Hemi-omnidirectional Lasing from a Cholesteric Liquid Crystal Layer on a 1D Photonic Crystal Film

We herein report on a hybrid photonic band gap (PBG) system, which was fabricated using a cholesteric liquid crystal (CLC) layer on a 1-dimensional (1D) photonic crystal (PC) film, i.e., hybrid 'CLC/1D PC'. The CLC layer is made of nematic liquid crystal monomers embedded in polymeric helical CLC networks, thereby exhibiting a field-induced reorientational undulation of the helical axis. It is shown that intensity-controllable circularly polarized laser emissions may be generated at the wavelength of the high-energy band edge mode of the CLC layer in the dye-doped 'CLC/1D PC' PBG structure. The handedness of the lasing light corresponds to the handedness of the CLC layer used. Moreover, the direction of propagation of laser emissions could be manipulated from uni- to hemi-omnidirectional for the hybrid 'CLC/1D PC' PBG structure by applying an electric field.