Maruthi Brundavanam | IIT Kharagpur (original) (raw)
Uploads
Papers by Maruthi Brundavanam
Proceedings of SPIE, Dec 29, 2010
We present experimental results on the effect of incident beam polarization on the spectral and p... more We present experimental results on the effect of incident beam polarization on the spectral and polarization characteristics of the output spectrum due to a single filament generated in BK7 glass using focused femtosecond laser pulses. It is observed that the spectral characteristics of the output spectrum are different both in the spectral content as well as the peak wavelength of
Social Science Research Network, Dec 31, 2022
arXiv (Cornell University), May 15, 2019
Fractional optical vortex beam is generated by the diffraction of a Gaussian beam using computer ... more Fractional optical vortex beam is generated by the diffraction of a Gaussian beam using computer generated hologram embedded with mixed screw-edge dislocation. Unfolding of the generated fractional vortex beam into eigen-polarization components with orthogonal polarization results in the conversion of scalar phase singularity to vector polarization singularities in the beam cross-section. The evolution of the singularities of the ellipse field namely C-points (points of undefined major axis) and L-lines (lines of undefined handedness) in the state of polarization distribution on a transverse plane quantifies the transformation. The effect of the phase morphology dictated by the fractional order of the dislocation, transverse spatial separation and longitudinal relative phase of the two eigen-polarization components on determining the complex transverse polarization structure is investigated. The nature of the generated Poincaré beam is also indicated by projecting the states of polarization on to the Poincaré sphere. With increasing order of dislocation from 0.0 to 1.0 in fractional steps and with increasing relative phase, the partial Poincaré beam is transformed to a full Poincaré beam. The transformation of the local structure around the C-points is measured through the geometric phase due to the Poincaré sphere contour around the C-points for different dynamic phase difference of the unfolded FOV beams generated from different fractional order of dislocation. This study can be useful for different geometric phase based application of optical vortex beams.
arXiv (Cornell University), May 15, 2019
Journal of optics, Feb 29, 2024
Optics Communications, Aug 1, 2020
A Highly flexible and efficient method of generating stable radially and Azimuthally polarized pe... more A Highly flexible and efficient method of generating stable radially and Azimuthally polarized perfect optical vortex beams and all higher order cylindrical vector vortex beams, is proposed and demonstrated. The method is the most convenient implementation of the superposition of two orthogonally circularly polarized optical vortex beams of arbitrary integer topological charges. By simply controlling the relative amplitude and phase between vertical and horizontal polarization component of an input perfect vortex beam on a phase sensitive Spatial Light Modulator (SLM) and using a common-path interferometry, all arbitrary order Poincaré beams are prepared. Calibration curve of relative phase vs gray-scale of the phase function on the SLM is drawn to facilitate the determination of required phase-offset using pre-calculated gray-scale color-map. Generated beams states of polarization are uniformly distributed throughout the beam cross-section. The interference pattern of the two beam in a projected linear polarization state also gives the cylindrically symmetric petal beams with a control over the number and orientation of petals.
Physical review, Feb 16, 2023
The disorder induced feedback makes random lasers very susceptible to any changes in the scatteri... more The disorder induced feedback makes random lasers very susceptible to any changes in the scattering medium. The sensitivity of the lasing modes to perturbations in the disordered systems have been utilized to map the regions of perturbation. A tracking parameter, that takes into account the cumulative effect of changes in the spatial distribution of the lasing modes of the system has been defined to locate the region in which a scatterer is displaced by a few nanometers. We show numerically that the precision of the method increases with the number of modes. The proposed method opens up the possibility of application of random lasers as a tool for monitoring locations of nanoscale displacement which can be useful for single particle detection and monitoring.
Proceedings of SPIE, Feb 12, 2009
We report the synthesis of polystyrene (PS) nanospheres through emulsion polymerization and fabri... more We report the synthesis of polystyrene (PS) nanospheres through emulsion polymerization and fabrication of three dimensional PS photonic crystals (PhCs) with good crystalline quality using vertical deposition method. The reflection and transmission spectral characteristics of the PhCs fabricated from the pure and dye doped PS nanospheres are compared.
