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The paper presents the latest experimental results on influence of temperature and external electrical fields on propagation properties of a photonic liquid-crystal fiber composed of a photonic crystal fiber infilled with a nematic liquid crystal characterized by either extremely low (of the order ~ 0.05) or relatively high (of the order ~ 0.3) material birefringence. The nematic liquid crystal was introduced into the micro holes of the photonic crystal fiber by the capillary effect. Due to anisotropic properties of the obtained photonic liquid-crystal fiber, switching between different guiding mechanisms has also been demonstrated.

Measurements of the temperature dependence of the quadratic electrooptic coefficient |g 1111 -g 2211 | of ADP were made. The coefficient is found to decrease with an increase in temperature. The results show that the intrinsic quadratic electrooptic coefficient |M 1111 -M 2211 | defined in terms of polarization also dependes on temperature. Employing the temperature dependence of |M 1111 -M 2211 | estimation of antipolarization in lowtemperature antiferroelectric phase of ADP is made.

The isotopic effect on the magnitude of quadratic electrooptic coefficients in KDP is investigated. By employing both the Miller rule and assumption of a rough constancy of intrinsic electrooptic coefficients, one can expect these quadratic electrooptic coefficients which are related to the electric field applied in the [100] direction, i.e. the coefficients g1111, g2211 and g3311 to be in DKDP almost twice larger than that for KDP. Our measurements of the relative quadratic coefficient n03g1111‐ne3g3311 in DKDP are in contradiction with the prediction. We found g1111, g2211 and g3311 to be weakly dependent on the deuteration.