Poling nonlinear materials

Fig. 3.3 SHG measuiement for poled materials. The fundamental beam is incident at angle (p on a nonlinear material of thickness L. The angles of fundamental and SH beams are (p 2o> and

As is a third-rank tensor, it is effective only for noncentrosymmetric media. Therefore, the medium used for the second-order nonlinear optical effect must have a noncentrosymmetric ordering of the NLO dipoles, possibly by spontaneous ordering or by electric field poling (39). In contrast, order is not required for third-order nonlinear materials (e.g., conjugated polymers), but the of a given material is given by (40) ... 

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