Two-photon absorption spectra of fluorene derivatives

Summary form only given. Two-photon absorption (2PA) has achieved appreciable interest in a wide array of fields including all-optical switching, two-photon fluorescence microscopy, and optical power limiting. Consequently, it is a goal to find materials that exhibit large 2PA cross-sections. Organic materials are strong candidates for these applications because their material properties can be tailored through molecular engineering. This not only allows organics to be utilized in a wide variety of applications, but also provides a means to analyze structure-property relationships for a class of samples. We present a method for rapid characterization of 2PA materials using a femtosecond white-light continuum (WLC) pump-probe nonlinear spectrometer. In this experimental instrument, a strong pump beam induces a nonlinear response in the system under investigation and a weak, broad-band WLC beam probes the induced nonlinearity. The 2PA process requires simultaneous absorption of one photon from both the pump and probe beams and the outcome is the nondegenerate 2PA spectrum of the sample. We have synthesized a group of fluorene derivatives in order to investigate the structure-property relationships of these dyes.