Low-switching-energy and high-repetition-frequency all-optical flip-flop operations of a polarization bistable vertical-cavity surface-emitting laser

Subfemtojoule polarization bistable switching in a vertical-cavity surface-emitting laser (VCSEL) is experimentally demonstrated. All-optical flip-flop operation of the VCSEL was performed using two orthogonally polarized injection light pulses. The optimum wavelengths of the two injection pulses for achieving minimum switching power were different and corresponded to the lasing wavelengths of the two polarization states of the laser. The pulse width/switching frequency dependence of the injection pulses showed that a minimum switching energy was obtained at 1 ns/500 MHz. A record low switching energy of 0.3 fJ has been achieved as well as a record high switching frequency of 10 GHz.