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 (missing reference)

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 [1,2,3,4]


Full list here.

  1. Precise Control and Measurement of Solid–Liquid Interfacial Temperature and Viscosity Using Dual-Beam Femtosecond Optical Tweezers in the Condensed Phase. D. Mondal, P. Mathur, and D. Goswami, Physical Chemistry Chemical Physics 18(37), 25823–25830 (2016) [Abstract] [PDF] [BibTeX]

    Abstract: We present a novel method of microrheology based on femtosecond optical tweezers, which in turn enables us to directly measure and control in situ temperature at microscale volumes at the solid–liquid interface. A noninvasive pulsed 780 nm trapped bead spontaneously responds to changes in its environment induced by a co-propagating 1560 nm pulsed laser due to mutual energy transfer between the solvent molecules and the trapped bead. Strong absorption of the hydroxyl group by the 1560 nm laser creates local heating in individual and binary mixtures of water and alcohols. “Hot Brownian motion” of the trapped polystyrene bead is reflected in the corner frequency deduced from the power spectrum. Changes in corner frequency values enable us to calculate the viscosity as well as temperature at the solid–liquid interface. We show that these experimental results can also be theoretically ratified.

     BibTeX: @article{mondalPreciseControlMeasurement2016b,
      title = {Precise Control and Measurement of Solid–Liquid Interfacial Temperature and Viscosity Using Dual-Beam Femtosecond Optical Tweezers in the Condensed Phase},
      author = {Mondal, Dipankar and Mathur, Paresh and Goswami, Debabrata},
      date = {2016},
      journaltitle = {Physical Chemistry Chemical Physics},
      volume = {18},
      pages = {25823--25830},
      doi = {10/gf5mr8},
      url = {},
      urldate = {2019-08-01},
      keywords = {_tablet},
      langid = {english},
      number = {37}
  2. 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},
      langid = {english}
  3. 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{mondalOntheFlyCalibratedMeasure2018a,
      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},
      pages = {12304--12311},
      issn = {2470-1343, 2470-1343},
      doi = {10/gff5s6},
      url = {},
      urldate = {2019-08-01},
      keywords = {_tablet},
      langid = {english},
      number = {9}
  4. 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{mondalSensitiveSituNanothermometer2016a,
      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},
      pages = {026013},
      issn = {1934-2608, 1934-2608},
      doi = {10/f832c9},
      url = {},
      urldate = {2019-08-01},
      keywords = {_tablet},
      number = {2}