Third Order Nonlinear Optical Effects in Conjugated Polymers

The conjugated quasi-one dimensional polymers are characterized by a strong delocalization of π electrons. This highly polarizable electronic cloud responds nonlinearly to the exiting external field. The resultant bulk polarization can be developed into the external field power series and its component along x is given by $${P_x}(t) = \sum\limits_{y,z,u,...} {\left( {x_{xy}^{(1)}{E_y}(t) + x_{xyz}^{(2)}{E_y}(t) + x_{xyzu}^{(3)}{E_y}(t){E_z}(t){E_u}(t) + ...} \right)} $$ (1) where x (1), x (2) … x (4) are (n+1) rank tensors describing nonlinear optical response of the medium and Ey(t), Ex(t) … Eu(t) are electric field components in y, z, … u direction.