Study On Tuning Fiber Random Laser Based On Photonic Crystal Fibers Filled By Liquid Crystals

Since the Russell's research group from the University of Bath in the UK prepared the first photonic crystal fiber successfully,the photonic crystal fibers have exhibited a rapid development.As a branch of the development of the filled photonic crystal fiber,the liquid crystal filled photonic crystal fiber has presented potential applications in many fields.The liquid crystal filled photonic crystal fiber combines the excellent optical performance of liquid crystal and the special microstructure of the photonic crystal fiber,so that the liquid crystal filled photonic crystal fiber can be designed into various optical devices,such as filters,polarization beam splitters,modulators and thermo-optical switches,etc.Among them,the application of thermo-optical switches made of liquid crystal filled photonic crystal fibers is of great significance in the O-band and C-band of the communication window.In this thesis,we filled the E7 liquid crystal into the photonic crystal fiber to make a thermo-optical switch that can control two communication windows at the same time,and use the thermo-optical switch characteristics of the liquid crystal-filled photonic crystal fiber to control the erbium-doped fiber random laser.The main research contents of the thesis are as follows:(1)The temperature characteristics of the liquid crystal filled photonic crystal fiber.A compact multi-band thermo-optical switch and a temperature sensor were fabricated by the photonic crystal fibers filled with the E7 liquid crystal.Near the clearing point temperature of the liquid crystal,both 8 mm and 10 mm liquid crystal filled photonic crystal fibers used for a multi-band thermo-optic switch.When the temperature is lower than the clearing point temperature of the liquid crystal,the transmission spectrum of the liquid crystal-filled photonic crystal fiber will have a red shift as the temperature rises,and it has a non-linear temperature sensing characteristic.When the temperature is higher than the clearing point temperature,the transmission spectrum of the liquid crystal filled photonic crystal exhibits a blue shift with increaseing the temperature,and it has high linear temperature sensitivity.(2)The laser threshold and output laser intensity of the erbium-doped fiber have been studied.Fiber random laser was generated by pumping a 10 m erbium-doped fiber with a 980 nm fiber laser.The weak Rayleigh scattering in the single-mode fiber provides random feedback for the random laser of the erbium-doped fiber.Different lengths of single-mode fibers will accumulate different degrees of feedback,and affect the properties of the forward and backward output laser in the 10 m erbium-doped fiber.After 10 m erbium-doped fiber is fed back by 25 km,30 km,and 50 km single-mode feedback,the random laser thresholds for both the forward and backward output laser decrease,and the intensity of the output random laser increases.(3)Tuning the erbium-doped fiber random laser by liquid crystal filled photonic crystal fiber.The 8 mm liquid crystal-filled photonic crystal fiber was connected to the forward and backward output ports of the erbium-doped fiber,and the thermo-optical switching performance of the 8 mm liquid crystal-filled photonic crystal fiber was used to adjust the forward and backward output random laser intensity of the erbium-doped fiber.The intensity of the forward and backward output random laser for the 8 mm liquid crystal filled photonic crystal fiber to a single 10 m erbium-doped fiber and 10 m erbium-doped fiber under single-mode feedback of 25 km,30 km and 50 km,are around 30 d Bm.