IIT Kanpur

Education / Work History

  • M.Tech, CELP, IIT Kanpur (2015-2017)

Research Topic / Interest

Contact me to know my current interests.

Publications

These include only those published in our lab.

  1. Excited State Absorption and Relaxation Dynamics in a Series of Heptamethine Dyes under Femtosecond and Nanosecond Excitations. K. Makhal, S. Maurya, and D. Goswami, Physica Scripta 94(9), 095501 (2019) [Abstract] [PDF] [BibTeX]

    Abstract: We show that the near-infrared-absorbing polymethine cyanine dyes exhibit nonlinear absorption (NLA) in the visible region, where they have negligible or very low linear absorption. In chloroform solvent, the studied cyanines were found to be photo-unstable and exhibited photo-degradation under prolonged exposures as compared to methanol and dimethyl sulphoxide solvents, where they were stable. Excitation with femtosecond (fs) pulses in the visible region (400–750 nm) exhibits excited state absorption (ESA) as characterized by positive differential absorption (ΔOD) in transient absorption signal. Non-resonant excitations in the visible region are governed by reverse saturable absorption (RSA) mechanism leading to ESA. Excitation with nanosecond pulses also shows NLA owing to ESA from triplet states as compared to that from singlet states under fs excitations. Single beam Z-scan studies were performed with nanosecond (ns) pulses to evaluate ground (σ gr) and excited state (σ ex) absorption cross-sections, which confirms the mechanism of RSA as σ ex were found to be greater than σ gr. The population relaxation from higher excited singlet states shows ultrafast behavior with multi-exponential decay components. The fast time component decay varies from a few hundreds of fs (τ 1) to some hundreds of picoseconds (τ 2), and the long-time decay is in the ns domain (τ 3).

     BibTeX: @article{makhalExcitedStateAbsorption2019,
      langid = {english},
      title = {Excited State Absorption and Relaxation Dynamics in a Series of Heptamethine Dyes under Femtosecond and Nanosecond Excitations},
      volume = {94},
      issn = {1402-4896},
      url = {https://doi.org/10.1088%2F1402-4896%2Fab0064},
      doi = {10/gf5mpz},
      number = {9},
      journaltitle = {Physica Scripta},
      shortjournal = {Phys. Scr.},
      urldate = {2019-08-01},
      date = {2019-06},
      pages = {095501},
      author = {Makhal, Krishnandu and Maurya, Sidharth and Goswami, Debabrata}
    }
    
  2. Extracting Third Order Optical Nonlinearities of Mn(III)-Phthalocyanine Chloride Using High Repetition Rate Femtosecond Pulses. K. Makhal, P. Mathur, S. Maurya, and D. Goswami, Journal of Applied Physics 121(5), 053103 (2017) [PDF] [BibTeX]
     BibTeX: @article{makhalExtractingThirdOrder2017,
      title = {Extracting Third Order Optical Nonlinearities of {{Mn}}({{III}})-{{Phthalocyanine}} Chloride Using High Repetition Rate Femtosecond Pulses},
      volume = {121},
      issn = {0021-8979},
      url = {https://aip.scitation.org/doi/abs/10.1063/1.4974966},
      doi = {10/gf5mrh},
      number = {5},
      journaltitle = {Journal of Applied Physics},
      shortjournal = {Journal of Applied Physics},
      urldate = {2019-08-01},
      date = {2017-02-06},
      pages = {053103},
      author = {Makhal, Krishnandu and Mathur, Paresh and Maurya, Sidharth and Goswami, Debabrata}
    }
    
  3. Reverse Saturable Absorption Followed by Anomalous Saturable Absorption in Rhodamine-700. K. Makhal, S. Maurya, and D. Goswami, in 13th International Conference on Fiber Optics and Photonics (OSA, 2016), p. Tu5D.2 [Abstract] [PDF] [BibTeX]

    Abstract: Anomalous SA (saturable absorption) in presence of reverse saturable absorption (RSA) in Rhodamine-700 is reported employing Z-scan with 100 ns, 250 Hz pulses in methanol. SA is observed only at a particular intensity range otherwise RSA survives.

     BibTeX: @inproceedings{makhalReverseSaturableAbsorption2016,
      langid = {english},
      location = {{Kharagpur}},
      title = {Reverse {{Saturable Absorption}} Followed by {{Anomalous Saturable Absorption}} in {{Rhodamine}}-700},
      isbn = {978-1-943580-22-4},
      url = {https://www.osapublishing.org/abstract.cfm?URI=Photonics-2016-Tu5D.2},
      doi = {10.1364/PHOTONICS.2016.Tu5D.2},
      eventtitle = {International {{Conference}} on {{Fibre Optics}} and {{Photonics}}},
      booktitle = {13th {{International Conference}} on {{Fiber Optics}} and {{Photonics}}},
      publisher = {{OSA}},
      urldate = {2019-08-01},
      date = {2016},
      pages = {Tu5D.2},
      author = {Makhal, Krishnandu and Maurya, Sidharth and Goswami, Debabrata}
    }
    
