Subwavelength semiconductor lasers for dense chip-scale integration

Abstract

Metal-clad subwavelength lasers have recently become excellent candidates for light sources in densely packed chip-scale photonic circuits. In this review, we summarize recent research efforts in the theory, design, fabrication, and characterization of such lasers. We detail advancements of both the metallo-dielectric and the coaxial type lasers: for the metallo-dielectric type, we discuss operation with both optical pumping and electrical pumping. For the coaxial type, we discuss operation with all spontaneous emission coupled into the lasing mode, as well as the smallest metal-clad lasers to date operating at room temperature. A formal treatment of the Purcell effect, the modification of the spontaneous emission rate by a subwavelength cavity, is then presented to assist in better understanding the quantum effects in these nanoscale semiconductor lasers. This formalism is developed for the transparent medium condition, using the emitter-field-reservoir model in the quantum theory of damping. We show its utility through the analysis and design of subwavelength lasers. Finally, we discuss future research directions toward high-efficiency nanolasers and potential applications, such as creating planar arrays of uncoupled lasers with emitter densities near the resolution limit.