Sandeep Tauro
Technical University of Denmark
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Publication
Featured researches published by Sandeep Tauro.
Optics Express | 2010
Sandeep Tauro; Andrew Rafael Bañas; Darwin Palima; Jesper Glückstad
Optical trapping in a counter-propagating (CP) beam-geometry provides unique advantages in terms of working distance, aberration requirements and intensity hotspots. However, its axial performance is governed by the wave propagation of the opposing beams, which can limit the practical geometries. Here we propose a dynamic method for controlling axial forces to overcome this constraint. The technique uses computer-vision object tracking of the axial position, in conjunction with software-based feedback, for dynamically stabilizing the axial forces. We present proof-of-concept experiments showing real-time rapid repositioning coupled with a strongly enhanced axial trapping for a plurality of particles of varying sizes. We also demonstrate the techniques adaptability for real-time reconfigurable feedback-trapping of a dynamically growing structure that mimics a continuously dividing cell colony. Advanced implementation of this feedback-driven approach can help make CP-trapping resistant to a host of perturbations such as laser fluctuations, mechanical vibrations and other distortions emphasizing its experimental versatility.
Optics Express | 2011
Sandeep Tauro; Andrew Rafael Bañas; Darwin Palima; Jesper Glückstad
We report the first experimental demonstration of Gaussian beam-shaping based on the Generalized Phase Contrast (GPC) approach. We show that, when using a dynamic spatial light modulator (SLM), this approach can rapidly generate arbitrarily shaped beams. Moreover, we demonstrate that low-cost binary-phase optics fabricated using photolithography and chemical etching techniques can replace the SLM in static and high power beam shaping applications. The design parameters for the binary-phase elements of the module are chosen according to the results of our previously conducted analysis and numerical demonstrations [Opt. Express 15, 11971 (2007)]. Beams with a variety of cross-sections such as circular, rectangular and square, with near flat-top intensity distributions are demonstrated. GPC-based beam shaping is inherently speckle-free and the shaped beams maintain a flat output phase. The non-absorbing components used in this beam-shaping approach have a high-damage-threshold and are thus ideally suited for high power applications.
Proceedings of SPIE | 2011
Tomoyo Matsuoka; Masayuki Nishi; Masaaki Sakakura; Kiyotaka Miura; Kazuyuki Hirao; Darwin Palima; Sandeep Tauro; Andrew Rafael Bañas; Jesper Glückstad
In its standard version, our BioPhotonics Workstation (BWS) can generate multiple controllable counter-propagating beams to create real-time user-programmable optical traps for stable three-dimensional control and manipulation of a plurality of particles. The combination of the platform with microstructures fabricated by two-photon polymerization (2PP) can lead to completely new methods to communicate with micro- and nano-sized objects in 3D and potentially open enormous possibilities in nano-biophotonics applications. In this work, we demonstrate that the structures can be used as microsensors on the BWS platform by functionalizing them with silica-based sol-gel materials inside which dyes can be entrapped.
Journal of Optics | 2011
Darwin Palima; Thue B. Lindballe; Martin Kristensen; Sandeep Tauro; Henrik Stapelfeldt; S. R. Keiding; Jesper Glückstad
Counter-propagating beams have enabled the first stable three-dimensional optical trapping of microparticles and this procedure has been enhanced and developed over the years to achieve independent and interactive manipulation of multiple particles. In this work, we analyse counter-propagating shaped-beam traps that depart from the conventional geometry based on symmetric, coaxial counter-propagating beams. We show that projecting shaped beams with separation distances previously considered axially unstable can, in fact, enhance the axial and transverse trapping stiffnesses. We also show that deviating from using perfectly counter-propagating beams to use oblique beams can improve the axial stability of the traps and improve the axial trapping stiffness. These alternative geometries can be particularly useful for handling larger particles. These results hint at a rich potential for light shaping for optical trapping and manipulation using patterned counter-propagating beams, which still remains to be fully tapped.
Proceedings of SPIE | 2010
Darwin Palima; Thue B. Lindballe; Martin Kristensen; Sandeep Tauro; Andrew Rafael Bañas; Henrik Stapelfeldt; S. R. Keiding; Jesper Glückstad
The counter-propagating geometry opens an extra degree of freedom for shaping light while subsuming single-sided illumination as a special case (i.e., one beam set turned off). In its conventional operation, our BioPhotonics Workstation (BWS) uses symmetric, co-axial counter-propagating beams for stable three-dimensional manipulation of multiple particles. In this work, we analyze counter-propagating shaped-beam traps that depart from this conventional geometry. We show that projecting shaped beams with separation distances previously considered axially unstable can, in fact, enhance the trap by improving axial and transverse trapping stiffness. We also show interesting results of trapping and micromanipulation experiments that combine optical forces with fluidic forces. These results hint about the rich potential of using patterned counter-propagating beams for optical trapping and manipulation, which still remains to be fully tapped.
Proceedings of SPIE | 2011
Andrew Rafael Bañas; Darwin Palima; Sandeep Tauro; Jesper Glückstad
Optical trapping and manipulation have established a track record for cell handling in small volumes. However, this cell handling capability is often not simultaneously utilized in experiments using other methods for measuring single cell properties such as fluorescent labeling. Such methods often limit the trapping range because of high numerical aperture and imaging requirements. To circumvent these issues, we are developing a BioPhotonics Workstation platform that supports extension modules through a long working distance geometry. Furthermore, a long range axial manipulation range is achieved by the use of counter-propagating beam traps coupled with the long working distance. This geometry provides three dimensional and real time manipulation of a plurality of traps - currently 100 independently reconfigurable - facilitating precise control and a rapid response in all sorts of optical manipulation undertakings. We present ongoing research activities for constructing a compact next generation BioPhotonics Workstation.
Proceedings of SPIE | 2011
Jesper Glückstad; Andrew Rafael Bañas; Sandeep Tauro; Darwin Palima
Conventional optical trapping or tweezing is often limited in the achievable trapping range because of high numerical aperture and imaging requirements. To circumvent this, we are developing a next generation BioPhotonics Workstation platform that supports extension modules through a long working distance geometry. This geometry provides three dimensional and real time manipulation of a plurality of traps facilitating precise control and a rapid response in all sorts of optical manipulation undertakings. We present ongoing research and development activities for constructing a compact next generation BioPhotonics Workstation to be applied in three-dimensional studies on regulated microbial cell growth including their underlying physiological mechanisms, in vivo characterization of cell constituents and manufacturing of nanostructures and new materials.
DOPS-NYT | 2012
Andrew Rafael Bañas; Darwin Palima; Sandeep Tauro; Finn Pedersen; Jesper Glückstad
2nd Annual Workshop on Photonic Technologies for Access and Biophotonics | 2011
Tomoyo Matsuoka; Masayuki Nishi; Masaaki Sakakura; Kiyotaka Miura; Kazuyuki Hirao; Darwin Palima; Sandeep Tauro; Andrew Rafael Bañas; Jesper Glückstad
Trends in Optical Micromanipulation II | 2010
Sandeep Tauro; Darwin Palima; Ivan R. Perch-Nielsen; Lóránd Kelemen; Pál Ormos; Jesper Glückstad