A second laser, a cw CO2 laser, has its beam transmitted through the dichroic to follow {HEAD ~ the HeNe beam} into {TAIL ~ the unstable resonator laser aperture} 
into
A second laser , a cw CO2 laser , has its beam transmitted through the dichroic to follow { HEAD ~ the HeNe beam } into { TAIL ~ the unstable resonator laser aperture }
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 REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL