期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2014
卷号：111
期号：39
页码：14042-14046
DOI：10.1073/pnas.1415464111
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceThe III-nitride family of materials has already demonstrated tremendous optical efficiency and versatility for devices across a broad range of wavelengths. Quantum dots formed in these materials, with advantages such as improved carrier confinement, should offer even greater device efficiency. They are also important constituents for fundamental studies of light-matter interaction. However, that promise has been far from realized, and this is a complex problem to address. This work, through a comparative study of quantum dot, quantum well, and fragmented quantum well gain media in compact microdisk cavities, allows better understanding of the limitations to lasing for the quantum dot samples. These results allow both improved device efficiency and fundamental insights into quantum dot-cavity interactions in these materials. Low-threshold lasers realized within compact, high-quality optical cavities enable a variety of nanophotonics applications. Gallium nitride 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 use the distinctive, high-quality (Q[~]5,500) 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.
