Emerging photonic devices based on photonic liquid crystal fibers

Abstract

Abstract-Photonic liquid crystal fibers (PLCFs) define a new class of optical waveguides that combines unique properties of microstructured photonic crystal fibers and liquid crystals. Current progress of research in the field of PLCFs means that a new class of emerging photonics devices can be expected, i.e. tunable attenuators, tunable broad-band filters, tunable polarizers (with an arbitrary PDL and a variable axis of polarization), tunable waveplates, and tunable phase shifters with high retardance will appear in the near future. In this work we would like to discuss this perspective, paying special attention to two most challenging technological issues such as control of LC molecules orientation and permanent connecting of PLCFs to standard fibers.Transmission properties of photonic crystal fibers (PCFs) can be tailored in a wide range by changing geometry of their microstructured cladding [1]. Generally, in the PCFs light can be guided by two different mechanisms: indexguiding (similar to the classical waveguide effect based on mTIR-modified total internal reflection) and the photonic band-gap (PBG) effect. The PBG propagation occurs when the effective refractive index of the microstructured cladding is higher than the refractive index of the core, and in this case only selected wavelengths can be guided [1]. Transmission properties of PCFs can be also arbitrarily changed by filling their micro-holes with various substances [2] and liquid crystals (LCs) belong to the most interesting materials for these applications due to the high sensitivities to external physical fields. The first paper on photonic liquid crystal fibers (PLCFs) has been published in 2003 [3]. Since that time there has been a continuous increase in the number of research groups working in the field, and thermal tuning of the photonic band-gap in the PLCFs has been shortly reported also by different authors [4][5][6] Electrical tuning in a hollow-core liquid-crystal photonic crystal fiber was demonstrated in 2004 [7] and also in silica glass-core photonic liquid crystals fibers [8][9]. In Ref.[9] thermal tuning of the PLCF guiding mechanism was presented by using a special lowbirefringence LC mixture with the ordinary refractive index lower (in a certain temperature range) than the refractive index of the silica glass. The efficiency of electrical tuning could be significantly improved by using dual-frequency liquid crystals [10][11] [11,[17][18][19] have been obtained in silica-based PCFs filled with LCs. Other interesting effects observed in the LC-PCFs were based on a PCF made of multi-component glasses, with increased value of the refractive index, so that index-guiding propagation was possible even after infiltration with LCs. In particular, low-loss propagation and continuously tunable birefringence was experimentally demonstrated [20].Recently, a number of prototype tunable devices based on PLCFs have been developed in our laboratory [21,22]. These devices include tunable attenuators, tunable broadband filters, tunable polarizers ...

Guided-wave liquid-crystal photonics

“…As arc-fusion can easily lead to LC damage, mechanical splicing is the safest way for the interconnection of LC-PCF fiber segments, with ''cold'' splicing with a UV-curable adhesive being a possible alternative solution. 153 The employment of SU-8 fixing structures as demonstrated in Fig. 15(a) has been shown to minimize the misalignment of fiber coupling and reduce the total insertion loss of the device, 154,155 whose assembly can be further strengthened by sealing with epoxy glues.…”

Full-Vectorial Description of the Light Guidance in Anisotropic Photonic Liquid Crystal Fibers

“…High tunability of optical properties of PLCFs, achieved by applying external factors like temperature, strain, pressure, electric or/and magnetic elds, as well as by the light-beam itself (e.g., when nonlinear eects are considered), brings various potential applications to the eld of ber optics [48, 10,11]. However, it has to be underlined that owing to their quasi-crystalline and non-uniform nature, LCs introduce further challenge in theoretical and experimental characterization of the corresponding ber optics elements and components.…”

Birefringence measurement of polymer photonic crystal fibers infiltrated with liquid crystals by depolarization of light effect

“…Nowadays there has been growing interest in photonic liquid crystal fibers (PLCFs) and their applications in different areas of technology [1][2][3][4]. PLCFs combine the properties of a photonic crystal structure with electrooptical properties of liquid crystals (LCs).…”