Abstract
Three-dimensional (3D) photonic crystals like Blue Phases, self-assemble in highly organized structures with a sub-micrometer range periodicity, producing selective Bragg reflections in narrow bands. Current fabrication techniques are emerging at a fast pace, however, manufacturing large 3D monocrystals still remains a challenge, and controlling the crystal orientation of large crystals has not yet been achieved. In this work, we prepared ideal 3D Blue Phase macrocrystals with a controlled crystal orientation. We designed a method to obtain large monocrystals at a desired orientation and lattice size (or reflection wavelength) by adjusting the precursor materials formulation and a simple surface treatment. Moreover, using the same method, it is possible to predict unknown lattice orientations of Blue Phases without resorting to Kossel analysis. Producing large 3D photonic crystals that are also functional tunable structures is likely to have a direct impact on new photonic applications, like microcavity lasers, displays, 3D lasers, or biosensors.
Highlights
Three-dimensional (3D) photonic crystals like Blue Phases, self-assemble in highly organized structures with a sub-micrometer range periodicity, producing selective Bragg reflections in narrow bands
Each group is composed by a host nematic liquid crystal mixture base, a chiral dopant (CD) and a mesogenic monomer mixture
The same host nematic mixture was used for all groups so that only the CD type was different among groups
Summary
Three-dimensional (3D) photonic crystals like Blue Phases, self-assemble in highly organized structures with a sub-micrometer range periodicity, producing selective Bragg reflections in narrow bands. We designed a method to obtain large monocrystals at a desired orientation and lattice size (or reflection wavelength) by adjusting the precursor materials formulation and a simple surface treatment. BPs exhibit a highly organized 3D structure with a sub-micrometer range periodicity, as opposed to other liquid crystal phases This 3D organization is achieved by the self-assembly of the liquid crystal molecules into periodic cubic structures that produce bright selective Bragg reflection in narrow bands and are optically isotropic. Despite the great progress in techniques and materials, producing ideal BP crystals in large volumes is still problematic, since the current produced BP crystals are oftentimes polycrystalline (platelet structure), the single crystal size is limited (in the micrometer range) or the BP liquid crystal is not stabilized in temperature, among other issues. The same method can be employed for predicting unknown BP crystal lattice orientations without the need of Kossel analysis
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