We use a plane-wave analysis to examine a singly resonant, cavity-enhanced, frequency doubler containing an intracavity sum-frequency interaction that frequency sums the resonant fundamental with the second harmonic to produce the third harmonic of the resonant field. We derive expressions for the steady-state performance of the device. We determine the input coupler intensity reflectivity and the ratio of nonlinear drives between the second-harmonic generation (SHG) and sum-frequency generation (SFG) stages for optimum third-harmonic conversion efficiency. We also examine the optimum SHG interaction length under conditions of limited total interaction length. We find that numerical simulations modeling three spatial dimensions can be closely approximated by appropriately scaled plane-wave results. As an example, we consider frequency tripling of a 350-mW, 1319-nm, cw laser in two consecutive nonlinear gratings in periodically poled lithium niobate and find third-harmonic power-conversion efficiency of 85.3% when first-order quasi-phase-matching (QPM) is used for the SFG process and 51.0% when third-order SFG QPM is used. We also consider frequency tripling of a 20-W, 1064-nm, continuous-wave mode-locked laser in two lithium triborate crystals and find a time-averaged third-harmonic power-conversion efficiency of 56.0% from modeling three spatial dimensions.
© 1999 Optical Society of AmericaFull Article | PDF Article
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