Tight-binding photonic molecule modes of resonant bispheres

We observe coherent resonant coupling of optical whispering-gallery modes i n fluorescence from dye doped polymer bispheres with diameters ranging from 2 to 5 mu m. By monitoring the frequencies of fluorescence peaks of indivi dual spheres, we sort out two spheres with appropriate size matching and br ing them into contact. Wave optics calculation also gives good agreement wi th the experiment. By taking into account harmonic coupling of the whisperi ng-gallery modes, the obtained features of normal mode splitting are well e xplained by the tight-binding photon picture. [S0031-9007(99)09349-7].