| Fused silica glasses are macroscopic central inversion symmetry materials which do not possess second-order nonlinear optical effects.The thermal poling breaks the symmetry structure and induce considerable second-order nonlinearity(SON).In this paper,transmission and poling properties of two-hole multimode fiber are investigated with various fiber structure parameters,A single mode-multimode-single mode(SMS)fiber optical switch based on thermally poled two-hole multimode fiber is proposed.For the thermal poling of two-hole multimode fiber,the results show that the thermally poling fiber of the double-anode structure has a higher second-order nonlinearity than the single-anode structure in the multimode fiber.For the double anode structure and single anode structure,the effective refractive index difference increases and then decreases with the increase of the poling time.At the same poling time,the effective refractive index difference decreases with the increase of the core radius or the distance between the core and the anode.The poling time at which the effective refractive index difference appears maximized decreases as the core radius and the distance between the anode and the core decreases.With thermally poled multimode fiber,the tunable propertiy of the proposed optical switch could be easily implemented and the switch function could be achieved with applying voltage.the propagation loss of the incident wave decreases with increasing core-holes distance and the radius of core.The switching voltage can be reduced by extending the thermally poled multimode fiber length or decreasing the distance between core and anode.The switching voltage could be decreased by completely covering fiber core by the depletion layer.The conclusion of this paper give insight into the poling properties of multimode fiber,provide guidance for thermal poling multimode fiber fabrication and are of significance for designing functional thermally poled multimode fiber devices. |
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