Whispering gallery mode microsphere resonator with microsphere-microsphere coupling

We demonstrate a new type of whispering gallery mode microsphere resonator with microsphere-microsphere coupling. The device is based on two cascaded microspheres glued on a single mode fiber tip. The incident light from the fiber core diverges in the first microsphere and part of light is coupled to the surface of the second microsphere, exciting whispering gallery mode resonance when the angle between the connection line of the two microsphere centers and the fiber axis is appropriate. Such a whispering gallery mode microsphere resonator is robust in structure, compact in size, easy in fabrication and stable in operation.