Fabrication of a simultaneous red–green–blue reflector using single-pitched cholesteric liquid crystals

Abstract

A cholesteric liquid crystal (CLC) is a self-assembled photonic crystal formed by rodlike molecules, including chiral molecules, that arrange themselves in a helical fashion. The CLC has a single photonic bandgap and an associated one-colour reflection band for circularly polarized light with the same handedness as the CLC helix (selective reflection). These optical characteristics, particularly the circular polarization of the reflected light, are attractive for applications in reflective colour displays without using a backlight, for use as polarizers or colour filters and for mirrorless lasing. Recently, we showed by numerical simulation that simultaneous multicolour reflection is possible by introducing fibonaccian phase defects. Here, we design and fabricate a CLC system consisting of thin isotropic films and of polymeric CLC films, and demonstrate experimentally simultaneous red, green and blue reflections (multiple photonic bandgaps) using the single-pitched polymeric CLC films. The experimental reflection spectra are well simulated by calculations. The presented system can extend applications of CLCs to a wide-band region and could give rise to new photonic devices, in which white or multicolour light is manipulated.

Ultrafast Optical Signal Processing with Bragg Structures

“…In CLC, the birefringent molecules self-assemble with the director (crystalline) axis arranged in a spiral, with a pitch on the order of the optical wavelength stretching from the UV to the infrared regime, as seen in Figure 12. As a result, CLC's possess not only the advantageous features of liquid crystals such as fabrication ease and low cost, and a very wide spectral dynamic range of operation [68,69], but also the 1-D photonic crystals' unique ability to enhance the nonlinear ultrafast all-optical responses of the CLC constituent molecules [mostly due to the nematic constituent], in addition to the dispersion effect at the photonic band-edges. A typical magnitude of the non-resonant nonlinear index coefficient n 2 is in the order of 10 −14 -10 −13 cm 2 /W, but owing to the photonic crystal band-edge enhancement, the magnitude of the effective n 2 can be as large as 10 −12 -10 −11 cm 2 /W.…”

Optically pumped mirrorless lasing. A Review. Part II. Lasing in photonic crystals and microcavities

“…Multilayered structures of the dye-doped ChLCs used in the study [114] have revealed lasing thresholds as low as 12 nJ/pulse, which is an order of magnitude lower than that for the equivalent single-layer ChLC cell. Introduction of defects of certain sequences such as Fibonacci [115][116][117], Thue-Morse [118], Rudin-Shapiro [119], etc. is attractive for fabricating the photonic structures with the multiple PhBGs.…”

Materials and 3D Designs of Helix Nanostructures for Chirality at Optical Frequencies

“…[10] Otherwise, superchiral light is required, [11,12] downscaling the helical pitch of the circularly polarized light to the material one. Especially, in the last years, boosted by advanced nanotechnology capabilities, artificial nanomaterials exhibiting chirality have been proposed under several schemes, with the main target to induce large chiro-optical effects related to the polarization control in the linear and non-linear regime.…”