A New Class of Heterocyclic Compounds for Nonlinear Optics

We discuss both theoretically and experimentally a new class of second-order nonlinear optical materials which utilizes the coupling of electron-rich and electron-deficient aromatic heterocyclic units to provide the charge asymmetry necessary for the nonlinear optical effect. This new class of nonlinear optical materials as compared with the previously known materials has the following merits: (i) wide optical transparency, high molecular nonlinear coefficient and small dipole moment; (ii) independent manipulation of the nonlinear coefficient and ground-state dipole moment by using multiple heterocyclic (oligomeric) units or appropriately modified heterocycles as well as by varying the linkage position; (iii) potentially greater thermal stability of the heterocyclic units; (iv) the potential for greatly reduced chemical toxicity.