Methods for determination of the main refractive indices of anisotropic layers

Dascalu, C. F.; Zelinschi, Beatrice Carmen; Dorohoi, Dana Ortansa

doi:10.1117/12.888339

Cited by 3 publications

(3 citation statements)

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“…R-square = 0.99, Figure 3C). [23][24][25][26] Using the effective Δn dispersion and Equation 1, k can be calculated as a function of λ, which reveals that we obtained a full-wave plate for a λ of 715 nm ( Figure 3D). We assume that the relative Δn decrease upon heating is similar for all wavelengths.…”

Section: Fabrication Of the Temperature-responsive Polymer Wave Platementioning

confidence: 81%

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Temperature‐Responsive Polymer Wave Plates as Tunable Polarization Converters

Kragt

Gessel

Schenning

et al. 2019

Advanced Optical Materials

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components of electro-magnetic waves. The simplest wave plates have a homogeneous uniaxial birefringence (Δn) with a thickness (d) and induce a phase shift between the two orthogonal waves according toin which λ is the wavelength and k the induced phase shift divided by 2π. [1,8,9] Liquid crystals (LCs) are frequently used as wave plate materials. By programming the Δn and d of a uniaxial aligned LC quarter-and half-wave plates can be easily fabricated. Also achromatic polarization converters can be obtained by stacking multiple wave plates using the principle of retardation compensation or using configurations involving twisted nematic LCs. [1,[8][9][10][11][12][13][14][15][16][17][18] Wave plates based on nonpolymerized LCs in cells can also be switched using electric fields, which among others resulted in the billion dollar LC display industry. [1,19,20] To widen its application range it would be appealing to make wave plate films that are responsive to other stimuli such as temperature. However, stimuli-responsive polymer wave plates have never been reported so far.We recently reported on a reflective LC coating based on a semi-interpenetrating polymer network (semi-IPN) composed of a LC elastomer (LCE) and a helical LC network (LCN). The coating showed a fast and reversible decrease in reflection band intensity with increasing temperature, which could be tuned by the polymer network density. [21] In this work, we developed temperature-responsive polymer wave plates, which reversibly change from a full-wave to a half-wave plate upon heating. The wave plate consists of a uniaxial aligned nematic semi-IPN in which a non-crosslinked LCE interpenetrates through an LCN. Upon heating above the nematic-to-isotropic transition temperature (T N-I ) of the semi-IPN, the LCE loses order and the effective Δn of the material halves, while d remains constant, thereby changing the polymer film from a full-wave to a half-wave plate. We demonstrate its function by sandwiching the temperatureresponsive wave plate between two identical cholesteric LC (CLC) polarizers reflecting right-handed circular polarized (CP) light around the λ for which the wave plate is operative (Figure 1). Below the T N-I , the left-handed CP light transmitted by the first polarizer is effectively not affected by the full-wave plate and thus also transmitted by the second polarizer, resulting in an overall reflectivity of 50%. Upon heating above T N-I , the wave plate turns into a half-wave plate, which converts the A temperature-responsive polarization converter, which reversibly changes from a full-wave to a half-wave plate upon heating, is developed. The polymer wave plate has a controlled thickness and is based on a uniaxial aligned nematic semi-interpenetrating network coating containing a specific concentration of a non-crosslinked liquid crystal elastomer. Upon heating, the effective birefringence of the wave plate halves without changing the thickness. The function of the wave plate is demonstrated by sandwiching the tunable polarization conver...

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Section: Fabrication Of the Temperature-responsive Polymer Wave Platementioning

confidence: 81%

“…where A and B are fitting parameters. [23][24][25][26] Thickness Measurements: The thicknesses of the temperatureresponsive wave plate coatings were measured with an interferometer (Forgale Zoomsurf 3D).…”

Section: Methodsmentioning

confidence: 99%

Temperature‐Responsive Polymer Wave Plates as Tunable Polarization Converters

Kragt

Gessel

Schenning

et al. 2019

Advanced Optical Materials

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“…Some organic substances pass from crystaline, solid to isotropic, liquid states, not directly, but through a phase [1,2]. The mechanical and symmetrical properties of these phases are intermediate to the properties of liquids and crystals [3,4]. Because of this, these substances are called liquid crystals or liquid anisotropic crystals.…”

Section: Introductionmentioning

confidence: 99%

QSPR Analysis of a Set of Liquid Crystals in the Benzylideneaniline Class According to their Transition Temperature

Dippong¹,

Avram²,

Goga³

2018

Studia UBB Chemia

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The present paper focuses on the connection amongst the structure of 25 liquid crystals in the benzylideneaniline class and some of their physico-chemical properties. Simple and multiple correlations between transition temperatures and 34 calculated molecular descriptors (25 topological indices and 12 Van der Waals parameters), for each compound, were made. Simple and multiple correlations amongst topological indices and Van der Waals parameters, respectively, observing the variations taking place, are presented.

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