Cascaded fifth-harmonic generation in single cubic nonlinear medium by focused laser beam

摘要

Generation of fifth harmonic by cascading of two phase-matched or two near phase-matched third order processes in single cubic nonlinear medium with focused fundamental beam is investigated theoretically. With the help of analytical and numerical investigations the optimized conditions for maximum conversion into fifth harmonic are found. In general the optimal position of focusing depends on the values of the mismatches Δk_1 and Δk_2 for both "steps" of the third order cascading (ω+ω+ω=3ω; 3ω+ω+ω=5ω). It is shown that for best efficiency this method of fifth harmonic generation requires specially chosen Δk_(1,opt) and Δk_(2,opt) and focusing in the center of the nonlinear media. If the phase matching parameters are fixed and they deviate from the optimal values, then the optimal strength of focusing and position of the focus spot should be calculated according the analysis presented here.