Thermal Effects and Sensing

Molecular Dynamics and Interfaces

Spectroscopy and insights in-to thermal effects. Breaking barriers to establish state-of-the-art sensing technology.

In our lab we go across different phases of matter: solids, liquids and gases. We have solids where we do studies in crystals and glass plates. We have looked at thin films. Then we go to liquids; we do dynamics of liquids, measure two-photon fluorescence, two-photon absorption, two-photon cross-sections etc. We have a molecular beam chamber. Also we work in interfaces which are between liquid-liquid, and liquid-solid. The basic idea behind doing this is, it has connection to biology. Another very interesting work is, how long phenomena effecting short term phenomena like temperature. Temperature as all know that is long term phenomena. But we have found that a long term phenomenon has important impact on short term phenomena. The important work in this direction started form the time of Mathies and Shank, where they showed that the ultimate concept of our vision which is in nanoseconds or longer actually starts at femtoseconds. They showed that the primary proton transfer process occurs in less than femtoseconds which is the trigger for the rhodopsin molecules to start the process of optical nerve firing and that finally gives rise to the image. We are interested in seeing how these eventual phenomena are actually connected.

Our work in this field spans decades from [1,2,3,4] to [5,6]

In particular, the lab has generated breakthrough insights into the thermal relaxation process and has gone on to show usage in nano-scale temperature sensing in [7,8,9,10]


Full list here.

  1. Laser-Enhanced NMR Spectroscopy. W. S. Warren, S. Mayr, D. Goswami, and A. P. West, Science 255(5052), 1683–1685 (1992) [Abstract] [PDF] [BibTeX]

    Abstract: Experimental studies show that optical irradiation far from any absorption bands can shift the resonances in a nuclear magnetic resonance (NMR) spectrum without significant heating. This effect may lead to increased dispersion in NMR studies of complex molecules.

     BibTeX: @article{warrenLaserenhancedNMRSpectroscopy1992,
      title = {Laser-Enhanced {{NMR}} Spectroscopy},
      author = {Warren, W. S. and Mayr, S. and Goswami, D. and West, A. P.},
      date = {1992-03-27},
      journaltitle = {Science},
      volume = {255},
      number = {5052},
      eprint = {1553555},
      eprinttype = {pmid},
      pages = {1683--1685},
      issn = {0036-8075, 1095-9203},
      doi = {10/fr8pjn},
      url = {},
      urldate = {2019-08-14}
  2. Control of Chemical Dynamics by Restricting Intramolecular Vibrational Relaxation. D. Goswami and W. S. Warren, The Journal of Chemical Physics 99(6), 4509–4517 (1993) [Abstract] [PDF] [BibTeX]

    Abstract: We address the issue of localization of bond energy in a molecule by stopping intramolecular vibrational relaxation (IVR). We show through model calculations that appropriate frequency sweeps permit selective locking over a well‐defined range of resonance frequencies, with little excitation outside that range. We also propose a modified version of an adiabatic half passage experiment that will perform photon locking without complications from inhomogeneities or partial excitation of other transitions for a bright state coupled to a finite number of dark states.

     BibTeX: @article{goswamiControlChemicalDynamics1993,
      title = {Control of Chemical Dynamics by Restricting Intramolecular Vibrational Relaxation},
      author = {Goswami, Debabrata and Warren, Warren S.},
      date = {1993-09-15},
      journaltitle = {The Journal of Chemical Physics},
      shortjournal = {J. Chem. Phys.},
      volume = {99},
      number = {6},
      pages = {4509--4517},
      issn = {0021-9606},
      doi = {10/bjh64b},
      url = {},
      urldate = {2019-08-14}
  3. Altering Excitation Dynamics in Optically Dense Media Using Shaped Ultrafast Laser Pulses. J. C. Davis, M. R. Fetterman, D. Goswami, Wei Guo Yang, D. Keusters, and W. S. Warren, in Technical Digest. Summaries of Papers Presented at the Quantum Electronics and Laser Science Conference (1999), pp. 107–108 [Abstract] [BibTeX]

