Slawomir Ertman

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.

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 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.

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).

Index Guiding Photonic Liquid Crystal Fibers for Practical Applications

Photonic liquid crystal fibers (PLCFs) can be categorized in two principal groups: index guiding PLCFs and photonic bandgap PLCFs. In this paper we focus on index guiding PLCFs in which effective refractive index of the micro structured cladding filled with liquid crystal is lower than refractive index of the fiber core. In these fibers broadband propagation of light is observed and also effective tuning of guiding properties is possible. In this paper PLCFs with tunable attenuation, retardation and polarization dependent losses are reported. We also enumerate some potential applications of index-guiding PLCFs, together with discussion of few technical issues important in the context of future development (i.e., effective electrical steering and connecting with standard fibers).

Polarization Optics of Microstructured Liquid Crystal Fibers

The present paper discusses polarization phenomena occurring in microstructrured liquid crystal fibers and in particular solid-core photonic crystal fibers infiltrated with liquid crystals. We report on the latest experimental polarization characteristics of microstructured photonic crystal fibers filled with prototype nematic liquid crystal guest materials characterized by either extremely low (of the order ∼ 0.05) or medium (of the order ∼ 0.2) material birefringence. Due to anisotropic properties of the microstructrured liquid crystal fibers switching between different guiding mechanisms as well as electrically and temperature-induced tuning of light propagation have been demonstrated. These preliminary results hold great potential for both fiber-optic sensing and in-fiber polarization mode dispersion control and compensation.

Temperature tuning of polarization mode dispersion in single-core and two-core photonic liquid crystal fibers

In this paper we present numerical and experimental results of propagation and polarization properties of the photonic liquid crystal fibers (PLCFs) in which only selected micro holes were filled with nematic liquid crystal (LC) guest materials. As a host photonic crystal fiber (PCF) structure, we used a commercially available highly birefringent PCF (Blazephotonics, UK). A tunable laser operated at infrared has powered the PLCFs under investigation infiltrated by the 1550 nematic LC synthesized at the Military University of Technology. Temperature induced changes of the polarization mode dispersion (PMD) as well switching between fundamental and higher order modes and also single-core and two-core propagation were successfully demonstrated.

Patterned alignment of liquid crystal molecules in silica micro-capillaries

Controllable alignment of liquid crystal molecules inside micro-capillaries is an essential issue to obtain repeatable devices based on photonic liquid crystal fibres. In this paper we describe in detail the photo-alignment technique for micro-capillaries based on sulfuric azo dye SD-1 which allows for stable alignment of liquid crystal molecules in the direction defined by the polarisation of ultraviolet light. Two-step selective irradiation allowed for periodic patterns in which two different alignment configurations were observed simultaneously within a single capillary. The obtained alignment was very stable, even in capillaries as thick as 125 μm of internal diameter.

Liquid crystal molecular orientation in photonic liquid crystal fibers with photopolymer layers

Photonic liquid crystal fibers (PLCFs) combine unique properties of photonic crystal fibers and liquid crystals (LCs). Liquid crystal molecules orientation within the PLCFs has crucial impact on their optical properties since it determines the radial refractive index profile of the LC-filled micro-holes. There are many techniques used for LC molecules orientation control, but most of them are not suitable for application in microstructured fibers characterized by holes with diameters in the order of few micrometers. It seems that the only method that could be applied in PLCFs is using of thin photopolymer layers, in which surface anisotropy can be induced in the way of photochemical reactions. In this paper we present preliminary experimental results of the photoinduced molecular alignment in the PLCF induced by a thin polyvinylcinnamate (PVCi) film irradiated with the linearly polarized ultraviolet light.