IIT Kanpur

Education / Work History

  • Postdoctoral Fellow, University of Colorado (2019-present)
  • Ph.D. Scholar, IIT Kanpur (2010-2018)

Publications

These include only those published in our lab.

  1. Exploring the Critical Role of Detection Aperture in Thermal Lens Measurements. S. Singhal, I. Bhattacharyya, and D. Goswami, in 2015 Workshop on Recent Advances in Photonics (WRAP) (2015), pp. 1–4 [Abstract] [BibTeX]

    Abstract: The critical role of the detection aperture size on the measurement of thermal lens signals has been explored by using mode-mismatched pump-probe thermal lens spectroscopy in pure methanol. Femtosecond laser pulses at 1560 nm are used to create thermal lens signal, which is simultaneously probed by a collinear 780 nm pulse train through a partially open aperture of different sizes placed after the sample. The trend in the time resolved thermal lens signals reveals that aperture size allowing less than half of the incident probe light is critical in providing accuracy of the thermal lens spectroscopy.

     BibTeX: @inproceedings{singhalExploringCriticalRole2015,
      title = {Exploring the Critical Role of Detection Aperture in Thermal Lens Measurements},
      booktitle = {2015 {{Workshop}} on {{Recent Advances}} in {{Photonics}} ({{WRAP}})},
      author = {Singhal, S. and Bhattacharyya, I. and Goswami, D.},
      date = {2015-12},
      pages = {1--4},
      doi = {10/gf5msd},
      eventtitle = {2015 {{Workshop}} on {{Recent Advances}} in {{Photonics}} ({{WRAP}})},
      file = {/run/media/haozeke/Storage/Zotero/storage/6C4TYZ3Q/dgoswamiFemtoLab-Singhal_et_al_2015_Exploring_the_critical_role_of_detection_aperture_in_thermal_lens_measurements.pdf;/run/media/haozeke/Storage/Zotero/storage/W2UHRH86/7806016.html},
      keywords = {_tablet,collinear pulse train,detection aperture size,femtosecond laser,femtosecond laser pulses,incident probe light,measurement by laser beam,mode-mismatched pump-probe thermal lens spectroscopy,optical pulse generation,optical pumping,organic compounds,pure methanol,thermal conduction,thermal convection,thermal lens measurements,thermal lens signal,thermal lensing,time resolved thermal lens signals,wavelength 1560 nm,wavelength 780 nm}
    }
    
  2. Importance of Hydrogen Bonding in Thermal Lens Study of Highly Absorbing Liquids. S. Singhal, P. P. Roy, and D. Goswami, in Frontiers in Optics 2015 (2015), Paper FTu5E.5 (Optical Society of America, 2015), p. FTu5E.5 [Abstract] [PDF] [BibTeX]

    Abstract: Effect of thermal load on highly absorbing hydrogen bonded liquids are explored. We find heat transfer is better facilitated in lesser hydrogen bonded liquids by convection through molecular motion in addition to conduction.

     BibTeX: @inproceedings{singhalImportanceHydrogenBonding2015,
      title = {Importance of {{Hydrogen Bonding}} in {{Thermal Lens Study}} of {{Highly Absorbing Liquids}}},
      booktitle = {Frontiers in {{Optics}} 2015 (2015), Paper {{FTu5E}}.5},
      author = {Singhal, Sumit and Roy, Partha Pratim and Goswami, Debabrata},
      date = {2015-10-18},
      pages = {FTu5E.5},
      publisher = {{Optical Society of America}},
      doi = {10/gf5msf},
      url = {https://www.osapublishing.org/abstract.cfm?uri=FiO-2015-FTu5E.5},
      urldate = {2019-08-01},
      eventtitle = {Frontiers in {{Optics}}},
      file = {/run/media/haozeke/Storage/Zotero/storage/E29QKCA3/abstract.html},
      keywords = {Femtosecond pulses,Molecules,Refractive index,Spectroscopy,Temperature,Thermal lensing},
      langid = {english}
    }
    
