Energy attenuations in single microfiber and double-loop cavity supported by optical substrate.

We report on the characterization of energy losses in single-silica microfiber and double-loop microcavity deposited on MgF2 substrate. When the bending radius is less than similar to 37 pm, the bending loss rate of a 1.4 mu m diameter microfiber exceeds its propagation loss (similar to 0.039 dB/pm), which becomes the main source of energy attenuation. Furthermore, we measured the transmission energy losses during the assembling process of a double-loop cavity. The transmission loss in a double-loop cavity varies by adjusting the shape of the cavity. It is also found that a similar to 30 pm radius cavity has a similar bending loss to that of a curved microfiber with the two bending radii of 6 mu m, which demonstrates that the cavity can provide a more compact structure than a curved microfiber in integrated photonic circuits. By further bending the input end of a cavity, the output energy can be greatly attenuated, which indicates that the double-loop cavity is no longer suitable for integration. (C) 2018 Optical Society of America