Twist Cylinders Structure Liquid Crystal And Its Photonic Applications

Blue phase liquid crystals(BPLCs)and sphere phase liquid crystals(SPLCs)are consisting of twist cylinders structure.BPLCs consist of double twist cylinders(DTCs)structure.BPLCs usually exist in a narrow temperature range,between isotropic phase and chiral nematic(N*)phases.Compared with the conventional liquid crystal materials,BPLCs show several attractive features,such as sub-millisecond response time;alignment free because of its self-assembled structure;Optical isotopic status no need electric fields;no need compensation film.BPLCs usually exist in several temperature ranges,which is the major reason why BPLCs cannot be widely applied.In 2002,polymer-stabilized blue phase liquid crystals(PS-BPLCs)have been raised which exhibits great performance on broadening the temperature range of BPLCs to more than 60 ~oC,which makes BPLCs become the hot spots and focus once again in the display domain and attracts people's interest for its great potential in photonic researches.Besides BPLCs,SPLCs consist of three-dimensional twist sphere(3-DTS)structures and disclinations among them.SPLCs exist in a narrow temperature range,approximately several degrees centigrade,between isotropic phase and N*or between isotropic phase and blue phase.Inspired by PS-BPLCs,the temperature range of SPLCs has been broadened extensively,greater than 80 ~0C,because we found that the disclinations lines has been stabilized by the polymer chains.Besides wide range temperature,SPLCs also shows several attractive features,such as quick sub-millisecond response time;wide field angles.Based on these characteristics,SPLCs show great potential in displays,phase modulation and random lasing.Although polymer network broadens the temperature range of BPLCs and SPLCs,some extra issues have been brought in such as high driving voltage,residual birefringence and hysteresis.Recently,a template technique has been raised to PS-BPLC,broadening the temperature range of BPLC to more than 250~0C.In consideration of BPLCs and SPLCs having the similar twist cylinders structures,we broadened the temperature range of SPLCs to more than 175~0C by templated SPLCs,which improves the thermal stability of SPLCs greatly.To optimize the material systems of the templated sphere phase,the dissertation has investigated the threshold polymer concentration of the template to reconstruct the SP,whose technology has a positive effect on the application of the BPLCs.The dissertation also investigates the application on photonic domain by templated SPLCs;using the templated SPLCs induces random lasing.Though temperature could induce random lasers,the temperature range of random lasing exists in a narrow range and the random lasing can not exists in room temperature.The template method effectively improves the shortcomings mentioned above.We can not only induce the random lasing in room temperature,but also induce the wide temperature one,which is about 175~oC.Besides,with different polymer concentrations,the reconstructed SPLC random lasing may achieve more than 40nm wavelength continuous shifting by electric field modulation.Templated SPLCs show great potential for photonic applications.