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