Rijuparna Chakraborty - Academia.edu (original) (raw)

Papers by Rijuparna Chakraborty

2020 4th International Conference on Electronics, Materials Engineering & Nano-Technology (IEMENTech), 2020

An authentication scheme for free-space communication with singular laser beam has been discussed... more An authentication scheme for free-space communication with singular laser beam has been discussed. A known order of singularity was imposed on the beam, which generates its characteristic fingerprint structure. At the receiver end, in order to check that fingerprint pattern, a part of the received beam was first interfered with a locally generated plane wave and then Fourier transformed. This frequency distribution pattern, captured by a CCD camera, gives the final fingerprint pattern of the known order vortex beam. An application software compares this pattern with the previously stored ones and generates a ‘high’ signal upon successful match. This ‘high’ signal eventually set the final AND gate open for passing the digitized message through it.

International Journal of Pediatrics, 2019

Background. Newborn hyperbilirubinemia is considered a worldwide health problem that demands medi... more Background. Newborn hyperbilirubinemia is considered a worldwide health problem that demands medical evaluation. Noninvasive transcutaneous bilirubin (TcB) has been used as a screening method with different devices but there has not been any evaluation of reproducibility of the same brand devices. The BiliCare™ system is evaluated to demonstrate consistency between measurements with four different devices. Methods. 336 TcB measurements were obtained with four BiliCare™ devices in 21 Mexican icteric newborns with a mean postnatal age of 44.1 hours of life and 38 weeks of gestation (33–41). Two measurements were taken in the same ear alternatively at the scaphoid fossa with each device. TcB values were compared between devices. Validity was compared with total serum bilirubin (TB). Results. intraclass correlation coefficient demonstrates a minimum limit in the study of 0.945 and maximum of 0.988 with the same device. Correlations with serum and between devices gave results above 0.932...

A technique for generation of three-dimensionally modified dark-hollow-beams has been reported he... more A technique for generation of three-dimensionally modified dark-hollow-beams has been reported here. Manipulation of the three-dimensional spatial frequencies for the dark-hollow-beams, its nature can be altered and theoretically it can be made any shape in space retaining its dark-hollow nature and the optical vortex. The mask needed to generate such a beam must be three dimensional one and can be achieved using stack of diffractive-optical-elements. Two different examples of such beams have been discussed. Use of such beam in optical tweezers can guide a particle to bend over an obstruction in its path.

Engineering Research Express

Threshold Logic Gate (TLG) is a potential alternative of Boolean Logic circuit. It is one of the ... more Threshold Logic Gate (TLG) is a potential alternative of Boolean Logic circuit. It is one of the fundamental components of neural network. An Optical Threshold Logic Gate (OTLG) has been designed in this paper, using a reflector telescopic system and a resonant Fabry-Perot cavity. Threshold logic gate consists of a weighted summing unit followed by a comparator. In the proposed OTLG, the weight of the input signal is varied using a polarizer-analyser combination. The threshold value, which is the reference of the comparator, is applied into the Fabry–Perot cavity with the help of a Beam splitter . AND, OR and NOT gates are implemented by setting the threshold values of the proposed OTLG.The system has been modelled analytically and studied using MATLAB and FINESSE. The simulation results for OTLG based Basic Gates are presented here.

Optics letters, 2006

In an elliptic coordinate system the solution for a diffraction-free beam is given by a Mathieu b... more In an elliptic coordinate system the solution for a diffraction-free beam is given by a Mathieu beam, which is mathematically complicated and therefore takes considerable computational time and a large memory space. A technique is reported for the generation of elliptic hollow beams, which are actually scaled versions of higher-order Bessel beams. The analysis is based on the fact that stretching coordinates in the space domain results in a contraction of the coordinates in the frequency domain, along with a change in the overall amplitude of the spectrum. The beam, produced holographically, is structurally stable and retains its shape up to approximately 1 m.

