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