{TAIL ~ The first mirror} is configured to receive a first incident laser beam from the first end and to reflect a first reflected beam to reflect as {HEAD ~ a third reflected beam} from the third mirror 
{ TAIL ~ The first mirror } is configured to receive a first incident laser beam from the first end and to reflect a first reflected beam to reflect as { HEAD ~ a third reflected beam } from the third mirror
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH