Frozen-in Electrical Field in Thermally Poled Fibers

Abstract We have experimentally verified existence of the frozen-in field in thermally poled fiber devices using a Mach–Zehnder interferometer. This technique can be used to measure both the magnitude and the direction of the frozen-in field. This same technique can also be used to measure the third-order nonlinearity χ (3) of unpoled fibers and poled fibers. We find out that χ (3) of fibers has increased by a factor of ∼ 2 after thermal poling.