基于Ag_(2)Se量子点的近红外自组装激光器

Near-infrared self-assembled laser based on Ag_(2)Se quantum dots

铅盐量子点的最低量子态的多重简并和胶体量子点与谐振腔耦合难度大,阻碍了近红外胶体量子点激光器的发展.本文利用基于Ag_(2)Se量子点的自组装激光器解决了上述问题.利用最低量子态二重简并的Ag_(2)Se量子点代替铅盐量子点来实现低阈值的近红外光增益.使用有限元法深入分析了咖啡环微腔的模场分布和振荡机制,结果表明光场在横截面内沿之字形路径传播振荡,量子点与腔模式实现了强耦合.分析了腔长与自由光谱范围和激光发射波长的关系,基于此关系以及Ag_(2)Se量子点的增益谱特性设计了单模近红外激光器,分析了该激光器的激光特性.以仿真结果为指导,实验制备了阈值低至158μJ/cm^(2),线宽为0.3 nm的单模近红外激光器.通过增加激光器腔长,使发射波长从1300 nm增至1323 nm.此外,由于Ag_(2)Se量子点的毒性几乎可以忽略,所以本文推进了环境友好的近红外激光器向实用型激光器发展.

The development of colloidal near-infrared quantum dot(QD)lasers has been hindered by the high state degeneracy of lead salt QDs and the difficulty in coupling colloidal QDs to the resonant cavity.In this study,we show that the above challenges can be addressed by the self-assembly laser based on Ag_(2)Se QDs.The Ag_(2)Se QDs with the lowest quantized states 2-fold degeneracy are used to replace lead salt quantum dots to achieve low threshold near-infrared optical gain.We employ the finite element method to in depth analyze the mode field distribution and oscillation mechanism of the coffee-ring microcavity.Our results reveal that the light field oscillates in a zig-zag path along the cross-sectional area,indicating strong coupling between the QDs and the cavity mode.Furthermore,we investigate the relationship of cavity length with free spectrum range and laser emission wavelength.Using this relationship and the gain spectrum characteristics of Ag_(2)Se QDs,we design a single-mode near-infrared laser and conduct a comprehensive analysis.The simulation results are used to fabricate a single-mode near-infrared Ag_(2)Se QD coffee-ring microlaser,which exhibits a linewidth of 0.3 nm and a threshold of 158μJ/cm^(2).Currently,it holds the record for the lowest laser threshold among near-infrared colloidal QD lasers.The increasing of the laser cavity length leads the emission wavelength to increase from 1300 nm to 1323 nm.In addition,the toxicity of Ag_(2)Se QD is remarkably negligible.Our work promotes the development of environment-friendly near-infrared lasers toward practical lasers.