Dimensional properties of Laguerre–Gaussian vortex beams

Author(s):

Jie Zhang, Su-Juan Huang, Fu-Quan Zhu, Wei Shao, and Mu-Sheng Chen

Abstract:

“We derive and analyze the dimensional properties of Laguerre–Gaussian vortex beams theoretically and numerically. The analytical expressions of inner and outer radii are given out and proved to be proportional to the transverse beam size, when the topological charge remains. The ratio of the outer and inner radius only depends on the topological charge, having nothing to do with the waist radius and the propagation distance, and the ratio decreases as the topological charge increases. Using a spatial light modulator loaded with computer-generated holograms, we generate vortex beams. The experimental results are in good agreement with our numerical simulations. This research may provide useful insights into the study of the optical vortex beam and its further applications.”

Link to Publications Page

Publication: Applied Optics
Issue/Year: Applied Optics Volume 56, Issue 12 pp. 3556-3561 (2017)
DOI: 10.1364/AO.56.003556

Bessel beams with spatial oscillating polarization

Author(s):

Fu, Shiyao and Zhang, Shikun and Gao, Chunqing

Abstract:

“Bessel beams are widely used in optical metrology mainly because of their large Rayleigh range (focal length). Radial/azimuthal polarization of such beams is of interest in the fields of material processing, plasma absorption or communication. In this paper an experimental set-up is presented, which generates a Bessel-type vector beam with a spatial polarization, oscillating along the optical axis, when propagating in free space. A first holographic axicon (HA) HA1 produces a normal, linearly polarized Bessel beam, which by a second HA2 is converted into the spatial oscillating polarized beam. The theory is briefly discussed, the set-up and the experimental results are presented in detail.”

Link to Publications Page

Publication: Scientific Reports
Issue/Year: Scientific Reports volume 6, Article number: 30765 (2016)
DOI: 10.1038/srep30765

Orbital-angular-momentum crosstalk and temporal fading in a terrestrial laser link using single-mode fiber coupling

Author(s):

Funes, Gustavo; Vial, Matias & Anguita, Jaime A.

Abstract:

“Using a mobile experimental testbed, we perform a series of measurements on the detection of laser beams carrying orbital angular momentum (OAM) to evaluate turbulent channel distortions and crosstalk among receive states in an 84-m roofed optical link. We find that a receiver assembly using single-mode fiber coupling serves as a good signal selector in terms of crosstalk rejection. From the recorded temporal channel waveforms, we estimate average crosstalk profiles and propose an appropriate probability density function for the fluctuations of the detected OAM signal. Further measurements of OAM crosstalk are described for a horizontal 400-m link established over our campus.”

Link to Publications Page

Publication: Opt. Express
Issue/Year: Opt. Express, Volume 23; Number 18; Pages 23133-23142; 2015
DOI: 10.1364/OE.23.023133

Detection of Bessel beams with digital axicons

Author(s):

Abderrahmen Trichili and Thandeka Mhlanga and Yaseera Ismail and Filippus S. Roux and Melanie McLaren and Mourad Zghal and Andrew Forbes

Abstract:

“We propose a simple method for the detection of Bessel beams with arbitrary radial and azimuthal indices, and then demonstrate it in an all-digital setup with a spatial light modulator. We confirm that the fidelity of the detection method is very high, with modal cross-talk below 5%, even for high orbital angular momentum carrying fields with long propagation ranges. To illustrate the versatility of the approach we use it to observe the modal spectrum changes during the self-reconstruction process of Bessel beams after encountering an obstruction, as well as to characterize modal distortions of Bessel beams propagating through atmospheric turbulence.”

Link to Publications Page

Publication: Optics Express
Issue/Year: Optics Express, Vol. 22 , Issue 14, pp. 17553- 17560 (2014)
DOI: 10.1364/OE.22.017553

Optical eigenmodes; exploiting the quadratic nature of the energy flux and of scattering interactions

Author(s):

Mazilu, Michael and Baumgartl, J and Kosmeier, S and Dholakia, K

Abstract:

“We report a mathematically rigorous technique which facilitates the optimization of various optical properties of electromagnetic fields in free space and including scattering interactions. The technique exploits the linearity of electromagnetic fields along with the quadratic nature of the intensity to define specific Optical Eigenmodes (OEi) that are pertinent to the interaction considered. Key applications include the optimization of the size of a focused spot, the transmission through sub-wavelength apertures, and of the optical force acting on microparticles. We verify experimentally the OEi approach by minimising the size of a focused optical field using a superposition of Bessel beams.”

