Sub-picosecond coherent VUV source on the Elettra storage ring

Spezzani, C.; Allaria, E.; Cautero, G.; Coreno, Marcello; Curbis, Francesca; Danailov, M. B.; Demidovich, Alexander; Diviacco, B.; Karantzoulis, E.; Ivanov, Rosen; Pittana, P.; Romanzin, L.; Sergo, R.; Sigalotti, Paolo; Tileva, S.; Trovò, M.; Ninno, G. De

doi:10.1016/j.nima.2008.08.005

Cited by 6 publications

(6 citation statements)

References 18 publications

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“…Intermediate values of the ratio B x /B y result in an elliptical polarized emission. This kind of undulators is commonly employed in synchrotron storage rings and FELs [10,11] to vary the polarization of the fundamental synchrotron radiation. As it is well known, in case of planar undulators, on-axis NHG occurs only at odd harmonics, while even harmonics are present only off-axis [12].…”

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confidence: 99%

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Coherent Light with Tunable Polarization from Single-Pass Free-Electron Lasers

Spezzani

Allaria

Coreno³

et al. 2011

Phys. Rev. Lett.

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Tunable polarization over a wide spectral range is a required feature of light sources employed to investigate the properties of local symmetry in both condensed and low-density matter. Among new-generation sources, free-electron lasers possess a unique combination of very attractive features, as they allow to generate powerful and coherent ultra-short optical pulses in the VUV and X-ray spectral range. However, the question remains open about the possibility to freely vary the light polarization of a free-electron laser, when the latter is operated in the so-called nonlinear harmonic-generation regime. In such configuration, one collects the harmonics of the free-electron laser fundamental emission, gaining access to the shortest possible wavelengths the device can generate. In this letter we provide the first experimental characterization of the polarization of the harmonic light produced by a free-electron laser and we demonstrate a method to obtain tunable polarization in the VUV and X-ray spectral range. Experimental results are successfully compared to those obtained using a theoretical model based on the paraxial solution of Maxwells equations. Our findings can be expected to have a deep impact on the design and realization of experiments requiring full control of light polarization to explore the symmetry properties of matter samples.

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“…The experiments we present have been carried out using the single-pass FEL installed on the Elettra storage ring [10,20]. The Elettra FEL relies on two independent helical (APPLE-type) undulators (with λ u = 10 cm), separated by a dispersive section, and on a Ti:sapphire laser.…”

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confidence: 99%

Coherent Light with Tunable Polarization from Single-Pass Free-Electron Lasers

Spezzani

Allaria

Coreno³

et al. 2011

Phys. Rev. Lett.

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“…The modulator is tuned to the same frequency ν 0 and to the same polarization of the seed laser, thus satisfying a resonant condition that allows optimizing the energy transfer from the laser to the electrons. Such an energy transfer results For a detailed description of the system, see [14].…”

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Experimental demonstration of frequency pulling in single-pass free-electron lasers

Allaria¹,

Ninno²,

Spezzani³

2011

Opt. Express

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Frequency pulling is a well-known phenomenon in standard laser physics, leading to a shift of the laser frequency when the cavity and maximum gain frequencies are detuned. In this letter we present the first experimental demonstration of frequency pulling in single-pass free-electron lasers. Measurements are performed using the single-pass free-electron laser installed on the Elettra storage ring. PACS numbers:Frequency pulling is a well-known phenomenon in standard lasers, taking place when the peak of the gain spectrum is slightly detuned with respect to the frequency of one of the modes selected by the laser cavity. When this occurs, the lasing frequency is close to the one of the selected mode, but slightly "pulled" towards the maximum of the gain curve [1]. While generally investigated in the case of the continuous-wave operation of laser oscillators close to threshold, frequency-pulling has more recently become of interest also to other laser configurations [2]. As an example, the importance of frequency pulling for a correct estimate of the laser-pulse parameters in the case of a mode-locked laser has been theoretically predicted and experimentally confirmed in [3]. Moreover, frequency pulling has been exploited for the fine tuning of the laser frequency [4] and for beat-stabilization in multimode laser operations [5].In a free-electron lasers (FEL) [6], the light amplification is not due to the stimulated emission of an atomic system (like in standard lasers), but is instead relying on the coherent emission of relativistic electrons oscillating into a periodic magnetic field generated by an undulator. In the early days of FEL's, the study of frequency pulling has been focused on (low-gain) oscillator systems [6]. For such FEL configuration, the effect of frequency pulling is similar to that taking place in standard lasers: the laser frequency is determined by the interplay between the proper frequencies of the cavity and that for which the gain is maximum [7,8]. In the case of highgain FEL's [9], the light amplification takes place during a single-pass of the electrons through undulators, without the use of a laser cavity. This motivates the strong interest in single-pass FEL's: being optics-free devices, they offer the unique opportunity to provide coherent and powerful emission in the spectral range from VUV to x-rays. In fact, the coherence of a single-pass FEL can be drastically improved if, before emitting, electrons are brought into interaction with an external coherent "seed" source (e.g., a laser). As described more in detail in the following, such a seed determines the resonant frequencies at which the lasing effect occurs. Therefore, its action is somehow similar to the one of an optical cavity in standard lasers and oscillators FEL's. In a recent work [10], we have theoretically predicted that, also in seeded FEL's, a mismatch between the frequencies "selected" by the seed and the peak of the FEL gain curve may lead to a frequency-pulling effect. Based on numerical simulations, we proposed an ...

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“…The laser pulse and the electron bunch duration are, respectively, 120 fs (rms) and about 35 ps (rms). A stable laser-electron synchronization with a jitter of few ps [26] guarantees an efficient and stable seeding process, with shot-to-shot fluctuations of the order of few percent. The main experimental parameters, also used to obtain the theoretical angular spectral flux reported in Figs.…”

Section: Fig 4: Schematic Layout Of the Elettra Storage-ring Felmentioning

confidence: 99%

“…In Section III we present the experimental device we used to perform the measurements, i.e. the FEL installed at the Elettra storage-ring [25,26]. In Section IV, experimental data are presented and compared to theoretical predictions.…”

Section: Introductionmentioning

confidence: 99%

Angular distribution of nonlinear harmonic generation in helical undulators: A comparison between experiments and theory

Allaria¹,

Ninno²,

Geloni³

et al. 2011

Nuclear Instruments and Methods in Physics Research Section A:

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Using harmonic emission from circularly polarized undulator is a procedure that is normally employed on synchrotron beamlines in order to extend the covered spectral range. A similar capability is likewise beneficial for next generation free-electron lasers. In this paper, we perform a first quantitative experimental analysis of the angular distribution of free-electron laser harmonic emission from helical undulators. Experimental results are compared to those obtained by means of a theoretical model based on the paraxial solution of Maxwell's equations.PACS numbers:

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Sub-picosecond coherent VUV source on the Elettra storage ring

Cited by 6 publications

References 18 publications

Coherent Light with Tunable Polarization from Single-Pass Free-Electron Lasers

Coherent Light with Tunable Polarization from Single-Pass Free-Electron Lasers

Experimental demonstration of frequency pulling in single-pass free-electron lasers

Angular distribution of nonlinear harmonic generation in helical undulators: A comparison between experiments and theory

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