In-fiber optical microresonators and couplers

A method for forming an optical fiber having at least one microresonator and at least one coupler integrated therein, comprising:

• providing an optical fiber having a light guiding core;
• modifying a first region of the optical fiber as an intended region for the at least one microresonator and a second region of the optical fiber as an intended region for the at least one coupler using an ultrafast laser;
• immersing the optical fiber having the first region and the second region as modified inside an etchant to selectively etch the first region and the second region as modified and thereby shape the at least one microresonator and the at least one coupler integrated in the optical fiber at the light guiding core, wherein the etchant is hydrofluoric acid (HF), potassium hydroxide (KOH), or a combination thereof;
• removing the optical fiber from the etchant;
• and
• heating the optical fiber to smoothen surface irregularities of the at least one microresonator and the at least one coupler, wherein heating the optical fiber comprises performing at leastone of:
• a laser reflow process on the optical fiberusinga carbon dioxide (CO2) laser to irradiate and heat the optical fiber and direct heating using a heating apparatus, wherein the heating apparatus is at least one of a furnace, electric arcs, and a flame,
• wherein the at least one microresonator comprises at least two microresonators that share a common coupler and are oriented in different azimuthal dimensions from one another.