scholarly journals Shack-Hartmann Wavefront Sensing of Ultrashort Optical Vortices

Sensors ◽  
2021 ◽  
Vol 22 (1) ◽  
pp. 132
Author(s):  
Alok Kumar Pandey ◽  
Tanguy Larrieu ◽  
Guillaume Dovillaire ◽  
Sophie Kazamias ◽  
Olivier Guilbaud
Keyword(s):  
Topological Charge ◽  
Helical Structure ◽  
Wavefront Sensor ◽  
Optical Vortices ◽  
Wavefront Sensing ◽  
Single Shot ◽  
Azimuthal Mode ◽  
Light Matter Interaction ◽  
Vortex Beams ◽  
Light Beams

Light beams carrying Orbital Angular Momentum (OAM), also known as optical vortices (OV), have led to fascinating new developments in fields ranging from quantum communication to novel light–matter interaction aspects. Even though several techniques have emerged to synthesize these structured-beams, their detection, in particular, single-shot amplitude, wavefront, and modal content characterization, remains a challenging task. Here, we report the single-shot amplitude, wavefront, and modal content characterization of ultrashort OV using a Shack-Hartmann wavefront sensor. These vortex beams are obtained using spiral phase plates (SPPs) that are frequently used for high-intensity applications. The reconstructed wavefronts display a helical structure compatible with the topological charge induced by the SPPs. We affirm the accuracy of the optical field reconstruction by the wavefront sensor through an excellent agreement between the numerically backpropagated and experimentally obtained intensity distribution at the waist. Consequently, through Laguerre–Gauss (LG) decomposition of the reconstructed fields, we reveal the radial and azimuthal mode composition of vortex beams under different conditions. The potential of our method is further illustrated by characterizing asymmetric Gaussian vortices carrying fractional average OAM, and a realtime topological charge measurement at a 10Hz repetition rate. These results can promote Shack-Hartmann wavefront sensing as a single-shot OV characterization tool.

scholarly journals Topological charge and angular momentum of light beams carrying optical vortices

2004 ◽  
Author(s):  
M S Soskin ◽  
V N Gorshkov ◽  
M V Vasnctsov ◽  
J T Malos ◽  
N R Heckenberg
Keyword(s):  
Angular Momentum ◽  
Topological Charge ◽  
Optical Vortices ◽  
Light Beams

scholarly journals Topological charge and angular momentum of light beams carrying optical vortices

1997 ◽  
Vol 56 (5) ◽  
pp. 4064-4075 ◽  
Author(s):  
M. S. Soskin ◽  
V. N. Gorshkov ◽  
M. V. Vasnetsov ◽  
J. T. Malos ◽  
N. R. Heckenberg
Keyword(s):  
Angular Momentum ◽  
Topological Charge ◽  
Optical Vortices ◽  
Light Beams

scholarly journals Determining Vortex-Beam Superpositions by Shear Interferometry

Photonics ◽  
2018 ◽  
Vol 5 (3) ◽  
pp. 16 ◽  
Author(s):  
Behzad Khajavi ◽  
Junior Ureta ◽  
Enrique Galvez
Keyword(s):  
Topological Charge ◽  
Effective Means ◽  
Optical Vortices ◽  
Vortex Beam ◽  
Mode Content ◽  
Optical Modes ◽  
Vital Component ◽  
Light Beams ◽  
Comparable Magnitude ◽  
Do So

Optical modes bearing optical vortices are important light systems in which to encode information. Optical vortices are robust features of optical beams that do not dissipate upon propagation. Thus, decoding the modal content of a beam is a vital component of the process. In this work, we present a method to decode modal superpositions of light beams that contain optical vortices. We do so using shear interferometry, which presents a simple and effective means of determining the vortex content of a beam, and extract the parameters of the component vortex modes that constitute them. We find that optical modes in a beam are easily determined. Its modal content can be extracted when they are of comparable magnitude. The use of modes of well-defined topological charge, but not well-defined radial-mode content, such as those produced by phase-only encoding, are much easier to diagnose than pure Laguerre–Gauss modes.

