Distinctive Signature of Indium Gallium Nitride Quantum Dot Lasing in Microdisks Cavities

TL;DR

This study investigates the lasing behavior of InGaN quantum dots in microdisk cavities, revealing a unique lasing signature and insights into light-matter interactions that could improve low-threshold laser designs.

Contribution

It provides the first detailed comparison of lasing dynamics in microdisk cavities with different InGaN gain media, highlighting the distinctive lasing signature of quantum dots.

Findings

Quantum dots lase at shorter wavelengths than the peak gain emission.

Lasing threshold and wavelength vary with gain medium type.

Identified a distinctive lasing signature for quantum dot materials.

Abstract

Low threshold lasers realized within compact, high quality optical cavities enable a variety of nanophotonics applications. Gallium nitride (GaN) materials containing indium gallium nitride (InGaN) quantum dots and quantum wells offer an outstanding platform to study light matter interactions and realize practical devices such as efficient light emitting diodes and nanolasers. Despite progress in the growth and characterization of InGaN quantum dots, their advantages as the gain medium in low threshold lasers have not been clearly demonstrated. This work seeks to better understand the reasons for these limitations by focusing on the simpler, limited-mode microdisk cavities, and by carrying out comparisons of lasing dynamics in those cavities using varying gain media including InGaN quantum wells, fragmented quantum wells, and a combination of fragmented quantum wells with quantum dots. For each gain medium, we utilize the distinctive, high quality (Q~5500) modes of the cavities, and the change in the highest intensity mode as a function of pump power to better understand the dominant radiative processes. The variations of threshold power and lasing wavelength as a function of gain medium help us identify the possible limitations to lower-threshold lasing with quantum dot active medium. In addition, we have identified a distinctive lasing signature for quantum dot materials, which consistently lase at wavelengths shorter than the peak of the room temperature gain emission. These findings not only provide better understanding of lasing in nitride-based quantum dot cavity systems, but also shed insight into the more fundamental issues of light matter coupling in such systems.