Optics Letters, 2006

In an elliptic coordinate system the solution for a diffraction-free beam is given by a Mathieu b... more In an elliptic coordinate system the solution for a diffraction-free beam is given by a Mathieu beam, which is mathematically complicated and therefore takes considerable computational time and a large memory space. A technique is reported for the generation of elliptic hollow beams, which are actually scaled versions of higher-order Bessel beams. The analysis is based on the fact that

2016 IEEE 7th Annual Information Technology, Electronics and Mobile Communication Conference (IEMCON), 2016

Optical and Infrared Interferometry and Imaging V, 2016

Optik - International Journal for Light and Electron Optics, 2016

Bessel and LG beam of different orders are generated using Spatial Light Modulator (SLM) and also... more Bessel and LG beam of different orders are generated using Spatial Light Modulator (SLM) and also rotating Bessel and LG beam with programmable speed using the same SLM are produced, which needs no extra component or mechanical motion and can be used to rotate the micro particles with controlled speed, with a beam of particular mode, i.e., with a particular radius beam. The radius of a particular mode can also be changed if necessary.

Strong regenerated gratings with a maximum grating strength exceeding (40-50) dB are fabricated i... more Strong regenerated gratings with a maximum grating strength exceeding (40-50) dB are fabricated inside an optical fibre by bulk macro thermal processing ~900 0 C using a UV-laser seeded Bragg grating. Further annealing between 1000 and 1100°C leads to a stabilised grating ~18dB in strength. This suffers no further degradation at 1100°C for the period monitored, over 4 hrs. To determine the potential resolution of this process, two regenerated complex profiles with no phase difference between seed and processed structures is reported. This opens the way for nano-engineering of materials using thermal processing and seed templates.

20th International Conference on Optical Fibre Sensors, 2009

ABSTRACT Complex regenerated Bragg gratings, seeded by complex type-I gratings in H2 loaded germa... more ABSTRACT Complex regenerated Bragg gratings, seeded by complex type-I gratings in H2 loaded germanosilicate optical fibre is reported. By this means, dual channel grating filters which are stable beyond 1000°C are produced. These high temperature stable co-located dual gratings have potential application in sensing and multi-wavelength high power lasers.

Optical and Infrared Interferometry III, 2012

ABSTRACT For information-rich direct images at high resolution, hypertelescopes combine light fro... more ABSTRACT For information-rich direct images at high resolution, hypertelescopes combine light from a sparse array of many subapertures, using pupil densification. Among the possible architectures, the Arecibo-like spherical class has fixed mirrors arrayed as elements of a common spherical locus, matching approximately the natural curvature of a crater or valley. A focal gondola suspended on the focal sphere, is tracking the primary star image, and several more can be added for independent observations of di.erent sources. Since no delay lines are needed, hundred of mirrors can be used for reaching the theoretical information gain with respect to fewer apertures. The aperture size of such instruments may range from 50 to perhaps 1200m at available terrestrial sites. As an example of their broad science capabilities, we have simulated the resolved and spectro-imaging- of an exoplanet transiting across the disk of its parent star, achievable with adaptive optics. Faint cosmological sources may also become observable if a Laser Guide Star can be fitted. We describe the current construction and in situ opto-mechanical testing of a 57m hypertelescope, later expandable to 200 with 100 or more sub-apertures. The preliminary operating experience gained in a year, without stellar fringes yet, indicates the likely feasibility of larger versions at suitable sites. Labeyrie et al., (this conference) discuss an "Extremely Large Hypertelescope" (ELHyT) having 1200m sparse aperture and, at similar cost, a larger collection area and higher limiting magnitude than a 40m ELT.

Integrated Modeling of Complex Optomechanical Systems, 2011

ABSTRACT The Carlina hypertelescope is a planned sparse aperture 100 m telescope with pupil densi... more ABSTRACT The Carlina hypertelescope is a planned sparse aperture 100 m telescope with pupil densification. The telescope has a spherical primary with segments located in a valley between mountains, and additional optical elements in a gondola suspended in eight cables some 100 m above the primary mirror. The resolution is about 1.2×10-3 arcsec. It is imperative that the position and attitude of the gondola be maintained within tight tolerances during observation and star tracking. The present design has servo-controlled winches on the ground for control of the gondola via the cables. An integrated model of the system, including optics, cables, gondola, position and attitude control system, and wind disturbances has been set up. The structural and control models are linear. Calculations in the frequency domain and simulations in the time domain show that the performance of the telescope with the present design seems adequate for short exposures. However, for long-exposure operation, the gondola stability should be improved by about two orders of magnitude. Recommendations are given on possible approaches for performance improvement.

