Waveguide design for minimum nonlinear effectivearea and switchingenergy in AlGaAs at half the bandgap

The authors report a waveguide design which has been optimised to allow efficient, all-optical switching, in AlGaAs at half the bandgap. The effective area has been reduced to 6 µm2, allowing us to observe a nonlinear phase shift of > 5π. Nonlinear directional couplers, fabricated in the same material, exhibit a critical power of 42 W of energy of 31 pJ.