Observation of an x-ray vortex

Peele, Andrew G.; McMahon, P. J.; Paterson, David; Tran, Chanh Q.; Mancuso, Adrian P.; Nugent, Keith A.; Hayes, Jason P.; Harvey, Erol C.; Lai, Barry; McNulty, Ian

doi:10.1364/ol.27.001752

Cited by 128 publications

(81 citation statements)

References 13 publications

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“…Traditionally, these "optical vortices" are created by shaping of the phase front of a laser as it passes through different optical media [11][12][13], such as spiral phase plates [14] or computer generated holograms [15]. Analogous techniques have also been used to transform x-rays into vortices at synchrotron light sources [16,17], and alternate methods suggest vortex beams can be created through Compton back-scattering [18] or harmonic emission in undulators [19]. Here, we report on a completely different technique in which a simple Gaussian laser pulse is used to generate fully coherent l = 1 OAM light purely through its interaction with a relativistic electron beam (e-beam).…”

Section: Introductionmentioning

confidence: 99%

Coherent optical vortices from relativistic electron beams

et al. 2013

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Recent advances in the production and control of high-brightness electron beams (e-beams) have enabled a new class of intense light sources based on the free electron laser (FEL) that can examine matter atÅngstrom length and femtosecond time scales. The free, or unbound, electrons act as the lasing medium, which provides unique opportunities to exquisitely control the spatial and temporal structure of the emitted light through precision manipulation of the electron distribution. We present an experimental demonstration of light with orbital angular momentum (OAM) generated from a relativistic e-beam rearranged into an optical scale helix by a laser. With this technique, we show that a Gaussian laser mode can be effectively up-converted to an OAM mode in an FEL using only the e-beam as a mode-convertor. Results confirm theoretical predictions, and pave the way for the production of coherent OAM light with unprecedented brightness down to hard x-ray wavelengths for wide ranging applications in modern light sources.

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Section: Introductionmentioning

confidence: 99%

Coherent optical vortices from relativistic electron beams

et al. 2013

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“…This technique has been used in the past to produce XUV or x-ray beams that carry OAM [33,34]. However, for high-brightness short-wavelength FEL radiation, the damage threshold of optical elements placed into the beam path, and the difficulties in the fabrication of high quality optical surfaces, impose strong limitations on the use of this method.…”

mentioning

confidence: 99%

Generation of Coherent Extreme-Ultraviolet Radiation Carrying Orbital Angular Momentum

2014

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We propose an effective scheme for the generation of intense coherent extreme ultraviolet light beams carrying orbital angular momentum (OAM). The light is produced by a high-gain harmonicgeneration free-electron laser (FEL), seeded using a laser pulse with a transverse staircase-like phase pattern. During amplification, diffraction and mode selection drive the radiation profile towards a dominant OAM mode at saturation. With a seed laser at 260 nm, gigawatt power levels are obtained at wavelengths approaching those of soft x-rays. Compared to other proposed schemes to generate OAM with FELs, our approach is robust, easier to implement, and can be integrated into already existing FEL facilities without extensive modifications of the machine layout.PACS numbers: 42.50. Tx, 42.65.Ky, 41.60.Cr Modern generation free-electron lasers (FELs) delivering high-brightness optical beams in the extreme ultraviolet (XUV) [1] and x-ray regions [2,3] have become indispensable tools for probing structural and chemical properties of matter at femtosecond temporal and nanometer spatial resolutions [4]. At present, transverse radiation profiles from FELs working at saturation are limited to a fundamental Gaussian-like mode with no azimuthal phase variation. This is true for FELs based on selfamplified spontaneous emission (SASE), where the amplification starts from electron shot-noise [5][6][7][8][9][10][11][12][13][14], as well as for seeded FELs, such as those based on high-gain harmonic-generation (HGHG), where the amplification process is triggered by a coherent input signal [1,15,16].Generation of high-order radiation modes, however, is a subject of strong interest, not only from the fundamental point of view but also in practical applications. In particular, helically phased light beams or optical vortices with a field dependence of exp (ilφ), where φ is the azimuthal coordinate and l an integer referred to as the topological charge, are currently among intensively studied topics in optics. These light beams, which carry orbital angular momentum (OAM) [17] that can be transferred to atoms, molecules, and nanostructures [18][19][20][21][22][23], have already been utilized at visible and infrared wavelengths in a wide variety of applications, ranging from micromanipulation [24], detection of spinning objects [25], microscopy [26], and optical data transmission [27][28][29]. Perhaps the most promising applications of vortex beams at short wavelengths are in x-ray magnetic circular dichroism, where different OAM states allow the separation of quadrupolar and dipolar transitions [30], photoionization experiments, where the dipolar selection rules are violated giving rise to new phenomena beyond the standard effect [31], and in resonant inelastic x-ray scattering, where vortex-beam-mediated coupling to vibrational degrees of freedom could provide important information on a wide range of molecular materials [32].In the case of visible light, OAM is commonly generated by sending the beam through a suitable optical element (e.g., ...

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“…In addition to the theoretical results presented in this study, several groups have confirmed production of the xray vortex beams carrying well-defined angular momentum and radial variation in direct comparison to similar beams in other spectral regions. [43][44][45] Also, several groups of researchers around the world have proposed and tested methods for focusing x-rays from modern sources to beam sizes tens to hundreds of nm's across. [46][47][48] While many of these techniques focus on hard x-rays whose energy exceeds that of core electronic transitions, there is no a priori reason why similar techniques cannot be applied in the region of 200-1000 eV.…”

Section: Spontaneous Inelastic Scattering Of Lg Beams From Vibromentioning

confidence: 99%

Examining resonant inelastic spontaneous scattering of classical Laguerre-Gauss beams from molecules

Rury

2013

Phys. Rev. A

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This paper theoretically treats the spontaneous resonant inelastic scattering of Laguerre-Gauss (LG) beams from the totally symmetric vibrations of complex polyatomic molecules within the semiclassical framework. We develop an interaction Hamiltonian that accounts for the position of the molecule within the excitation beam to derive the effective differential scattering cross-section of a classical LG beam from a molecule using the frequency domain third order nonlinear optical response function. To gain physical insight into this scattering process, we utilize a model vibronic molecule to study the changes to this scattering process. For specific molecular parameters including vibrational frequency and relative displacement of the involved electronic states, this investigation shows that an incident LG beam asymmetrically enhances one of two participating excitation transitions causing modulation of the interference present in the scattering process. This modulation allows a pathway to coherent control of resonant inelastic scattering from complex, poly-atomic molecules. We discuss the possible application of this control to the resonant x-ray inelastic scattering (RIXS) of small poly-atomic molecules central to applications ranging from single molecule electronics to solar energy science.

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Observation of an x-ray vortex

Cited by 128 publications

References 13 publications

Coherent optical vortices from relativistic electron beams

Coherent optical vortices from relativistic electron beams

Generation of Coherent Extreme-Ultraviolet Radiation Carrying Orbital Angular Momentum

Examining resonant inelastic spontaneous scattering of classical Laguerre-Gauss beams from molecules

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