Indrajit Bhattacharyya

• Researchgate

Education / Work History

• Ph.D. Scholar, IIT Kanpur (2010)
• M.Sc., University of Kalyani (2003)
• B.Sc., University of Kalyani (2001)

Thesis Abstract

Femtosecond Non-linear and Thermo-optical Spectroscopy for Studying Chemical Systems

The present thesis focuses on the study of chemical systems with nonlinear and thermo-optical spectroscopic techniques by femtosecond lasers. It includes the construction and alignment details of the each individual optical set ups. Mainly the third order optical nonlinearity and the thermal lens spectroscopic techniques have been utilized to exploit the nature of the chemical systems. Chapter 1 starts with brief historical backgrounds, the basic concepts, general behavioral aspects and different applications of Nonlinear Optical Spectroscopy and Thermo-optical Spectroscopic techniques. In Chapter 2, the description of all the laser systems used during the experiments and the principles and technical details of all the measurement techniques, characterization and calibration of laser pulses in the optical set ups have been provided. In Chapter 3, pulse characterization techniques like FROG and STRUT, which are based on Fourier domain inversion algorithms, have been implemented. A spectral windowing analysis is presented, which shows how to enhance the sensitivity and the resolution of the retrieval schemes at very low signal constraints particularly when the pulses are very weak and complex. In Chapter 4, ultrafast single beam Z-scan technique is used to measure the third order optical response in a series of homologues alcohols at 1560nm, where a frequency optimized optical chopper is used to minimize the thermal corruption arising from the cumulative heating effect in HRR laser systems. The thermal relaxation dynamics of the samples also has been explored by using 1560nm pump and 780nm probe thermal-lens study. Chapter 5 deals with the study of binary liquid mixtures of methanol diluted with carbon tetrachloride, dichloromethane, dimethylsulfoxide and water by Thermo-optical Spectroscopic technique. The deviations between calculated and measured TL trends have been attributed to the molecular properties of the samples under the experimental conditions. In Chapter 6, the effect of isotopic substitution (deuteration) on TL pump-probe signals has been explored by using binary liquid solution of methanol with each of CD3OD, H2O and D2O. The change in the trends of the TL pump-probe signal has been explained in terms of proton transfer behavior of the binary liquid mixtures under the experimental condition.

Research Topic / Interest

Contact me to know my current interests.

Publications

These include only those published in our lab.

1. Decoding Coherent Information in Femtosecond Shaped Laser Pulses. I. Bhattacharyya, A. Dutta, S. Ashtekar, S. K. Maurya, and D. Goswami, CURRENT SCIENCE 99(4), 10 (2010) [Abstract] [BibTeX]

   Abstract: We report here an experimental demonstration of a pulse decoding technique from spectral analysis of femtosecond pulses. This technique is based on a single-step Fourier domain inversion algorithm and shows the impact of the spectral window function on the retrieval of the signal pulse. Using two femtosecond laser pulses at 780 and 1560 nm from a fibre laser, we have shown that even when the spectral content of the reference pulse is far from a narrow band limit (as much as a quarter of its entire spectral content for our conditions), the single-step retrieval analysis using spectral windowing in the Fourier domain works efficiently. The enhanced signal levels possible due to the wider spectral window are critical in the unambiguous description of laser pulses, which would have potential application in the retrieval of comparatively weak and complex ultra-short pulses as is often needed in pulse shaping applications and coherent optical communications.

    BibTeX: @article{bhattacharyyaDecodingCoherentInformation2010,
     title = {Decoding Coherent Information in Femtosecond Shaped Laser Pulses},
     author = {Bhattacharyya, Indrajit and Dutta, Aveek and Ashtekar, Sumit and Maurya, Sandeep Kumar and Goswami, Debabrata},
     date = {2010},
     journaltitle = {CURRENT SCIENCE},
     volume = {99},
     number = {4},
     pages = {10}
   }
   

2. Effect of Isotope Substitution in Binary Liquids with Thermal-Lens Spectroscopy. I. Bhattacharyya, P. Kumar, and D. Goswami, Chemical Physics Letters 598, 35–38 (2014) [Abstract] [PDF] [BibTeX]

   Abstract: Effect of isotope substitution from the modulation of Thermal-Lens (TL) signals in binary liquid mixtures is explored using femtosecond pump–probe mode-mismatched Z-scan TL spectroscopy. Binary solutions of water and heavy water with pure methanol at various concentrations are used for the study, where pure methanol acts as the TL marker across the different samples. The TL signal is found to be effectively modulated by isotope substitution under the experimental conditions, indicating that TL signal depends on hydrogen bonding.

