On second harmonic generation in sculptured nematic thin films (SNTFs)

The generation of second harmonic (SH) waves in a sculptured nematic thin film (SNTF) is theoretically examined when the fundamental waves propagate in the morphologically significant plane of the SNTF. The SNTF is assumed to possess either a Trigonal 3 or a Tetragonal 4 reference symmetry. The propagation of waves at the fundamental frequency and the generation of SH fields are shown to be described by two 2 × 2 matrix ordinary differential equations. Both ordinary and extraordinary waves are shown to exist at the fundamental as well as the SH frequencies. Local characteristics of SH generation are identified in relation to the reference symmetries of SNTFs.