Injection-induced, tunable all-optical gating in a two-state quantum dot laser.

We demonstrate a tunable all-optical gating phenomenon in a single-section quantum dot laser. The free-running operation of the device is emission from the excited state. Optical injection into the ground state of the material can induce a switch to emission from the ground state with complete suppression of the excited state. If the master laser is detuned from the ground-state emitting frequency, a periodic train of ground-state dropouts can be obtained. These dropouts act as gates for excited-state pulsations: during the dropout, the gate is opened and gain is made available for the excited state, and the gate is closed again when the dropout ends. Numerical simulations using a rate equation model are in excellent agreement with experimental results.