    BibTeX: @article{bhattacharyyaEffectIsotopeSubstitution2014,
     title = {Effect of Isotope Substitution in Binary Liquids with {{Thermal-Lens}} Spectroscopy},
     author = {Bhattacharyya, Indrajit and Kumar, Pardeep and Goswami, Debabrata},
     date = {2014-04-08},
     journaltitle = {Chemical Physics Letters},
     shortjournal = {Chemical Physics Letters},
     volume = {598},
     pages = {35--38},
     issn = {0009-2614},
     doi = {10/f5xrr2},
     url = {http://pc.cd/PORctalK},
     urldate = {2019-08-02}
   }
   

3. Molecular Structure-Property Correlations from Optical Nonlinearity and Thermal-Relaxation Dynamics. I. Bhattacharyya, S. Priyadarshi, and D. Goswami, Chemical Physics Letters 469(1), 104–109 (2009) [Abstract] [PDF] [BibTeX]

   Abstract: We apply ultrafast single beam Z-scan technique to measure saturation absorption coefficients and nonlinear-refraction coefficients of primary alcohols at 1560nm. The nonlinear effects result from vibronic transitions and cubic nonlinear-refraction. To measure the pure total third-order nonlinear susceptibility, we removed thermal effects with a frequency optimized optical-chopper. Our measurements of thermal-relaxation dynamics of alcohols, from 1560nm thermal lens pump and 780nm probe experiments revealed faster and slower thermal-relaxation timescales, respectively, from conduction and convection. The faster timescale accurately predicts thermal-diffusivity, which decreases linearly with alcohol chain-lengths since thermal-relaxation is slower in heavier molecules. The relation between thermal-diffusivity and alcohol chain-length confirms structure-property relationship.

    BibTeX: @article{bhattacharyyaMolecularStructurepropertyCorrelations2009,
     title = {Molecular Structure-Property Correlations from Optical Nonlinearity and Thermal-Relaxation Dynamics},
     author = {Bhattacharyya, Indrajit and Priyadarshi, Shekhar and Goswami, Debabrata},
     date = {2009-02-03},
     journaltitle = {Chemical Physics Letters},
     shortjournal = {Chemical Physics Letters},
     volume = {469},
     number = {1},
     pages = {104--109},
     issn = {0009-2614},
     doi = {10/cpq233},
     url = {http://www.sciencedirect.com/science/article/pii/S0009261408017028},
     urldate = {2019-08-14}
   }
   

4. Probing Intermolecular Interaction through Thermal-Lens Spectroscopy. I. Bhattacharyya, P. Kumar, and D. Goswami, The Journal of Physical Chemistry B 115(2), 262–268 (2011) [Abstract] [PDF] [BibTeX]

   Abstract: Binary liquid mixtures are studied using femtosecond pump−probe thermal-lens (TL) spectroscopy. Changes in the measured TL signals as a function of relative concentration of binary mixtures show that these result from a combined effect of physical and molecular properties of the constituent binary liquids. The experimental TL values deviate from the ones calculated from phenomenological equations. These, we argue, are due to an underestimation of the influence of molecular interactions when the TL signals are calculated by using physical parameters only.

