Mr. Vignesh Mukund Profile

Vignesh Mukund

Doctoral Researcher at IMEC

Publications (3)

Proceedings Article | 27 July 2016 Presentation

Density controlled nanophotonic waveguide gratings for efficient on-chip out-coupling in the near field (Conference Presentation)

Dries Vercruysse, Vignesh Mukund, Roelof Jansen, Richard Stahl, Pol Van Dorpe, Liesbet Lagae, Xavier Rottenberg

Proceedings Volume 9891, 98910A (2016) https://doi.org/10.1117/12.2227919

KEYWORDS: Waveguides, Diffraction gratings, Near field, Nanophotonics, Near field optics, Algorithm development, Holography, Optical components, Integrated photonics, Polarization

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Waveguide optics takes up a prominent role in the progressing miniaturization of optical devices. Chip integrated photonic waveguides especially allow for complex routing schemes of light across a chip. In/out-coupling diffraction gratings form an essential tool in waveguide systems, as they facilitate the interaction between the waveguide system and the near or far-field.[1,2] Ideally, these gratings would couple out all light in the waveguide into a beam with a predefined polarization and, phase and intensity profile. As such they should be able to produce any functional beam that is typically prepared by free space optics. Yet, in practice there is typically a design trade-off between beam quality and out-coupling efficiency.[2] Light in the waveguide has to travel laterally through the grating to be coupled out. The light therefore decays exponentially over the grating, causing much more light to be coupled out at the start of the grating than at the end. This asymmetry results in a warped out-coupling intensity that heavily influences the light beam’s intensity profile. Especially when the grating is addressing points in the near field, as is the case for focusing waveguide grating couplers, this effect can be highly disruptive.

In this work we present a grating constructed from a field of sub-wavelength scatterers, rather than full grating lines. By tuning the position and the density of the scatterers, the phase and the intensity of the out-coupled light can be set precisely over large grating areas. An iterative design algorithm is developed that carefully tunes the density so as to control the light intensity in the waveguide and the amount of out-coupled light. Using FDTD simulations we show that these gratings can efficiently couple out light into a nearly diffraction limited spot with an even angular intensity. We verify this experimentally by fabricating these gratings in the SiN/SiO2 system using e-beam lithography. In addition, we also show that these gratings can couple out more complex holographic patterns.

These density controlled out-coupling gratings let us efficiently address the near-field on optical chips, making them ideal waveguide components for on-chip optical trapping, holographic imaging or fluorescent excitation.[3]

Proceedings Article | 13 May 2016 Paper

On-chip fluorescence excitation and collection by focusing grating couplers

Sarp Kerman, Dries Vercruysse, Tom Claes, Mahmud Ul Hasan, Pieter Neutens, Vignesh Mukund, Xavier Rottenberg, Liesbet Lagae, Pol Van Dorpe

Proceedings Volume 9891, 98911L (2016) https://doi.org/10.1117/12.2227740

KEYWORDS: Luminescence, Waveguides, Silicon, Fluorescence spectroscopy, Microscopes, Microfluidics, Photonics, Diffraction gratings, Silicon photonics, Integrated optics, Etching, Finite-difference time-domain method, Visible radiation, Optical design, Optical fiber cables

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Proceedings Article | 2 March 2015 Paper

Microscope-on-chip: combining lens-free microscopy with integrated photonics

Richard Stahl, Dries Vercruysse, Tom Claes, Geert Vanmeerbeeck, Vignesh Mukund, Roelof Jansen, Jeonghwan Song, Luis Hoffman, Xavier Rottenberg, Andy Lambrechts, Liesbet Lagae

Proceedings Volume 9328, 93281C (2015) https://doi.org/10.1117/12.2077484

KEYWORDS: Imaging systems, Photonics, Prototyping, Image sensors, Image resolution, Microscopes, Waveguides, Light sources, Phased arrays, Microscopy

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