Disclosed are optical resonators having low OH content in at least the near-surface region and a process for making low OH glass article by chlorine treatment of consolidated glass of the article. Cl2 gas was used to remove OH from depth as deep as 350 μm from the surface of the consolidated glass. The process can be used for treating flame-polished preformed optical resonator disks. A new process involving hot pressing or thermal reflowing for making planar optical resonator disks without the use of flame polishing is also disclosed.