Pump-Controlled Modal Interactions in Microdisk Lasers

We demonstrate an effective control of nonlinear interactions of lasing modes in a semiconductor microdisk cavity by shaping the pump profile. A target mode is selected at the expense of its competing modes either by increasing their lasing thresholds or suppressing their power slopes above the lasing threshold. Despite of strong spatial overlap of the lasing modes at the disk boundary, adaptive pumping enables an efficient selection of any lasing mode to be the dominant one, leading to a switch of lasing frequency. The theoretical analysis illustrates both linear and nonlinear effects of selective pumping, and quantify their contributions to lasing mode selection. This work shows that adaptive pumping not only provides a powerful tool of controlling the nonlinear process in multimode lasers, but also enables the tuning of lasing characteristic after the lasers have been fabricated.