Cerenkov second-harmonic generation in the strong conversion limit: New effects

Using beam propagation method calculations, we show that new effects occur for second-harmonic generation in the Čerenkov regime when it is optimized for efficient coupling to leaky modes. The fundamental throughput becomes independent of the input power over a few decades; i.e., optical power limiting is found. At even higher input powers, the fundamental throughput abruptly switches back to approximately the input power as a consequence of generating coupled second-harmonic-fundamental solitary waves in the waveguide because of the cascading effect.