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Microdisk lasers: quantum dot lasing and bistability

The microdisk laser is a microcavity laser, which strongly confines the whispering gallery mode and realizes the ultralow threshold lasing and large scale integration. This paper presents two recent topics related with this laser. The first topic is the microdisk with InAs quantum-dot active layer. It is not only promising for ultimate low threshold operation but also has the potential of a high-speed single photon emitter because of the atom-like electron transition in quantum-dots and the large Purcell effect in the microcavity. In this study, we obtained the room temperature operation in this device, for the first time, by photopumping with a low effective threshold of less than 1 milliwatt. The second topic is the photonic molecule consisting of evanescent-coupled multiple microdisks based on GaInAsP materials. As well as the unique behavior of coupled modes in this structure, we also observed the bistable lasing by the nonuniform photopumping, which was considered to be arising from the saturable absorption. Due to its low threshold of 70 microwatts, this device is expected to be an optical memory and flip-flop device by photonic integration.