<title>Space processing of biopolymer/metal composites for NLO applications</title>

Abstract

specimens are obtained in the absence of gravity-fueled convection. Defect-free orgnaic crystals are of particular interestbecause they can exhibit high optical nonlinearities. However, as these are molecular crystals, they tend to be brittle andcannot be easily fabricated into thin films or fibers as can polymer analogs. Polymers having a controlled supramolecularstructure and morphology are even more promising candidates as nonlinear optical materials (NLOM). We have previouslydemonstrated the rationale for orienting biopolymers, materials with known supramolecular structure, in an electric field undermicrogravity conditions in order to optimize the nonlinearity of the biopolymer. Now focusing on the feasibility of improvingupon the NLO activity of the biopolymer system by using a metal dopant, we report on the morphological characterization ofelectric field aligned polymer/silver colloid composites. By analogy to the microgravity processing of metal/ceramic alloys(known as 'cermets'), the resulting 'polymet' should benefit from homogeneous orientation of the minor metal phase withinthe polymer phase and further contribute to the potential of polymeric NLOM.Keywords: nonlinear optical polymers, poling, metal colloids, polymets, microgravity processing1. INTRODUCTIONThe development of materials with large second and third order nonlinear effects has generated enthusiastic interest inapplications to future commercial electronic and telecommunication systems. The ideal nonlinear optical material (NLOM) formost applications would have a very large nonlinear response, extremely low switching thresholds and rapid switching times.For practical commercial applications, NLOM should also be inexpensive, mechanically tough, formable into thin films, andshould be resistant to laser irradiation, temperature changes, and be chemically resistant.Areas of application include opto-electronic interconnects to replace metal interconnects in computers for increased signalpropagation rates and reduced crosstalk. The performance of spatial light modulators, used in most optical computing systems,is at present limited by the uniformity, reproducibility and cost ofthe NLOM used in their manufacture. Another application isto memory systems. NLOM have the potential of reducing random access times and cost per stored bit while simultaneouslyincreasing storage density. Finally NLOM are of potential utility in protective sensors such as for the human eye, as well as of