Study on laser action from UV-curable chiral nematic liquid crystals

This paper describes the study on laser action from UV-curable chiral nematic liquid crystals (CLCs) doped with a fluorescent dye before and after photopolymerization of CLC host. When an optically active agent without crosslinkable moiety was doped in a UV-curable nematic liquid crystal, the laser action from the CLC cell was quite different before and after photopolymerization. Before the polymerization, optically pumping of dye-doped CLC cells with a linearly polarized laser beam gave rise to the laser emission with circular polarization at the band edge of CLC reflection as a consequence of the internal distributed feedback effect. Successively, photopolymerization of the CLC with 365 nm light brought about the thorough disappearance of the CLC reflection band probably due to the phase separation leading to the emergence of amplified spontaneous emission of fluorescent dye by optically pumping. In contrast, the dye-doped CLC cell including a crosslinkable agent with a cholesteryl residue enabled the mirrorless laser action after photopolymerization. This is because the selective reflection band of CLC host was retained by the planar structure of cholesteric polymer network.