Varying the overlap of direct-coupling between Spiral and semicircle semiconductor microdisk lasers

We present the lasing characteristics of a directly coupled spiral-shaped and semicircle-shaped 2-d microdisk device using a single quantum well AlGaAs heterostructure. Different degrees of coupling, as well as mode selection are achieved by altering the length along which the spiral and semicircle cavities are coupled and the curvature of the coupling junction. Because of the spiral's chirality, the high quality factor and low threshold of the spiral microdisk are preserved when coupled to a semicircle microdisk. A three-element device consisting of a spiral microdisk coupled to two semicircle microdisks is also considered and it is found to control the amount of gain to the spiral output.