The Design And Properties Research Of Functional Devices Based On Filled Photonic Crystal Fiber

The study of the interaction between light,metal and dielectric micro-nano structures is one of the core scientific issues in the field of optoelectronics.Photonic crystal fibers(PCFs)filled with metal wire or coated with metal films have the dual advantages of surface plasmon resonance(SPR)effect and flexible design of optical fiber structure,which provides a new carrier and break through point for the development of new optoelectronic devices.PCF polarization filter based on SPR technology has the characteristics of small size,easy integration and high extinction ratio.PCF sensor based on SPR effect has the characteristics of high sensitivity and wide detection range.In this paper,a variety of metal filled photonic crystal fiber polarization filters and sensors for special applications are designed and simulated by the finite element method.The characteristics of temperature sensor based on alcohol filled photonic crystal fiber are experimentally studied,which can provide important reference for further research and development of filled photonic crystal fiber polarization filters and sensors.The main works of this paper are as follow:First,two kinds of high extinction ratio photonic crystal fiber polarization filters with large air holes coated with gold film are proposed.They all contain two gold-plated large air holes.The asymmetry structure makes the resonance positions of two vertical polarization states well separated.Because the presence of gold layer,the loss of one polarization direction is much larger than that of another perpendicular polarization direction,so the polarization filtering is realized effectively.The influence of the thickness of gold layer,the diameter of pores,and the position of pores center on the fiber is analyzed by the finite element method and mode coupling theory.By adjusting the structure parameters,effective polarization filter is realized at two typical optical communication wavelengths of 1.31 ?m and 1.55 ?m.The polarization filter has the characteristics of simple structure,short length and high extinction ratio.Second,two kinds of broad band photonic crystal fiber polarization filters based on surface plasmon resonance are designed.One is the circular pore hexagonal arrangement optical fiber modulated by gold film.Another is the elliptical pore hexagonal arrangement optical fiber modulated by gold wire.The transmission characteristics of these two filters are studied by using the finite element method and the mode coupling theory.And the influences of the structural parameters on the fiber loss and dispersion are analyzed.By optimizing structure parameters of circular pore hexagonal arrangement PCF modulated by gold film,the extinction ratio can reach 2084 dB and 1902 dB at 1.55 ?m and 1.48 ?m respectively when the fiber length is 3 mm.The usable bandwidth that extinction ratio value is greater than 20 dB is 1000 nm,covering the whole optical communication band from 1 ?m to 2 ?m.Third,two kinds of gold coated D-shape photonic crystal fiber refractive index sensor and temperature sensors are designed.Surface plasmon resonance can be realized by depositing gold layer on D-shape surface.The uniformity of metal coating is better,the preparation process is more mature.At the same time,D-shape optical fibers provide window for the optical field leakage of fiber core,which enhances the coupling resonance intensity between the core mode and surface plasmon mode.The resonance effect and coupling mechanism between plasmon mode and core mode on the D-shape surface of optical fiber are simulated and investigated by finite element method,and the influence of fiber structure parameters on the sensing characteristics is further analyzed.The maximum sensitivity of the optimized D-shape refractive index sensor can reach 31000 nm/RIU,and the detection range is from 1.31 to 1.40.The sensitivity of D-shaped temperature sensor can reach 36.86 nm/°C and the detection range is from 10 °C to 85 °C.At the same time,a kind of outside ring gold plating temperature sensor is proposed,its transmission mode and sensitivity are studied.The maximum sensitivity of this sensor is 9.11 nm/°C and the detection range is from 0 °C to 60 °C.Finally,the temperature sensing characteristics of filled photonic crystal fiber are experimentally tested and analyzed.An experimental study on temperature sensing was carried out by seven-core,hollow-core,grapefruit type and silver-wire photonic crystal fiber made by our research group,filling with alcohol as temperature sensitive material.First,the air holes of photonic crystal fiber are all filled with alcohol by the method of combining capillary effect and pressure difference.Then the filled PCF was fused with ordinary single mode fiber by fiber fusion machine.Finally,the optical path is constructed,its output spectrum is tested and its sensing characteristics are analyzed.The experimental results show that the temperature sensing sensitivity of seven-core photonic crystal fiber is-4.65 counts/°C,the sensitivity of hollow-core fiber temperature sensor is 13.17 counts/°C,the temperature sensing sensitivity of D-shape grapefruit type silver film coated PCF is 16.32 counts/°C,and the temperature sensing sensitivity of silver wire filled PCF is 38.11 counts/°C.Among them,the silver wire filled PCF has the highest sensitivity,the second is D-shape grapefruit type silver film coated PCF,which reflects the advantage of the fiber temperature sensor based on surface plasmon resonance.