Approaching the microjoule frontier with femtosecond laser oscillators

Naumov, S.; Fernández, A.; Graf, Roswitha; Dombi, Péter; Krausz, Ferenc; Apolonski, Alexander

doi:10.1088/1367-2630/7/1/216

Cited by 149 publications

(79 citation statements)

References 19 publications

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“…In our experiment we focus laser pulses derived from a long-cavity Titanium:sapphire oscillator [17] f rep = 2.7 MHz, pulse duration of τ p = 110 fs and focal waist radius of w l = (9 ± 0.4) µm. We chose the grating period to λ p = 750 nm, hence the third spatial harmonic (n = 3) is synchronous with 27.9 keV electrons and decays with Γ = 42 nm.…”

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confidence: 99%

Laser-Based Acceleration of Nonrelativistic Electrons at a Dielectric Structure

2013

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A proof-of-principle experiment demonstrating dielectric laser acceleration of non-relativistic electrons in the vicinity of a fused-silica grating is reported. The grating structure is utilized to generate an electromagnetic surface wave that travels synchronously with and efficiently imparts momentum on 28 keV electrons. We observe a maximum acceleration gradient of 25 MeV/m. We investigate in detail the parameter dependencies and find excellent agreement with numerical simulations. With the availability of compact and efficient fiber laser technology, these findings may pave the way towards an all-optical compact particle accelerator. This work also represents the demonstration of the inverse Smith-Purcell effect in the optical regime.The acceleration gradients of linear accelerators are limited by breakdown phenomena at the accelerating structures under the influence of large surface fields. Today's accelerators, which are based on metal structures driven by radio frequency fields, operate at acceleration gradients of ∼20-50 MeV/m. The upper limit in future radio frequency accelerators, such as the discussed CLIC and ILC, is ∼100 MeV/m, given by the damage threshold of the metal surfaces [1][2][3]. At optical frequencies dielectric materials withstand roughly two orders of magnitude larger field amplitudes than metals [4]. Together with the large optical field strength attainable with short laser pulses, dielectric laser accelerators (DLAs) hence may support acceleration gradients in the multi-GeV/m range [5]. With this technology lab-size accelerators, providing particle beams with energies currently only available at km-long facilities, seem feasible. Here we demonstrate the efficacy of the concept.Charged particle acceleration with oscillating fields requires an electromagnetic wave with a phase speed equal to the particle's velocity and an electric field component parallel to the particle's trajectory. So far, laserbased particle acceleration schemes employ the longitudinal electric field component of a plasma wave [6][7][8] or of a tightly focused laser beam [9], but in both schemes the accelerating mode has a phase velocity that does not match the speed of light. Therefore, relativistic particles can only be accelerated over short distances and the maximum attainable energies of these devices are limited. Exploiting the near-field of periodic structures, for example of optical gratings, offers the possibility to continuously accelerate non-relativistic as well as relativistic particles. In essence, the effect of the grating is to rectify the oscillating field in the frame co-moving with the electron, conceptually similar to conventional radio frequency devices. Single gratings can only be used to accelerate non-relativistic electrons, an effect also known as the inverse Smith-Purcell effect [10][11][12]. However, double grating structures, in which electrons propagate in a channel between two gratings facing each other, support a longitudinal, accelerating speed-of-light eigenmode that can be used to a...

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Laser-Based Acceleration of Nonrelativistic Electrons at a Dielectric Structure

2013

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“…For the anode either a 1-cm-thick copper disk with a hole 1 mm in diameter or, alternatively, a thin metal net with a mesh size of 83 µm was used. The detector The laser used for operating the electron gun has been described elsewhere [13]. In short, it is a Kerr-lens-modelocked fsec titanium:sapphire chirped-pulse oscillator operated with a net positive intracavity group delay dispersion.…”

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confidence: 99%

Ultrashort pulse electron gun with a MHz repetition rate

et al. 2009

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We report the construction of an electron gun emitting ultrashort pulses with a repetition rate of 2.7 MHz. The gun works at an acceleration voltage of 20 kV and is operated with a laser oscillator having an ultralong cavity. A low number of electrons per pulse eliminates space charge broadening. Electron yield and beam profiles are measured for operation with laser wavelengths of 800, 400, and 266 nm. The initial energy spread of the electrons is determined for these three wavelengths, and pulse durations of 600, 390, and 270 fs are inferred from the data.