Nano Letters, Jun 7, 2022
Spin-valley coupling in monolayer transition metal dichalcogenides gives rise to valley polarizat... more Spin-valley coupling in monolayer transition metal dichalcogenides gives rise to valley polarization and coherence effect, limited by intervalley scattering caused by exciton-phonon, exciton-impurity, and electron-hole exchange interaction (EHEI). We explore an approach to tune the EHEI by controlling excitons center of mass momentum (COM) utilizing the photon distribution of higher-order optical vortex beam. By virtue of this, we have observed excitons COM-dependent valley depolarization and decoherence which gives us the ability to probe the valley relaxation timescale in a steady-state measurement. Our steady-state technique to probe the valley dynamics can open up a new paradigm to explore the physics of excitons in two-dimensional systems.
Optics Letters, Apr 25, 2019
The topological transformation of optical vortex beams from fractional fork holograms induced by ... more The topological transformation of optical vortex beams from fractional fork holograms induced by the modulation of controlled Gouy phase (GP) is demonstrated. The GP change is tuned by varying the wavefront curvature of the input beam on the plane of the fractional phase generating optic. The locus of the point of singularity traces a semi-circle about the beam axis for maximum possible change of the associated GP. The morphology parameters describing the anisotropic vortex phases of generated optical vortices are tuned in the experiment by varying the input wavefront curvature. Through the transformation of the transverse Poynting vector of the fractional vortex beams, control of the extrinsic orbital angular momentum is demonstrated for the first time, to the best of our knowledge. This could enable better manipulation of an optically trapped micro-particle and be used in optically driven micro-machines.
Physical review applied, Nov 22, 2019
Off-axis vortex beams are generated by superposing a Gaussian beam onto a symmetric optical vorte... more Off-axis vortex beams are generated by superposing a Gaussian beam onto a symmetric optical vortex beam of unit topological charge in a single-path interferometer with a control of their relative intensities and phases. The radial displacement of the point vortex from the center of the beam is controlled by varying the relative intensity of the superposed beams, while the azimuthal displacement of the vortex is controlled by the phase difference between the superposed beams. This phase difference is employed through the Pancharatnam-Berry geometric phase by different cyclic evolutions of the polarization states of the superposed beams on the Poincaré sphere. Interferometric field reconstruction of the resultant beams from experiment, simulation, and numerical calculations are used to obtain the transverse linear momentum density. The net transverse linear momentum vector and the resulting extrinsic orbital angular momentum in an off-axis vortex beam is demonstrated to be related to the radial and azimuthal position of the vortex across the beam. Controlling the Pancharatnam-Berry geometric phase and intensity ratio of the component beams is thus proposed as an effective and robust technique to tune the extrinsic orbital angular momentum of off-axis vortex beams. The presented results can be useful in applications ranging from optical manipulation of trapped microparticles, controlling micromachines using light with orbital angular momentum to enabling more flexibility in superresolution microscopy and controlled asymmetric interaction of light with atom, molecule, and Bose-Einstein condensate.
Asian Journal of Physics, Jun 30, 2021
Dedicated to Professor D N Rao for his significant contributions and pioneering works in the fiel... more Dedicated to Professor D N Rao for his significant contributions and pioneering works in the fields of spectroscopy, optics, nonlinear optics and photonics Optical beams nesting single or more off-axial distribution of point vortices is considered. The effective topological charge carried out by the beam is explored when the beam is nesting a fractional order vortex phase, beam containing an arbitrary distribution of point vortices as well as when two or more integer order vortex fields are superposed. The orbital angular momentum (OAM) carried out by this beam is generally a fractional number when average OAM per photon is considered. Depending on the distribution of the point vortices the beam may carry a net transverse linear momentum which dictates the nature of the OAM carried out by the beams. When more than one off-axis vortex is present within the beam, the transverse Poynting vector also exhibits saddle points which reveal intricate topological structure of such optical vortex beams.
Journal of Optics, Mar 19, 2018
Optical vortex beams with fractional topological charges (TCs) are generated by the diffraction o... more Optical vortex beams with fractional topological charges (TCs) are generated by the diffraction of a Gaussian beam using computer generated holograms embedded with mixed screw-edge dislocations. When the input Gaussian beam has a finite wave-front curvature, the generated fractional vortex beams show distinct topological transformations in comparison to the integer charge optical vortices. The topological transformations at different fractional TCs are investigated through the birth and evolution of the points of phase singularity, the azimuthal momentum transformation, occurrence of critical points in the transverse momentum and the vorticity around the singular points. This study is helpful to achieve better control in optical micro-manipulation applications.
Physical Chemistry Chemical Physics
Metal nanoparticles (NPs) can be employed to modify the emission level of a dye emitter by tailor... more Metal nanoparticles (NPs) can be employed to modify the emission level of a dye emitter by tailoring the spectral overlap of the optical gain and localized surface plasmon resonance (LSPR)....