    BibTeX: @article{bhattacharyyaProbingIntermolecularInteraction2011,
     title = {Probing {{Intermolecular Interaction}} through {{Thermal-Lens Spectroscopy}}},
     author = {Bhattacharyya, Indrajit and Kumar, Pardeep and Goswami, Debabrata},
     date = {2011-01-20},
     journaltitle = {The Journal of Physical Chemistry B},
     shortjournal = {J. Phys. Chem. B},
     volume = {115},
     number = {2},
     pages = {262--268},
     issn = {1520-6106},
     doi = {10/d9mz5f},
     url = {https://doi.org/10.1021/jp1062429},
     urldate = {2019-08-14}
   }
   

5. Thermal-Lens Spectroscopy in Binary Liquids Mixtures. I. Bhattacharyya, P. Kumar, and D. Goswami, in Frontiers in Optics 2010/Laser Science XXVI (2010), Paper FWX1 (Optical Society of America, 2010), p. FWX1 [Abstract] [PDF] [BibTeX]

   Abstract: Using femtosecond pump-probe thermal-lens (TL) spectroscopy, experiments in binary-mixtures are presented where trends in TL are modulated by physical and molecular properties. Deviations of experimental results from phenomenological models indicate possible underestimation of molecular interactions.

    BibTeX: @inproceedings{bhattacharyyaThermalLensSpectroscopyBinary2010,
     title = {Thermal-{{Lens}} Spectroscopy in Binary Liquids Mixtures},
     booktitle = {Frontiers in {{Optics}} 2010/{{Laser Science XXVI}} (2010), Paper {{FWX1}}},
     author = {Bhattacharyya, Indrajit and Kumar, Pardeep and Goswami, Debabrata},
     date = {2010-10-24},
     pages = {FWX1},
     publisher = {{Optical Society of America}},
     doi = {10/gf6c8z},
     url = {https://www.osapublishing.org/abstract.cfm?uri=FiO-2010-FWX1},
     urldate = {2019-08-14},
     eventtitle = {Frontiers in {{Optics}}}
   }
   

6. Two-Dimensional Imaging of a Second-Order Nonlinear Optical Process. I. Bhattacharyya and D. Goswami, Current Science 112(04), 830 (2017) [Abstract] [PDF] [BibTeX]

   Abstract: Spatiotemporal imaging of sum-frequency generation process through second-order nonlinear optical interaction in a nonlinear crystal under femtosecond pulsed illumination is presented. Two focal points in the spatial dimension that result from use of widely separated wavelengths (780 and 1560 nm) including their appropriate intensity ratios are captured accurately, emphasizing the sensitivity and robustness of this detection scheme. Most importantly, crosscorrelation width that is used as characteristic measure from such techniques remains constant at the two focal points. However, this highlights the critical role of nonlinear crystal position along beam propagation axis during such collinear intensity cross-correlation measurements involving different wavelengths.

    BibTeX: @article{bhattacharyyaTwoDimensionalImagingSecondOrder2017,
     title = {Two-{{Dimensional Imaging}} of a {{Second-Order Nonlinear Optical Process}}},
     author = {Bhattacharyya, Indrajit and Goswami, Debabrata},
     date = {2017-02-01},
     journaltitle = {Current Science},
     volume = {112},
     number = {04},
     pages = {830},
     issn = {0011-3891},
     doi = {10/f92q98},
     url = {http://pc.cd/mxLctalK},
     urldate = {2019-08-01}
   }
   

7. Spatiotemporal Control of Degenerate Multiphoton Fluorescence Microscopy with Delay-Tunable Femtosecond Pulse Pairs. D. Das, I. Bhattacharyya, and D. Goswami, Chemical Physics Letters 657, 72–77 (2016) [Abstract] [PDF] [BibTeX]

   Abstract: Selective excitation of a particular fluorophore in an ensemble of different fluorophores with overlapping fluorescence spectra is shown to be dependent on the time delay of femtosecond pulse pairs in multiphoton fluorescence microscopy. In particular, the two-photon fluorescence behavior of the Texas Red and DAPI dye pair inside Bovine Pulmonary Artery Endothelial (BPAE) cells depends strongly on the center wavelength of the laser, as well as the delay between two identical laser pulses in one-color femtosecond pulse-pair excitation scheme. Thus, we present a novel design concept using pairs of femtosecond pulses at different central wavelengths and tunable pulse separations for controlling the image contrast between two spatially and spectrally overlapping fluorophores. This femtosecond pulse-pair technique is unique in utilizing the variation of dye dynamics inside biological cells as a contrast mode in microscopy of different fluorophores.

