Vector photochromism in polarization-sensitive materials

Abstract

The phenomenon of vector photochromism was observed in some high-efficient polarization-sensitive materials depending on the radiant exposure of the inducing linearly polarized actinic light. The phenomenon has the purely vector nature because the absorption of the irradiated and unirradiated areas of the material is practically identical when we use unpolarized probing light. However, an essential change in the absorption spectrum was observed under probing the sample by linearly polarized nonactinic light when it passes through an analyzer, and this change depends on the value of radiant exposure. The kinetics of the photoanisotropy induced by linearly polarized actinic light at 457 nm was studied in case of wavelengths of 532 and 635 nm of the probing beam. The noticeable difference in absorbance was observed with increase in radiant exposure from 60 J/cm² up to 250 J/cm² for the used wavelengths of the probing beam. The experimental results obtained in polarization-sensitive material based on the ammonium salt of the azodye Mordant pure yellow in a gelatin matrix are presented. The dependence of the effective anisotropy on the material thickness has been investigated. The mechanism of the phenomenon is discussed. The observed effect can be used for creating dynamic polarization spectral filters controlled by light and the spectrally selective dynamic polarization holographic gratings.

Liquid Crystal Pancharatnam–Berry Micro‐Optical Elements for Laser Beam Shaping

“…On the substrates with exposed photoalignment materials, a toluene solution of RM257 (Wilshire technology) and photoinitiator I651 (CIBA-GEIGY Corp.) is spin coated with 3000 RPM spin speed for 30 s and then cured with UV light (365 nm, 80 nm bandwidth) for 15 min in vacuum at room temperature. [58,59] To achieve high spatial resolution, we used two 20 × objectives with the same numerical aperture (NA = 0.42) for 1:1 projection (i.e., OB1 and OB2 in Figure 1d). The total phase retardation of the LC film is monitored for each additional RM257 layer by using a PolScope, [56] and the spin-speed or the RM257 concentration is fine tuned to achieve the target phase retardation of 266 nm, i.e., half of the working laser wavelength (λ 0 = 532 nm).…”

“…As the photoalignment material, we used Mordant Pure Yellow, an azo-dye molecule [57] which has a molecular structure and performance similar as the SD-1 (sulfuric biazo dye). [58,59] To achieve high spatial resolution, we used two 20 × objectives with the same numerical aperture (NA = 0.42) for 1:1 projection (i.e., OB1 and OB2 in Figure 1d). The spatial resolution of the photopatterning system with a 0.45 µm exposure wavelength can be estimated by using the Rayleigh resolution limit:…”

Photoanisotropy in polarization-sensitive polymer materials based on the media with covalently-bonded components

“…The preliminary results of the investigation of this phenomenon were already presented. [11][12][13] In Ref. [12,13] we used the high-efficient polarization-sensitive material which is a solid solution by its compositions based on MPY-NH 4 the ammonium salt of the polyhydric acid azodye Mordant Pure Yellow [also known as Mordant Yellow 26 (MY-26)] in the matrix of photogelatin.…”

“…[4][5][6][7][8][9][10] Unlike this in some high-efficient polarization-sensitive materials obtained by us, we have observed the anomalous kinetics of photoanisotropy induction after reaching its maximum value when material is exposed by actinic linearly polarized radiation and simultaneously is probed by monochromatic nonactinic linearly polarized light beam. [11][12][13] After reaching the maximum the intensity of the transmitted probing beam starts decreasing with radiant exposure of inducing light increasing and almost reaches zero for the given wavelength of the probing beam ( Figure 1, curve 2). The intensity of the probing beam passing through the exposed material essentially depends on radiant exposure of the inducing light, on a wavelength of the probing beam and on the thickness of the emulsion layer.…”

“…The intensity of the probing beam passing through the exposed material essentially depends on radiant exposure of the inducing light, on a wavelength of the probing beam and on the thickness of the emulsion layer. It was shown [11][12][13] that this phenomenon has the purely vector nature because the transmission of the material during probing by nonpolarized light is practically unchanged at different radiant exposures. However, an essential change in transmission was observed under probing the sample by linearly polarized nonactinic light.…”