Shadow Effects in Spiral Phase Contrast Microscopy

Jesacher, Alexander; Fürhapter, Severin; Bernet, Stefan; Ritsch‐Marte, Monika

doi:10.1103/physrevlett.94.233902

Cited by 211 publications

(108 citation statements)

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“…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].…”

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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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Generation of Coherent Extreme-Ultraviolet Radiation Carrying Orbital Angular Momentum

2014

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“…Light beams carrying phase singularities possess a nonzero azimuthal energy flow [3] and are known as optical vortices. Such beams carry nonzero orbital angular momentum [4] and have many applications, which include micromanipulation [5][6][7], microscopy [8,9], quantum information [10], or astronomical imaging [11].…”

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Optical Vortices from Liquid Crystal Droplets

et al. 2009

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We report on the generation of mono-and polychromatic optical phase singularities from micron-sized birefringent droplets. This is done experimentally by using liquid crystal droplets whose three dimensional architecture of the optical axis is controlled within the bulk by surfactant agents. Because of its microscopic size these optical vortex generators are optically trapped and manipulated at will, thus realizing a robust self-aligned micro-optical device for orbital angular momentum conversion. Experimental observations are supported by a simple model of optical spin-orbit coupling in uniaxial dielectrics that emphasizes the prominent role of the transverse optical anisotropy with respect to the beam propagation direction.

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“…The phase front of the propagating wave is a corkscrew-type phase advance with the sign of the topological charge positive, for clockwise rotation, or negative, for counter-clockwise rotation. These vortex waves have been found to be useful in an extremely diverse range of applications from communications 6,9-13 and imaging [14][15][16] to particle manipulation [17][18][19] over a wide range of length scales. In the most widely examined application, vortex waves have been harnessed for use in electromagnetic and quantum communications.…”

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Generation of topologically diverse acoustic vortex beams using a compact metamaterial aperture

Naify

Rohde

Martin

et al. 2016

Applied Physics Letters

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Vortex waves, which carry orbital angular momentum, have found use in a range of fields from quantum communications to particle manipulation. Due to their widespread influence, significant attention has been paid to the methods by which vortex waves are generated. For example, active phased arrays generate diverse vortex modes at the cost of electronic complexity and power consumption [1][2][3][4] . Conversely, analog apertures, such as spiral phase plates 1,5 , metasurfaces 6 , and gratings 7 require separate apertures to generate each mode. Here we present a new class of metamaterial-based acoustic vortex generators, which are both geometrically and electronically simple, and topologically tunable. Our metamaterial approach generates vortex waves by wrapping an acoustic leaky wave antenna 8 back upon itself. Exploiting the antennas frequency-varying refractive index, we demonstrate experimentally and analytically that this analog structure generates both integer, and noninteger vortex modes. The metamaterial design makes the aperture compact and can thus be integrated into high-density systems.The total angular momentum of a system can be divided into two components, spin angular momentum, and orbital angular momentum (OAM). Although acoustic waves do not possess spin angular momentum they have been shown to carry OAM 1,2 . A drawing of a single mode helical wave with value L = −2 is shown in Fig. 1(a) where L is the OAM topological mode number. A wave with OAM index L = 0 describes a system with no helical phase front. The phase front of the propagating wave is a corkscrew-type phase advance with the sign of the topological charge positive, for clockwise rotation, or negative, for counter-clockwise rotation. These vortex waves have been found to be useful in an extremely diverse range of applications from communications 6,9-13 and imaging 14-16 to particle manipulation 17-19 over a wide range of length scales. In the most widely examined application, vortex waves have been harnessed for use in electromagnetic and quantum 2 communications.The importance of both topological diversity, and aperture simplicity in vortex mode generation becomes immediately evident when considering the applications of vortex waves. Inspired by recent research on acoustic leaky-wave antennas 8,23 , we present an air-acoustic vortex beam emitter which generates topologically diverse vortex waves using a single transducer coupled to a single analog metamaterial aperture. A leaky wave antenna is a device comprised of a one-or two-dimensional waveguide which leaks power along it's length with either a continuous leaking slot or sub-wavelength radiating shunts. Leaky wave antennas rely on geometry-controlled dispersion to tune the refractive index of the fluid inside the waveguide. The leaked energy then refracts from the antenna at an angle θ(ω), similar to the refraction mechanism of a prism. The value of θ(ω) is determined by the ratio of 3 wavenumber β(ω) inside the waveguide to the wavenumber in the surrounding area kAlthough not in...

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Shadow Effects in Spiral Phase Contrast Microscopy

Cited by 211 publications

References 10 publications

Generation of Coherent Extreme-Ultraviolet Radiation Carrying Orbital Angular Momentum

Generation of Coherent Extreme-Ultraviolet Radiation Carrying Orbital Angular Momentum

Optical Vortices from Liquid Crystal Droplets

Generation of topologically diverse acoustic vortex beams using a compact metamaterial aperture

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