Novel design method for all-optical ultrafast gate switches using cascaded second-order nonlinear effect in quasi-phase matched LiNbO3 devices

The authors propose a novel method of designing all-optical ultrafast gate switches that employ the cascade of the second harmonic generation and difference frequency mixing in quasi-phase matched LiNbO/sub 3/ devices. In this design method, the device length is maximized under the condition that crosstalk of the switch is maintained below a certain allowable value at a given bit rate. Following the design method, the authors find that the switching efficiency can significantly be enhanced by compensation for the walkoff between the fundamental and second harmonic pulses.