The paper presents our latest experimental results on the influence of temperature, an external electric field, and hydrostatic pressure on propagation properties of the photonic crystal fibers infiltrated with liquid crystals of low and medium material anisotropies. Measurand-induced shifts of the photonic bandgap wavelengths give information about the value of temperature, voltage, and pressure. Moreover, temperature-dependent positions of the photonic bandgap wavelengths in the transmission spectrum can serve to determine the thermal characteristics of the liquid crystal ordinary refractive index.

An all-normal dispersion supercontinuum generation in the range of 950 ÷ 1100 nm in photonic crystal fiber with core infiltrated with toluene is reported. The regular lattice hollow core photonic crystal fiber with a large core of 12 μm was designed and developed. The photonic crystal fiber core was selectively filled with toluene. The investigated fiber has normal dispersion in the wavelength range of 0.5 ÷ 2μm, while the absolute value of dispersion varies from 150 to 5 ps/nm/km in the range of 1 ÷ 2µm wavelength. The fiber nonlinear coefficient is 130 W⁻¹km⁻¹ as a result of the trade-off of high nonlinearity of toluene and a large mode area of the fundamental mode. The large mode area is required for the efficient delivery of high power pulses from large mode area input fiber in an all fiber system. As a pump source, a standard subpicosecond fiber laser emitting at 1030 nm with 10nJ pulse energy was used.

All-normal dispersion supercontinuum generation (SG) in a large hollow core photonic crystal fiber (PCF) infiltrated with carbon tetrachloride is studied experimentally. The PCF is optimized to have a flat normal dispersion in a broadband range (0.8–1.7 µm) varying from -150 to 0 ps/nm/km. The effective mode area at pump wavelength (λ=1030 nm) is as large as 42.2 µm² and readily meets the requirements for an all-fiber supercontinuum system. Infiltration of the core with carbon tetrachloride ensures a high nonlinear coefficient of the fiber equal to 22 1/W/km. Using an off-the-shelf 1030 nm fiber laser with 400 fs and 25 nJ input pulses, we generated an all-normal supercontinuum in the 850–1250 nm wavelength range.

The paper reviews and discusses the latest developments in the field of the photonic liquid crystal fibers that have occurred for the last three years in view of new challenges for both fiber optics and liquid crystal photonics. In particular, we present the latest experimental results on electrically induced birefringence in photonic liquid crystal fibers and discuss possibilities and directions of future developments.

Experimental investigations of microstructured fibers filled with liquid crystals (LCs) have so far been performed only by using host fibers made of the silica glass. In this paper, the host photonic crystal fiber (PCF) was made of the PBG08 high-refractive index glass (~1.95) that is much higher than silica glass index (~1.46) and also higher then both ordinary and extraordinary refractive indices of the majority of LCs. As a result, low-loss and index-guiding propagation is observed regardless of the LC molecules orientation. Attenuation of the host PCF was measured to be ~0.15 dB/cm and for the PCF infiltrated with 5CB LC was slightly higher (~0.19 dB/cm), resulting in a significant reduction to ~0.04 dB/cm of the scattering losses caused by the LC. Moreover, an external transverse electric field applied to the effective photonic liquid crystal fiber (PLCF) allowed for continuous phase birefringence tuning from 0 to 2·10⁻⁴.