Study On Thermal Poling Of Multi-hole Optical Fiber

In recent years it was found that thermal poling technique could eliminate the macroscopic central symmetry of silica material and introduce second-order nonlinearity. Thermal poling technique has an important influence on manufacturing new types of optical fiber and optical fiber devices.In this paper, four-hole and six-hole optical fibers are designed for thermal poling. The thermal poling processes are investigated based on two-dimensional (2D) charge dynamics model. The influence of the distribution of holes, the size of holes, the distance between core and hole on the profile of charge carriers and frozen-in electric field are also investigated. It was found that for the four-hole optical fiber, the average electric field in fiber core increases with the increase of air hole radius and the decrease of air hole-core distance. However, the holes have very low impact on average electric field in fiber core when the depletion region can not overlap the holes. The average electric field in fiber core in asymmetrical diagonal double-anode configuration is more than twice as large as that in anode-cathode twin-hole optical fiber. The adjacent anode-anode electrodes configuration could increase the average electric field in fiber core of x-axis largely and induces the average electric field in fiber core of y-axis. For the six-hole optical fiber, the influence of the size of holes and the core-hole distance on average electric field in fiber core is similar to that in four-hole optical fiber while the average electric field in fiber core in anode-cathode four-hole optical fiber is larger than that in six-hole optical fiber. The six-holes provide many anode-cathode-air-hole configurations. The results show that the amount of anode and cathode influences the average electric field in fiber core. The average electric field in fiber core is larger in six-hole optical fiber with fewer cathodes. With the increase of the amount of anodes, the average electric field in fiber core increases largely and the time of thermal poling decreases largely. In asymmetrical three anode three air hole configuration, the largest average electric field in fiber core is achieved.The results are important for designing new types of thermal poling optical fiber, increasing the second order nonlinearity in thermally poled optical fibers.