Abstract

We have undertaken a program of femtosecond non-linear optical (NLO) spectroscopy in which the NLO properties of chromophores are interrogated both in solution (as isolated molecules) and in the polymeric or crystalline solid which will be used in actual photonic devices. The materials investigated are either χ² or χ³ materials in their primary applications, although the results of these studies may indicate substantial cross-functionality. The laser source used for these studies, a synchronously pumped Ti:Sapphire laser which was developed in-house, was choosen for it’s broad tunability in a spectral region (680 nanometers to 1050 nanometers) which spans both nonresonant and resonant laser-material interactions in many candidate photonic materials. The short (nominally 40 femtoseconds at the sample position) pulse duration of this source coupled with optical heterodyne detection of the nonlinear optical response of the sample material permits interrogation of the complex χ³ over a bandwidth of nearly 700 cm⁻¹ around the center frequency of the laser throughout the nearly 400 nanometer tuning range. Apart from the primary goal of merely measuring the magnitude and dispersion of the electronic and vibrational contributions to χ³ as an electronic resonance is approached, the more ambitious goal of these studies is to understand the effects of structure in the solid state upon the bulk NLO properties once the (isolated) molecular properties are ‘in hand’.

© 1993 Optical Society of America