Integration of an optical fiber taper with an optical microresonator   fabricated in glass by femtosecond laser 3D micromachining
  We report on fabrication of a microtoroid resonator of a high-quality factor (i. e., Q-factor of ~3.24x10^6 measured under the critical coupling condition) using femtosecond laser three-dimensional (3D) micromachining. Coupling of light into and out of the microresonator has been realized with a fiber taper that is reliably assembled with the microtoroid. The assembly of the fiber taper to the microtoroid is achieved by welding the fiber taper onto the sidewall of the microtoroid using CO2 laser irradiation. The integrated microresonator maintains a high Q-factor of 3.21x10^5 as measured in air. 
Jiangxin Song, Jintian Lin, Jialei Tang, Lingling Qiao, Ya Cheng
physics.optics