Overcoming the impeding effect of core-cladding interface on the progression of the second-order nonlinearity in thermally poled optical fibers

摘要

The spatial distribution of the second-order optical nonlinearity in thermally poled optical fibers was characterized with second-harmonic microscopy. The second-order optical nonlinearity (SON) was found to be distributed in a layer, the progression of which was impeded at the core-cladding interface, which acted as an extra potential barrier to the migrating ions. At higher poling voltages and temperatures, the SON layer could overcome this barrier and extend further into the fiber core. The polarization dependence of the optical nonlinearity within the fiber core was also checked and found to be almost negligible.