Gravitational optics:: Self-phase modulation and harmonic cascades -: art. no. 104009

A nonlinear wave interaction of low amplitude gravitational waves in flat space-time is considered. An analogy with optics is established. It is shown that the flat metric space-time is equivalent to a centrosymmetric optical medium, with no second order susceptibility. The lowest order nonlinear effects are those due to the third order nonlinearity and include self-phase modulation and high harmonic generation. These processes lead to an efficient energy dilution of the gravitational wave energy over an increasingly large spectral range.