Hole coupling in free electron lasers

Faatz, B.; Best, R.W.B.; Oepts, D.; Amersfoort, P.W. van

doi:10.1109/3.237498

Cited by 16 publications

(4 citation statements)

References 12 publications

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“…However, with the introduction of an on-axis hole, there is clearly going to be a substantial perturbation to the equilibrium mode and hence the FEL performance [12,17,18]. Here we introduce an outcoupling hole on the downstream mirror and study the situation systematically, as a function of cavity length (i.e.…”

Section: Cavity With Hole Outcouplingmentioning

confidence: 99%

Resonator stability and higher-order modes in free-electron laser oscillators

Pathak

Krishnagopal

2014

Phys. Rev. ST Accel. Beams

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Three-dimensional simulation codes GENESIS and OPC are used to investigate the dependence of the resonator stability of free-electron laser (FEL) oscillators on the stability parameter, laser wavelength, outcoupling hole size and mirror tilt. We find that to have stable lasing over a wide range of wavelengths, the FEL cavity configuration should be carefully chosen. Broadly, the concentric configuration gives near-Gaussian modes and the best performance. At intermediate configurations the dominant mode often switches to a higher-order mode, which kills lasing. For the same reason, the outcoupled power can also be less. We have constructed a simple analytic model to study resonator stability which gives results that are in excellent agreement with the simulations. This suggests that modes in FEL oscillators are determined more by the cavity configuration and radiation propagation than by the details of the FEL interaction. We find (as in experiments at the CLIO FEL) that tilting the mirror can, for some configurations, lead to more outcoupled power than a perfectly aligned mirror because the mode is now a more compact higher-order mode, which may have implications for the mode quality for user experiments. Finally, we show that the higher-order mode obtained is usually a single Gauss-Laguerre mode, and therefore it should be possible to filter out the mode using suitable intracavity elements, leading to better FEL performance.

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Section: Cavity With Hole Outcouplingmentioning

confidence: 99%

Resonator stability and higher-order modes in free-electron laser oscillators

Pathak

Krishnagopal

2014

Phys. Rev. ST Accel. Beams

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“…Having these advantages and allowing the electron beam to be injected directly into the optical cavity through the hole in the upstream mirror, [2][3][4][5] hole coupling resonators have been studied for free-electron laser ͑FEL͒ application at several FEL research sites, such as FELIX, 5 Lawrence Berkeley Laboratory, 6 and Stanford. Even in the near-infrared region, where partially transparent mirrors are available, hole coupling based on metal mirrors could be superior due to its broader tuning range and higher damage threshold.…”

Section: Introductionmentioning

confidence: 99%

“…Even in the near-infrared region, where partially transparent mirrors are available, hole coupling based on metal mirrors could be superior due to its broader tuning range and higher damage threshold. 2,5,6 The presence of the gain medium is neglected in early calculations of hole coupling included in FELs. 7,8 In using hole coupling, it is important to know the extraction ratio defined as the fraction of intracavity power that is coupled out of the cavity through the hole per round trip, and the total loss of the cavity that should be smaller than the FEL gain in order to achieve laser oscillation.…”

Section: Introductionmentioning

confidence: 99%

“…7,8 In using hole coupling, it is important to know the extraction ratio defined as the fraction of intracavity power that is coupled out of the cavity through the hole per round trip, and the total loss of the cavity that should be smaller than the FEL gain in order to achieve laser oscillation. 2,5 However, recently a high loss as much as 20% in a hole-coupling resonator of a far-infrared waveguide FEL has been shown in experiments 7 and numerical calculations 8 by taking into account the effect of the FEL interaction on the cavity mode because of the unequal gain among transverse modes. 2,5,6 The presence of the gain medium is neglected in early calculations of hole coupling included in FELs.…”

Section: Introductionmentioning

confidence: 99%

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Reducing loss of a hole-coupled resonator for a free-electron laser with partially reflecting meshes

Shu

Wang

Jiang

et al. 1999

Review of Scientific Instruments

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Articles you may be interested in X-ray laser resonator for the kilo-electron-volt range Appl. Phys. Lett. 102, 174101 (2013); 10.1063/1.4803071Multi-range free-electron laser with a pair of dielectric multilayer mirrorsWe propose a method to reduce the loss of a hole-coupled resonator for a free-electron laser ͑FEL͒ oscillator. A mesh with a reflectivity of 50%-70%, which is quite easy to be produced, can be used to cover the hole. Both the extraction and diffraction losses can be reduced effectively to obtain higher net gain, which allows the FEL oscillator to be operated under worse conditions. These advantages and properties are confirmed by numerical simulations using a three-dimensional code with the parameters of a compact far-infrared FEL oscillator built at the China Academy of Engineering Physics. Furthermore, it can be used as a electron transparent mirror to make the FEL device more compact and less expensive.

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Introduction

Freund,

Antonsen,

2023

Principles of Free Electron Lasers

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Hole coupling in free electron lasers

Cited by 16 publications

References 12 publications

Resonator stability and higher-order modes in free-electron laser oscillators

Resonator stability and higher-order modes in free-electron laser oscillators

Reducing loss of a hole-coupled resonator for a free-electron laser with partially reflecting meshes

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