Whispering gallery mode microsphere resonator integrated inside a microstructured optical fiber.

A compact and robust scheme for broadband excitation of whispering gallery mode (WGM) resonances into a microsphere is demonstrated. A polymer microsphere (10 μm) is encapsulated into the capillary of a microstructured optical fiber, in direct contact with the guiding core. Such a configuration allows efficient and reproducible excitation of the in-MOF-microsphere resonator that is characterized by two launch/collection schemes: core input/scattering output, and sphere input/core output. The latter allows an excitation of the microsphere WGMs externally to the fiber. Numerically calculated WGM spectra are in agreement with experiments. Q factors in the range of 10(3) are typically measured.