Pressure tunable cascaded third order nonlinearity and temporal pulse switching

Effects based on the χ⁽³⁾-nonlinearity are arguably the most commonly discussed nonlinear interactions in photonics. In the description of pulse propagation, however, the generation of the third harmonic (TH) is commonly neglected, because it is strongly phase mismatched in most materials and waveguide geometries and thus of negligible influence to the overall dynamics. This mismatch is characterized by a very short coherence length, calculated by the inverse of the wave-number mismatch Δβ = 3β(ω) - β(3ω). Thus the coherence length is much smaller than any other dynamic length of the system and the generation of TH can be neglected.