    Abstract: Summary form only given. We study the interaction between intense (50 MW peak power), shaped ultrafast laser pulses and optically dense samples of Rb vapor. In particular, we concentrate our attention on laser pulses with a the complex hyperbolic secant envelope, or equivalently, a sech electric field envelope with a tanh frequency sweep. In order to produce and characterize the shaped laser pulses used in our experiments, we exploited several new technologies: amplified, shaped laser pulses were generated using an acousto-optic modulator-based system combined with a chirped-pulse regenerative amplifier. The amplitude and phase of these pulses were then characterized by the STRUT (spectrally and temporally resolved upconversion technique). The STRUT was used to measure the laser pulses both before and after propagating through Rb vapor. Examples of such experimental STRUT images are presented. The complex sech pulse was selected because, in optically thin media, only it and rectangular pulses give complete analytical solutions to the Bloch equations. This shape has been found to generate complete population inversion over a well-defined and amplitude-insensitive bandwidth. In optically dense samples the excited state dynamics are not so straightforward. We have found, both in experiments and theoretically, that the extent and character of the population inversion is related to the frequency sweep of the laser pulses as does the amount of residual excited population after the pulse and any subsequent stimulated emission.

     BibTeX: @inproceedings{davisAlteringExcitationDynamics1999,
      title = {Altering Excitation Dynamics in Optically Dense Media Using Shaped Ultrafast Laser Pulses},
      booktitle = {Technical {{Digest}}. {{Summaries}} of {{Papers Presented}} at the {{Quantum Electronics}} and {{Laser Science Conference}}},
      author = {Davis, J. C. and Fetterman, M. R. and Goswami, D. and {Wei Guo Yang} and Keusters, D. and Warren, W. S.},
      date = {1999-05},
      pages = {107--108},
      doi = {10/cbtw6x},
      eventtitle = {Technical {{Digest}}. {{Summaries}} of {{Papers Presented}} at the {{Quantum Electronics}} and {{Laser Science Conference}}}
  4. Protein Dynamics Derived from Clusters of Crystal Structures. Biophysical Journal 73(6), 2891–2896 (1997) [Abstract] [PDF] [BibTeX]

    Abstract: A method is presented to mathematically extract concerted structural transitions in proteins from collections of crystal structures. The "essential dynamics" procedure is used to filter out small-amplitude fluctuations from such a set of structures; the remaining large conformational changes describe motions such as those important for the uptake/release of substrate/ligand and in catalytic reactions. The method is applied to sets of x-ray structures for a number of proteins, and the results are compared with the results from essential dynamics as applied to molecular dynamics simulations of those proteins. A significant degree of similarity is found, thereby providing a direct experimental basis for the application of such simulations to the description of large concerted motions in proteins.

     BibTeX: @article{vanaaltenProteinDynamicsDerived1997,
      title = {Protein Dynamics Derived from Clusters of Crystal Structures},
      author = {},
      date = {1997-12-01},
      journaltitle = {Biophysical Journal},
      shortjournal = {Biophysical Journal},
      volume = {73},
      number = {6},
      pages = {2891--2896},
      issn = {0006-3495},
      doi = {10/bkftm3},
      url = {},
      urldate = {2019-10-01}
  5. Controlling and Tracking of Colloidal Nanostructures through Two-Photon Fluorescence. D. Mondal and D. Goswami, Methods and Applications in Fluorescence 4(4), 044004 (2016) [Abstract] [PDF] [BibTeX]

    Abstract: Multiphoton absorbing dye-coated trapped spherical bead at the focal plane of femtosecond optical tweezers shows nonlinear optical (NLO) phenomena. One such NLO process of two-photon fluorescence (TPF) has been used for the background-free imaging of a femtosecond laser-trapping event. Due to the high peak powers of femtosecond laser pulses with low average powers, it is possible to not only trap single nanospheres, but encourage optically directed self-assembly. The TPF signatures of trapped particles show evidence of such a directed self-assembly process which, in turn, can provide information about the structural dynamics during the process of cluster formation. We are able to trap and characterize structure and dynamics in 3D until pentamer formation from the decay characteristics of trapping at the focal plane.

