A demonstration of multiplex biosensing using whispering gallery mode microspheres positioned onto a microstructured optical fiber tip

Here, we show that multiplexed Whispering Gallery Modes sensing can be achieved using two dye-doped microspheres positioned onto the tip of a Microstructured Optical Fiber. By operating the dye-doped microspheres below their lasing threshold, the individual resonances of each sphere overlap and therefore cannot be distinguished. However, when excited above their lasing threshold results in a de-convoluted spectrum where the resonances belonging to the individual spheres can be determined, enabling the detection of a specific interaction in one resonator and using the second as a dynamic reference, or monitoring different specific interactions with both spheres.