  3. Measurement of Pure Optical Nonlinearity in Carbon Disulfide with a High-Repetition-Rate Femtosecond Laser. S. Singhal, S. Dinda, and D. Goswami, Applied Optics 56(3), 644 (2017) [PDF] [BibTeX]
     BibTeX: @article{singhalMeasurementPureOptical2017,
      title = {Measurement of Pure Optical Nonlinearity in Carbon Disulfide with a High-Repetition-Rate Femtosecond Laser},
      author = {Singhal, Sumit and Dinda, Sirshendu and Goswami, Debabrata},
      date = {2017-01-20},
      journaltitle = {Applied Optics},
      shortjournal = {Appl. Opt.},
      volume = {56},
      pages = {644},
      issn = {0003-6935, 1539-4522},
      doi = {10/gf5mrm},
      url = {https://www.osapublishing.org/abstract.cfm?URI=ao-56-3-644},
      urldate = {2019-08-01},
      file = {/run/media/haozeke/Storage/Zotero/storage/NIGDGEXQ/dgoswamiFemtoLab-Singhal_et_al_2017_Measurement_of_pure_optical_nonlinearity_in_carbon_disulfide_with_a.pdf},
      keywords = {_tablet},
      langid = {english},
      number = {3}
    }
    
  4. Molecular Size and Mass Sensitive Femtosecond Thermal Spectrometer. S. Singhal, S. Goswami, A. Banerjee, and D. Goswami, in 2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) (2019), pp. 1–3 [Abstract] [BibTeX]

    Abstract: Though a single ultrashort pulse has inconceivable thermal effect, highly repetitive femtosecond lasers often result in some heating effects. Instead of fretting over the thermal effect, we have used this to develop the time-resolved photothermal lens spectroscopy for molecular sensitivity.

     BibTeX: @inproceedings{singhalMolecularSizeMass2019,
      title = {Molecular {{Size}} and {{Mass Sensitive Femtosecond Thermal Spectrometer}}},
      booktitle = {2019 {{URSI Asia}}-{{Pacific Radio Science Conference}} ({{AP}}-{{RASC}})},
      author = {Singhal, Sumit and Goswami, Sonaly and Banerjee, A. and Goswami, Debabrata},
      date = {2019-03},
      pages = {1--3},
      doi = {10/gf5mqh},
      eventtitle = {2019 {{URSI Asia}}-{{Pacific Radio Science Conference}} ({{AP}}-{{RASC}})},
      file = {/run/media/haozeke/Storage/Zotero/storage/63S9ESEQ/dgoswamiFemtoLab-Singhal_et_al_2019_Molecular_Size_and_Mass_Sensitive_Femtosecond_Thermal_Spectrometer.pdf;/run/media/haozeke/Storage/Zotero/storage/QYIN97QW/8738561.html},
      keywords = {_tablet,heating effects,high-speed optical techniques,highly repetitive femtosecond lasers,inconceivable thermal effect,Laser beams,Laser excitation,laser materials processing,lenses,Measurement by laser beam,molecular sensitivity,photothermal effects,Probes,Pulsed laser deposition,Sensitivity,single ultrashort pulse,Spectroscopy}
    }
    
  5. Sensitive Dual Beam Thermal Lens Detection of Convection in Methanol. S. Singhal and D. Goswami, in 13th International Conference on Fiber Optics and Photonics (OSA, 2016), p. P1A.16 [Abstract] [PDF] [BibTeX]

    Abstract: We show that dual beam mode mismatched thermal lens (TL) technique is more sensitive than the single beam one. Presence of unusual peak inside the dual beam TL signal directly indicates strong convection.

     BibTeX: @inproceedings{singhalSensitiveDualBeam2016,
      title = {Sensitive Dual Beam Thermal Lens Detection of Convection in Methanol},
      booktitle = {13th {{International Conference}} on {{Fiber Optics}} and {{Photonics}}},
      author = {Singhal, Sumit and Goswami, Debabrata},
      date = {2016},
      pages = {P1A.16},
      publisher = {{OSA}},
      location = {{Kanpur}},
      doi = {10.1364/PHOTONICS.2016.P1A.16},
      url = {https://www.osapublishing.org/abstract.cfm?URI=Photonics-2016-P1A.16},
      urldate = {2019-08-01},
      eventtitle = {International {{Conference}} on {{Fibre Optics}} and {{Photonics}}},
      file = {/run/media/haozeke/Storage/Zotero/storage/55LUUQTG/dgoswamiFemtoLab-Singhal_Goswami_2016_Sensitive_dual_beam_thermal_lens_detection_of_convection_in_methanol.pdf},
      isbn = {978-1-943580-22-4},
      keywords = {_tablet},
      langid = {english}
    }
    
