Nonphotochemical laser-induced nucleation of nematic phase and alignment of nematic director from a supercooled thermotropic liquid crystal

A nonphotochemical laser-induced phase transition was studied in a supercooled 4^'1000-0ptn-pentyl-4-cyanobiphenyl (5CB, also referred to as PCB and K15) liquid crystal, using linearly polarized 450.3em0exps light pulses at a wavelength of 5320.3em0exnm. The laser induced nucleation from the metastable supercooled isotropic phase to the nematic phase during slow cooling (0.0010.2em0ex^∘C∕min) and high light intensity (3.90.3em0exMW∕cm²). The resulting nematic director tended to be aligned along the direction of the plane of polarization of the light. At the intensities used, there is no observable laser-induced realignment of the director once the sample is in the nematic phase, nor any permanent laser-induced ordering when the sample is illuminated only in the stable isotropic phase during slow cooling. These experimental results are consistent with a mechanism based on optical Kerr alignment.