Reveal linear optical effects of the liquid crystal by Stokes-Mueller calculus and θ-scan technology

Abstract

Based on the Stokes-Mueller calculus, linear optical effects of liquid crystals were investigated using the θ-scan technology. Usually, when a circularly polarized light beam passes through an anisotropic optical medium, the transmitted light beam behaves as elliptically polarized light. The Stokes-Mueller calculus shows that the change of the transmitted light intensity includes the linear optical characteristics of the medium, such as dichroism, birefringence, and ellipticity. Meanwhile, these optical characteristics can be probed simultaneously from the transmittance curve using an angular scan (T-θ), i.e., θ-scan technology. As the nanoparticle (NP) concentration in the liquid crystal increases from 0 to 0.1 wt%, the apparent dichroism monotonously decreases with the NP concentration. LC molecules are highly birefringent, resulting in Nπ uncertainty on the T-θ curve. As a result, when the NP concentration rises from 0 to 0.06 wt %, the ellipticity decreases; when the NP concentration rises from 0.06 wt % to 0.1 wt %, the ellipticity increases. However, from the change in the apparent phase delay with the NP concentration, Nπ can be distinguished. As well, birefringence decreases monotonously with the NP concentration.