High-order reflections from a cholesteric helix induced by an electric field

Blinov, L. M.; Belyaev, Sergey V.; Kizel, V. A.

doi:10.1016/0375-9601(78)90124-x

Cited by 19 publications

(5 citation statements)

References 5 publications

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“…The field of the light wave decays exponentially over a distance L c ∼ ε −1 a and does not "see" the remaining thickness of the cholesteric LC. 96 Comparing results described here with the experimental investigations of the pitch increase in a low-frequency electric field lying in the plane of the cholesteric LC layer, [145][146][147] it is possible to say that the electric field reached in our experiments was much higher than the unwinding field in Refs. 145-147 (∼ 10 4 V/cm).…”

Section: Time Interval Min Output Power W T 1 T 2 T 1 T 2 T 2 Tsupporting

confidence: 70%

Nonlinear Optical Response of Cyanobiphenyl Liquid Crystals to High-Power, Nanosecond Laser Radiation

Lukishova

2000

J. Nonlinear Optic. Phys. Mat.

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Results from investigations are summarized into: (1) transient refractive and absorptive (two-photon) nonlinearities at 0.532 μm by the Z-scan method, and (2) reflective nonlinearity in the near-IR, of linearly nonabsorbing cyanobiphenyl liquid crystals under nanosecond laser irradiation. (1) For isotropic liquid crystals at the several-nanosecond time scale and several tens-micrometers beam-waist-diameter, transient molecular-reorientation and thermal/density refractive nonlinearities compete in changing the sign of the total transient refractive nonlinearity. For the different, given pulse durations, the influence of coupled thermal and density effects on nonlinear refraction depends, through buildup time, on the beam-waist diameter. Nonlinear absorption coefficients depend on the incident intensity. For planar nematic layers, cumulative effects in heating (and in refractive nonlinearity) were observed even at low, 2–10 Hz pulse repetition rate. These results are useful for optical power limiting applications, and for intensity and beam-quality sensors of pulsed, high-power lasers. (2) Reflective nonlinearity of chiral-nematic (cholesteric) mirrors near selective reflection conditions for circular polarized light at λ=1.064 μm was studied both under free space irradiation and inside a laser resonator. Specially chosen experimental irradiation conditions make it possible to attribute the observed changing of reflectivity to athermal helix unwinding by the optical field. The results can find applications in laser-resonator mirrors, Q-switches and soft apertures for beam-profile formation, and also in showing the limits of use cholesteric optical elements in high-power laser beams.

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Section: Time Interval Min Output Power W T 1 T 2 T 1 T 2 T 2 Tsupporting

confidence: 70%

Nonlinear Optical Response of Cyanobiphenyl Liquid Crystals to High-Power, Nanosecond Laser Radiation

Lukishova

2000

J. Nonlinear Optic. Phys. Mat.

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“…In the circularly polarized light field the electric-field vector changes direction throughout the CLC-layer thickness (while the low-frequency-field vector orientation remains fixed), suffering an exponential drop in magnitude over the critical length L cr ~ ε a -1 and, thus, remaining unable to "see" further into the CLC layer 21 . A comparison of our results with those on helix pitch dilation in a low-frequency field directed along the plane of a planar-alignment of a CLC layer [31][32][33][34] shows our optical field strength to considerably exceed the value of ~ 10 4 V/cm proven adequate [31][32][33][34] for helix untwisting at low frequencies.…”

Section: Discussion Of the Results On Nonlinear Selective Reflection mentioning

confidence: 84%

Liquid crystals under high-power, nanosecond laser irradiation

Lukishova

2013

SPIE Proceedings

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High-damage threshold liquid crystal optical elements are used for high-power laser applications as mirrors, waveplates and optical power limiters. Several nonlinear optical effects under high-power, nanosecond laser irradiation of liquid crystals will be outlined: (1) athermal helical pitch dilation and unwinding of cholesteric mirrors by the field of a light wave (in free space and in a laser resonator); (2) dependence of nonlinear refraction of liquid crystal on the laser beam diameter in presence of two-photon absorption; (3) cumulative effects in nonlinear absorption and refraction at low repetition rate (5-10 Hz); (4) feedback-free kaleidoscope of patterns in dye-doped liquid crystals (hexagons/stripes).

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“…[ 33 ] While strain‐induced depolarization of CLCEs has been demonstrated, [ 14,34,35 ] the appearance of higher‐order reflection bands in CLCE is distinctive in the literature. These bands have been shown in non‐elastomeric CLC materials by using complex preparation methods such as interdigitated electrodes, [ 36,37 ] dichroic initiators, [ 38–41 ] or polarized argon lasers. [ 42 ] Here we show that shifting the reflection wavelength to longer pitches in CLCE capable of large deformation allows for the observation of the mechanically induced higher order reflection bands.…”

Section: Resultsmentioning

confidence: 99%

Large Range Thermochromism in Liquid Crystalline Elastomers Prepared with Intra‐Mesogenic Supramolecular Bonds

Schlafmann,

Alahmed,

Lewis

et al. 2023

Adv Funct Materials

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Liquid crystalline elastomers (LCEs) that retain the cholesteric phase (CLCEs) are soft, polymeric materials that retain periodic structure and exhibit a selective reflection. While prior studies have examined thermochromism in CLCEs, the association of temperature change and reflection wavelength shift has been limited to 1.4 nm °C−1. Here, CLCEs with intra‐mesogenic supramolecular bonds are prepared to enhance tunability as well triple the rate (e.g., 4.8 nm °C−1). Specifically, these materials incorporate liquid crystalline monomers based on dimerized oxy‐benzoic acid (OBA) derivatives. Increasing the concentration of the OBA comonomers increases the magnitude of red‐shifting thermochromism of the selective reflection. At and above a threshold concentration, the selective reflection in the CLCEs can disappear upon heating, analogous to on‐off “switching.” Further, the introduction of the supramolecular bonds within the CLCE enable mechanical programming and enhanced one‐time tunable thermochromism via a one‐way shape memory process. Accordingly, this research could enable functional use in low temperature sensitive optical elements, fail‐safe thermal indicators for food packaging, and smart window coatings.

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High-order reflections from a cholesteric helix induced by an electric field

Cited by 19 publications

References 5 publications

Nonlinear Optical Response of Cyanobiphenyl Liquid Crystals to High-Power, Nanosecond Laser Radiation

Nonlinear Optical Response of Cyanobiphenyl Liquid Crystals to High-Power, Nanosecond Laser Radiation

Liquid crystals under high-power, nanosecond laser irradiation

Large Range Thermochromism in Liquid Crystalline Elastomers Prepared with Intra‐Mesogenic Supramolecular Bonds

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