Frontiers in Optics, 2006

ABSTRACT Diffraction-free incomplete annular beam is produced using destructive interference betw... more ABSTRACT Diffraction-free incomplete annular beam is produced using destructive interference between two modified and unmodified annular beams, where modification is done on its pitch using modulo operation. The holographically generated beam remains unchanged up to 1.5cm.

Frontiers in Optics, 2006

ABSTRACT Propagation invariant hyperbolic beam, with and without optical vortex, is produced usin... more ABSTRACT Propagation invariant hyperbolic beam, with and without optical vortex, is produced using Fourier-transform holography, which keeps its shape unchanged up to 45cm. Bessel function with arguments having hyperbolic locus are used to generate the mask.

Optics Letters, 2006

In an elliptic coordinate system the solution for a diffraction-free beam is given by a Mathieu b... more In an elliptic coordinate system the solution for a diffraction-free beam is given by a Mathieu beam, which is mathematically complicated and therefore takes considerable computational time and a large memory space. A technique is reported for the generation of elliptic hollow beams, which are actually scaled versions of higher-order Bessel beams. The analysis is based on the fact that stretching coordinates in the space domain results in a contraction of the coordinates in the frequency domain, along with a change in the overall amplitude of the spectrum. The beam, produced holographically, is structurally stable and retains its shape up to approximately 1 m.

Journal of the Optical Society of America A, 2006

A new (to our knowledge) technique for the generation of a propagation-invariant elliptic hollow ... more A new (to our knowledge) technique for the generation of a propagation-invariant elliptic hollow beam is reported. It avoids the use of the radial Mathieu function and hence is mathematically simpler. Bessel functions with their arguments having elliptic locus are used to generate the mask, which is then recorded using holographic technique. To generate such an elliptic beam, both the angular Mathieu function, i.e., elliptic vortex term, and the expression for the circular vortex are used separately. The resultant mask is illuminated with a plane beam, and the proper filtering of its Fourier transform generates the expected elliptic beam. Results with both vortex terms are satisfactory. It has been observed that even for higher ellipticity the vortices do not separate.

2020 4th International Conference on Electronics, Materials Engineering & Nano-Technology (IEMENTech), 2020

An authentication scheme for free-space communication with singular laser beam has been discussed... more An authentication scheme for free-space communication with singular laser beam has been discussed. A known order of singularity was imposed on the beam, which generates its characteristic fingerprint structure. At the receiver end, in order to check that fingerprint pattern, a part of the received beam was first interfered with a locally generated plane wave and then Fourier transformed. This frequency distribution pattern, captured by a CCD camera, gives the final fingerprint pattern of the known order vortex beam. An application software compares this pattern with the previously stored ones and generates a ‘high’ signal upon successful match. This ‘high’ signal eventually set the final AND gate open for passing the digitized message through it.

International Journal of Pediatrics, 2019

Background. Newborn hyperbilirubinemia is considered a worldwide health problem that demands medi... more Background. Newborn hyperbilirubinemia is considered a worldwide health problem that demands medical evaluation. Noninvasive transcutaneous bilirubin (TcB) has been used as a screening method with different devices but there has not been any evaluation of reproducibility of the same brand devices. The BiliCare™ system is evaluated to demonstrate consistency between measurements with four different devices. Methods. 336 TcB measurements were obtained with four BiliCare™ devices in 21 Mexican icteric newborns with a mean postnatal age of 44.1 hours of life and 38 weeks of gestation (33–41). Two measurements were taken in the same ear alternatively at the scaphoid fossa with each device. TcB values were compared between devices. Validity was compared with total serum bilirubin (TB). Results. intraclass correlation coefficient demonstrates a minimum limit in the study of 0.945 and maximum of 0.988 with the same device. Correlations with serum and between devices gave results above 0.932...

A technique for generation of three-dimensionally modified dark-hollow-beams has been reported he... more A technique for generation of three-dimensionally modified dark-hollow-beams has been reported here. Manipulation of the three-dimensional spatial frequencies for the dark-hollow-beams, its nature can be altered and theoretically it can be made any shape in space retaining its dark-hollow nature and the optical vortex. The mask needed to generate such a beam must be three dimensional one and can be achieved using stack of diffractive-optical-elements. Two different examples of such beams have been discussed. Use of such beam in optical tweezers can guide a particle to bend over an obstruction in its path.