scholarly journals Time-varying optical vortices enabled by time-modulated metasurfaces

Nanophotonics ◽  
2020 ◽  
Vol 9 (9) ◽  
pp. 2957-2976
Author(s):  
Hooman Barati Sedeh ◽  
Mohammad Mahdi Salary ◽  
Hossein Mosallaei
Keyword(s):  
Indium Tin Oxide ◽  
Topological Charge ◽  
Communication Systems ◽  
Structured Light ◽  
Angular Acceleration ◽  
Optical Vortices ◽  
Time Varying ◽  
Phase Gradient ◽  
Light Beams ◽  
Frequency Gradient

AbstractIn this paper, generation of optical vortices with time-varying orbital angular momentum (OAM) and topological charge is theoretically demonstrated based on time-modulated metasurfaces with a linearly azimuthal frequency gradient. The topological charge of such dynamic structured light beams is shown to continuously and periodically change with time evolution while possessing a linear dependence on time and azimuthal frequency offset. The temporal variation of OAM yields a self-torqued beam exhibiting a continuous angular acceleration of light. The phenomenon is attributed to the azimuthal phase gradient in space-time generated by virtue of the spatiotemporal coherent path in the interference between different frequencies. In order to numerically authenticate this newly introduced concept, a reflective dielectric metasurface is modelled consisting of silicon nanodisk heterostructures integrated with indium-tin-oxide and gate dielectric layers on top of a mirror-backed silicon slab which renders an electrically tunable guided mode resonance mirror in near-infrared regime. The metasurface is divided into several azimuthal sections wherein nanodisk heterostructures are interconnected via nanobars serving as biasing lines. Addressing azimuthal sections with radio-frequency biasing signals of different frequencies, the direct dynamic photonic transitions of leaky-guided modes are leveraged for realization of an azimuthal frequency gradient in the optical field. Generation of dynamic twisted light beams with time-varying OAM by the metasurface is verified via performing several numerical simulations. Moreover, the role of modulation waveform and frequency gradient on the temporal evolution and diversity of generated optical vortices is investigated which offer a robust electrical control over the number of dynamic beams and their degree of self-torque. Our results point toward a new class of structured light for time-division multiple access in optical and quantum communication systems as well as unprecedented optomechanical manipulation of objects.

scholarly journals X-ray free-electron laser wavefront sensing using the fractional Talbot effect

2020 ◽  
Vol 27 (2) ◽  
pp. 254-261 ◽  
Author(s):  
Yanwei Liu ◽  
Matthew Seaberg ◽  
Yiping Feng ◽  
Kenan Li ◽  
Yuantao Ding ◽  
...  
Keyword(s):  
Free Electron ◽  
Free Electron Laser ◽  
Average Power ◽  
Wavefront Sensor ◽  
Wavefront Sensing ◽  
Single Shot ◽  
Free Electron Lasers ◽  
X Ray ◽  
Wide Range ◽  
Linac Coherent Light Source

Wavefront sensing at X-ray free-electron lasers is important for quantitatively understanding the fundamental properties of the laser, for aligning X-ray instruments and for conducting scientific experimental analysis. A fractional Talbot wavefront sensor has been developed. This wavefront sensor enables measurements over a wide range of energies, as is common on X-ray instruments, with simplified mechanical requirements and is compatible with the high average power pulses expected in upcoming X-ray free-electron laser upgrades. Single-shot measurements were performed at 500 eV, 1000 eV and 1500 eV at the Linac Coherent Light Source. These measurements were applied to study both mirror alignment and the effects of undulator tapering schemes on source properties. The beamline focal plane position was tracked to an uncertainty of 0.12 mm, and the source location for various undulator tapering schemes to an uncertainty of 1 m, demonstrating excellent sensitivity. These findings pave the way to use the fractional Talbot wavefront sensor as a routine, robust and sensitive tool at X-ray free-electron lasers as well as other high-brightness X-ray sources.

scholarly journals Aberration-resistible topological charge determination of annular-shaped optical vortex beams using Shack–Hartmann wavefront sensor

