Quasi-phase-matched (QPM) second-order nonlinear effects are studied in three aspects: simulation, fabrication, and application. In the numerical simulation, two iterative beam propagation methods (BPM) are proposed to model the wave evolution in the presence of second-order nonlinearities. Comparisons with published methods show the superiority of the proposed schemes. Some cases are also studied to demonstrate the use of numerical tools in the optimization of practical designs. As to the device fabrication, spikelike anti-domains in LiNbO3 are induced by one-direction-heated proton exchange. These domains can be much deeper than those produced by ordinary chemical diffusion methods. Also with the same process, intriguing deep anti-domains are observed, which might suggest new research directions. Finally, the generation of mid-IR radiation by QPM-DFG is theoretically evaluated. Single-crystal, angle-tuned, wide-band mid-IR generation is shown to be feasible in these evaluations. A 1064nm diode-pumped Nd:YVO4 solid-state laser necessary in this experiment is established with 24% slope efficiency. In addition, a temperature-controllable crystal mount is designed and manufactured. The angular and temperature precision of this mount is well within the acceptance of this experiment. |
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