Whispering Gallery mode lasing with continuous-wave pumping from micro-neck structured fiber containing CdZnSe/CdS quantum dots

Whispering gallery mode (WGM) resonators provide remarkable optical amplification due to their high Q-factor and low optical losses. While the use of pulsed lasers facilitates lasing, their optoelectronic device integration has proven to be more challenging. Although CW lasers are a good alternative, their low instantaneous power density and high heat generation cause permanent damage to the gain media even before they reach the lasing threshold, making them impractical. Here, a specialized micro-neck structured fiber-capillary made out of AgNP-PVA composite is proposed. The core is filled with parabolic potential surface CdZnSe/CdS QDs with a reduced Auger recombination rate and large Stoke's shift eliminating the problem of reabsorption. Further, AgNP's LSPR band has been employed to boost QD emission by raising the excitation rate. Thus helped realize effective WGM lasing with CW excitation. Quality factor as high as 2026 has been achieved with these specialised fiber based resonators. Finally, decrease in quality factor and increase in lasing threshold, with decrease in the diameter of the micro-neck structure has also been observed.