Biphotonic laser-induced ripple structures in dye-doped liquid crystal films

In this study we investigate biphotonic laser-induced ripple structures (BLIRSs) on dye-doped liquid crystal (DDLC) films. A BLIRS is formed by competing red and green light interfering fields, generated by the interference of incident red and green light with the corresponding surface scattering lights. The structures are fabricated by the adsorption of dyes induced by green light and the inhibition of the adsorption by red light in trans-cis and cis-trans inverse isomerization, respectively. The morphology of the BLIRS is analyzed using scanning electron microscopy and atomic force microscopy. Experimental results indicate that not only the ratio of the intensity of red light to that of green light, but also the wavelength and polarization of the red and green light markedly affect the periodicity and orientation of the BLIRS. Additionally, the amplitude of the BLIRS decreases as the ambient temperature increases, finally disappearing at a critical temperature.