Coupled spherical-cavities

Abstract

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.

Cavity continuum

“…Despite that, coupling many high-Q microresonators into a continuous array was rarely studied, not even theoretically [48][49][50]. Following the recent demonstration of optical coupling between several droplet resonators [19], we extend this ensemble here to a cavity continuum that is practically unlimited in size. The current practical limit on the size of our array is near 400, limited by the sensitivity of our camera.…”

“…Cascading three cavities allowed flattened bandpass filters [18]. Then, going to several resonators exhibited families of modes, repeating every free spectral range [19,20]. Clusters of 5 microparticles [21], each with Q near 1000, allowed biosensing via the ensemble's spectral fingerprint.…”

“…On another extreme, random lasers [23][24][25][26] represent a structure where coincident multi-scattering, e.g., by porous media, provides feedback, while each scatterer is a non-resonant body or, in different words, with a very low Q, typically near 1. As for the arrangement of resonators [27,28], cavities can be coupled in a linear array [29][30][31]19], branched structures [32,33], 3D structures [22,34,35], and a close-packed layer that we present here.…”

“…The current practical limit on the size of our array is near 400, limited by the sensitivity of our camera. [51,29,21,16,[52][53][54]33,39,19,22] represents a trade-off between the quality factor and the number of resonators. Our work on the top right uniquely combines high optical Q with a large number of resonators.…”

“…In a similar manner, the optical modes of a water fiber were mapped [59]. Later on, modes of a few-droplet ensemble [19] were fluorescently mapped.…”