Fabrication of an Array of Hemispherical Microlasers Using Optical Vortex Laser-Induced Forward Transfer

We We demonstrate optical vortex laser-induced forward transfer of high-viscosity liquid microdroplets to produce hemispherical microlasers which lase on whispering gallery modes with a Q factor of >10(3). In this work, it is shown that the illumination of a high-viscosity liquid film using an optical vortex pulse enables high-definition, two-dimensional printing of uniform, hemispherical microdroplets with a positional error of similar to 10% and without undesired satellite droplets. In contrast, illumination with a Gaussian beam produces nonuniform droplets with numerous satellite droplets at irregular positions. The temporal evolution of the ejection of a microdroplet is directly observed using an ultrahigh-speed camera with a frame rate of 10(7) frames/sec. The optical vortex pulse distends the irradiated film, from which a jet of material is produced, and then, microdroplet ejection occurs. This characteristic is not observed when using a Gaussian beam, and rather, bursting of the irradiated film occurs. This work demonstrates the potential of optical vortex laser-induced forward transfer as an advanced, cost- and time-effective microprinting technology.