Progress in Preforming Whispering Gallery Mode Resonant Disks via Femtosecond Laser Machining

Whispering gallery mode resonators (WGMR) have received extensive interest recently, as they provide a promising range of compact and versatile components [1]. Among the available substrates, fluoride crystals have attracted particular attention as they combine good optical and mechanical properties together with excellent linear and non-linear behavior [2]. However, crystalline disks with diameters in the millimeter range have so far been realized through mechanical grinding and polishing, which presents strong drawbacks. In this submission we report on the femtosecond laser cutting and shaping of 12 mm-diameter CaF2 resonant disks. The finalized components featured an intrinsic Q-factor of 9.1 10 ⁸ with significantly reduced processing times as compared to prior methods.