser-induced sinusoidal modulation has been performed. In particular, we focus on experimental tunability curves, and power scalings with current and laser power. Theoretically, we simplify the problem formulation using the slowly varying envelope approximation. At low powers, the scaling with laser power
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Les Lasers à électrons libres (LEL) sont des lasers particuliers basés sur des accélérateurs. Leurs principaux atouts par rapport aux lasers dit conventionnels résident dans leur accordabilité et leur large gamme spectrale (IR-UV/X).... more
Les Lasers à électrons libres (LEL) sont des lasers particuliers basés sur des accélérateurs. Leurs principaux atouts par rapport aux lasers dit conventionnels résident dans leur accordabilité et leur large gamme spectrale (IR-UV/X). Cependant le temps restreint d'accès aux grands instruments tels que les LEL limite leur étude dynamique. Par conséquent, une maquette de LEL permettrait de préparer les expériences
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. We investigate the efficiency of the pulsed regime stabilization by feedback control in a free electron laser (FEL) in oscillator configuration. We show that a hidden dynamics remains in the controlled FEL. Though not visible in the... more
. We investigate the efficiency of the pulsed regime stabilization by feedback control in a free electron laser (FEL) in oscillator configuration. We show that a hidden dynamics remains in the controlled FEL. Though not visible in the evolution of the pulse envelope, this dynamics affects the internal pulse shape evolution, and thus the FEL spectrum and coherence properties. The
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... Ï Ú ÐÒØ ´¼º¾ »Úºµ Fa st tim e θ (2 5 p s/ div .) Slow time T (500 ms/div.) ËÐÓÛ Ø Ñ Ì ´ Ñ×» Úºµ (a) (b) ... Opt. Lett., 21, 770, (1996). [19] N. Joly, S. Bielawski. Suppression of Q-switch instabilities by feedback control in... more
... Ï Ú ÐÒØ ´¼º¾ »Úºµ Fa st tim e θ (2 5 p s/ div .) Slow time T (500 ms/div.) ËÐÓÛ Ø Ñ Ì ´ Ñ×» Úºµ (a) (b) ... Opt. Lett., 21, 770, (1996). [19] N. Joly, S. Bielawski. Suppression of Q-switch instabilities by feedback control in pas-sively mode-locked lasers, Opt. Lett., 26, 692694, (2001). ...
It is well known that broadband coherent synchrotron ra- diation (CSR) is emitted by an electron bunch whose length is shorter than radiation wavelength. However, even a long electron bunch can emit CSR when it has micro-density structure... more
It is well known that broadband coherent synchrotron ra- diation (CSR) is emitted by an electron bunch whose length is shorter than radiation wavelength. However, even a long electron bunch can emit CSR when it has micro-density structure whose characteristic length is equal to the radi- ation wavelength. Recently, we have demonstrated that, by injecting amplitude modulated laser pulses into