Tunable complex photonic chiral lattices by reconfigurable optical phase engineering

Author(s): Jolly Xavier and Joby Joseph

Abstract:

“We present a novel single-step fabrication approach, based on optical phase engineering, for tunable complex photonic chiral lattices of diverse geometries in a large area. By means of engineered reconfigurable phase patterns, we computationally simulate as well as experimentally investigate these complex structures. We show the generation of both periodic right- and left-handed chiral structures as well as photonic transversely quasi-crystallographic chiral structures. These complex chiral lattices are also demonstrated in a photorefractive material, and the lattice formation is analyzed by plane-wave-guided imaging as well as diffraction pattern imaging. Furthermore, complex photonic chiral structures with engineered tunable relative phase shifts between adjacent spiral units realizable in a single step are explored and analyzed.”

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Publication:Optics Letters
Issue/Year: Optics Letters, Vol. 36, Issue 3, pp. 403-405 (2011)
DOI: 10.1364/OL.36.000403

Dynamic generation of Debye diffraction-limited multifocal arrays for direct laser printing nanofabrication

Author(s): Han Lin, Baohua Jia, and Min Gu

Abstract:

“We propose a Debye-theory-based iterative method to produce accurate phase patterns for generating highly uniform diffraction-limited multifocal arrays with a high-NA objective. It is shown that by using the Debye method, the uniformity of the diffraction-limited focal arrays can reach 99%, owing to the critical consideration of the depolarization effect associated with high-NA objectives. The generated phase patterns are implemented in fast dynamic laser printing nanofabrication for the generation of individually controlled high-quality microvoid arrays in a solid polymer material by a single exposure of a femtosecond laser beam. As a result of the high-quality multifocal arrays, functional three-dimensional photonic crystals possessing multiple stopgaps with suppression up to 80% in transmission spectra are demonstrated.”

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Publication: Optics Letters
Issue/Year: Optics Letters, Vol. 36, Issue 3, pp. 406-408 (2011)
DOI: 10.1364/OL.36.000406

Frequency bandwidth of light focused through turbid media

Author(s): Frerik van Beijnum, Elbert G. van Putten, Ad Lagendijk, and Allard P. Mosk

Abstract:

“We study the effect of frequency detuning on light focused through turbid media. By shaping the wavefront of the incident beam light is focused through an opaque scattering layer. When detuning the laser we observe a gradual decrease of the focus intensity, while the position, size,and shape of the focus remain the same within experimental accuracy. The frequency dependence of the focus intensity follows a measured speckle correlation function. We support our experimental findings with calculations based on transport theory. Our results imply wavefront shaping methods can be generalized to allow focusing of optical pulses in turbid media.”

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Publication: Optics Letters
Issue/Year: Optics Letters, Vol. 36, Issue 3, pp. 373-375 (2011)
DOI: 10.1364/OL.36.000373

Constructing petal modes from the coherent superposition of Laguerre-Gaussian modes

Author(s): Darryl Naidoo, Andrew Forbes, Kamel Ait-Ameur, Marc Brunel

Abstract:

“An experimental approach in generating Petal-like transverse modes, which are similar to what is seen in porro-prism resonators, has been successfully demonstrated. We hypothesize that the petal-like structures are generated from a coherent superposition of Laguerre-Gaussian modes of zero radial order and opposite azimuthal order. To verify this hypothesis, visually based comparisons such as petal peak to peak diameter and the angle between adjacent petals are drawn between experimental data and simulated data. The beam quality factor of the Petal-like transverse modes and an inner product interaction is also experimentally compared to numerical results.”

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Publication: SPIE Proceedings
Issue/Year: Proc. SPIE 7913, 791304 (2011)
DOI: 10.1117/12.876854

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.”

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

What spatial light modulators can do for optical microscopy

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

Abstract:

“With the availability of high-resolution miniature spatial light modulators (SLMs) new methods in optical microscopy have become feasible. The SLMs discussed in this review consist of miniature liquid crystal displays with micron-sized pixels that can modulate the phase and/or amplitude of an optical wavefront. In microscopy they can be used to control and shape the sample illumination, or they can act as spatial Fourier filters in the imaging path. Some of these applications are reviewed in this article. One of them, called spiral phase contrast, generates isotropic edge enhancement of thin phase samples or spiral-shaped interference fringes for thicker phase samples, which can be used to reconstruct the phase topography from a single on-axis interferogram. If SLMs are used for both illumination control and spatial Fourier filtering, this combination for instance allows for the generalization of the Zernike phase contrast principle. The new SLM-based approach improves the effective resolution and avoids some shortcomings and artifacts of the traditional method. The main advantage of SLMs in microscopy is their flexibility, as one can realize various operation modes in the same setup, without the need for changing any hardware components, simply by electronically switching the phase pattern displayed on the SLMs.”

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Publication:Laser & Photonics Reviews
Issue/Year: Laser & Photonics Reviews, Volume 5, Issue 1, pages 81–101, January 2011
DOI: 10.1002/lpor.200900047