Mechanisms of ultrafast refractive index change in organic system

Kenji Kamada

doi:10.1117/12.456000

14 February 2003 Mechanisms of ultrafast refractive index change in organic system

Kenji Kamada

Proceedings Volume 4797, Multiphoton Absorption and Nonlinear Transmission Processes: Materials, Theory, and Applications; (2003) https://doi.org/10.1117/12.456000
Event: International Symposium on Optical Science and Technology, 2002, Seattle, WA, United States

Abstract

The elementary processes contributing to the ultrafast change of refractive index were studied for organic molecular system. The ultrafast change was measured by optical heterodyne detected optical Kerr effect with femtosecond laser pulses. The observed responses were separated into the electronic and nuclear nonlinearities by an analytical method based on the Fourier transform. Second hyperpolarizability γ was determined from the separated electronic contribution, and is discussed in terms of the structure-property relationship for four thiophene homologues. The γ value was found to increase systematically, which is explained with change of the energy levels of the excited states affected by the hetero atom in their aromatic rings. The structure-property relationship of the nuclear nonlinearity was also discussed for CS₂ and CCl₄. Their pulse width dependences of the nonlinear optical response were demonstrated, which brings the problems of CS₂ as a standard material of femtosecond χ⁽³⁾ measurement to light. Also accumulated thermal effect, which can be a measurement artifact, is demonstrated for femtosecond closed-aperture Z-scan measurements of dye solution. The thermal effect was found to appear at the laser repetition rate as low as 1 kHz and gave apparent large nonlinearity with negative sign.

Citation Download Citation

Kenji Kamada "Mechanisms of ultrafast refractive index change in organic system", Proc. SPIE 4797, Multiphoton Absorption and Nonlinear Transmission Processes: Materials, Theory, and Applications, (14 February 2003); https://doi.org/10.1117/12.456000

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