Intracellular microlasers

Optical microresonators(1) which confine light within a small cavity are widely exploited for various applications ranging from the realization of lasers(2) and nonlinear devices(3, 4, 5) to biochemical and optomechanical sensing(6, 7, 8, 9, 10, 11). Here we employ microresonators and suitable optical gain materials inside biological cells to demonstrate various optical functions in vitro including lasing. We explored two distinct types of microresonators: soft and hard, that support whispering-gallery modes (WGM). Soft droplets formed by injecting oil or using natural lipid droplets support intracellular laser action. The laser spectra from oil-droplet microlasers can chart cytoplasmic internal stress (~500 pN/μm(2)) and its dynamic fluctuations at a sensitivity of 20 pN/μm(2) (20 Pa). In a second form, WGMs within phagocytized polystyrene beads of different sizes enable individual tagging of thousands of cells easily and, in principle, a much larger number by multiplexing with different dyes.