    BibTeX: @article{dasSpatiotemporalControlDegenerate2016,
     title = {Spatiotemporal Control of Degenerate Multiphoton Fluorescence Microscopy with Delay-Tunable Femtosecond Pulse Pairs},
     author = {Das, Dhiman and Bhattacharyya, Indrajit and Goswami, Debabrata},
     date = {2016-07-16},
     journaltitle = {Chemical Physics Letters},
     shortjournal = {Chemical Physics Letters},
     volume = {657},
     pages = {72--77},
     issn = {0009-2614},
     doi = {10/f84rwd},
     url = {https://my.pcloud.com/publink/show?code=XZ1Axr7ZxiTGNbfEV1bmLPqho9PtQzSq3qUk},
     urldate = {2019-08-01}
   }
   

8. Thermal-Lens Spectroscopy in Binary Liquids Mixtures: Effect of Isotope Substitution. P. Kumar, I. Bhattacharyya, and D. Goswami, in Frontiers in Optics 2011/Laser Science XXVII (2011), Paper JTuA25 (Optical Society of America, 2011), p. JTuA25 [Abstract] [PDF] [BibTeX]

   Abstract: Using femtosecond pump-probe thermal lens (TL) spectroscopy, we show that the effect of isotope substitution can be monitored through a modulation of TL signals in binary liquids showing the important of molecular properties on TL.

    BibTeX: @inproceedings{kumarThermalLensSpectroscopyBinary2011,
     title = {Thermal-{{Lens Spectroscopy}} in {{Binary Liquids Mixtures}}: {{Effect}} of {{Isotope Substitution}}},
     shorttitle = {Thermal-{{Lens Spectroscopy}} in {{Binary Liquids Mixtures}}},
     booktitle = {Frontiers in {{Optics}} 2011/{{Laser Science XXVII}} (2011), Paper {{JTuA25}}},
     author = {Kumar, Pardeep and Bhattacharyya, Indrajit and Goswami, Debabrata},
     date = {2011-10-16},
     pages = {JTuA25},
     publisher = {{Optical Society of America}},
     doi = {10/gf5nqg},
     url = {https://www.osapublishing.org/abstract.cfm?uri=FiO-2011-JTuA25},
     urldate = {2019-08-02},
     eventtitle = {Frontiers in {{Optics}}}
   }
   

9. Molecular Structure-Property Correlations from Optical Nonlinearity and Thermal-Relaxation Dynamics. I. Bhattacharyya, S. Priyadarshi, and D. Goswami, Chemical Physics Letters 469(1), 104–109 (2009) [Abstract] [PDF] [BibTeX]

   Abstract: We apply ultrafast single beam Z-scan technique to measure saturation absorption coefficients and nonlinear-refraction coefficients of primary alcohols at 1560nm. The nonlinear effects result from vibronic transitions and cubic nonlinear-refraction. To measure the pure total third-order nonlinear susceptibility, we removed thermal effects with a frequency optimized optical-chopper. Our measurements of thermal-relaxation dynamics of alcohols, from 1560nm thermal lens pump and 780nm probe experiments revealed faster and slower thermal-relaxation timescales, respectively, from conduction and convection. The faster timescale accurately predicts thermal-diffusivity, which decreases linearly with alcohol chain-lengths since thermal-relaxation is slower in heavier molecules. The relation between thermal-diffusivity and alcohol chain-length confirms structure-property relationship.

