Dhiman Das

09 March 2026

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Education / Work History

• Ph.D. Scholar, IIT Kanpur (2017)
• M.Sc., IIT Guwahati (2008-2010)

Thesis Abstract

Spatiotemporal Approaches Towards Enhancing the Efficiency of Laser Scanning Fluorescence Microscopy in Condensed Phase

This thesis mainly focuses on application of third-order nonlinear optical phenomena including self-defocusing effect of binary liquid mixtures to probe intermolecular interaction and modulation of two photon fluorescence in far-field microscopy. Spatiotemporal control of two photon fluorescence (TPF) as well as resolution benefits obtained with temporally controlled femtosecond pulse in the field of multi-photon fluorescence microscopy are the major highlights of this thesis. It begins with a discussion on the chronological evolution of fluorescence experiments and their applications, continuing all the way to the development of modern super-resolved fluorescence microscopy (Chapter 1). This sets up the motivation of the present work reported in the thesis as well as discusses the existing open problems about control of TPF in microscopy. Chapter 2 describes the instrumentation part in detail for all the experiments being presented in this thesis. Chapter 3 involves a brief discussion on measurement of third-order optical nonlinearity, in particular, on nonlinear absorption and nonlinear refraction and the standard home-built z-scan technique to simultaneously measure nonlinear absorption and nonlinear refraction in solids, liquids and liquid solutions within the “thin sample approximation”. In Chapter 4, it has been shown that such thermo-optic results can have a far-reaching impact on molecular properties and intermolecular interactions in binary liquid mixtures. Chapter 5 aims at focusing on photo-physical processes that occur in a typical fluorophore and their association to one-photon and two photon fluorescence microscopy. In Chapter 6, control of TPF in microscopy is discussed with one color pulse-pair excitation scheme using femtosecond laser pulses. Chapter 7 focuses on the effect of our one color pulse-pair technique to enhance the axial resolution as a function of the relative time delay between the pulse pair in two photon fluorescence microscopy. Chapter 8 is the concluding chapter that summarizes how to probe intermolecular interactions in binary liquid mixtures using HRR femtosecond laser induced self-defocusing nonlinearity under non-resonant condition. Most importantly, we have shown spatiotemporal control of the two-photon fluorescence process and consequent resolution enhancement in both lateral and axial direction in two photon fluorescence microscopy. Based on the current results and discussions presented in this thesis, further possible experiments have been proposed. The work presented in this thesis is the endeavor to bring the concept of dynamical control to a new horizon and to throw a deeper insight on the spatiotemporal control of two photon fluorescence process in far-field microscopy. Further advances in this emerging research field are expected to enrich our understanding in condensed phase molecular dynamics at the single molecular level.

Research Topic / Interest

Contact me to know my current interests.

Publications

These include only those published in our lab.

1. Direct Observation of Diatoms Pair Formation in Aqueous Solution Under Laser Scanning Fluorescence Microscopy. D. Das and D. Goswami, in 13th International Conference on Fiber Optics and Photonics (OSA, 2016), p. Tu2B.3 [BibTeX]

    BibTeX: @inproceedings{dasDirectObservationDiatoms2016,
     title = {Direct {{Observation}} of {{Diatoms Pair Formation}} in {{Aqueous Solution Under Laser Scanning Fluorescence Microscopy}}},
     booktitle = {13th {{International Conference}} on {{Fiber Optics}} and {{Photonics}}},
     author = {Das, Dhiman and Goswami, Debabrata},
     year = {2016},
     pages = {Tu2B.3},
     publisher = {OSA},
     address = {Kharagpur},
     doi = {10/gf5mrq},
     urldate = {2019-08-01},
     isbn = {978-1-943580-22-4},
     langid = {english},
     annotation = {GSCC: 0000000 \\
     0 citations (Crossref) [2024-05-28]\\
     00000}
   }
   

2. 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) [BibTeX]

    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},
     year = {2016},
     month = jul,
     journal = {Chemical Physics Letters},
     volume = {657},
     pages = {72--77},
     issn = {0009-2614},
     doi = {10/f84rwd},
     urldate = {2019-08-01},
     annotation = {GSCC: 0000003 \\
     3 citations (Crossref) [2024-05-28]\\
     00000}
   }
   

3. Resolution Enhancement through Microscopic Spatiotemporal Control. D. Goswami, D. Das, and S. N. Bandyopadhyay, Faraday Discussions 177(0), 203–212 (2015) [BibTeX]

    BibTeX: @article{goswamiResolutionEnhancementMicroscopic2015,
     title = {Resolution Enhancement through Microscopic Spatiotemporal Control},
     author = {Goswami, Debabrata and Das, Dhiman and Bandyopadhyay, Soumendra Nath},
     year = {2015},
     month = apr,
     journal = {Faraday Discussions},
     volume = {177},
     number = {0},
     pages = {203--212},
     issn = {1364-5498},
     doi = {10/gf5msv},
     urldate = {2019-08-01},
     langid = {english},
     annotation = {GSCC: 0000114 \\
     2 citations (Crossref) [2024-05-28]\\
     00000}
   }
   

