Status of Research on Colloidal Quantum Dot Lasers and Their Prospects(Invited)
Significance Colloidal quantum dots exhibit a unique electronic structure and solution-processing characteristics,making them suitable for the development of low-cost and high-performance lasers.However,colloidal quantum dot lasers have not yet been commercialized,indicating a lack of understanding of the fundamental physics and a failure to master the key fabrication technologies.In recent years,significant progress has been made in CdSe-based colloidal quantum dot lasers,including the achievement of continuous wave-pumped lasers and electrical injection light amplification.These recently achieved milestones suggest that colloidal quantum dot lasers may become practical instruments in our daily lives in the near future.On this basis,this article reviews the various types of colloidal quantum dot lasers developed in recent years and discusses the inherent challenges.Then,we propose feasible solutions for the issues and summarize the technological advancements in this field.We highlight the essential need to investigate the fundamental physics and key technologies to develop electrically pumped quantum dot lasers.Moreover,this review provides insights for future research directions,such as developing new theories,disruptive technologies,novel gain mechanisms,and unprecedented cavity structures.The article suggests the necessity of utilizing state-of-the-art simulation techniques to predict the physical properties and performance of quantum dot lasers.Finally,we emphasize the need to investigate potential applications of colloidal quantum dot lasers,such as integrating them with flexible substrates to create bendable and foldable laser devices and exploring new application areas in displays and sensors.Progress This article provides a summary of the recent progress in research on semiconductor lasers based on colloidal quantum dots,along with their prospects(Fig.1).First,the advantages of colloidal quantum dots as gain materials for lasers are introduced.Then,we focus on the study of electrically pumped colloidal quantum dot lasers.The discussion begins with research on continuous-wave pumped lasers(Figs.2-4)and is then extended to optically pumped liquid lasers(Figs.5 and 6)with the potential for commercial applications.Next,we discuss the recent progress on environmentally friendly colloidal quantum dot lasers(Figs.7 and 8).Finally,the latest advancements in electrically pumped quantum dot lasers are discussed in detail(Figs.9-12).The article points out that the current challenge lies in obtaining quantum dot gain media with low thresholds,high gain coefficients,long gain lifetimes,and high stability.Representative works in the field of Cd-based colloidal quantum dots(Table 1)and emerging colloidal quantum dot laser research(Table 2)in recent years are presented.Because of the lack of standardized synthesis and characterization methods for colloidal quantum dot lasers,there are substantial variations in the reported gains and laser performances across different countries and laboratories.This lack of consistency impairs reproducibility and consequently hinders the development of high-gain quantum dot media.Currently,electrically pumped quantum dot lasers have not been realized,indicating that challenges still exist in understanding the fundamental physics and mastering the key technologies needed for quantum dot laser devices.Considering the advantages of the distinct electronic structure and cost-effective processing methods of colloidal quantum dots compared to those of organic materials and epitaxial semiconductors,it is imperative to develop novel quantum dots,high-quality resonators,and new lasing mechanisms to push colloidal quantum dot lasers into commercial products.Conclusions and Prospects Colloidal quantum dot lasers processed using wet solutions will potentially play important roles in various fields.This paper focuses on the significance of colloidal quantum dots as gain media and highlights the recent advances in the field of quantum dot lasers,focusing on four main types:continuous-wave pumped colloidal quantum dot lasers,optically pumped colloidal quantum dot lasers in a liquid phase,environmentally friendly colloidal quantum dot lasers,and electrically pumped colloidal quantum dot lasers.The article discusses the universal approaches to suppressing nonradiative Auger recombination,methods for managing Joule heating,the modulation of optical gain mechanisms,and the selection of different types of cavities.In future work,optically pumped and electrically pumped quantum dot lasers should be investigated simultaneously,and both may play important roles in fundamental research and practical applications.Several issues need to be addressed in the process of commercializing colloidal quantum dot lasers.Further,it is still necessary to explore how to fully exploit the unique properties and functions of colloidal quantum dot lasers.There is no doubt that new theories and technological instruments such as AI are required to accelerate the advance of colloidal quantum dot lasers.Finally,greater effort should be devoted to the exploration of the potential applications of colloidal quantum dot lasers.
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