A laser system (52A) is illustrated having a laser cavity (54) that generates a laser beam (78). An outcoupling resonator box (62) has a reflective mirror (70) therein. A return resonator box (64) has a reflective mirror (72) therein. A first solid window assembly (66) is disposed between the outcoupling resonator box (62) and the laser cavity (54). A second solid window assembly (68) is disposed between the return resonator box (64) and the laser cavity (54) so that the beam (78) is directed through the solid window assemblies (66), (68) during operation of the laser system, thereby isolating the usually caustic environment of laser cavity (54) from that of mirrors (70), (72) that are housed in said resonator boxes (62), (64), without the use of isolation valves and optical tunnels as in traditional arrangements.