Microfiber knot dye laser based on the evanescent-wave-coupled gain

The authors demonstrate a composite microring laser formed by immersing a silica microfiber knot in a rhodamine 6G dye solution. When the dye molecules are evanescently pumped by 532nm wavelength laser pulses guided along a 350μm diameter knot, lasing oscillation occurs inside the evanescently coupled closed-ring microcavity with a linewidth of about 0.06nm. Laser emission around 570 and 580nm wavelengths, which is evanescently coupled back into the microfiber, is observed with a threshold of about 9.2μJ∕pulse. The use of the microfiber knot cavity suggests a convenient and efficient approach to both pumping and collection of the evanescent-wave-coupled dye laser.