Nonlinear optical properties of composites based on conductive metal-alkanoate liquid crystals

Abstract

The dynamic holography in new composite materials based on a novel class of metal-alkanoate ionic liquid crystals (ILCs) is studied experimentally and theoretically. The composites are formed as a dielectric dye film covered by lyotropic metal-alkanoate ILC and ionic smectic glasses with doped dye molecules. The dynamic gratings are created by nanosecond pulses of double frequency Nd:YAP laser, the recording demonstrates fast erasure time of residual thermal gratings. The nonlinear optical properties are determined by the resonance nonlinearity in photosensitive centres of ILC. Note, that permanent relief gratings will be formed on a dielectric dye film only as well as in composite cells either with nematic LC or with polymers under action of pulsed laser radiation. Lyotropic ILC layer applied over the dye film provides the dynamic regime of grating recording in composite cells. We found a secondary thermal grating is much smaller, the conductive ILC matrix provides effective heat dissipation and erasure of this thermal grating. A theory of Raman-Nath self-diffraction holography on thin films followed from the wave equation and the nonlinear mechanism of absorption saturation is developed to explain experimental results.

Synthesis, NMR, Raman, thermal and nonlinear optical properties of dicationic ionic liquids from experimental and theoretical studies

“…In order to determine the relation between NLO properties of ILs, Águila et al [15] indicated that these ILs are good candidates for the development of NLO devices. Ostroverkhova et al [24] showed that ILs can be used in materials for optical holographic recording, in catalysis [25] and for electrical-controlled memory systems [26]. It is possible to increase the NLO response of ILs, with the increase of the π-conjugation group and introduce strong anion.…”

Tunable optical and nonlinear optical response of smectic glasses based on cobalt alkanoates

“…Recently, a variety of metal alkanoates and their various phase states have been used to fabricate optical and nonlinear optical materials, for instance double-layer cells such as "photosensitive film -ionic lyotropic liquid crystal" [5], ionic lyotropic liquid crystals doped with electrochromic impurities [5,6], and mesomorphic glasses containing dissolved dye molecules [7]. It may be noted that all the composite materials mentioned can also be considered to be homogeneous or inhomogeneous "guest-host" systems, the guest being photosensitive dopants or films with strong and rapid nonlinear optical response, and the host being soft or rigid mesomorphic ionic matrices which can be used as orienting, holding, viscoelastic, transport or heatconducting anisotropic media [5][6][7][8][9]. Such novel guesthost composite materials exhibit rapid (∼ ns-ps) and sufficiently strong (χ (3) ∼10-8 esu) cubic nonlinear optical response, and are promising for a variety of applications.…”

Mechanism of Dimerization of Viologens in Liquid Crystalline Medium

“…While thermotropic liquid crystals, when being in the mesophase or glassed mesophase [5,6], have significant optical absorption in the visible region, metal alkanoates that form the lyotropic liquid crystalline phase generally do not absorb. To provide liquid crystalline materials with desired optical properties, one needs to combine lyotropic ionic liquid crystals (LILC) and different impurities, namely polymethine dyes [7], viologens, etc. Particularly, the introduction of photo-and electrochromic impurities such as viologens allows creating materials with optical properties that could be regulated, by using the ultraviolet irradiation or application of an external electric field.…”