Femtojoule optical switching in nonlinear semiconductor laser amplifiers

We have demonstrated the operation of an optical switch requiring less than 1 f J (<7000 photons) of incident optical energy. The switch operates at room temperature, is compatible with optical communication systems, and is cascadable because it has gain. The switching times (on and off) are determined to be less than 1 ns. This device significantly advances the possibility for realization of high throughput optical signal processing and digital optical computing.