Optical Sciences

Biomolecules and nanostructures

The Optical Sciences group studies the interaction of light and matter at the nanoscale. We do this by exploring ways to shape light and its environment. It's what we call active and passive control. Our current focus is on the interaction of light with biomolecules and nanostructures. We are part of Twente University's Department of Science and Technology and member of the MESA+ institute.
We participate in the EU-COST actions MP1102: Coherent Raman microscopy (MicroCor) and CM1202: Supramolecular photocatalytic water splitting (PERSPECT-H2O)

 

Shaped Coherent Anti-Stokes Raman Scattering


  • Jennifer Herek - Chair
  • Herman Offerhaus - Scientific Staff
  • Frank Timmermans - Former member
  • Sytse Postma - Former member
  • Alexander van Rhijn - Former member


  • Coherent anti-Stokes Raman scattering (CARS) has been successfully used in spectroscopy and microscopy since the development of (tunable) pulsed laser sources. In CARS, molecular vibrations are excited coherently by the pump (ωp) and Stokes (ωs) pulses. Subsequently a probe (ωpr) pulse, which is often derived from the same pulse as the pump, generates the anti-Stokes signal (ωc = ωp - ωs + ωpr). The energy diagram for a narrow band resonant CARS process is given in figure 1.


    Figure 1: Narrowband Coherent anti-Stokes Raman Scattering (CARS)

    In addition to the resonant CARS signal, there is a nonresonant four-wave mixing contribution, also known as the nonresonant background, which interferes with the detection of the resonant CARS signal.

    We apply a broadband CARS method with a broad pump and probe and a narrow Stokes, shown in figure 2, which allows us to excite multiple vibrational coherences at once. With this method we investigate vibrational responses around 3000 cm-1. Using a high resolution phase shaper to scan a p-phase step through the broadband pump/probe spectrum we are able to obtain non-resonant background-free CARS spectra with a precision of 1 cm-1. The non-resonant background is removed by substracting the inverse phase-profile signal from the original scan, exploiting the time-reversal asymmetry of the resonant signal.


    Figure 2: Broadband pump/probe CARS and the corresponding nonresonant background

    Using spectral phase shaping we can also create molecule-specific pulses where the specificity is based on the interferences between multiple transitions. Using precise positioning of π-phase steps, selective imaging for selected compounds of interest can be easily obtained by altering the phase profile of the broadband pump/probe pulse, as shown in figure 3.


    Figure 3: Chemically selective imaging of substances with overlapping resonances. The sample consists of 4μm diameter polystyrene and PMMA beads. Both images are obtained with the same broadband pump/probe pulse exciting all of the Raman resonances shown. (A) Selective excitation of the PMMA beads. (B) Selective imaging of the polystyrene beads.

    Imaging with increased selectivity and rejected background will be the aim of further research. Applying more complex phase profiles, that exploit the full vibrational spectrum of the target molecules, will increase specificity and selectivity even more. By lowering the difference frequency between the pump and Stokes pulses the fingerprint (~100 1100 cm-1) region can be accessed.


    Articles

    The following articles have been published regarding this project:

    Computational optimization of phase shaped CARS

    (abstract) (full pdf)
    Alexander C.W. van Rhijn, Aliakbar Jafarpour, Jennifer L. Herek, and Herman L. Offerhaus
    Multiphoton Microscopy in the Biomedical Sciences XII
    Vol. 8226, 82262B january 22, 2012
    doi:10.1117/12.906630

    Coherent control of vibrational transitions: Discriminating molecules in mixtures

    (abstract) (full pdf)
    A. C. W. van Rhijn, A. Jafarpour, M. Jurna, H. L. Offerhaus and J. L. Herek
    Faraday Discussions
    issue 0, 153, 227-235 July 20, 2011
    doi:10.1039/C1FD00040C

    Phase-shaping strategies for coherent anti-Stokes Raman scattering

    (abstract) (full pdf)
    A.C.W. van Rhijn, M. Jurna, A. Jafarpour, J.L. Herek and H.L. Offerhaus
    Journal of Raman Spectroscopy
    Vol. 42, Issue 4, April 2011
    doi:10.1002/jrs.2922

    Exploring, tailoring, and traversing the solution landscape of a phase-shaped CARS process

    (abstract) (full pdf)
    Alexander C.W. van Rhijn, Herman L. Offerhaus, Peter van der Walle, Jennifer L. Herek, and Aliakbar Jafarpour
    Optics Express
    Vol. 18, Issue 3, pp. 2695-2709 feb 01, 2010
    doi:10.1364/OE.18.002695

    Chemically selective imaging by spectral phase shaping for broadband CARS around 3000 cm−1

    (abstract) (full pdf)
    A. C. W. van Rhijn, S. Postma, J. P. Korterik, J. L. Herek, and H. L. Offerhaus
    Journal of the Optical Society of America B
    vol. 26 issue 3 p559-563, march 2009

    Spectral phase shaping for high resolution CARS

    (abstract) (full pdf)
    A. C. W. van Rhijn, S. Postma, J. P. Korterik, J. L. Herek, and H. L. Offerhaus
    SPIE proceedings
    vol 7183 p.71830X february 13, 2009
    doi:10.1117/12.808792

    Application of spectral phase shaping to high resolution CARS spectroscopy

    (abstract) (full pdf)
    S. Postma, A. C. W. van Rhijn, J. P. Korterik, P. Gross, J. L. Herek, and H. L. Offerhaus
    Optics Express
    Vol. 16 No. 11 p.7985-7996 may 26 2008

    Compact high-resolution spectral phase shaper

    (abstract) (full pdf)
    S. Postma, P. van der Walle, H.L. Offerhaus, and N.F. van Hulst
    Review of scientific instruments
    vol. 76, issue 12, p. 123105 (4 pages) dec 14 2005
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