The generator comprises an envelope and {HEAD ~ two mirrors} defining {TAIL ~ a resonant cavity}, in which is maintained a monolithic wave guide with a capillary 
defining
The generator comprises an envelope and { HEAD ~ two mirrors } defining { TAIL ~ a resonant cavity } , in which is maintained a monolithic wave guide with a capillary
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH