个人简介

Education: B.Sc., National University of Singapore; M.A., Ph.D., Princeton University, Post-doc: Stanford

研究领域

Ultrafast Laser Spectroscopy

Research Interest Many chemical reactions and dynamics happen in the femtosecond (10-15 sec) to picosecond time regime (10-12 sec). The only way to directly study systems at such short timescale is through ultrafast laser spectroscopy. Our research group’s interests are in the following area of ultrafast laser spectroscopy. Coherent Multidimensional Optical Spectroscopy We are developing novel techniques in multidimensional optical spectroscopy. Multidimensional optical spectroscopy is the optical analog of multidimensional nuclear magnetic resonance (NMR) spectroscopy such as COSY and NOESY. The femtosecond time resolution of ultrafast laser spectroscopy allows experimentalist to look at structural fluctuations of molecular systems at a much higher time resolution than NMR spectroscopy. Phase cycling multidimensional optical spectroscopy uses phase coherent laser pulse trains to perform the experiments. These phase coherent pulse trains can be produced using optical pulse shaping techniques. Ultrafast Optical Pulse Shaping Figure 1. Schematic of a Complete Amplitude, Phase & Polarization Ultrafast pulse Coherent Control in the Infrared by Nonlinear Optics (CAPPUCCINO) pulse shaper Using nonlinear optical techniques, we are developing new optical pulse shapers designs in the ultraviolet and mid infrared with full control of the optical pulses’ amplitude, phase and polarization profiles. These shaped pulses can be applied to Multidimensional Optical Spectroscopy and Optical Quantum Control experiments. Figure 2. Time-wavelength correlation or XFROG traces of the 0, 45 and 90 degrees components of a pulse train comprising two orthogonally polarized pulses created by the optical pulse shaper Ultrafast Transient Absorption Spectroscopy We are interested in using ultrafast vibrational pump probe spectroscopy to study the cis-trans isomerization process of photoisomers such as rhodopsins and xanthopsins. Upon excitation by a ultraviolet or visible pulse, these photoisomers undergo a cis-trans isomerization process. That typically occurs in a timescale of a few hundred femtoseconds. The consequent structural change of the associated biomolecules is key to many biological/chemical processes.

