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