A laser assembly generates continuous wave (CW) laser output light in the range of approximately 181 nm to approximately 185 nm by generating fourth harmonic light from first fundamental CW light having a first fundamental wavelength between 1 μm and 1.1 μm, generating fifth harmonic light by mixing the fourth harmonic light with the first fundamental CW light, and then mixing the fifth harmonic light with second fundamental or signal CW light having a second wavelength between 1.26 μm and 1.82 μm. The fifth harmonic light is generated using an external cavity that circulates first fundamental CW light through a first nonlinear crystal, and by directing the fourth harmonic light through the first nonlinear crystal. The laser output light is generated using a second cavity that passes circulated second fundamental or signal CW light through a second nonlinear crystal, and directing the fifth harmonic light through the second nonlinear crystal.