    BibTeX: @article{bhattacharyyaMolecularStructurepropertyCorrelations2010,
     title = {Molecular Structure-Property Correlations from Optical Nonlinearity and Thermal-Relaxation Dynamics},
     volume = {469},
     issn = {0009-2614},
     url = {http://www.sciencedirect.com/science/article/pii/S0009261408017028},
     doi = {10/cpq233},
     number = {1},
     journaltitle = {Chemical Physics Letters},
     urldate = {2019-08-14},
     date = {2009-02-03},
     pages = {104-109},
     author = {Bhattacharyya, Indrajit and Priyadarshi, Shekhar and Goswami, Debabrata}
   }
   

10. Two-Dimensional Imaging of a Second-Order Nonlinear Optical Process. I. Bhattacharyya and D. Goswami, Current Science 112(04), 830 (2017) [Abstract] [PDF] [BibTeX]

    Abstract: Spatiotemporal imaging of sum-frequency generation process through second-order nonlinear optical interaction in a nonlinear crystal under femtosecond pulsed illumination is presented. Two focal points in the spatial dimension that result from use of widely separated wavelengths (780 and 1560 nm) including their appropriate intensity ratios are captured accurately, emphasizing the sensitivity and robustness of this detection scheme. Most importantly, crosscorrelation width that is used as characteristic measure from such techniques remains constant at the two focal points. However, this highlights the critical role of nonlinear crystal position along beam propagation axis during such collinear intensity cross-correlation measurements involving different wavelengths.

     BibTeX: @article{bhattacharyyaTwoDimensionalImagingSecondOrder2018,
      langid = {english},
      title = {Two-{{Dimensional Imaging}} of a {{Second}}-{{Order Nonlinear Optical Process}}},
      volume = {112},
      issn = {0011-3891},
      url = {http://pc.cd/mxLctalK},
      doi = {10/f92q98},
      number = {04},
      journaltitle = {Current Science},
      urldate = {2019-08-01},
      date = {2017-02-01},
      pages = {830},
      author = {Bhattacharyya, Indrajit and Goswami, Debabrata}
    }
    

11. Spatiotemporal Control of Degenerate Multiphoton Fluorescence Microscopy with Delay-Tunable Femtosecond Pulse Pairs. D. Das, I. Bhattacharyya, and D. Goswami, Chemical Physics Letters 657, 72–77 (2016) [Abstract] [PDF] [BibTeX]

    Abstract: Selective excitation of a particular fluorophore in an ensemble of different fluorophores with overlapping fluorescence spectra is shown to be dependent on the time delay of femtosecond pulse pairs in multiphoton fluorescence microscopy. In particular, the two-photon fluorescence behavior of the Texas Red and DAPI dye pair inside Bovine Pulmonary Artery Endothelial (BPAE) cells depends strongly on the center wavelength of the laser, as well as the delay between two identical laser pulses in one-color femtosecond pulse-pair excitation scheme. Thus, we present a novel design concept using pairs of femtosecond pulses at different central wavelengths and tunable pulse separations for controlling the image contrast between two spatially and spectrally overlapping fluorophores. This femtosecond pulse-pair technique is unique in utilizing the variation of dye dynamics inside biological cells as a contrast mode in microscopy of different fluorophores.

     BibTeX: @article{dasSpatiotemporalControlDegenerate2017,
      title = {Spatiotemporal Control of Degenerate Multiphoton Fluorescence Microscopy with Delay-Tunable Femtosecond Pulse Pairs},
      volume = {657},
      issn = {0009-2614},
      url = {https://my.pcloud.com/publink/show?code=XZ1Axr7ZxiTGNbfEV1bmLPqho9PtQzSq3qUk},
      doi = {10/f84rwd},
      journaltitle = {Chemical Physics Letters},
      urldate = {2019-08-01},
      date = {2016-07-16},
      pages = {72-77},
      author = {Das, Dhiman and Bhattacharyya, Indrajit and Goswami, Debabrata}
    }
    

12. Effect of Isotope Substitution in Binary Liquids with Thermal-Lens Spectroscopy. I. Bhattacharyya, P. Kumar, and D. Goswami, Chemical Physics Letters 598, 35–38 (2014) [Abstract] [PDF] [BibTeX]

    Abstract: Effect of isotope substitution from the modulation of Thermal-Lens (TL) signals in binary liquid mixtures is explored using femtosecond pump–probe mode-mismatched Z-scan TL spectroscopy. Binary solutions of water and heavy water with pure methanol at various concentrations are used for the study, where pure methanol acts as the TL marker across the different samples. The TL signal is found to be effectively modulated by isotope substitution under the experimental conditions, indicating that TL signal depends on hydrogen bonding.

