Colloquiuim: Tatiana Novikova

    Date: 
    Thursday, April 21, 2016 - 3:30pm - 5:00pm
    Location: 
    Meinel 307
    Description: 

    Mueller Polarimetry of Structured and Random Media: Numerical Modeling and Applications

    Abstract(s): 

    The studies of polarized light interaction with a matter provide valuable information about the sample that can be used in a broad range of applications starting from metrological characterization of thin solid films to cancer detection and staging.  The basic advantages of polarimetric techniques consist in being relatively low-cost, fast and non-destructive, thus allowing the measurements even for in-situ applications.

    In this talk I will present both theoretical and experimental results on applications of polarized light for the characterization of complex media (layered, patterned, scattering, and absorbing).  Having access to complete set of polarimetric data, namely, spectrally or angularly resolved Mueller matrices of the samples, proves to be the key issue for the characterization of such samples.  The complete Mueller polarimeters (operating in either spectroscopic or imaging mode) were developed in LPICM, targeting new applications such as semiconductor test-structure metrology and biomedical diagnostics.

    Metrology.  We have shown that using spectral Mueller polarimetry data one can reconstruct the critical dimensions of microelectronic metrological structures:  (i) with better presicion compared to classical ellipsometry;  (ii) faster than with conventional characterization techniques, such as AFM and SEM; (111) in a non-destructive way contrary to SEM technique.  Mueller images of a back focal plane of a high numerical aperture objective were shown to be very sensitive to the overlay defects (break of structure symmetry) in microelectronic fabrication process.  Because of the linear dependence of polarimetric response on small perturbations of the symmetry of the structures the proposed approach does not require the solution of inverse problem given that two well calibrated targets (structures with known overlay) are available.  Our theoretical findings on this subject were confirmed by the experiments.

    Biomedicine.  Ex vivo studies of multi-spectral real space Mueller images of human colon have revealed the enhanced contrast between healthy and cancerous zones of the tissue compared to non-polarized intensity images.  The results of polarimetric measurements and numerical Monte Carlo modeling had confirmed the scattering of visible polarized light within the biological tissue by the scatterers which size is much smaller than the wavelength of probing light (so called Rayleigh regime).  Our experimental and theoretical findings have confirmed the feasibility of (i) non-invasive optical biopsy; (ii) ex vivo optical cancer stagingEx-vivo studies of uterine cervix tissue demonstrate both strong depolarization and birefringence of healthy zones, whereas the values of birefringence drop significantly within the zones of cervical intraepithelial neoplasia (CIN I-III).  The extensive studies of statistical correlation of the diagnosis obtained by Mueller polarimetry with the results of 'goldstandard' analysis of histological slides by the pathologist were performed.  The work is ongoig to improve the reliabilty of using the depolarization and birefringence values as optical markers of the precancerous zones of uterine cervix.

    The presented results may be used in semiconductor industry and photovoltaic, for target detection in turbid media and development of new polarmetric instrumentation for biomedical applications. 

     

    Speaker Bio(s): 

    Tatiana Novikova is a researcher at the Applied Optics and Polarimetry group of the Laboratory of Interfaces and Thin Films, Ecole polytechnique, France.  She received M.S. degree (Cum Laude) in Applied Mathematics from Moscow State University, Russia, PhD degree in Applied Physics and Mathematics from Moscow Institute of Mathematical Modeling, Russian Academy of Sciences and HDR (habilitation) in Physics from Paris-Sud University, Orsay, France.  Current research interests of Dr. Novikova focus on polarized light interaction with different media, including numerical modeling and practical applications of Mueller polarimetry to the problems of metrology for semiconductor industry, target detection and polarimetric imaging for biomedical applications.