Link to Publications Page

Publication: Optics Express
Issue/Year: Optics Express Volume 19, Issue 2 pp.933-945 (2011)
DOI: 10.1364/OE.19.000933

The dark spots of Arago

Author(s): Pascal Fischer, Susan E. Skelton, Christopher G. Leburn, Casey T. Streuber, Ewan M. Wright, and Kishan Dholakia

Abstract:

“We explore the diffraction and propagation of Laguerre- Gaussian beams of varying azimuthal index past a circular obstacle both experimentally and numerically. When the beam and obstacle centers are aligned the famous spot of Arago, which arises for zero azimuthal index, is replaced for non-zero azimuthal indices by a dark spot of Arago, a simple consequence of the conserved phase singularity at the beam center. We explore how the dark spot of Arago behaves as the beam and obstacle centers are progressively misaligned, and find that the central dark spot may break into several dark spots of Arago for higher incident azimuthal index beams. ”

Link to Publications Page

Publication: Optics Express
Issue/Year: Optics Express, Vol. 15, Issue 19, pp. 11860-11873
DOI: 10.1364/OE.15.011860

Ultrashort Laguerre-Gaussian pulses with angular and group velocity dispersion compensation

Author(s): I. Zeylikovich, H. I. Sztul, V. Kartazaev, T. Le, and R. R. Alfano

Abstract:

“Coherent optical vortices are generated from ultrashort 6.4 fs pulses. Our results demonstrate angular dispersion compensation of ultrashort 6.4 fs Laguerre-Gaussian (LG) pulses as well as what is believed to be the first direct autocorrelation measurement of 80 fs LG amplified pulses. A reflective-mirror-based 4f-compressor is proposed to compensate the angular and group velocity dispersion of the ultrashort LG pulses.”

Link to Publications Page

Publication: Optics Letters
Issue/Year: Optics Letters, Vol. 32, Issue 14, pp. 2025-2027 (2007)
DOI: 10.1364/OL.32.002025

Wavefront correction of spatial light modulators using an optical vortex image

Author(s): A. Jesacher, A. Schwaighofer, S. Fürhapter, C. Maurer, S. Bernet, and M. Ritsch-Marte

Abstract:

“We present a fast and flexible non-interferometric method for the correction of small surface deviations on spatial light modulators, based on the Gerchberg-Saxton algorithm. The surface distortion information is extracted from the shape of a single optical vortex, which is created by the light modulator. The method can be implemented in optical tweezers systems for an optimization of trapping fields, or in an imaging system for an optimization of the point-spread-function of the entire image path.”

Link to Publications Page

Publication:Optics Express
Issue/Year: Optics Express, Vol. 15, Issue 9, pp. 5801-5808
DOI: 10.1364/OE.15.005801

Direct measurement of the skew angle of the Poynting vector in a helically phased beam

Author(s): Jonathan Leach, Stephen Keen, Miles J. Padgett, Christopher Saunter, and Gordon D. Love

Abstract:

“We measure the local skew angle of the Poynting vector within a helically-phased, exp (il φ), beam using a Shack Hartmann wavefront sensor. It is the skew angle of the Poynting vector with respect to the beam axis that gives rise to the orbital angular momentum of a light beam. We confirm that this skew angle is l/kr, corresponding to an orbital angular momentum of lћ per photon. Measurement of orbital angular momentum in this way is an alternative to interferometric techniques giving a non-ambiguous result to both the magnitude and sign of l from a single measurement, without any restriction on the optical bandwidth.”

Link to Publications Page

Publication: Optics Express
Issue/Year: Optics Express, Vol. 14, Issue 25, pp. 11919-11924 (2006)
DOI: 10.1364/OE.14.011919

Reverse orbiting of microparticles in optical vortices

Author(s): A. Jesacher, S. Fürhapter, C. Maurer, S. Bernet, and M. Ritsch-Marte

Abstract:

“We report the observation of particles trapped at an air-water surface orbiting in a reverse direction with respect to the orbital angular momentum of the light field. The effect is explained by a combination of asymmetric particle shape and confinement of the particle on the 2D air-water interface. The experiment highlights the strong influence of the particle shape on the momentum transfer, an effect that is often not considered in optical trapping experiments.”

Link to Publications Page

Publication: Optics Letters
Issue/Year: Optics Letters, Vol. 31, Issue 19, pp. 2824-2826
DOI: 10.1364/OL.31.002824