  6. Thermal Lens Study of NIR Femtosecond Laser-Induced Convection in Alcohols. S. Singhal and D. Goswami, ACS Omega 4(1), 1889–1896 (2019) [Abstract] [PDF] [BibTeX]

    Abstract: We use time-resolved thermal lens (TL) experiments to examine the convective heat transfer at microscale in the first eight members of the homologous series of primary alcohols. TL measurements enable a direct study of these primary alcohols without adding any chromophore as a function of varying heat loads created via femtosecond laser pulses at 1560 nm. Convective heat transfer leads to the asymmetrical and reduced thermal gradient, which substantially weakens the TL signal. The inflection in the time profile of the TL signal of methanol at higher powers is attributed to the greater molecular convection in methanol compared to other samples. This inflection dies out with a decrease in laser power. Our results demonstrate that the convection is more prominent at higher laser powers in all samples, and it modifies the trend in the steady-state TL signal of different alcohols with pump laser power. Methanol also has the highest steady-state TL among the primary alcohol series at low laser powers. The maxima in the TL signal are shifted systematically from methanol to ethanol and then to propanol as the laser power increases. Semiempirical analysis of time-resolved TL signal by using the latest theoretical TL model enabled us to extract the coefficient of convective heat transfer in methanol at different laser powers. In addition to that, analysis of other members of alcohol series at the highest (7.3 mW) laser power shows that convection is more facile in short-chain alcohols compared to the long-chain alcohols.

     BibTeX: @article{singhalThermalLensStudy2019,
      title = {Thermal {{Lens Study}} of {{NIR Femtosecond Laser}}-{{Induced Convection}} in {{Alcohols}}},
      author = {Singhal, Sumit and Goswami, Debabrata},
      date = {2019-01-31},
      journaltitle = {ACS Omega},
      shortjournal = {ACS Omega},
      volume = {4},
      pages = {1889--1896},
      issn = {2470-1343, 2470-1343},
      doi = {10/gf5mp4},
      url = {http://pubs.acs.org/doi/10.1021/acsomega.8b02956},
      urldate = {2019-08-01},
      file = {/run/media/haozeke/Storage/Zotero/storage/PHP3T9BV/dgoswamiFemtoLab-Singhal_Goswami_2019_Thermal_Lens_Study_of_NIR_Femtosecond_Laser-Induced_Convection_in_Alcohols.pdf},
      keywords = {_tablet},
      langid = {english},
      number = {1}
    }
    
  7. Unraveling the Molecular Dependence of Femtosecond Laser-Induced Thermal Lens Spectroscopy in Fluids. S. Singhal and D. Goswami, The Analyst 10.1039.C9AN01082C (2020) [Abstract] [PDF] [BibTeX]

    Abstract: Fluid systems exhibit thermal lens effects due to laser irradiation accompanied by convection and in contrast primarily conductive heat dissipation is observed in solids. , Fluid systems exhibit thermal lens effects due to laser irradiation accompanied by convection and in contrast primarily conductive heat dissipation is observed in solids. The presence of a significant convective mode modifies the temperature gradient in fluids resulting in a deviation of the experimental results from theories that are based on pure conduction. Herein, we present a carefully designed femtosecond laser experiment that keeps the heat generation process constant in order to account for the effect of molecular properties on thermal dissipation. We derive a theoretical model that introduces and characterizes the additional convective heat transfer in thermal lens (TL) spectroscopy which explains our observed experimental results. We measured the TL signal for a series of liquid aliphatic alkanes, ranging from hexane to decane, and their comparison has proven the validity of our model. The influence of convective heat transfer on the TL signal is predicted in terms of the dimensionless Peclet number ( P E ). The lower values of P E for alkanes with longer carbon chains indicate that the convective flow of heat slows down substantially for larger molecules.