近期论文

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M. M. Enriquez, P. Ahktar, C. Zhang, G. Garab, P.H. Lambrev and H.-S. Tan. "Energy Transfer Dynamics in Trimers and Aggregates of Light-Harvesting Complex II Probed by 2D Electronic Spectroscopy", in prep. X. Wu, F. Liu, K.L. Wells, S.L.J. Tan, R.D. Webster, H.-S. Tan, D. Zhang, B. Xing, E.K.L. Yeow. “Interplay of Hole Transfer and Host-Guest Interaction in Molecular Dyad and Triad: Ensemble and Single-Molecule Spectroscopy and Sensing Applications”, Chem. Eur. J. 21, 3387-3398 (2015). K.L. Wells, P.H. Lambrev, Z. Zhang, G. Garab and H.-S. Tan. "Pathways of energy transfer in LHCII revealed by room-temperature 2D electronic spectroscopy" Phys. Chem. Chem. Phys. 16, 11640-11646 (2014). DOI: 10.1039/C4CP00365A Z. Zhang, and H.-S. Tan. "Multidimensional Optical Spectroscopy Using a Pump-probe Configuration: Some Implementation Details" in Ultrafast dynamics in molecules, nanostructures and interfaces (Series in Optics and Photonics. Vol. 8), G.G. Gurzadyan, G. Lanzani, C. Soci, and T.C. Sum eds. (World Scientific, Singapore, 2014), p. 29-35. Z. Zhang, K.L. Wells, M.T. Seidel and H.-S. Tan. "Fifth-order three-dimensional electronic spectroscopy using a pump-probe configuration" J. Phys. Chem. B, 117 (49), 15369–15385 (2013) K.L. Wells, Z. Zhang, J.R. Rouxel, and H.-S. Tan. "Measuring the spectral diffusion of chlorophyll a using two-dimensional electronic spectroscopy" J. Phys. Chem. B 117 (8), 2294–2299 (2013) Z. Zhang, K.L. Wells, and H.-S. Tan. "Purely absorptive fifth-order three-dimensional electronic spectroscopy" Opt. Lett. 37, 5058-5060 (2012) J. Shang, S. Yan, C. Cong, H.-S. Tan, T. Yu, and G.G. Gurzadyan. "Probing near Dirac point electron-phonon interaction in graphene" Opt. Mat. Express 2, 1713-1722 (2012) Z. Zhang, K.L. Wells, E.W.J. Hyland, and H.-S. Tan. "Phase Cycling Schemes for Pump-Probe Beam Geometry Two-dimensional Electronic Spectroscopy" Chem. Phys. Lett. 550, 156-161 (2012) S. Yan, M. T. Seidel and H.-S. Tan. "Perturbed Free Induction Decay in Ultrafast Mid-IR Pump-Probe Spectroscopy", Chem. Phys. Lett. 517, 36-40 (2011) M. T. Seidel, Z. Zhang, S. Yan, K. L. Wells and H.-S. Tan. "Characterization of Polarization Shaped Ultraviolet Femtosecond Laser Pulses", J. Opt. Soc. Am. B, 28, 2718-2725 (2011) S. Yan, M. T. Seidel, Z. Zhang, W. K.Leong and H.-S. Tan,"Ultrafast Vibrational Relaxation Dynamics of Carbonyl Stretching Modes of Os3CO12 ", J. Chem. Phys., 135, 024501 (2011) M. T. Seidel, Z. Zhang, S. Yan and H.-S. Tan,"Ultraviolet Polarization Pulse Shaping using sum-frequency generation", J. Opt. Soc. Am. B, 28, 1146-1151 (2011) M. T. Seidel, S. Yan, Z. Zhang, and H.-S. Tan, “Polarization Pulse Shaping using Nonlinear Optical Processes” in Ultrafast Phenomena XVII, M. Chergui, D. M. Jonas, E. Riedle, R. W. Schoenlein and A. J. Taylor, eds. (Oxford U.P., New York, 2011), p. 796. M. T. Seidel, S. Yan, and H.-S. Tan, “Mid-infrared polarization pulse shaping by parametric transfer", Opt. Lett., 35, 478-480, (2010). DOI:10.1364/OL.35.000478 S. Yan, and H.-S. Tan, “Phase cycling schemes for two-dimensional optical spectroscopy with a pump-probe beam geometry", Chem. Phys., 360, 110-115 (2009). DOI:10.1016/j.chemphys.2009.04.019 H.-S. Tan, “Theory and Phase Cycling Scheme Selection Principles of Collinear Phase Coherent Multi-dimensional Optical Spectroscopy", J. Chem. Phys., 129, 124501 (2008). DOI:10.1063/1.2978381 I. R. Piletics, H.-S. Tan, D. E. Moilanen, B. Spry and M. D. Fayer, “Vibrational Echo and Pump-Probe Spectroscopic Studies of the Dynamics of Water Molecules Confined to Nanoscopic Dimensions” in Femtochemistry VII : Fundamental Ultrafast Processes in Chemistry, Physics, and Biology, W. Castleman Jr., and M. Kimble, eds. (Elsevier, Amsterdam, 2006), p. 195. I.R. Piletic, H.-S. Tan, R.E. Riter, N.E. Levinger and M.D. Fayer, “Dynamics of Nanoscopic Water: Vibrational Echo and Infrared Pump-Probe Studies of Reverse Micelles”, J. Phys. Chem. B, 109, 21273-21284 (2005). H.-S. Tan, I.R. Piletic, and M.D. Fayer, “Polarization selective spectroscopy experiments: Methodology and pitfalls”, J. Opt. Soc. Am. B, 22, 2009-2017 (2005)