The growing interest in organic chromophore thin films for nonlinear optical applications stems from their ease of processing, high structural versatility, and the possibility to finely tune their optical and electronic properties through molecular design. These advantages make them particularly attractive for key photonic applications such as optical communication, all-optical switching, and frequency conversion. Among this class of materials, organic thin films exhibiting second-harmonic generation (SHG) have received considerable attention for data storage technologies, owing to their intrinsic nonlinearity and their potential for high-density, three-dimensional information encoding [1].
Within this framework, we have developed an original molecular engineering strategy based on the design of three-dimensional organic octupolar chromophores built around non-planar, extended bipyrimidine cores and functionalized with chiral side chains. This design induces spontaneous non-centrosymmetric organization at the supramolecular level, resulting in SHG-active liquid crystalline thin films [2,3]. A key advantage of this approach lies in its ability to generate macroscopic second-order nonlinear optical responses without resorting to external alignment methods such as corona poling or complex multilayer deposition techniques, which often limit long-term stability and reproducibility.
More recently, it has been demonstrated that information can be efficiently written and localized within these SHG-active liquid crystalline thin films through multiphoton absorption processes. Such nonlinear excitation mechanisms allow precise spatial control of the optical response within the material volume, thereby enabling true three-dimensional data inscription [4]. These results open promising perspectives for the development of advanced 3D optical data storage systems based on self-organized, nonlinear optically active organic materials.