Shirshendu Dinda

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Education / Work History

• Post Doctoral Research Associate, S. N. Bose National Centre for Basic Sciences (2017-present)
• Ph.D. Scholar, IIT Kanpur (2010-2017)
• M.Sc., IIT Kanpur

Thesis Abstract

Engineering Optical Spatiotemporal Properties to Impact Femtosecond Nonlinearities: Case Studies and Implementations

The subjects of this thesis revolve around processes that change or control Spatiotemporal properties of laser pulses and their interactions. In Chapter 1 brief history of light-matter interaction is described. Through their duality nature, one can comprehend such properties and interactions independently. The regimes where they act with each other differently are also described. Vectorial imaging is an integrated part of optical imaging and microscopy in general. The main goal in any kind of microscope is the enhancements of image quality, i.e. resolution, contrast, etc. One of the popular methods is to use high numerical aperture (NA) objective lens (OL). The properties in the focal region of a high NA OL is quite different from properties predicted by the Rayleigh postulate of imaging (i.e., diffraction limited spot-size). The vectorial properties of light (such as, the direction of electric field or polarization) plays a crucial role as the diffraction of light due to high NA OL changes intensity distribution of light in the focal region (hence the resolution) predicted by scalar imaging. The intensity distribution of light in the focal region of a high NA OL changes drastically as the shape of the light beam and the polarization change. In Chapter 2, mathematical and geometrical description of scalar and vector imaging are discussed. Depending on properties of the input beam one can generate several excitation spots in the focal region, which is quite useful in optical tweezers research. Changing the phase of the input beam creates an asymmetric distribution of light, which increases the spatial resolution. Chapter 3 is focused on optical pulse shaping. In general, optical pulses are very generic in their temporal shapes. Most common among them is the transform limited Gaussian pulse. Using basic principles of Fourier domain pulse modulation, one can transform properties of optical pulses into any arbitrary shapes and phases. There are several ways to implement this pulse shaping technique to generate desired pulses. AOM (acousto-optic modulator) method has been used to transfer desired information to the optical pulse, which is a fast modulator (much faster than the liquid crystal modulator, LCM) and generates background free shaped pulses. Though fast, AOM modulator cannot update the incoming modulation information faster than 100 kHz. In my work, I have shown that, though one cannot overcome this physical limit, there is a unique approach to generate average pulse shapes of the desired kind. In this technique one can generate an overwhelming number of output pulses with similar output envelops. Though envelops are same, many pulses are different in phase. This kind of pulse shaping is useful when one is performing experiments with fast sampling rate, where the exact phase of the optical pulse does not have a significant role. In Chapter 4, the generation process of femtosecond Supercontinuum (SC) in condensed (liquid) medium is explored. A brief description of the SC generation history and involved physical process are described in both graphical and mathematical representations. For better use of SC, we need to know how to control SC. In this chapter, we have generated SC in the near threshold regime and inspected the underlying processes involved in the SC generation process. Delicate interference structures appear in the supercontinuum in water and CCl4 as the energy of the input pulse crosses the threshold value. The fringe pattern in the SC spectrum gives information about the temporal separation and the quality of the SC sources.

Research Topic / Interest

• Solvation Dynamics in Deep Eutectic Solvents

Publications

These include only those published in our lab.

1. On the Interferometric Coherent Structures in Femtosecond Supercontinuum Generation. S. Dinda, S. N. Bandyopadhyay, and D. Goswami, Applied Physics B 122(5), 148 (2016) [Abstract] [PDF] [BibTeX]

   Abstract: We report structured interferometric features in femtosecond supercontinuum generation (FSG) with incident laser powers that are near threshold for FSG. We argue that near threshold, these structures arise from the coherent superposition of pulses that are split initially into two daughter pulses during FSG process. Increase in the input pulse energy generates multiple daughter fragments in the temporal domain to an extent that correlated interference structures are not measurable.

    BibTeX: @article{dindaInterferometricCoherentStructures2016,
     title = {On the Interferometric Coherent Structures in Femtosecond Supercontinuum Generation},
     author = {Dinda, Sirshendu and Bandyopadhyay, Soumendra Nath and Goswami, Debabrata},
     date = {2016-05-11},
     journaltitle = {Applied Physics B},
     shortjournal = {Appl. Phys. B},
     volume = {122},
     number = {5},
     pages = {148},
     issn = {1432-0649},
     doi = {10/gf5mr5},
     url = {https://my.pcloud.com/publink/show?code=XZfaxr7ZhXTWojTzmcfBOA16JDESUyR5fRWV},
     urldate = {2019-08-01}
   }
   

2. Rapid Programmable Pulse Shaping of Femtosecond Pulses at the MHz Repetition Rate. S. Dinda, S. N. Bandyopadhyay, and D. Goswami, OSA Continuum 2(4), 1386 (2019) [Abstract] [PDF] [BibTeX]

   Abstract: We have shown experimentally the successful engineering of femtosecond pulse shaping at a 76 MHz repetition rate input pulse with an acousto-optic modulator (AOM). High repetition rate (HRR) femtosecond laser pulse shaping using an AOM in the Fourier plane was incomprehensible because of its intrinsic 100 kHz acoustic update limit. We demonstrate an effective way of pulse selection and a calibration routine (Fourier shift theorem), which enables generation of ∼10 MHz shaped output pulses from the HRR input pulse train. We have generated a temporally shifted rectangular shaped pulse profile by applying modulation on both the phase and amplitude of the ‘sinc’ RF modulation function.

