Third order nonlinear optical interactions in thin films of poly-p-phenylenebenzobisthiazole polymer investigated by picosecond and subpicosecond degenerate four wave mixing

Abstract

The third order nonlinear optical susceptibility has been measured by degenerate four wave mixing in a 33-μm-thick biaxial film of a conjugated aromatic heterocyclic polymer, poly-p-phenylenebenzobisthiazole, commonly known as PBT, which has a very high mechanical strength due to its rigid rod conformation as well as environmental stability and a high laser damage threshold. For the first time, the response of the optical nonlinearity in the π-electron conjugated system has been experimentally verified to be in subpicoseconds. The value of χ(3) is found to be about an order of magnitude larger than that of CS2. The measurement at two different wavelengths suggests that they are nonresonant χ(3) values. The measured anisotropy of χ(3) as a function of angular orientation at two different sets of laser polarization is explained by using the tensor properties of χ(3) in an anisotropic medium.

Nonlinear Optical Properties of Rigid Rod Polymers and Model Compounds

“…These results have already been published [5]. We have also investigated the effect of processing conditions on the X(3) value of the PBT film.…”

Rigid‐Rod Polymers

“…The optical anisotropy with birefringence of PBZT films is as large as 0.5 (317,318), and the average excitation radius of PBZT, measured from the electroabsorption spectrum of the PBZT films, is 13Å (319). Optical strength tests show that PBZT has an optical damage threshold (ODT) higher than 50 GW/cm 2 with picosecond laser pulses (303,312,(320)(321)(322)(323)(324). PBO fibers are used as a tension member material in optical cable to support a standoff mine detector employing optical sensors to detect TNT by fluorescence quenching technique (325)(326)(327).…”

Modern Polymer Topics

“…One of the great advantages of electromagnetic waves instead of electrons in communications is the reduction in cross-talk. Effects in the picosecond time range have been investigated by Prasad and co-workers (73,74) and Garito (75). With better polymer NLO materials, perhaps they will compete with the inorganic materials.…”