Spatiotemporal Control

Femtosecond optical tweezers, pulse shaping, and two-photon microscopy

01 June 2016

Femtosecond optical tweezers and pulse shaping for simultaneous spatial and temporal control of molecules and colloidal particles.

Spatiotemporal control unifies two capabilities: spatial manipulation through optical trapping and temporal manipulation through femtosecond pulse shaping. Where conventional optical tweezers use continuous-wave lasers, the lab employs pulsed femtosecond tweezers that impart both spatial and temporal control simultaneously.

Femtosecond optical tweezers

Controlled spatial manipulation of translational degrees of freedom is essential for engineering intermolecular interactions and implementing molecular quantum logic. The lab’s femtosecond tweezers induce an effective molecular polarizability through ultrafast temporal modulations while simultaneously exploiting macroscopic light properties (polarization, photon flux) for spatial control. This allows trapping and steering of colloidal particles with femtosecond temporal resolution.

Pulse shaping as a Fourier bridge

The femtosecond pulse shaper converts between time and frequency domains via Fourier transform, serving as a bridge between spectroscopy, microscopy, and coherent control. The theoretical and experimental foundations of this approach are reviewed comprehensively in [1]. In spectroscopy the shaper provides frequency-domain selectivity; in microscopy it enables spatially resolved nonlinear excitation; in control it shapes the temporal profile of excitation pulses. This dual Fourier-domain picture connects applications ranging from biological imaging to quantum computing through the shared underlying physics of nonlinear light-matter interaction.

Two-photon studies

Two-photon absorption and fluorescence measurements probe molecular dynamics with intrinsic three-dimensional sectioning. Solvent effects on two-photon cross-sections and signal characteristics inform both the spectroscopy and the control aspects of the research program.

Representative work in this area includes [2,3,4].

Publications

Full list here.

1. Optical Pulse Shaping Approaches to Coherent Control. D. Goswami, Physics Reports 374(6), 385–481 (2003)

   BibTeX: @article{goswamiOpticalPulseShaping2003,
     title = {Optical Pulse Shaping Approaches to Coherent Control},
     author = {Goswami, Debabrata},
     year = {2003},
     month = feb,
     journal = {Physics Reports},
     volume = {374},
     number = {6},
     pages = {385--481},
     issn = {0370-1573},
     doi = {10/fwwrc5},
     urldate = {2019-08-14},
     annotation = {GSCC: 0000364 \\
     226 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: @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. Solvent Effect on Two-Photon Absorption and Fluorescence of Rhodamine Dyes. A. Nag and D. Goswami, Journal of Photochemistry and Photobiology A: Chemistry 206(2), 188–197 (2009)

   BibTeX: @article{nagSolventEffectTwophoton2009,
     title = {Solvent Effect on Two-Photon Absorption and Fluorescence of Rhodamine Dyes},
     author = {Nag, Amit and Goswami, Debabrata},
     year = {2009},
     month = aug,
     journal = {Journal of Photochemistry and Photobiology A: Chemistry},
     volume = {206},
     number = {2},
     pages = {188--197},
     issn = {1010-6030},
     doi = {10/c4zdx8},
     urldate = {2019-08-14},
     annotation = {GSCC: 0000110 \\
     83 citations (Crossref) [2024-05-28]\\
     00063}
   }
   

4. A Simple Twist for Signal Enhancement in Non-Linear Optical Microscopy. A. K. De and D. Goswami, Journal of Microscopy 235(2), 119–123 (2009)

   BibTeX: @article{deSimpleTwistSignal2009,
     title = {A Simple Twist for Signal Enhancement in Non-Linear Optical Microscopy},
     author = {De, A. K. and Goswami, D.},
     year = {2009},
     journal = {Journal of Microscopy},
     volume = {235},
     number = {2},
     pages = {119--123},
     issn = {1365-2818},
     doi = {10/ckpt72},
     urldate = {2019-08-14},
     copyright = {\copyright{} 2009 The Authors Journal compilation \copyright{} 2009 The Royal Microscopical Society},
     langid = {english},
     annotation = {GSCC: 0000011 \\
     2 citations (Crossref) [2024-05-28]\\
     00010}
   }