Toward temperature-insensitive near-infrared optical gain using low-toxicity Ag₂Se quantum dots

With the growing demand for developing lasers with high stability and integration, temperature-insensitive gain materials are highly desirable. Here, temperature-insensitive near-infrared (NIR) optical gain from low-toxicity Ag₂Se quantum dots (QDs) is reported. Due to the large energy splitting between the band-edge hole state and the following state (∼430 meV), the thermal depopulation of the band-edge hole state in Ag₂Se QDs is significantly suppressed. The long biexciton lifetime (245 ps at 300 K) of the QDs is sufficient to support the establishment of amplified spontaneous emission (ASE). Consequently, the characteristic temperature of the ASE threshold for the Ag₂Se QD film is as high as 360 K, and efficient NIR ASE is observed up to 340 K. In addition, when the temperature is lower than 200 K, the ASE peak position is temperature insensitive because acoustic phonons cannot be effectively excited. Our findings reveal that Ag₂Se QDs can be utilized as an excellent gain material for environmentally friendly temperature-insensitive NIR lasers.