Study On The Laser Properties Of Cholesteric Liquid Crystals With Core-shell-type Compound Photonic Crystal Microstructure

Compared with other traditional lasers,the dye-doped cholesteric liquid crystal laser does not require an external resonant cavity,and has the characteristics of simple preparation,low threshold and small volume.This kind of laser has many application prospects in many fields such as flat display,medical equipment,photon integration and so on.However,the band-edge lasing only occurs in the tens of micrometers in the pumping area,and the lasing range is very small.When the liquid crystal molecules in the planar cholesteric liquid crystal lasers are packed in a box with a thickness of micrometers and a length of centimeters,it cannot be directly used as the study of Point light source,thus the study of planar cholesteric liquid crystal lasers will be limited,so the miniaturization of liquid crystal lasers has become a relatively popular research trend.Microfluidic technology,as a new method for manipulating small volumes of liquids,has gradually become a research hotspot in chemistry,medicine,biology,materials science and other disciplines because of its small size,simplicity and speed,and low consumption.This technology mainly integrates channels on the micrometer scale(tens to hundreds of micron).Through the control and manipulation of the designed device channels,sample preparation,separation,reaction and detection will be achieved.Microfluidic technology can be used to prepare the microstructures of single and multiple emulsion,the microstructures have adjustable morphology and controllable and uniform size,which is an effective method for preparing micronano structures.In summary,the complex core-shell-type structure of cholesteric liquid crystals can be prepared by microfluidic technology.There are multiple laser modes in the prepared core-shell-type structure,which provides a new idea for miniaturization of dye-doped liquid crystal lasers.The thesis mainly uses the coaxial glass capillary microfluidic device to prepare O/W/O/W and W/O/W multiple emulsion microstructures.The laser pump test system designed and constructed by the research group can be used to test the laser characteristics of the sample.Study and analyze the laser resonance mechanism in the core-shell microstructure.In the O/W/O/W structure,internal phase is dye doped isotropic material,the shell phase material is cholesteric liquid crystal,forming a single-gain triple emulsion microstructure;W/O/W structure introduced colloid Photonic crystals,as water phase materials,form a double emulsion structure with double reflection bands;the materials and structures of the two microstructures will lead to different lasing behaviors,which can be used as a new type of micro laser in the "Lab"(lab-on-chip,LOC).