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“…The spectrum of femtosecond oscillator pulses with up to ~30 nJ energy can be efficiently broadened in short single-mode glass fibers with 2 -5 μm core diameter [5] whereas the ~mJ pulses of femtosecond amplifiers can be efficiently guided and broadened in gas-filled capillaries [7]. With the recent advent of femtosecond technology resulting in high-energy, 100 nJ…several μJ pulses with > 1 MHz repetition rate [8][9][10] (in the Ti:sapphire case, directly from the oscillator), new methods for pulse compression have to be devised for these novel parameter regimes. This has to take into account the desired spectral broadening and the damage threshold of nonlinear optical elements.…”

Section: Femtosecond Pulse Compression Considerationsmentioning

confidence: 99%

Pulse compression with large-mode-area photonic crystal fibres

Dombi

2014

2014 16th International Conference on Transparent Optical Networks (ICTON)

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Photonic crystal fibres (PCFs) are established tools for supercontinuum generation and femtosecond pulse compression down to the few-femtosecond regime. With the advent of femtosecond oscillators delivering ever higher pulse energy, one needs a pulse energy scalable technique to achieve these goals. Therefore, I will review the usage of large-mode-area PCFs for femtosecond applications and introduce some related new nonlinear fiber phenomena. Keywords: photonic crystal fibres, microstructured fibres, femtosecond pulse compression, nonlinear fibre optics. FEMTOSECOND PULSE COMPRESSION CONSIDERATIONSNonlinear optical phenomena such as self phase modulation, four wave mixing and Raman processes in various fiber and bulk media can be efficiently exploited for the compression of femtosecond pulses. These techniques are particularly important in few-cycle and single-cycle laser pulse generation [1][2][3] and other cases where shorter pulses are required than the gain and/or dispersion bandwidth allowed by laser oscillator or amplifier architectures. Therefore, one has to perform extra cavity pulse compression which necessitates (i) nonlinearities to increase the spectral content of the pulse and (ii) proper spectral phase management in order to end up with a pulse which is as close to the transform limit as possible. In some cases, elements (i) and (ii) are realized in the same medium making use of the strong interplay of linear and nonlinear phenomena during the compression process. Examples include self-compression in filaments [4] or in the soliton regime. For most input pulses, however, more robust and broadband solutions are offered by schemes where the spectral broadening and pulse compression stages are separated [5][6][7]. In these cases, the spectral broadening stage usually consists of single-mode solid-core, multi-mode, rod-type or gas-filled hollow-core fibers. The spectrum of femtosecond oscillator pulses with up to ~30 nJ energy can be efficiently broadened in short single-mode glass fibers with 2 -5 μm core diameter [5] whereas the ~mJ pulses of femtosecond amplifiers can be efficiently guided and broadened in gas-filled capillaries [7]. With the recent advent of femtosecond technology resulting in high-energy, 100 nJ…several μJ pulses with > 1 MHz repetition rate [8][9][10] (in the Ti:sapphire case, directly from the oscillator), new methods for pulse compression have to be devised for these novel parameter regimes. This has to take into account the desired spectral broadening and the damage threshold of nonlinear optical elements. A particular challenge for Ti:sapphire oscillators is also represented by the large bandwidth of both the source and the required spectral broadening, therefore, schemes devised for the compression of multi-100-fs pulses can not be implemented. PULSE COMPRESSION WITH LARGE-MODE-AREA FIBERSLarge mode area (LMA) photonic crystal fibers (PCFs) offer endlessly single mode guiding combined with a mode field diameter of up to around 100 μm and an M 2 value of 1.05 -1.2 at ...

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Approaching the microjoule frontier with femtosecond laser oscillators

Cited by 149 publications

References 19 publications

Laser-Based Acceleration of Nonrelativistic Electrons at a Dielectric Structure

Laser-Based Acceleration of Nonrelativistic Electrons at a Dielectric Structure

Ultrashort pulse electron gun with a MHz repetition rate

Pulse compression with large-mode-area photonic crystal fibres

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