  4. Excited State Absorption and Relaxation Dynamics in a Series of Heptamethine Dyes under Femtosecond and Nanosecond Excitations. K. Makhal, S. Maurya, and D. Goswami, Phys. Scr. 94(9), 095501 (2019) [Abstract] [PDF] [BibTeX]

    Abstract: We show that the near-infrared-absorbing polymethine cyanine dyes exhibit nonlinear absorption (NLA) in the visible region, where they have negligible or very low linear absorption. In chloroform solvent, the studied cyanines were found to be photo-unstable and exhibited photo-degradation under prolonged exposures as compared to methanol and dimethyl sulphoxide solvents, where they were stable. Excitation with femtosecond (fs) pulses in the visible region (400–750 nm) exhibits excited state absorption (ESA) as characterized by positive differential absorption (ΔOD) in transient absorption signal. Non-resonant excitations in the visible region are governed by reverse saturable absorption (RSA) mechanism leading to ESA. Excitation with nanosecond pulses also shows NLA owing to ESA from triplet states as compared to that from singlet states under fs excitations. Single beam Z-scan studies were performed with nanosecond (ns) pulses to evaluate ground (σ gr) and excited state (σ ex) absorption cross-sections, which confirms the mechanism of RSA as σ ex were found to be greater than σ gr. The population relaxation from higher excited singlet states shows ultrafast behavior with multi-exponential decay components. The fast time component decay varies from a few hundreds of fs (τ 1) to some hundreds of picoseconds (τ 2), and the long-time decay is in the ns domain (τ 3).

     BibTeX: @article{makhalExcitedStateAbsorption2020,
      langid = {english},
      title = {Excited State Absorption and Relaxation Dynamics in a Series of Heptamethine Dyes under Femtosecond and Nanosecond Excitations},
      volume = {94},
      issn = {1402-4896},
      url = {https://doi.org/10.1088%2F1402-4896%2Fab0064},
      doi = {10/gf5mpz},
      number = {9},
      journaltitle = {Phys. Scr.},
      urldate = {2019-08-01},
      date = {2019-06},
      pages = {095501},
      author = {Makhal, Krishnandu and Maurya, Sidharth and Goswami, Debabrata}
    }
    
  5. Extracting Third Order Optical Nonlinearities of Mn(III)-Phthalocyanine Chloride Using High Repetition Rate Femtosecond Pulses. K. Makhal, P. Mathur, S. Maurya, and D. Goswami, Journal of Applied Physics 121(5), 053103 (2017) [PDF] [BibTeX]
     BibTeX: @article{makhalExtractingThirdOrder2018,
      title = {Extracting Third Order Optical Nonlinearities of {{Mn}}({{III}})-{{Phthalocyanine}} Chloride Using High Repetition Rate Femtosecond Pulses},
      volume = {121},
      issn = {0021-8979},
      url = {https://aip.scitation.org/doi/abs/10.1063/1.4974966},
      doi = {10/gf5mrh},
      number = {5},
      journaltitle = {Journal of Applied Physics},
      urldate = {2019-08-01},
      date = {2017-02-06},
      pages = {053103},
      author = {Makhal, Krishnandu and Mathur, Paresh and Maurya, Sidharth and Goswami, Debabrata}
    }
    
  6. Reverse Saturable Absorption Followed by Anomalous Saturable Absorption in Rhodamine-700. K. Makhal, S. Maurya, and D. Goswami, in 13th International Conference on Fiber Optics and Photonics (OSA, 2016), p. Tu5D.2 [Abstract] [PDF] [BibTeX]

    Abstract: Anomalous SA (saturable absorption) in presence of reverse saturable absorption (RSA) in Rhodamine-700 is reported employing Z-scan with 100 ns, 250 Hz pulses in methanol. SA is observed only at a particular intensity range otherwise RSA survives.

     BibTeX: @inproceedings{makhalReverseSaturableAbsorption2017,
      langid = {english},
      location = {{Kharagpur}},
      title = {Reverse {{Saturable Absorption}} Followed by {{Anomalous Saturable Absorption}} in {{Rhodamine}}-700},
      isbn = {978-1-943580-22-4},
      url = {https://www.osapublishing.org/abstract.cfm?URI=Photonics-2016-Tu5D.2},
      doi = {10.1364/PHOTONICS.2016.Tu5D.2},
      eventtitle = {International {{Conference}} on {{Fibre Optics}} and {{Photonics}}},
      booktitle = {13th {{International Conference}} on {{Fiber Optics}} and {{Photonics}}},
      publisher = {{OSA}},
      urldate = {2019-08-01},
      date = {2016},
      pages = {Tu5D.2},
      author = {Makhal, Krishnandu and Maurya, Sidharth and Goswami, Debabrata}
    }