Dr. Praveen Parthasarathi Profile

Dr. Praveen Parthasarathi

Postdoc at Raman Research Institute

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Publications (6)

Proceedings Article | 16 September 2016 Paper

Probing the interaction between two microspheres in a single Gaussian beam optical trap

Praveen Parthasarathi, Shruthi Subhash Iyengar, Yogesha Lakkegowda, Sarbari Bhattacharya, Sharath Ananthamurthy

Proceedings Volume 9922, 99222M (2016) https://doi.org/10.1117/12.2237600

KEYWORDS: Gaussian beams, Optical tweezers, Laser beam propagation, Laser scattering, Scattering, Backscatter, Sensors, Objectives, Light scattering, Optical filters

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Proceedings Article | 21 April 2016 Paper

Autocorrelation and relaxation time measurements on metal oxide core: dielectric shell beads in an optical trap

Shruthi Iyengar, Praveen Parthasarathi, Rekha Selvan, Sarbari Bhattacharya, Sharath Ananthamurthy

Proceedings Volume 9884, 98842P (2016) https://doi.org/10.1117/12.2227406

KEYWORDS: Dielectrics, Particles, Optical tweezers, Metals, Oxides, Polarizability, Reflectivity, Transmittance, Laser scattering, Scattering, Time metrology, Silica, Objectives, Magnetism

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Optical Tweezers are capable of trapping individual particles of sizes that range from micrometers to sub micrometers. One can compute the trap strength experienced by a particle by analyzing the fluctuations in the position of the trapped particle with time. It is reported that the trap strength of a dielectric bead increases linearly with increase in the power of the trapping laser. The situation with metallic particles, however, is strongly dependent on the particle size. Available literature shows that metallic Rayleigh particles experience enhanced trap strengths when compared to dielectric particles of similar sizes due to a larger polarizability. On the contrary, micrometer sized metallic particles are poor candidates for trapping due to high reflectivity. We report here that commercially available micrometer sized metal oxide core - dielectric shell (core – shell) beads are trapped in a single beam optical tweezer in a manner similar to dielectric beads. However as the laser power is increased these core – shell beads are trapped with a reduced corner frequency, which represents a lowered trap strength, in contrast to the situation with ordinary dielectric beads. We attribute this anomaly to an increase in the temperature of the medium in the vicinity of the core – shell bead due to an enhanced dissipation of the laser power as heat. We have computed autocorrelation functions for both types of beads at various trapping laser powers and observe that the variation in the relaxation times with laser power for core - shell beads is opposite in trend to that of ordinary dielectric beads. This supports our claim of an enhanced medium temperature about the trapped core – shell bead. Since an increase in temperature should lead to a change in the local viscosity of the medium, we have estimated the ratio of viscosity to temperature for core – shell and dielectric beads of the same size. We observe that while for ordinary dielectric beads this ratio remains a constant with increasing laser power, there is a decrease for core – shell beads. We plan to extend this work towards studying the hydrodynamic correlations between a pair of trapped beads where one of the beads acts as a heat source.

Proceedings Article | 15 June 2015 Paper

Conical Fresnel zone lens for optical trapping

A. Vijayakumar, Praveen Parthasarathi, Shruthi Iyengar, Rekha Selvan, Sharath Ananthamurthy, Shanti Bhattacharya, Sarbari Bhattacharya

Proceedings Volume 9654, 965426 (2015) https://doi.org/10.1117/12.2180850

KEYWORDS: Etching, Optical tweezers, Axicons, Optical components, Borosilicate glass, Confocal microscopy, Microscopes, Particles, Chemical elements, Optical lithography

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SPIE Journal Paper | 14 November 2014 Open Access

Birefringence of a normal human red blood cell and related optomechanics in an optical trap

Belavadi Venkatakrishnaiah Nagesh, . Yogesha, Ramarao Pratibha, Praveen Parthasarathi, Shruthi Subhash Iyengar, Sarbari Bhattacharya, Sharath Ananthamurthy

JBO, Vol. 19, Issue 11, 115004, (November 2014) https://doi.org/10.1117/12.10.1117/1.JBO.19.11.115004

KEYWORDS: Birefringence, Molecules, Blood, Optical tweezers, Polarizers, Microscopes, Optomechanical design, Polarization, Polarizability, Wave plates

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Proceedings Article | 4 March 2014 Paper

Optical properties of red blood cells: an optical tweezer based analysis

B. Nagesh, Yogesha Lakkegowda, R. Pratibha, P. Praveen, Sarbari Bhattacharya, Sharath Ananthamurthy

Proceedings Volume 8947, 89471P (2014) https://doi.org/10.1117/12.2039222

KEYWORDS: Birefringence, Optical tweezers, Molecules, Polarization, Polarizers, Blood, Wave plates, Microscopes, Optical properties, Physics

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SPIE Journal Paper | 4 February 2013 Open Access

Orientational dynamics of human red blood cells in an optical trap

Praveen Parthasarathi, Belavadi Nagesh, Yogesha Lakkegowda, Shruthi Lyengar, Sharath Ananthamurthy, Sarbari Bhattacharya

JBO, Vol. 18, Issue 02, 025001, (February 2013) https://doi.org/10.1117/12.10.1117/1.JBO.18.2.025001

KEYWORDS: Optical tweezers, Blood, Solids, Laser beam propagation, Time metrology, Video, Microscopes, Beam propagation method, Image processing, Eye

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