FIGS. 1M-1N illustrate the multi-pass optical assembly 102 including one or more retro-reflector assemblies arranged in a resonator configuration, in accordance with one or more embodiments of the present disclosure. In one embodiment, as shown in FIG. 1M, the multi-pass optical assembly 102 may include, but is not limited to, two or more retro-reflectors 116a, 116b arranged in a resonator configuration. In this regard, the first retro-reflector 116a and the second retro-reflector 116b form a resonator. In this embodiment, following the first pass of pump illumination 101 through the plasma 106, mirrors 110a, 110b collect and direct the unabsorbed pump illumination 101 back through the plasma 106 to execute a second pass. In turn, the first retro-reflector 116a (e.g., spherical mirror), receives the unabsorbed pump illumination from the second pass and reflects the pump illumination back through the plasma 106 to execute a third pass of pump illumination 101 through the plasma 106. In turn, mirrors 110b, 110a then return the light of the third pass back through the plasma 106 to execute a fourth pass through the plasma 106. Then, the second retro-reflector 116b receives the light from the fourth pass and repeats the optical path sequence.