     BibTeX: @article{bhattacharyyaEffectIsotopeSubstitution2015,
      title = {Effect of Isotope Substitution in Binary Liquids with {{Thermal}}-{{Lens}} Spectroscopy},
      volume = {598},
      issn = {0009-2614},
      url = {http://pc.cd/PORctalK},
      doi = {10/f5xrr2},
      journaltitle = {Chemical Physics Letters},
      urldate = {2019-08-02},
      date = {2014-04-08},
      pages = {35-38},
      author = {Bhattacharyya, Indrajit and Kumar, Pardeep and Goswami, Debabrata}
    }
    

13. Thermal-Lens Spectroscopy in Binary Liquids Mixtures: Effect of Isotope Substitution. P. Kumar, I. Bhattacharyya, and D. Goswami, in Frontiers in Optics 2011/Laser Science XXVII (2011), Paper JTuA25 (Optical Society of America, 2011), p. JTuA25 [Abstract] [PDF] [BibTeX]

    Abstract: Using femtosecond pump-probe thermal lens (TL) spectroscopy, we show that the effect of isotope substitution can be monitored through a modulation of TL signals in binary liquids showing the important of molecular properties on TL.

     BibTeX: @inproceedings{kumarThermalLensSpectroscopyBinary2012,
      langid = {english},
      title = {Thermal-{{Lens Spectroscopy}} in {{Binary Liquids Mixtures}}: {{Effect}} of {{Isotope Substitution}}},
      url = {https://www.osapublishing.org/abstract.cfm?uri=FiO-2011-JTuA25},
      doi = {10/gf5nqg},
      shorttitle = {Thermal-{{Lens Spectroscopy}} in {{Binary Liquids Mixtures}}},
      eventtitle = {Frontiers in {{Optics}}},
      booktitle = {Frontiers in {{Optics}} 2011/{{Laser Science XXVII}} (2011), Paper {{JTuA25}}},
      publisher = {{Optical Society of America}},
      urldate = {2019-08-02},
      date = {2011-10-16},
      pages = {JTuA25},
      author = {Kumar, Pardeep and Bhattacharyya, Indrajit and Goswami, Debabrata}
    }
    

14. Probing Intermolecular Interaction through Thermal-Lens Spectroscopy. I. Bhattacharyya, P. Kumar, and D. Goswami, J. Phys. Chem. B 115(2), 262–268 (2011) [Abstract] [PDF] [BibTeX]

    Abstract: Binary liquid mixtures are studied using femtosecond pump−probe thermal-lens (TL) spectroscopy. Changes in the measured TL signals as a function of relative concentration of binary mixtures show that these result from a combined effect of physical and molecular properties of the constituent binary liquids. The experimental TL values deviate from the ones calculated from phenomenological equations. These, we argue, are due to an underestimation of the influence of molecular interactions when the TL signals are calculated by using physical parameters only.

     BibTeX: @article{bhattacharyyaProbingIntermolecularInteraction2012,
      title = {Probing {{Intermolecular Interaction}} through {{Thermal}}-{{Lens Spectroscopy}}},
      volume = {115},
      issn = {1520-6106},
      url = {https://doi.org/10.1021/jp1062429},
      doi = {10/d9mz5f},
      number = {2},
      journaltitle = {J. Phys. Chem. B},
      urldate = {2019-08-14},
      date = {2011-01-20},
      pages = {262-268},
      author = {Bhattacharyya, Indrajit and Kumar, Pardeep and Goswami, Debabrata}
    }
    

15. Thermal-Lens Spectroscopy in Binary Liquids Mixtures. I. Bhattacharyya, P. Kumar, and D. Goswami, in Frontiers in Optics 2010/Laser Science XXVI (2010), Paper FWX1 (Optical Society of America, 2010), p. FWX1 [Abstract] [PDF] [BibTeX]

    Abstract: Using femtosecond pump-probe thermal-lens (TL) spectroscopy, experiments in binary-mixtures are presented where trends in TL are modulated by physical and molecular properties. Deviations of experimental results from phenomenological models indicate possible underestimation of molecular interactions.

