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The tuning curves with temperature and incidence angle for second-harmonic generation were asymmetrically distorted and broadened with increasing intensity for narrow input fundamental beams in periodically poled KTiOPO4. Multiple phenomena including mutual self-focusing of the fundamental and harmonic, cascading, quadratic soliton generation, and artificially induced walk-off (for light incidence away from the poling axis) contribute, in good agreement with theory.
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Kim et al. (2002) studied this question.
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