Abstract

Currently, considerable effort is being centered on designing new organic crystals for efficient bulk second harmonic generation (SHG) and frequency upconversion of diode laser sources from the near IR to the blue visible region. The molecular second-order susceptibilities can be enhanced by designing compounds possessing a large change in dipole moment between the ground and first excited states, which usually leads to molecule structures having a highly polar ground state. These conditions, together with a desired crystal structure in which the ground state dipole moments of individual molecular sites are partially aligned along a common axis, present a natural dilemma since the ground state dipole-dipole interaction raises the energy of a parallel aligned noncentrosymmetric configuration compared with an antiparallel aligned centrosymmetric configuration.

© 1990 Optical Society of America