spherical virtual confocal unstable resonator

• 英?[?sf??r?k?l ?v?:tju?l k?n?f?ukl ?n?ste?b?l ?rez?neit?]
• 美?[?sf?r?k?l ?v?t?u?l kɑn?fok?l ?n?steb?l ?r?z??net?]