Loss-induced Onset of Lasing (IMAGE) Washington University in St. Louis Caption This image depicts loss-induced onset of lasing in coupled microresonators. In the upper image, two directly coupled whispering-gallery silica resonators are illustrated with two supermodes whose fields are equally distributed between the resonators (symmetrical distribution). A 'pump' laser (yellow line) providing optical gain via Raman process cannot generate Raman laser if the provided gain does not surpass the total loss of the resonators. If the loss of the second resonator is further increased by introducing a nanostructure (black circle in the lower image, which absorbs the pump power, the distribution of the modes become asymmetrical. The pump field is strongly localized in the first resonator, which couples directly with the fiber taper waveguide; both the intensity of the light inside the first resonator and the sum of the intensities of the two resonators increase despite increasing loss. As a result Raman gain in the first resonator surpasses the losses and leads to onset of Raman lasing (red line): A direct manifestation of system dynamics in the vicinity of an 'Exceptional point.' The patterns in the circular rings are the images of fields inside the resonators. Credit Image by J. Zhu, B. Peng, S.K. Ozdemir, L. Yang Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.