     BibTeX: @article{mondalControllingTrackingColloidal2016,
      title = {Controlling and Tracking of Colloidal Nanostructures through Two-Photon Fluorescence},
      author = {Mondal, Dipankar and Goswami, Debabrata},
      date = {2016-10-07},
      journaltitle = {Methods and Applications in Fluorescence},
      shortjournal = {Methods Appl. Fluoresc.},
      volume = {4},
      number = {4},
      pages = {044004},
      issn = {2050-6120},
      doi = {10/gf5mrw},
      url = {},
      urldate = {2019-08-01}
  6. Two Photon Spectroscopy Can Serve as a Marker of Protein Denaturation Pathway. D. K. Das, S. I. Islam, N. Samanta, Y. Yadav, D. Goswami, and R. K. Mitra, Journal of Fluorescence 28(3), 855–862 (2018) [PDF] [BibTeX]
     BibTeX: @article{dasTwoPhotonSpectroscopy2018,
      title = {Two {{Photon Spectroscopy Can Serve}} as a {{Marker}} of {{Protein Denaturation Pathway}}},
      author = {Das, Dipak Kumar and Islam, Sk Imadul and Samanta, Nirnay and Yadav, Yogendra and Goswami, Debabrata and Mitra, Rajib Kumar},
      date = {2018-05},
      journaltitle = {Journal of Fluorescence},
      shortjournal = {J Fluoresc},
      volume = {28},
      number = {3},
      pages = {855--862},
      issn = {1053-0509, 1573-4994},
      doi = {10/gd2g84},
      url = {},
      urldate = {2019-08-01}
  7. Precise Control and Measurement of Temperature with Femtosecond Optical Tweezers. D. Mondal and D. Goswami, Biophysical Journal 110(3), 500a (2016) [Abstract] [PDF] [BibTeX]

    Abstract: Optical traps have often been used for physical manipulation and transport within liquids for studying bio-systems. In this connection, though a lot of work has focused on the property of the trapped particle, there is little effort on utilizing the effect of the trapping environment. Here we demonstrate a novel method for exploiting the effect of trapping environment in observing the temperature rise in liquids directly at the vicinity of an optical trap center. Our approach utilizes the photo-thermal effect at micro-volume dimension to measure temperature, which could eventually be extended to in-vivo conditions. Our two-color experiment is a unique combination of a non-heating femtosecond trapping laser at 780 nm, which is coupled to a femtosecond infrared heating laser at 1560 nm. Femtosecond pulsed laser heating is much more effective than the traditional continuous-wave laser, which increases the sensitivity of our measurements. The heating laser precisely controls temperature at the focal volume of the trap center using low powers at high repetition rate. The changed values of corner frequency of the optical trap due to this local heating is recognized from its power spectra. The solvent having hydroxyl group is very sensitive to 1560 nm laser due to non-radiative relaxation from their higher excited state. Since most bio-systems contain hydroxyl group, they would be highly responsive to our heating laser, while our trapping laser is highly transparent for such systems. Our method could be used to specifically heat a particular cell to evaluate its faster cell division and also can be utilized for the possible phototherapy of cancer cells. The advantage of this technique over the conventional phototherapy is that this is highly localized due to focusing through high numerical aperture resulting in a high gradient of temperature.

     BibTeX: @article{mondalPreciseControlMeasurement2016,
      title = {Precise {{Control}} and {{Measurement}} of {{Temperature}} with {{Femtosecond Optical Tweezers}}},
      author = {Mondal, Dipankar and Goswami, Debabrata},
      date = {2016-02},
      journaltitle = {Biophysical Journal},
      shortjournal = {Biophysical Journal},
      volume = {110},
      number = {3},
      pages = {500a},
      issn = {00063495},
      doi = {10/gf5mr6},
      url = {},
      urldate = {2019-08-01}
  8. Effect of Femtosecond Laser Pulse Repetition Rate on Nonlinear Optical Properties of Organic Liquids. S. K. Maurya, D. Yadav, and D. Goswami, PeerJ Physical Chemistry 1, e1 (2019) [Abstract] [PDF] [BibTeX]

    Abstract: The effect of the repetition rate of femtosecond laser pulses on the two-photon absorption and nonlinear refraction of pure organic liquids is presented using the conventional Z-scan technique. Such a study provides a way to determine the nature of light-matter interaction, explicitly enabling the identification of the linear versus nonlinear regimes. Based on the type of light-matter interaction, we have identified the thermal load dissipation time for the organic liquids. Our experimental results are in good agreement with the theoretically calculated decay time for the dissipation of thermal load.

