Tomasz R. Wolinski

Influence of temperature and electrical fields on propagation properties of photonic liquid-crystal fibres

The paper reports temperature and external electrical field effects on propagation properties of a photonic liquid-crystal fibre composed of a solid-core photonic crystal fibre filled either with a prototype nematic liquid crystal characterized by extremely low (of the order of ~0.05) material birefringence or with a typical nematic pentylo-cyano-biphenyl, PCB (birefringence of the order of ~0.2). The nematic liquid crystal was introduced into the micro holes of the photonic crystal fibre by the capillary effect. Depending on the liquid crystal material introduced into the micro holes and due to anisotropic properties of the photonic liquid-crystal fibre, switching between different guiding mechanisms controlled by temperature and an external electric field has been demonstrated. This creates great potential in fibre optic sensing and optical processing application.

Influence of high hydrostatic pressure on beat length in highly birefringent single-mode bow tie fibers

New experimental studies on the effects of high hydrostatic pressure on highly birefringent optical fibers are presented. Using Rayleigh scattering, the effect of beat length modification in highly birefringent singlemode bow tie fibers under high pressure up to 100 MPa was investigated. The results indicate that the beat length decreases with pressure, with the mean coefficient of 1/L(B0)|dL(B)/dp| = 0.15%/MPa. A similar decrease of beat length was observed when uniaxial longitudinal stress was applied to the bow tie fiber. A more developed semiphenomenological interpretation of these experimental results is also presented in the paper.

Polarization effects in photonic liquid crystal fibers

In this paper we present experimental results of polarization properties of photonic liquid crystal fibers, also with permanent anisotropy achieved by using photo-aligning layers within the micro holes. Single-polarization propagation has been demonstrated in three ways: either by application of an external electric field, by using special aligning layers or by using an anisotropic host—commercially available highly birefringent Blazephotonics photonic crystal fiber infiltrated with liquid crystals. The possibility of thermal birefringence tuning in photonic liquid crystal fibers by using low-birefringence liquid crystals is also presented.

Photonic crystal fiber tip interferometer for refractive index sensing

In this paper we present an interferometer based on photonic crystal fiber (PCF) tip ended with a solid silica-sphere for refractive index sensing. The sensor is fabricated by splicing one end of the holey PCF to a single mode fiber (SMF) and applying arc at the other end to form a solid sphere. The sensor has been experimentally tested for refractive index and temperature sensing by monitoring its wavelength shift. Measurement results show that the sensor has the resolution of the order of 8.7×10(-4) over the refractive index range of 1.33-1.40, and temperature sensitivity of the order of 10 pm/°C in the range of 20-100 °C.

Photonic Liquid Crystal Fibers for Sensing Applications

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.

Photonic liquid crystal fibers : a new challenge for fiber optics and liquid crystals photonics

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.

Self Focusing in Liquid Crystalline Waveguides

Abstract Nonlinear self-focusing of the laser beam in waveguide with nematic homeotropically aligned liquid crystalline layer is analysed theoretically and observed experimentally. The nonlinearity is caused by the reorientational effect and the stable self-trapped beams are created by the spatially periodic reorientation in the liquid crystalline layer.

Low-loss propagation and continuously tunable birefringence in high-index photonic crystal fibers filled with nematic liquid crystals

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 (approximately 1.95) that is much higher than silica glass index (approximately 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 approximately 0.15 dB/cm and for the PCF infiltrated with 5CB LC was slightly higher (approximately 0.19 dB/cm), resulting in a significant reduction to approximately 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).

Fabrication and Characterization of a Highly Temperature Sensitive Device Based on Nematic Liquid Crystal-Filled Photonic Crystal Fiber

We report on the fabrication and characterization of a highly sensitive temperature sensor by selectively filling the nematic liquid crystal (NLC) 6CHBT into a single void within the photonic crystal fiber (PCF) structure. The temperature response of the device is experimentally characterized, showing good linearity, repeatability, and sensitivity at around -3.90 nm/°C within the temperature range from 44°C to 53°C. The mode properties of the device are theoretically investigated, confirming the mode coupling principle and the temperature sensitivity of the device.

Novel Miniaturized Fabry–Perot Refractometer Based on a Simplified Hollow-Core Fiber With a Hollow Silica Sphere Tip

In this paper, we report and demonstrate a novel miniaturized intrinsic Fabry-Perot interferometer (IFPI) based on a simplified hollow core fiber ended with a hollow silica sphere tip. The hollow core fiber is spliced to single mode fiber and subsequently applied with fusion arc at the end, forming a hollow sphere with a thin silica wall. The reflection spectrum is modulated by the environment of the sensor head such as refractive index and temperature. By monitoring and measuring the fringe visibility, the measurement of refractive index of the calibrated solution is carried out experimentally. The achievable refractive index (RI) resolution is about 6.2 × 10-5 by measuring the fringe visibility. This sensor offers key features and advantages of IFPI including easy fabrication, low loss, low cost, and good fringe visibility. Furthermore, the sensor head is made of single material and therefore has the potential for measurements in harsh environments. Measurements at high temperatures up to ~ 1000°C are carried out. Results reveal that the sensor has low temperature.