Fabrication features of amorphous whispering gallery mode microresonators

Optical high-quality-factor microresonators with whispering gallery modes are extremely promising for various photonic devices, including for the mid-infrared range applications. This range is of great interest for both fundamental and applied problems due to the presence of the fundamental absorption bands of various molecules – the “fingerprint region”. The most promising materials for IR photonics based on optical microresonators are various amorphous materials suitable for mass production of microresonators with high-quality-factor in this range. The paper describes a technique for manufacturing high-quality-factor microresonators from arsenic sulfide (As$_2$S$_3$) and fluoride glass (ZBLAN) by melting optical fibers, and also examines various defects that arise during the manufacturing process and suggests methods for eliminating them. It is shown that the presented technique makes it possible to achieve a level of quality factor for microresonators limited by fundamental optical losses in the materials used.