     BibTeX: @article{singhalUnravelingMolecularDependence2020,
      title = {Unraveling the Molecular Dependence of Femtosecond Laser-Induced Thermal Lens Spectroscopy in Fluids},
      author = {Singhal, Sumit and Goswami, Debabrata},
      date = {2020},
      journaltitle = {The Analyst},
      shortjournal = {Analyst},
      pages = {10.1039.C9AN01082C},
      issn = {0003-2654, 1364-5528},
      doi = {10/ggfxvz},
      url = {http://xlink.rsc.org/?DOI=C9AN01082C},
      urldate = {2019-12-28},
      file = {/run/media/haozeke/Storage/Zotero/storage/3TH7X6G3/Singhal and Goswami - 2020 - Unraveling the molecular dependence of femtosecond.pdf},
      langid = {english}
    }
    
  8. Thermal Lens Study of NIR Femtosecond Laser-Induced Convection in Alcohols. S. Singhal and D. Goswami, ACS Omega 4(1), 1889–1896 (2019) [Abstract] [PDF] [BibTeX]

    Abstract: We use time-resolved thermal lens (TL) experiments to examine the convective heat transfer at microscale in the first eight members of the homologous series of primary alcohols. TL measurements enable a direct study of these primary alcohols without adding any chromophore as a function of varying heat loads created via femtosecond laser pulses at 1560 nm. Convective heat transfer leads to the asymmetrical and reduced thermal gradient, which substantially weakens the TL signal. The inflection in the time profile of the TL signal of methanol at higher powers is attributed to the greater molecular convection in methanol compared to other samples. This inflection dies out with a decrease in laser power. Our results demonstrate that the convection is more prominent at higher laser powers in all samples, and it modifies the trend in the steady-state TL signal of different alcohols with pump laser power. Methanol also has the highest steady-state TL among the primary alcohol series at low laser powers. The maxima in the TL signal are shifted systematically from methanol to ethanol and then to propanol as the laser power increases. Semiempirical analysis of time-resolved TL signal by using the latest theoretical TL model enabled us to extract the coefficient of convective heat transfer in methanol at different laser powers. In addition to that, analysis of other members of alcohol series at the highest (7.3 mW) laser power shows that convection is more facile in short-chain alcohols compared to the long-chain alcohols.

     BibTeX: @article{singhalThermalLensStudy2020,
      langid = {english},
      title = {Thermal {{Lens Study}} of {{NIR Femtosecond Laser}}-{{Induced Convection}} in {{Alcohols}}},
      volume = {4},
      issn = {2470-1343, 2470-1343},
      url = {http://pubs.acs.org/doi/10.1021/acsomega.8b02956},
      doi = {10/gf5mp4},
      number = {1},
      journaltitle = {ACS Omega},
      urldate = {2019-08-01},
      date = {2019-01-31},
      pages = {1889-1896},
      author = {Singhal, Sumit and Goswami, Debabrata}
    }
    
  9. Molecular Size and Mass Sensitive Femtosecond Thermal Spectrometer. S. Singhal, S. Goswami, A. Banerjee, and D. Goswami, in 2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) (2019), pp. 1–3 [Abstract] [BibTeX]

    Abstract: Though a single ultrashort pulse has inconceivable thermal effect, highly repetitive femtosecond lasers often result in some heating effects. Instead of fretting over the thermal effect, we have used this to develop the time-resolved photothermal lens spectroscopy for molecular sensitivity.

     BibTeX: @inproceedings{singhalMolecularSizeMass2020,
      title = {Molecular {{Size}} and {{Mass Sensitive Femtosecond Thermal Spectrometer}}},
      doi = {10/gf5mqh},
      eventtitle = {2019 {{URSI Asia}}-{{Pacific Radio Science Conference}} ({{AP}}-{{RASC}})},
      booktitle = {2019 {{URSI Asia}}-{{Pacific Radio Science Conference}} ({{AP}}-{{RASC}})},
      date = {2019-03},
      pages = {1-3},
      author = {Singhal, S. and Goswami, S. and Banerjee, A. and Goswami, D.}
    }
    
