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J. Eur. Opt. Society-Rapid Publ. 22, 44( 2026)
Figure 2.( a) Output power versus absorbed( bottom axis) and incident( top axis) pump power for three output couplers( OC = 0.6 % in red, 2 % in blue, 7.5 % in green) in free air( dashed) and under dry-air purging( solid). The slope efficiencies with respect to absorbed pump power are indicated next to each curve.( b) Normalized laser spectra for the three OCs in the purged cavity.( c) Wavelength tuning with OC = 0.6 %( red) and OC = 7.5 %( green) at pump powers slightly above threshold for purged operation; the calculated total cavity transmission( T cavity(%)) for each configuration is shown in black( right axis).( d) Measurement results of the beam propagation parameter M 2 for low power operation P pump = 1 W, yielding P laser = 0.26 W with corresponding M 2 fits; the inset shows the transverse beam profile.( e) same as( d) but for high-power operation at P pump = 10 W, yielding P laser = 3.9 W.
decrease in output power and efficiency in all OC configurations when compared to dry-air operation. This is expected since the laser naturally operates where the overall gain is the highest accommodating its CW spectrum between water absorption lines, and only a fraction of the generated spectrum is affected by water absorption.