In a general aspect, methods for manufacturing vapor cells are disclosed. In certain aspects, a method of manufacturing a vapor cell includes obtaining a dielectric body that has interior and exterior surfaces. The interior surface defines a cavity in the dielectric body, and the exterior surface defines an opening to the cavity. The method includes forming an antirelaxation coating on the interior surface of the dielectric body. The antirelaxation coating comprising an organosilane material. The method additionally includes disposing a vapor or a source of vapor in the cavity and obtaining an optical window that comprises a surface. The vapor or the source of vapor includes alkali metal atoms. The method also includes bonding the surface of the optical window to the exterior surface of the dielectric body to form a seal around the opening to the cavity.