2019 ◽  
Vol 27 (5) ◽  
pp. 7803 ◽  
Author(s):  
Daiyin Wang ◽  
Hongxin Huang ◽  
Yoshinori Matsui ◽  
Hiroshi Tanaka ◽  
Haruyoshi Toyoda ◽  
...  
Keyword(s):  
Topological Charge ◽  
Optical Vortex ◽  
Wavefront Sensor ◽  
Vortex Beams ◽  
Charge Determination

scholarly journals A minimal subwavelength focal spot for the energy flux

2021 ◽  
Vol 5 (45) ◽  
pp. 685-691
Author(s):  
S.S. Stafeev ◽  
V.D. Zaicev
Keyword(s):  
Energy Flux ◽  
Topological Charge ◽  
Focal Spot ◽  
Polarized Light ◽  
Spot Size ◽  
Optical Vortices ◽  
Matter Interaction ◽  
Linearly Polarized ◽  
Light Matter Interaction ◽  
Tight Focus

It is shown theoretically and numerically that circularly and linearly polarized incident beams produce at the tight focus identical circularly symmetric distributions of an on-axis energy flux. It is also shown that the on-axis energy fluxes from radially and azimuthally polarized optical vortices with unit topological charge are equal to each other. An optical vortex with azimuthal polarization is found to generate the minimum focal spot measured for the intensity (all other parameters being equal). Slightly larger (by a fraction of a percent) is the spot size calculated for the energy flux for the circularly and linearly polarized light. The spot size in terms of intensity is of importance in light-matter interaction, whereas the spot size in terms of energy flux affects the resolution in optical microscopy.

scholarly journals Optical beams with an infinite number of vortices

2021 ◽  
Vol 45 (4) ◽  
pp. 490-496
Author(s):  
V.V. Kotlyar
Keyword(s):  
Angular Momentum ◽  
Cross Section ◽  
Data Transmission ◽  
Topological Charge ◽  
Laser Beams ◽  
Optical Data ◽  
Optical Vortices ◽  
Straight Line ◽  
Phase Singularities ◽  
Light Beams

In optical data transmission with using vortex laser beams, data can be encoded by the topo-logical charge, which is theoretically unlimited. However, the topological charge of a single sepa-rate vortex is limited by possibilities of its generating. Therefore, in this work, we analyze light beams with an unbounded (countable) set of optical vortices. The summary topological charge of such beams is infinite. Phase singularities (isolated intensity nulls) in such beams typically have a unit topological charge and reside equidistantly (or not equidistantly) on a straight line in the beam cross section. Such beams are form-invariant and, on propagation in space, change only in scale and rotate. Orbital angular momentum of such multivortex beams is finite, since only a finite number of optical vortices fall into the area, where the Gaussian beam has a notable intensity. Other phase singularities are located in the periphery (and at the infinity), where the intensity is almost zero.

scholarly journals Determining Vortex-Beam Superpositions by Shear Interferometry

2018 ◽  
Author(s):  
Behzad Khajavi ◽  
Junior R. Gonzales Ureta ◽  
Enrique J. Galvez
Keyword(s):  
Topological Charge ◽  
Effective Means ◽  
Optical Vortices ◽  
Vortex Beam ◽  
Mode Content ◽  
Optical Modes ◽  
Vital Component ◽  
Light Beams ◽  
Comparable Magnitude ◽  
Do So

Optical modes bearing optical vortices are important light systems in which to encode information. Optical vortices are robust features of optical beams that do not dissipate upon propagation. Thus decoding the modal content of a beam is a vital component of the process. In this work we present a method to decode modal superpositions of light beams that contain optical vortices. We do so using shear interferometry, which presents a simple and effective means of determining the vortex content of a beam, and extract the parameters of the component vortex modes that constitute them. We find that optical modes in a beam are easily determined. Its modal content can be extracted when they are of comparable magnitude. The use of modes of well defined topological charge but not well defined radial-mode content, such as those produced by phase-only encoding, are much easier to diagnose than pure Laguerre-Gauss modes.

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