     BibTeX: @inproceedings{bhattacharyyaThermalLensSpectroscopyBinary2011,
      langid = {english},
      title = {Thermal-{{Lens}} Spectroscopy in Binary Liquids Mixtures},
      url = {https://www.osapublishing.org/abstract.cfm?uri=FiO-2010-FWX1},
      doi = {10.1364/FIO.2010.FWX1},
      eventtitle = {Frontiers in {{Optics}}},
      booktitle = {Frontiers in {{Optics}} 2010/{{Laser Science XXVI}} (2010), Paper {{FWX1}}},
      publisher = {{Optical Society of America}},
      urldate = {2019-08-14},
      date = {2010-10-24},
      pages = {FWX1},
      author = {Bhattacharyya, Indrajit and Kumar, Pardeep and Goswami, Debabrata}
    }
    

16. Decoding Coherent Information in Femtosecond Shaped Laser Pulses. I. Bhattacharyya, A. Dutta, S. Ashtekar, S. K. Maurya, and D. Goswami, CURRENT SCIENCE 99(4), 10 (2010) [Abstract] [BibTeX]

    Abstract: We report here an experimental demonstration of a pulse decoding technique from spectral analysis of femtosecond pulses. This technique is based on a single-step Fourier domain inversion algorithm and shows the impact of the spectral window function on the retrieval of the signal pulse. Using two femtosecond laser pulses at 780 and 1560 nm from a fibre laser, we have shown that even when the spectral content of the reference pulse is far from a narrow band limit (as much as a quarter of its entire spectral content for our conditions), the single-step retrieval analysis using spectral windowing in the Fourier domain works efficiently. The enhanced signal levels possible due to the wider spectral window are critical in the unambiguous description of laser pulses, which would have potential application in the retrieval of comparatively weak and complex ultra-short pulses as is often needed in pulse shaping applications and coherent optical communications.

     BibTeX: @article{bhattacharyyaDecodingCoherentInformation2011,
      langid = {english},
      title = {Decoding Coherent Information in Femtosecond Shaped Laser Pulses},
      volume = {99},
      number = {4},
      journaltitle = {CURRENT SCIENCE},
      date = {2010},
      pages = {10},
      author = {Bhattacharyya, Indrajit and Dutta, Aveek and Ashtekar, Sumit and Maurya, Sandeep Kumar and Goswami, Debabrata}
    }
    

17. Molecular Structure-Property Correlations from Optical Nonlinearity and Thermal-Relaxation Dynamics. I. Bhattacharyya, S. Priyadarshi, and D. Goswami, Chemical Physics Letters 469(1), 104–109 (2009) [Abstract] [PDF] [BibTeX]

    Abstract: We apply ultrafast single beam Z-scan technique to measure saturation absorption coefficients and nonlinear-refraction coefficients of primary alcohols at 1560nm. The nonlinear effects result from vibronic transitions and cubic nonlinear-refraction. To measure the pure total third-order nonlinear susceptibility, we removed thermal effects with a frequency optimized optical-chopper. Our measurements of thermal-relaxation dynamics of alcohols, from 1560nm thermal lens pump and 780nm probe experiments revealed faster and slower thermal-relaxation timescales, respectively, from conduction and convection. The faster timescale accurately predicts thermal-diffusivity, which decreases linearly with alcohol chain-lengths since thermal-relaxation is slower in heavier molecules. The relation between thermal-diffusivity and alcohol chain-length confirms structure-property relationship.

     BibTeX: @article{bhattacharyyaMolecularStructurepropertyCorrelations2011,
      title = {Molecular Structure-Property Correlations from Optical Nonlinearity and Thermal-Relaxation Dynamics},
      volume = {469},
      issn = {0009-2614},
      url = {http://www.sciencedirect.com/science/article/pii/S0009261408017028},
      doi = {10/cpq233},
      number = {1},
      journaltitle = {Chemical Physics Letters},
      urldate = {2019-08-14},
      date = {2009-02-03},
      pages = {104-109},
      author = {Bhattacharyya, Indrajit and Priyadarshi, Shekhar and Goswami, Debabrata}
    }