    BibTeX: @article{dindaRapidProgrammablePulse2019,
     title = {Rapid Programmable Pulse Shaping of Femtosecond Pulses at the {{MHz}} Repetition Rate},
     author = {Dinda, Sirshendu and Bandyopadhyay, Soumendra Nath and Goswami, Debabrata},
     date = {2019-04-15},
     journaltitle = {OSA Continuum},
     shortjournal = {OSA Continuum},
     volume = {2},
     number = {4},
     pages = {1386},
     issn = {2578-7519},
     doi = {10/gf4gtf},
     url = {https://www.osapublishing.org/abstract.cfm?URI=osac-2-4-1386},
     urldate = {2019-06-30}
   }
   

3. Vectorial Imaging Techniques for Insights into the Principles of Optical Tweezers. S. Dinda and D. Goswami, Asian Journal of Physics 28(10-12), 989–1013 (2020) [Abstract] [BibTeX]

   Abstract: Optical tweezers work on the principle that microscopic particles may be immobilized by the application of an intense photon flux, which may be attained under tight focusing conditions. To elucidate the behaviour and mechanism of this tweezing action, herein we perform numerical studies and investigate the intensity distribution at the focusing spot under tight focusing conditions. With a high numerical aperture optical lens, the influence of the incident beam polarization on the intensity distribution of focusing spot is very significant. A linearly polarized incident beam induces an asymmetric focusing spot, which is elongated along the polarization direction of the incident beam. The incident beam profile influences the shape of the focusing spot. We show here how introducing an optical mask in front of the optical lens can induce many impressive results; e.g., incident beam modulated by an amplitude mask induces a sub-diffraction limit focusing spot which is relevant to further studies on optical tweezers. We also demonstrate the effects of considering interfaces of different numerical apertures in an optical setup. Thus, we report on the multiple aspects of light-matter interactions for high numerical aperture lens setups, wherein we show through simulations and experiments, the characteristics of such systems that are of use to the broader optics community.

    BibTeX: @article{dindaVectorialImagingTechniques2020,
     title = {Vectorial Imaging Techniques for Insights into the Principles of Optical Tweezers},
     author = {Dinda, Sirshendu and Goswami, Debabrata},
     date = {2020-05-01},
     journaltitle = {Asian Journal of Physics},
     shortjournal = {Asian J. Phys.},
     volume = {28},
     number = {10-12},
     pages = {989--1013}
   }
   

4. Rapid Programmable Pulse Shaping of Femtosecond Pulses at the MHz Repetition Rate. S. Dinda, S. N. Bandyopadhyay, and D. Goswami, OSA Continuum 2(4), 1386 (2019) [Abstract] [PDF] [BibTeX]

   Abstract: We have shown experimentally the successful engineering of femtosecond pulse shaping at a 76 MHz repetition rate input pulse with an acousto-optic modulator (AOM). High repetition rate (HRR) femtosecond laser pulse shaping using an AOM in the Fourier plane was incomprehensible because of its intrinsic 100 kHz acoustic update limit. We demonstrate an effective way of pulse selection and a calibration routine (Fourier shift theorem), which enables generation of ∼10 MHz shaped output pulses from the HRR input pulse train. We have generated a temporally shifted rectangular shaped pulse profile by applying modulation on both the phase and amplitude of the ‘sinc’ RF modulation function.

    BibTeX: @article{dindaRapidProgrammablePulse2019b,
     langid = {english},
     title = {Rapid Programmable Pulse Shaping of Femtosecond Pulses at the {{MHz}} Repetition Rate},
     volume = {2},
     issn = {2578-7519},
     url = {https://my.pcloud.com/publink/show?code=XZDaxr7Z7j2h0Ej5kjfj9pVqlqwvHViq6oeX},
     doi = {10.1364/OSAC.2.001386},
     number = {4},
     journaltitle = {OSA Continuum},
     urldate = {2019-08-01},
     date = {2019-04-15},
     pages = {1386},
     author = {Dinda, Sirshendu and Bandyopadhyay, Soumendra Nath and Goswami, Debabrata}
   }
   

5. On the Interferometric Coherent Structures in Femtosecond Supercontinuum Generation. S. Dinda, S. N. Bandyopadhyay, and D. Goswami, Appl. Phys. B 122(5), 148 (2016) [Abstract] [PDF] [BibTeX]

   Abstract: We report structured interferometric features in femtosecond supercontinuum generation (FSG) with incident laser powers that are near threshold for FSG. We argue that near threshold, these structures arise from the coherent superposition of pulses that are split initially into two daughter pulses during FSG process. Increase in the input pulse energy generates multiple daughter fragments in the temporal domain to an extent that correlated interference structures are not measurable.

    BibTeX: @article{dindaInterferometricCoherentStructures2017,
     langid = {english},
     title = {On the Interferometric Coherent Structures in Femtosecond Supercontinuum Generation},
     volume = {122},
     issn = {1432-0649},
     url = {https://my.pcloud.com/publink/show?code=XZfaxr7ZhXTWojTzmcfBOA16JDESUyR5fRWV},
     doi = {10/gf5mr5},
     number = {5},
     journaltitle = {Appl. Phys. B},
     urldate = {2019-08-01},
     date = {2016-05-11},
     pages = {148},
     author = {Dinda, Sirshendu and Bandyopadhyay, Soumendra Nath and Goswami, Debabrata}
   }