A PYROELECTRIC LIQUID-CRYSTAL POLYMER (PLCP) FOR 2ND-HARMONIC GENERATION

In order for a material to show a non-vanishing second order non-linea r susceptibility, the material has to have a polar axis. This is hard to achieve in a liquid crystal system because of the strong quadrupola r order along the director. Electrostatic poling of polymers and polym er liquid crystals at high temperature and subsequent quenching to low er temperature only gives a small value of the polar order parameter a nd, in addition, results in materials which are not in thermodynamic e quilibrium and therefore not stable over long times. Starting with a f erroelectric liquid crystal (which has polar order perpendicular to th e director) we have succeeded in making a material with true polar ord er. It is not ferroelectric, although the ferroelectric properties of the starting and intermediate materials are basic for the procedure an d for the final product which can be used for frequency doubling, of i mportance, for instance, in a wide area of optic communication applica tions.