A novel approach for the determination of birefringence dispersion in nematic liquid crystals by using the continuous wavelet transform

Abstract

Transmittance spectra of 5CB and ZLI-6000 coded nematic liquid crystals were acquired in the 12 600– 22 200 cm−1 region at room temperature. The continuous wavelet transform using the Morlet wavelet was applied to analyse the transmittance signal. Dispersion curves of the birefringence were obtained for 5CB and ZLI-6000 by this analysis and data were fitted to the Cauchy formula whereby the dispersion parameters were extracted. Results are found to be in favourable accordance with the published values.

Origin of stress and birefringence generation at hot‐stretching of poly(methyl methacrylate) containing low‐molecular‐weight compound

“…However, birefringence may be proportional to the applied tensile stress in all stages—including those after the cessation of stretching—at high temperatures, when the proportional constant must be the stress‐optical coefficient in the rubbery state. In other words, at such high temperatures, nematic interaction occurs from the beginning of stretching as demonstrated previously 34,44–47 …”

“…Assuming that the slope is a constant, the stress‐optical coefficient in stage B is calculated to be approximately 300 × 10 −12 /Pa. Considering that the intrinsic birefringence of 5CB is large and positive, 42,45 the value of the stress‐optical coefficient in this stage must be attributed to nematic interaction. The figure demonstrates that nematic interaction suddenly occurs just beyond the yield point, that is, the turning point between stages A and B.…”

“…Therefore, when the intrinsic birefringence of an LMC is significantly larger than that of a polymer, such as poly(methyl methacrylate) (PMMA) and 4‐cyano‐4′‐pentylbiphenyl (which is commonly known as 5CB), 43–45 the orientation birefringence is greatly affected by the LMC. In other words, the orientation of 5CB dispersed in PMMA during stretching is easily detected by measuring the birefringence.…”

Investigation of optical parameters of Ag–In–Se thin films deposited by e-beam technique

“…The refractive indices, n, of the films annealed at different temperatures were determined by both using the envelope method (EM) developed by Manifacier et al [17] and Swanepoel [18,19] and continuous wavelet transform (CWT) method [20,21], which was first introduced by Grossman et al [22]. EM permits the refractive index calculations of the films that exhibit at least two interference fringes in their weak absorption and transparent spectral region by constructing envelope curves of transmittance spectra.…”

Application of continuous wavelet transform for determination of fiber birefringence

“…The case, however, may be conveniently analyzed with the help of the Continuous Wavelet Transform (CWT) [20]. Note that CWT has already proved its usefulness for analysis of liquid crystal birefringence [21], but to our best knowledge, has never been applied for investigation of optical fibers.…”