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Recent developments in coherent nonlinear optical microscopy

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  • Visitor Seminars
When Oct 06, 2011
from 03:00 PM to 04:00 PM
Where 57-124 Engineering IV Bldg
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Varun Raghunathan

Department of Chemistry
University of California at Irvine
Irvine, CA 96212


Coherent nonlinear microscopy relies on the inherent nonlinear optical response of the sample to map its spatial profile, offering label-free, high sensitivity, fast, and three-dimensional imaging capability. Various coherent nonlinear optical effects based on electronic (second harmonic generation, third harmonic generation, and four-wave mixing) and vibrational (Coherent anti-Stokes Raman scattering, and Stimulated Raman scattering) response have been utilized in microscopy. These techniques are finding widespread applications in diverse areas, for example in biomedical - for imaging fat deposits in artery, consumer products – for monitoring efficacy of shampoos in hair treatment, and nanotechnology – for imaging single walled carbon nanotubes and semiconductor nanoparticles.

This talk will focus on some of the recent research progress in nonlinear imaging techniques aimed at improving the sensitivity, specificity, and resolution beyond what is being currently used in state-of-the-art nonlinear microscopes. We will discuss our recent demonstration of a fast, high sensitivity vibrational-resonance sum-frequency generation microscope, which is a resonant second-order nonlinear optical process and its application to collagen imaging in tissue samples. We will also present a new interferometric four-wave mixing microscope which can image complex nonlinear electronic response from nanoparticles. We have also combined this interferometric technique with spatial beam shaping of the input beam to image complex focal excitation profiles at focus of a high-NA objective. The application of this technique to image phase-resolved sub-diffraction focal volume segments is also discussed.


Varun Raghunathan is currently a postdoctoral scholar in the Chemistry department at University of California Irvine under the guidance of Prof. Eric Potma, where he is developing new nonlinear microscopy techniques for biological and nanostructure imaging. Before this he was working as senior member of technical staff at Ostendo Technologies, Carlsbad-CA, a startup company working in the area of GaN based light emitter arrays for pico-projector applications. Dr. Raghunathan obtained his PhD in 2007 from Electrical Engineering department at University of California Los Angeles under the guidance of Prof. Bahram Jalali in the area of silicon photonics.


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