Several attractive properties of hydrocarbon-linked mesogenic dimers have been discovered, a major feature of these has been the ability of dimers under confinement to form periodic patterns. At least six different types of stripe-like periodic patterns can be observed in these materials under various experimental conditions. Our most recent finding is the discovery of micrometre-scale periodic patterns at the N-N-tb phase transition interface, and sub-micrometre scale patterns in the N-tb phase. Layer-like sub-micrometre patterns were observed using three-photon excitation fluorescence polarizing microscopy, and these are being reported here.