Numerical simulation of a dual frequency all-optical flip-flop based on a nonlinear semiconductor distributed feedback laser structure

摘要

A new all-optical flip-flop generating light at two different wavelengths (lambda)_(1) (state "a"), or (lambda)_(2) (state "b") was suggested. It consists of an active layer and a nonlinear wave-guiding layer. Two parallel nonlinear gratings having different periods and periodic negative nonlinearities exist along the propagation direction in the wave-guiding layer. In state "a," the first grating provides the optical feedback for lasing, and the second grating is weak. In state "b," due to optical nonlinearity, the first grating weakens, and the second one provides the optical feedback for lasing. The refractive index nonlinearity is due to the direct absorption of photons at the Urbach tail. The device is triggered from state "a" to state "b" and vise versa by input optical pulses of wavelengths (lambda)_(2) and (lambda)_(1), respectively. The time domain simulations show switching dynamics in nanosecond time scale.