No abstract

A corrected measurement method based on the silicon photodiode detector was investigated.The silicon photodiode detector is a fast response, but the measured transmittance error between the light power meter occurs and depends on the incident light power. In our work, the nonlinear empirical formula was derived from the measured results of the silicon photodiode detector and light power meter. In addition, the formula was used to correct the measuring results of the polymer dispersed liquid crystal, and the corrected results are identical to those of the light power meter. The experimental results further show that the silicon photodiode detector is faster than the light power meter when measuring electro-optical response. As a result, the corrected method is reliable.

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.

A corrected measurement method based on the silicon photodiode detector was investigated. The silicon photodiode detector is a fast response, but the measured transmittance error between the light power meter occurs and depends on the incident light power. In our work, the non-linear empirical formula was derived from the measured results of the silicon photodiode detector and light power meter. In addition, the formula was used to correct the measuring results of the polymer dispersed liquid crystal, and the corrected results are identical to those of the light power meter. The experimental results further show that the silicon photodiode detector is faster than the light power meter when measuring electro-optical response. As a result, the corrected method is reliable.

Free ions are generally unfavorable in liquid crystal (LC) displays, and LC purification technologies are critically important. The colloidal γ-Fe2O3 magnetic nanoparticles (MNPs) have a high ratio of surface to volume, which may adsorb more free ions and are uniform in the LC at room temperature. The precipitation and separation of the doped colloidal γ-Fe2O3 MNPs resulting from the magnetic field accompanied by an isotropic-nematic phase transition are more efficient than in the single case of the phase transition or the magnetic field. The residual ion concentrations have decreased distinctly using the low gradient magnetic field (∇B ~ 2 T/m) with the phase transition. In addition, the higher the concentration of the doped colloidal γ-Fe2O3 MNPs, the lower the concentrations of the residual ions and γ-Fe2O3 MNPs. As a result, the commercial nematic LC can be purified by this approach based on nanotechnology in our study.