Engineering Research Express

Threshold Logic Gate (TLG) is a potential alternative of Boolean Logic circuit. It is one of the ... more Threshold Logic Gate (TLG) is a potential alternative of Boolean Logic circuit. It is one of the fundamental components of neural network. An Optical Threshold Logic Gate (OTLG) has been designed in this paper, using a reflector telescopic system and a resonant Fabry-Perot cavity. Threshold logic gate consists of a weighted summing unit followed by a comparator. In the proposed OTLG, the weight of the input signal is varied using a polarizer-analyser combination. The threshold value, which is the reference of the comparator, is applied into the Fabry–Perot cavity with the help of a Beam splitter . AND, OR and NOT gates are implemented by setting the threshold values of the proposed OTLG.The system has been modelled analytically and studied using MATLAB and FINESSE. The simulation results for OTLG based Basic Gates are presented here.

Optics letters, 2006

In an elliptic coordinate system the solution for a diffraction-free beam is given by a Mathieu b... more In an elliptic coordinate system the solution for a diffraction-free beam is given by a Mathieu beam, which is mathematically complicated and therefore takes considerable computational time and a large memory space. A technique is reported for the generation of elliptic hollow beams, which are actually scaled versions of higher-order Bessel beams. The analysis is based on the fact that stretching coordinates in the space domain results in a contraction of the coordinates in the frequency domain, along with a change in the overall amplitude of the spectrum. The beam, produced holographically, is structurally stable and retains its shape up to approximately 1 m.

Optics Letters, 2006

In an elliptic coordinate system the solution for a diffraction-free beam is given by a Mathieu b... more In an elliptic coordinate system the solution for a diffraction-free beam is given by a Mathieu beam, which is mathematically complicated and therefore takes considerable computational time and a large memory space. A technique is reported for the generation of elliptic hollow beams, which are actually scaled versions of higher-order Bessel beams. The analysis is based on the fact that

2016 IEEE 7th Annual Information Technology, Electronics and Mobile Communication Conference (IEMCON), 2016

Optical and Infrared Interferometry and Imaging V, 2016

Optik - International Journal for Light and Electron Optics, 2016

Bessel and LG beam of different orders are generated using Spatial Light Modulator (SLM) and also... more Bessel and LG beam of different orders are generated using Spatial Light Modulator (SLM) and also rotating Bessel and LG beam with programmable speed using the same SLM are produced, which needs no extra component or mechanical motion and can be used to rotate the micro particles with controlled speed, with a beam of particular mode, i.e., with a particular radius beam. The radius of a particular mode can also be changed if necessary.

Strong regenerated gratings with a maximum grating strength exceeding (40-50) dB are fabricated i... more Strong regenerated gratings with a maximum grating strength exceeding (40-50) dB are fabricated inside an optical fibre by bulk macro thermal processing ~900 0 C using a UV-laser seeded Bragg grating. Further annealing between 1000 and 1100°C leads to a stabilised grating ~18dB in strength. This suffers no further degradation at 1100°C for the period monitored, over 4 hrs. To determine the potential resolution of this process, two regenerated complex profiles with no phase difference between seed and processed structures is reported. This opens the way for nano-engineering of materials using thermal processing and seed templates.

20th International Conference on Optical Fibre Sensors, 2009

ABSTRACT Complex regenerated Bragg gratings, seeded by complex type-I gratings in H2 loaded germa... more ABSTRACT Complex regenerated Bragg gratings, seeded by complex type-I gratings in H2 loaded germanosilicate optical fibre is reported. By this means, dual channel grating filters which are stable beyond 1000°C are produced. These high temperature stable co-located dual gratings have potential application in sensing and multi-wavelength high power lasers.

