Optofluidic laser using photostable conjugated polymer (Conference Presentation)

Optofluidic laser, which incorporates optical cavities and luminescent probes in fluidic environments, has become a powerful platform for biosensing and medical diagnosis. To date, fluorescent dyes and proteins have been widely utilized as gain materials for biological analysis due to their good biocompatibility, but the limited photostability restricts their reliability and sensitivity. Here, we bridge this gap by demonstrating an optofluidic microlaser using the biocompatible conjugated polymer. Assisted by the ultrahigh-Q whispering gallery microcavity, the optofluidic laser is achieved with an ultra-low threshold down to 7.8 μJ/cm^2. More importantly, this conjugated polymer exhibits a significant enhancement in the lasing stability compared with a typical laser dye (Nile red). In the experiment, after 20 minutes of illumination with the excitation intensity of 23.2 MW/cm^2, the lasing intensity of the conjugated polymer experiences a decrease of less than 10%, while the lasing feature of Nile red completely disappears. Additionally, by mechanically stretching the resonator, the lasing frequency can be fine-tuned with the range of about 2 nm, which exceeds a free spectral range of the resonator.