  10. Measurement of Pure Optical Nonlinearity in Carbon Disulfide with a High-Repetition-Rate Femtosecond Laser. S. Singhal, S. Dinda, and D. Goswami, Appl. Opt. 56(3), 644 (2017) [PDF] [BibTeX]
     BibTeX: @article{singhalMeasurementPureOptical2018,
      langid = {english},
      title = {Measurement of Pure Optical Nonlinearity in Carbon Disulfide with a High-Repetition-Rate Femtosecond Laser},
      volume = {56},
      issn = {0003-6935, 1539-4522},
      url = {https://www.osapublishing.org/abstract.cfm?URI=ao-56-3-644},
      doi = {10/gf5mrm},
      number = {3},
      journaltitle = {Appl. Opt.},
      urldate = {2019-08-01},
      date = {2017-01-20},
      pages = {644},
      author = {Singhal, Sumit and Dinda, Sirshendu and Goswami, Debabrata}
    }
    
  11. Sensitive Dual Beam Thermal Lens Detection of Convection in Methanol. S. Singhal and D. Goswami, in 13th International Conference on Fiber Optics and Photonics (OSA, 2016), p. P1A.16 [Abstract] [PDF] [BibTeX]

    Abstract: We show that dual beam mode mismatched thermal lens (TL) technique is more sensitive than the single beam one. Presence of unusual peak inside the dual beam TL signal directly indicates strong convection.

     BibTeX: @inproceedings{singhalSensitiveDualBeam2017,
      langid = {english},
      location = {{Kanpur}},
      title = {Sensitive Dual Beam Thermal Lens Detection of Convection in Methanol},
      isbn = {978-1-943580-22-4},
      url = {https://www.osapublishing.org/abstract.cfm?URI=Photonics-2016-P1A.16},
      doi = {10.1364/PHOTONICS.2016.P1A.16},
      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 = {P1A.16},
      author = {Singhal, Sumit and Goswami, Debabrata}
    }
    
  12. Exploring the Critical Role of Detection Aperture in Thermal Lens Measurements. S. Singhal, I. Bhattacharyya, and D. Goswami, in 2015 Workshop on Recent Advances in Photonics (WRAP) (2015), pp. 1–4 [Abstract] [BibTeX]

    Abstract: The critical role of the detection aperture size on the measurement of thermal lens signals has been explored by using mode-mismatched pump-probe thermal lens spectroscopy in pure methanol. Femtosecond laser pulses at 1560 nm are used to create thermal lens signal, which is simultaneously probed by a collinear 780 nm pulse train through a partially open aperture of different sizes placed after the sample. The trend in the time resolved thermal lens signals reveals that aperture size allowing less than half of the incident probe light is critical in providing accuracy of the thermal lens spectroscopy.

     BibTeX: @inproceedings{singhalExploringCriticalRole2016,
      title = {Exploring the Critical Role of Detection Aperture in Thermal Lens Measurements},
      doi = {10/gf5msd},
      eventtitle = {2015 {{Workshop}} on {{Recent Advances}} in {{Photonics}} ({{WRAP}})},
      booktitle = {2015 {{Workshop}} on {{Recent Advances}} in {{Photonics}} ({{WRAP}})},
      date = {2015-12},
      pages = {1-4},
      author = {Singhal, S. and Bhattacharyya, I. and Goswami, D.}
    }
    
  13. Importance of Hydrogen Bonding in Thermal Lens Study of Highly Absorbing Liquids. S. Singhal, P. P. Roy, and D. Goswami, in Frontiers in Optics 2015 (2015), Paper FTu5E.5 (Optical Society of America, 2015), p. FTu5E.5 [Abstract] [PDF] [BibTeX]

    Abstract: Effect of thermal load on highly absorbing hydrogen bonded liquids are explored. We find heat transfer is better facilitated in lesser hydrogen bonded liquids by convection through molecular motion in addition to conduction.

     BibTeX: @inproceedings{singhalImportanceHydrogenBonding2016,
      langid = {english},
      title = {Importance of {{Hydrogen Bonding}} in {{Thermal Lens Study}} of {{Highly Absorbing Liquids}}},
      url = {https://www.osapublishing.org/abstract.cfm?uri=FiO-2015-FTu5E.5},
      doi = {10/gf5msf},
      eventtitle = {Frontiers in {{Optics}}},
      booktitle = {Frontiers in {{Optics}} 2015 (2015), Paper {{FTu5E}}.5},
      publisher = {{Optical Society of America}},
      urldate = {2019-08-01},
      date = {2015-10-18},
      pages = {FTu5E.5},
      author = {Singhal, Sumit and Roy, Partha Pratim and Goswami, Debabrata}
    }