Blue phase liquid crystals (BPLCs) are chiral mesophases with 3D order, which makes them a promising template for doping nanoparticles (NPs), yielding tunable nanomaterials attractive for microlasers and numerous microsensor applications. However, doping NPs to BPLCs causes BP lattice extension, which translates to elongation of operating wavelengths of light reflection. Here, it is demonstrated that small (2.4 nm diameter) achiral gold (Au) NPs decorated with designed LC-like ligands can enhance the chiral twist of BPLCs (i.e., reduce cell size of the single BP unit up to ∼14% and ∼7% for BPI and BPII, respectively), translating to a blue-shift of Bragg reflection. Doping NPs also significantly increases the thermal stability of BPs from 5.5 °C (for undoped BPLC) up to 22.8 °C (for doped BPLC). In line with our expectations, both effects are saturated, and their magnitude depends on the concentration of investigated nanodopants as well the BP phase type. Our research highlights the critical role of functionalization of Au NPs on the phase sequence of BPLCs. We show that inappropriate selection of surface ligands can destabilize BPs. Our BPLC and Au NPs are photochemically stable and exhibit great miscibility, preventing NP aggregation in the BPLC matrix over the long term. We believe that our findings will improve the fabrication of advanced nanomaterials into 3D periodic soft photonic structures.

In this work, optical properties of a cubic blue phase liquid crystal (BPLC) in photonic microstructures were investigated. The experiments were carried out in microcapillaries with different inner diameters and in a photonic crystal fiber (PCF). For the first time, white-light beam propagation through a BPLC (BP II) in a microcapillary with a 60-μm inner diameter at a distance of 26 mm was demonstrated. Furthermore, it was conclusively shown that the cylindrical geometry and the size of its inner diameter influence BP domains orientation, which can lead to a uniform texture of the BPLC with a dominant Bragg wavelength. This study also proves that a BPLC-filled PCF provides very attractive tunable properties. It was presented that by applying an external electric field, a control of the transmitted light intensity for particular wavelengths can be achieved, depending on the input polarization. Moreover, a range of the wavelengths corresponding to low transmission appeared to be tunable, whereas for x- and y-polarized light, respectively, both narrowing (from 16 nm to 9 nm) as well widening (from 13 nm to 22 nm) of the bandgaps were observed. Finally, the obtained experimental results were found qualitatively consistent.

Photonic crystal fibers (PCF) have been selectively filled with a cholesteric liquid crystal (ChLC) with special interest in the blue phase (BP) of the liquid crystal. It has been observed thermal tuning of the guided light in the visible region. A dramatically enhance appears when the phase of the liquid crystal changes from cholesteric to blue phase I (BPI). When a thermal range of the blue phase I is achieved, no changes are observed while increasing temperature from BPI through BPII and to the isotropic phase