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For the development of high-speed optical switches, modulators, lasers, and other photonic devices, understanding of nonlinear optical (NLO) properties under intense laser illumination is essential for any optical material. In this talk I shall focus on two important nonlinear optical process: two-photon absorption (TPA) and self-focusing due to nonlinear refraction (NR).
TPA finds application biological research, such as drug delivery and activation of drugs by TPA. Several theoretical models suggest about the techniques of TPA cross-section enhancement. We have checked that beside the reported techniques, helical structure can enhance intramolecular π-stacking, which may lead to enhanced TPA. Following these we had prepared an organic sample Foldamer-1 (F1) having a centro-symmetric D-π-A-π-D structure. NLO studies by open and closed-aperture z-scan measurements on F1 showed enhancements of TPA and NR coefficient in its helical form over the value achieved for F1 in non-helical structure. The enhancement of NLO coefficients for F1 in helical form may be attributed to the cooperative interactions of intramolecular π-stacking in helical foldamers.
On the other hand nonlinear refraction plays very important role in many electronic application. In my today’s talk I shall show by creating a thermal lens using the NR of the material, we were able to tune the deflection of the optical beam. Modern science utilizes deflection of optical beam in different aspect of applications such as Digital Light Processing (DLP); Coupling light with multiple optical fibres; Laser beam scanning of optical memory devices for read-in, read-out or erasure; Light detection and ranging (LiDAR) system etc. Few techniques make this deflection possible with the help of sophisticated instrumentation with high cost. I shall discuss in this talk an all-optical technique of beam deflection, which can deflect optical beam with high accuracy and high repeatability.
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