An optical resonator made from an elongated fiber having a proximal and distal end. A sphere is created on the distal end by locating the distal end in cylindrically symmetrical heating zone along a centerline. For some embodiments, the distal end is rapidly cooled by allowing it to retract away from the heating zone along the centerline during the formation and solidification of the molten microsphere. The resulting optical resonator has an intrinsic quality factor greater than 106 over the 2.0 to 3.2 μm MIR wavelength range.