Optical and Infrared Interferometry III, 2012

ABSTRACT For information-rich direct images at high resolution, hypertelescopes combine light fro... more ABSTRACT For information-rich direct images at high resolution, hypertelescopes combine light from a sparse array of many subapertures, using pupil densification. Among the possible architectures, the Arecibo-like spherical class has fixed mirrors arrayed as elements of a common spherical locus, matching approximately the natural curvature of a crater or valley. A focal gondola suspended on the focal sphere, is tracking the primary star image, and several more can be added for independent observations of di.erent sources. Since no delay lines are needed, hundred of mirrors can be used for reaching the theoretical information gain with respect to fewer apertures. The aperture size of such instruments may range from 50 to perhaps 1200m at available terrestrial sites. As an example of their broad science capabilities, we have simulated the resolved and spectro-imaging- of an exoplanet transiting across the disk of its parent star, achievable with adaptive optics. Faint cosmological sources may also become observable if a Laser Guide Star can be fitted. We describe the current construction and in situ opto-mechanical testing of a 57m hypertelescope, later expandable to 200 with 100 or more sub-apertures. The preliminary operating experience gained in a year, without stellar fringes yet, indicates the likely feasibility of larger versions at suitable sites. Labeyrie et al., (this conference) discuss an "Extremely Large Hypertelescope" (ELHyT) having 1200m sparse aperture and, at similar cost, a larger collection area and higher limiting magnitude than a 40m ELT.

Integrated Modeling of Complex Optomechanical Systems, 2011

ABSTRACT The Carlina hypertelescope is a planned sparse aperture 100 m telescope with pupil densi... more ABSTRACT The Carlina hypertelescope is a planned sparse aperture 100 m telescope with pupil densification. The telescope has a spherical primary with segments located in a valley between mountains, and additional optical elements in a gondola suspended in eight cables some 100 m above the primary mirror. The resolution is about 1.2×10-3 arcsec. It is imperative that the position and attitude of the gondola be maintained within tight tolerances during observation and star tracking. The present design has servo-controlled winches on the ground for control of the gondola via the cables. An integrated model of the system, including optics, cables, gondola, position and attitude control system, and wind disturbances has been set up. The structural and control models are linear. Calculations in the frequency domain and simulations in the time domain show that the performance of the telescope with the present design seems adequate for short exposures. However, for long-exposure operation, the gondola stability should be improved by about two orders of magnitude. Recommendations are given on possible approaches for performance improvement.

Frontiers in Optics, 2006

ABSTRACT Diffraction-free incomplete annular beam is produced using destructive interference betw... more ABSTRACT Diffraction-free incomplete annular beam is produced using destructive interference between two modified and unmodified annular beams, where modification is done on its pitch using modulo operation. The holographically generated beam remains unchanged up to 1.5cm.

Frontiers in Optics, 2006

ABSTRACT Propagation invariant hyperbolic beam, with and without optical vortex, is produced usin... more ABSTRACT Propagation invariant hyperbolic beam, with and without optical vortex, is produced using Fourier-transform holography, which keeps its shape unchanged up to 45cm. Bessel function with arguments having hyperbolic locus are used to generate the mask.

Optics Letters, 2006

In an elliptic coordinate system the solution for a diffraction-free beam is given by a Mathieu b... more In an elliptic coordinate system the solution for a diffraction-free beam is given by a Mathieu beam, which is mathematically complicated and therefore takes considerable computational time and a large memory space. A technique is reported for the generation of elliptic hollow beams, which are actually scaled versions of higher-order Bessel beams. The analysis is based on the fact that stretching coordinates in the space domain results in a contraction of the coordinates in the frequency domain, along with a change in the overall amplitude of the spectrum. The beam, produced holographically, is structurally stable and retains its shape up to approximately 1 m.

Journal of the Optical Society of America A, 2006

A new (to our knowledge) technique for the generation of a propagation-invariant elliptic hollow ... more A new (to our knowledge) technique for the generation of a propagation-invariant elliptic hollow beam is reported. It avoids the use of the radial Mathieu function and hence is mathematically simpler. Bessel functions with their arguments having elliptic locus are used to generate the mask, which is then recorded using holographic technique. To generate such an elliptic beam, both the angular Mathieu function, i.e., elliptic vortex term, and the expression for the circular vortex are used separately. The resultant mask is illuminated with a plane beam, and the proper filtering of its Fourier transform generates the expected elliptic beam. Results with both vortex terms are satisfactory. It has been observed that even for higher ellipticity the vortices do not separate.