Acoustically levitated whispering-gallery mode microlasers

Acoustic levitation has become a crucial technique for contactless manipulation in several fields, particularly in biological applications. However, its application in the photonics field remains largely unexplored. In this study, we implement an affordable and innovative phased-array levitator that enables stable trapping in the air of micrometer dye-doped droplets, thereby enabling the creation of microlasers. For the first time, this paper presents a detailed performance of the levitated microlaser cavity, supported by theoretical analysis concerning the hybrid technology based on the combination of whispering-gallery modes and acoustic fields. The pressure field distribution inside the acoustic cavity is numerically solved and qualitatively matched with the schlieren deflectometry technique. The optical lasing features of the levitated microlasers are highly comparable with those devices based On-a-Chip registering maximum Q-factors of similar to 105, and minimum lasing thresholds similar to 150 nJ cm-2. The emission comb is explained as a sum of multiple individual-supported whispering-gallery modes. The use of novel touchless micrometric lasers, produced with an acoustic levitator brings new technological opportunities based on photonic-acoustic technological platforms.

Automated summary

Acoustic levitation is an important contactless manipulation technique in various fields. This study presents an affordable phased-array levitator that can stably trap micrometer dye-doped droplets in the air, enabling the creation of microlasers. The levitated microlasers exhibit comparable optical lasing features to On-a-Chip devices, with a maximum Q-factor of approximately 105 and a minimum lasing threshold of approximately 150 nJ cm-2.