Study of Optical Bistability in Coupled Microdisks*

Semiconductor microcavities offer unique means of controlling light-matter interactions in confined geometries, resulting in a wide range of applications in optical communications. We report bi-stable lasing in coupled GaAs microdisks with quantum wells and interface-fluctuation quantum dots in the active region. The inter-disk coupling results in mode-splitting, with the higher energy resonance persistently achieving higher mode Q ($\sim $ 4000). The bi-stability manifests in the form of hysteresis in the intensity of the coupled modes on non-uniform excitation and can be attributed to saturable absorption. This property in the lasing characteristics of coupled cavities gives us a control on the gain modulation and mode-switching and would be useful for applications in optical memories and computing, and in next generation of low-threshold optoelectronic devices.