Proceedings of SPIE, Dec 29, 2010
We present experimental results on the effect of incident beam polarization on the spectral and p... more We present experimental results on the effect of incident beam polarization on the spectral and polarization characteristics of the output spectrum due to a single filament generated in BK7 glass using focused femtosecond laser pulses. It is observed that the spectral characteristics of the output spectrum are different both in the spectral content as well as the peak wavelength of
Social Science Research Network, Dec 31, 2022
arXiv (Cornell University), May 15, 2019
Fractional optical vortex beam is generated by the diffraction of a Gaussian beam using computer ... more Fractional optical vortex beam is generated by the diffraction of a Gaussian beam using computer generated hologram embedded with mixed screw-edge dislocation. Unfolding of the generated fractional vortex beam into eigen-polarization components with orthogonal polarization results in the conversion of scalar phase singularity to vector polarization singularities in the beam cross-section. The evolution of the singularities of the ellipse field namely C-points (points of undefined major axis) and L-lines (lines of undefined handedness) in the state of polarization distribution on a transverse plane quantifies the transformation. The effect of the phase morphology dictated by the fractional order of the dislocation, transverse spatial separation and longitudinal relative phase of the two eigen-polarization components on determining the complex transverse polarization structure is investigated. The nature of the generated Poincaré beam is also indicated by projecting the states of polarization on to the Poincaré sphere. With increasing order of dislocation from 0.0 to 1.0 in fractional steps and with increasing relative phase, the partial Poincaré beam is transformed to a full Poincaré beam. The transformation of the local structure around the C-points is measured through the geometric phase due to the Poincaré sphere contour around the C-points for different dynamic phase difference of the unfolded FOV beams generated from different fractional order of dislocation. This study can be useful for different geometric phase based application of optical vortex beams.
arXiv (Cornell University), May 15, 2019
Journal of optics, Feb 29, 2024
Optics Communications, Aug 1, 2020
A Highly flexible and efficient method of generating stable radially and Azimuthally polarized pe... more A Highly flexible and efficient method of generating stable radially and Azimuthally polarized perfect optical vortex beams and all higher order cylindrical vector vortex beams, is proposed and demonstrated. The method is the most convenient implementation of the superposition of two orthogonally circularly polarized optical vortex beams of arbitrary integer topological charges. By simply controlling the relative amplitude and phase between vertical and horizontal polarization component of an input perfect vortex beam on a phase sensitive Spatial Light Modulator (SLM) and using a common-path interferometry, all arbitrary order Poincaré beams are prepared. Calibration curve of relative phase vs gray-scale of the phase function on the SLM is drawn to facilitate the determination of required phase-offset using pre-calculated gray-scale color-map. Generated beams states of polarization are uniformly distributed throughout the beam cross-section. The interference pattern of the two beam in a projected linear polarization state also gives the cylindrically symmetric petal beams with a control over the number and orientation of petals.
Physical review, Feb 16, 2023
The disorder induced feedback makes random lasers very susceptible to any changes in the scatteri... more The disorder induced feedback makes random lasers very susceptible to any changes in the scattering medium. The sensitivity of the lasing modes to perturbations in the disordered systems have been utilized to map the regions of perturbation. A tracking parameter, that takes into account the cumulative effect of changes in the spatial distribution of the lasing modes of the system has been defined to locate the region in which a scatterer is displaced by a few nanometers. We show numerically that the precision of the method increases with the number of modes. The proposed method opens up the possibility of application of random lasers as a tool for monitoring locations of nanoscale displacement which can be useful for single particle detection and monitoring.
Proceedings of SPIE, Feb 12, 2009
We report the synthesis of polystyrene (PS) nanospheres through emulsion polymerization and fabri... more We report the synthesis of polystyrene (PS) nanospheres through emulsion polymerization and fabrication of three dimensional PS photonic crystals (PhCs) with good crystalline quality using vertical deposition method. The reflection and transmission spectral characteristics of the PhCs fabricated from the pure and dye doped PS nanospheres are compared.
Nano Letters, Jun 7, 2022
Spin-valley coupling in monolayer transition metal dichalcogenides gives rise to valley polarizat... more Spin-valley coupling in monolayer transition metal dichalcogenides gives rise to valley polarization and coherence effect, limited by intervalley scattering caused by exciton-phonon, exciton-impurity, and electron-hole exchange interaction (EHEI). We explore an approach to tune the EHEI by controlling excitons center of mass momentum (COM) utilizing the photon distribution of higher-order optical vortex beam. By virtue of this, we have observed excitons COM-dependent valley depolarization and decoherence which gives us the ability to probe the valley relaxation timescale in a steady-state measurement. Our steady-state technique to probe the valley dynamics can open up a new paradigm to explore the physics of excitons in two-dimensional systems.