4. Probing Intermolecular Interactions in Binary Liquid Mixtures Using Femtosecond Laser-Induced Self-Defocusing. S. K. Maurya, D. Das, and D. Goswami, Applied Spectroscopy 70(10), 1655–1661 (2016) [BibTeX]

    BibTeX: @article{mauryaProbingIntermolecularInteractions2016,
     title = {Probing {{Intermolecular Interactions}} in {{Binary Liquid Mixtures Using Femtosecond Laser-Induced Self-Defocusing}}},
     author = {Maurya, Sandeep Kumar and Das, Dhiman and Goswami, Debabrata},
     year = {2016},
     month = oct,
     journal = {Applied Spectroscopy},
     volume = {70},
     number = {10},
     pages = {1655--1661},
     issn = {0003-7028},
     doi = {10/gf5mrx},
     urldate = {2019-08-01},
     langid = {english},
     annotation = {GSCC: 0000006 \\
     5 citations (Crossref) [2024-05-28]\\
     00000}
   }
   

5. Direct Observation of Diatoms Pair Formation in Aqueous Solution Under Laser Scanning Fluorescence Microscopy. D. Das and D. Goswami, in 13th International Conference on Fiber Optics and Photonics (OSA, 2016), p. Tu2B.3 [BibTeX]

    BibTeX: @inproceedings{dasDirectObservationDiatoms2017,
     title = {Direct {{Observation}} of {{Diatoms Pair Formation}} in {{Aqueous Solution Under Laser Scanning Fluorescence Microscopy}}},
     booktitle = {13th {{International Conference}} on {{Fiber Optics}} and {{Photonics}}},
     author = {Das, Dhiman and Goswami, Debabrata},
     year = {2016},
     pages = {Tu2B.3},
     publisher = {OSA},
     address = {Kharagpur},
     doi = {10/gf5mrq},
     urldate = {2019-08-01},
     isbn = {978-1-943580-22-4},
     langid = {english},
     annotation = {GSCC: 0000000 \\
     0 citations (Crossref) [2024-05-28]\\
     00000}
   }
   

6. 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) [BibTeX]

    BibTeX: @article{dasSpatiotemporalControlDegenerate2017,
     title = {Spatiotemporal Control of Degenerate Multiphoton Fluorescence Microscopy with Delay-Tunable Femtosecond Pulse Pairs},
     author = {Das, Dhiman and Bhattacharyya, Indrajit and Goswami, Debabrata},
     year = {2016},
     month = jul,
     journal = {Chemical Physics Letters},
     volume = {657},
     pages = {72--77},
     issn = {0009-2614},
     doi = {10/f84rwd},
     urldate = {2019-08-01},
     annotation = {GSCC: 0000003 \\
     3 citations (Crossref) [2024-05-28]\\
     00000}
   }
   

7. Resolution Enhancement through Microscopic Spatiotemporal Control. D. Goswami, D. Das, and S. N. Bandyopadhyay, Faraday Discussions 177(0), 203–212 (2015) [BibTeX]

    BibTeX: @article{goswamiResolutionEnhancementMicroscopic2016,
     title = {Resolution Enhancement through Microscopic Spatiotemporal Control},
     author = {Goswami, Debabrata and Das, Dhiman and Bandyopadhyay, Soumendra Nath},
     year = {2015},
     month = apr,
     journal = {Faraday Discussions},
     volume = {177},
     number = {0},
     pages = {203--212},
     issn = {1364-5498},
     doi = {10/gf5msv},
     urldate = {2019-08-01},
     langid = {english},
     annotation = {GSCC: 0000114 \\
     2 citations (Crossref) [2024-05-28]\\
     00000}
   }
   

8. Probing Intermolecular Interactions in Binary Liquid Mixtures Using Femtosecond Laser-Induced Self-Defocusing. S. K. Maurya, D. Das, and D. Goswami, Applied Spectroscopy 70(10), 1655–1661 (2016) [BibTeX]

    BibTeX: @article{mauryaProbingIntermolecularInteractions2017,
     title = {Probing {{Intermolecular Interactions}} in {{Binary Liquid Mixtures Using Femtosecond Laser-Induced Self-Defocusing}}},
     author = {Maurya, Sandeep Kumar and Das, Dhiman and Goswami, Debabrata},
     year = {2016},
     month = oct,
     journal = {Applied Spectroscopy},
     volume = {70},
     number = {10},
     pages = {1655--1661},
     issn = {0003-7028},
     doi = {10/gf5mrx},
     urldate = {2019-08-01},
     langid = {english},
     annotation = {GSCC: 0000006 \\
     5 citations (Crossref) [2024-05-28]\\
     00000}
   }