Birefringence Engineering and High Nonlinearity in Eccentric-Core As $_{2}$ Se $_{3}$ -PMMA Microtapers

A hybrid fiber with an eccentric As₂Se₃ core and a PMMA cladding is tapered to a submicron diameter to achieve ultra high birefringence and a high nonlinearity. The high birefringence is induced by having the As₂Se₃ core eccentric with respect to the circular PMMA cladding symmetry and the high nonlinearity is induced from a tightly confining As₂Se₃ core. Microwires with high group birefringence up to b_g=0.018 and a high waveguide nonlinearity γ = 180 W^-1m^-1 are demonstrated.