     BibTeX: @article{mauryaEffectFemtosecondLaser2019,
      title = {Effect of Femtosecond Laser Pulse Repetition Rate on Nonlinear Optical Properties of Organic Liquids},
      author = {Maurya, Sandeep Kumar and Yadav, Dheerendra and Goswami, Debabrata},
      date = {2019-10-15},
      journaltitle = {PeerJ Physical Chemistry},
      volume = {1},
      pages = {e1},
      doi = {10/ggbzhh},
      url = {},
      urldate = {2019-10-29}
  9. On-the-Fly Calibrated Measure and Remote Control of Temperature and Viscosity at Nanoscale. D. Mondal, S. N. Bandyopadhyay, P. Mathur, and D. Goswami, ACS Omega 3(9), 12304–12311 (2018) [Abstract] [PDF] [BibTeX]

    Abstract: A novel on-the-f ly calibration method of optical tweezers is presented, which enables in situ control and measure of absolute temperature and viscosity at nanoscale dimensions. Such noncontact measurement and control at the nanoscale are challenging as the present techniques only provide off-line measurements that do not provide absolute values. Additionally, some of the present methods have a low spatial resolution. We simultaneously apply the high temporal sensitivity of position autocorrelation and equipartition theorem to precisely measure and control in situ temperature and the corresponding microrheological property around the focal volume of the trap at high spatial resolution. The femtosecond optical tweezers (FOTs) use a single-beam high repetition rate laser for optical trapping to result in finer temperature gradients in comparison to the continuous-wave laser tweezers. Such finer temperature gradients are due to the additional nonlinear optical (NLO) phenomena occurring only at the nanoscale focal plane of the FOTs. Because NLO processes are laser peak power-dependent, they promote an effective study of physical properties occurring only at the focal plane. Using FOTs at optically benign near-infrared wavelengths, we demonstrate microrheological control and measurement in water by adding a highly absorbing yet low fluorescent dye (IR780).

     BibTeX: @article{mondalOntheFlyCalibratedMeasure2018,
      title = {On-the-{{Fly Calibrated Measure}} and {{Remote Control}} of {{Temperature}} and {{Viscosity}} at {{Nanoscale}}},
      author = {Mondal, Dipankar and Bandyopadhyay, Soumendra Nath and Mathur, Paresh and Goswami, Debabrata},
      date = {2018-09-30},
      journaltitle = {ACS Omega},
      shortjournal = {ACS Omega},
      volume = {3},
      number = {9},
      pages = {12304--12311},
      issn = {2470-1343, 2470-1343},
      doi = {10/gff5s6},
      url = {},
      urldate = {2019-08-01}
  10. Sensitive in Situ Nanothermometer Using Femtosecond Optical Tweezers. D. Mondal and D. Goswami, Journal of Nanophotonics 10(2), 026013 (2016) [Abstract] [PDF] [BibTeX]

    Abstract: We report the rise in temperature in various liquid media adjacent to a trapped bead. A nonheating laser at 780 nm has been used to optically trap a 500-nm radius polystyrene bead, while a simultaneous irradiation with a copropagating 1560-nm high-repetition-rate femtosecond laser led to temperature rise in various trapping media. Vibrational combination band of the hydroxyl group in the trapping media resulted in high absorption of 1560-nm laser. This, in turn, gave us control over the trapping media temperature at the focus of the optical trap.

     BibTeX: @article{mondalSensitiveSituNanothermometer2016,
      title = {Sensitive in Situ Nanothermometer Using Femtosecond Optical Tweezers},
      author = {Mondal, Dipankar and Goswami, Debabrata},
      date = {2016-05},
      journaltitle = {Journal of Nanophotonics},
      shortjournal = {JNP},
      volume = {10},
      number = {2},
      pages = {026013},
      issn = {1934-2608, 1934-2608},
      doi = {10/f832c9},
      url = {},
      urldate = {2019-08-01}