Coupled spherical-cavities

In this work, we study theoretically and experimentally optical modes of photonic molecules—clusters of optically coupled spherical resonators. Unlike previous studies, we do not use stems to hold spheres in their positions relying, instead, on optical tweezers to maintain desired structures. The modes of the coupled resonators are excited using a tapered fiber and are observed as resonances with a quality factor as high as 107. Using the fluorescent mapping technique, we observe families of coupled modes with similar spatial and spectral shapes repeating every free spectral range (a spectral separation between adjacent resonances of individual spheres). Experimental results are compared with the results of numerical simulations based on a multi-sphere Mie theory. This work opens the door for developing large arrays of coupled high-Q spherical resonators.