Temperature-dependent optical band structure and defect mode in a one-dimensional photonic liquid crystal

ABSTRACT

We analysed the propagation of an electromagnetic wave in a one-dimensional periodic system composed of a finite set of E7 liquid crystal mixture slabs in a twisted configuration alternated by homogeneous and isotropic dielectric layers. For different incident angles of the circularly polarised wave, we studied the optical band structure for reflectance and transmittance considering that the dielectric matrix of the device depends on temperature and wavelength. We demonstrated that the position of the band can be moved from visible to short-infrared spectrum region by increasing the thickness of the layers. We found that for a fixed incident angle, the band spectrum shifts towards the short-wavelength region as the temperature gets increasing, whereas, for a constant temperature, such a spectrum moves towards larger frequencies as the incident angle increases. We show that when one of the homogeneous and isotropic slabs has a different size compared with the remaining ones, a defect mode is induced in the band structure whose frequency can be thermally tuned.

Graphical Abstract

KEYWORDS:

• Photonic crystals
• nematic liquid crystals
• thermally controlled band structure
• defect mode

Acknowledgement

Carlos G. Avendaño mentions that part of this work was performed during a research stay at Instituto de Física, UNAM, Ciudad de México, Mexico.