Enhanced Opitcal Limiting Effects In A Phthalocyaninato Rare Earth Complex Using Femtosecond Vector Field

The interaction of light with matter is always an important subject in the optical field. The state of polarization, as an basic elementary feature of the light, is almost one of the most hot research frontier. Completely different from the scalar light field, the interaction of vectorial light field with matter results in a lot of novel optical effects and has received particularly attention due to their potential applications in optical tweezers, super-resolution optical microscopy, and nonlinear optics. In this thesis, I focus our attention to investigate the interaction of nonlinear optical materials with femtosecond vectorial light field. There are two key points. Firstly, we report the open aperture (OA) Z-scan technique by using vetorial light field for characterizing third-order optical nonlinearity of two-photon absorption (2PA). Secondly, we first propose the large enhancement of optical limiting effects using radially polarized beams. The main points of this thesis are as follows:1. Femtosecond vector fields have been generated experimentally. By the method of wave-front shaping, attaching the computer-generated holographic grating on the spatial light modulator (SLM) and transforming by a 4f system, a femtosecond vector field with arbitrarily spatial polarization state distribution could be obtained. A variety of vector fields with different polarization was generated, such as azimuth, radial variant vector fields, or both variant vector fields. We also study the different generation methods between femtosecond vector field and continuous light field.2. A new study of OA Z-scan technique by using femtosecond vector field for characterizing 2PA have been proposed, for the first time to our knowledge. Based on the vectorial Rayleigh-Sommerfeld formulas and the properties of focused vector field under the paraxial approximations, we develop the Z-scan theories and nonlinear transmission under the excitation of cylindrical vector field. It is shown that the sensitivity of Z-scan technique using radially polarized field has the large enhancement compared with that using linearly polarized field. This Z-scan theory is also demonstrated experimentally.3. We investigated the third-order nonlinear effects and the enhanced optical limiting effects in a doule-decker bis(phthalocyaninato) rare earth complex using radially polarized field. By performing Z-scan and optical limiting measurements with femtosecond-pulsed radially polarized field at 800nm wavelength, we obtained the 2PA properties of a double-decker Pr[Pc(OC8H17)g]2 rare earth complex. The large 2PA effect we observed, which originates from strong intramolecular π-π interaction, could be exploited for optical limiting application. The results demonstrate the large enhancement of optical limiting effects using radially polarized field instead of linearly polarized field.