Optics Letters, Apr 25, 2019
The topological transformation of optical vortex beams from fractional fork holograms induced by ... more The topological transformation of optical vortex beams from fractional fork holograms induced by the modulation of controlled Gouy phase (GP) is demonstrated. The GP change is tuned by varying the wavefront curvature of the input beam on the plane of the fractional phase generating optic. The locus of the point of singularity traces a semi-circle about the beam axis for maximum possible change of the associated GP. The morphology parameters describing the anisotropic vortex phases of generated optical vortices are tuned in the experiment by varying the input wavefront curvature. Through the transformation of the transverse Poynting vector of the fractional vortex beams, control of the extrinsic orbital angular momentum is demonstrated for the first time, to the best of our knowledge. This could enable better manipulation of an optically trapped micro-particle and be used in optically driven micro-machines.
Physical review applied, Nov 22, 2019
Off-axis vortex beams are generated by superposing a Gaussian beam onto a symmetric optical vorte... more Off-axis vortex beams are generated by superposing a Gaussian beam onto a symmetric optical vortex beam of unit topological charge in a single-path interferometer with a control of their relative intensities and phases. The radial displacement of the point vortex from the center of the beam is controlled by varying the relative intensity of the superposed beams, while the azimuthal displacement of the vortex is controlled by the phase difference between the superposed beams. This phase difference is employed through the Pancharatnam-Berry geometric phase by different cyclic evolutions of the polarization states of the superposed beams on the Poincaré sphere. Interferometric field reconstruction of the resultant beams from experiment, simulation, and numerical calculations are used to obtain the transverse linear momentum density. The net transverse linear momentum vector and the resulting extrinsic orbital angular momentum in an off-axis vortex beam is demonstrated to be related to the radial and azimuthal position of the vortex across the beam. Controlling the Pancharatnam-Berry geometric phase and intensity ratio of the component beams is thus proposed as an effective and robust technique to tune the extrinsic orbital angular momentum of off-axis vortex beams. The presented results can be useful in applications ranging from optical manipulation of trapped microparticles, controlling micromachines using light with orbital angular momentum to enabling more flexibility in superresolution microscopy and controlled asymmetric interaction of light with atom, molecule, and Bose-Einstein condensate.
Asian Journal of Physics, Jun 30, 2021
Dedicated to Professor D N Rao for his significant contributions and pioneering works in the fiel... more Dedicated to Professor D N Rao for his significant contributions and pioneering works in the fields of spectroscopy, optics, nonlinear optics and photonics Optical beams nesting single or more off-axial distribution of point vortices is considered. The effective topological charge carried out by the beam is explored when the beam is nesting a fractional order vortex phase, beam containing an arbitrary distribution of point vortices as well as when two or more integer order vortex fields are superposed. The orbital angular momentum (OAM) carried out by this beam is generally a fractional number when average OAM per photon is considered. Depending on the distribution of the point vortices the beam may carry a net transverse linear momentum which dictates the nature of the OAM carried out by the beams. When more than one off-axis vortex is present within the beam, the transverse Poynting vector also exhibits saddle points which reveal intricate topological structure of such optical vortex beams.
Journal of Optics, Mar 19, 2018
Optical vortex beams with fractional topological charges (TCs) are generated by the diffraction o... more Optical vortex beams with fractional topological charges (TCs) are generated by the diffraction of a Gaussian beam using computer generated holograms embedded with mixed screw-edge dislocations. When the input Gaussian beam has a finite wave-front curvature, the generated fractional vortex beams show distinct topological transformations in comparison to the integer charge optical vortices. The topological transformations at different fractional TCs are investigated through the birth and evolution of the points of phase singularity, the azimuthal momentum transformation, occurrence of critical points in the transverse momentum and the vorticity around the singular points. This study is helpful to achieve better control in optical micro-manipulation applications.
Physical Chemistry Chemical Physics
Metal nanoparticles (NPs) can be employed to modify the emission level of a dye emitter by tailor... more Metal nanoparticles (NPs) can be employed to modify the emission level of a dye emitter by tailoring the spectral overlap of the optical gain and localized surface plasmon resonance (LSPR)....