A Demonstration of All-optical Phase Modulation in PTS-polydiacetylene Waveguides.

We present the first demonstration of all-optical phase modulation in the waveguides of an organic material (PTS-polydiacetylene). The phase change as a function of optical intensity has been measured via Mach-Zehnder interferometric method. A pi phase shift has been observed for a 2mm long waveguide as the peak intensity is increased by ~ 7 MW/cm sup 2 for polarization parallel to the chain axis (lambda=1.06micron). Through detailed polarization-selective measurements we have established that the observed phase change is electronic (nonthermal) in origin. The results are highly encouraging in terms of all-optical device applications of the material.