Spectral Invariance Propagation of Ultrashort Laser Pulses and Its Changes by Aperture

摘要

The condition of spectral invariance propagation of the spatially completely coherent light sources is studied from the diffraction theory. It is found that if the field distribution of light sources depends on frequency only through the variable ((k)~(1/2)x,(k)~(1/2)y), the spectrum of light will remain invariant on propagation. This scaling law may be generalized to the stationary light sources. But it can be destroyed by aperture. The spectral shifts of few cycle ultrashort pulses from aperture diffraction and a laser resonator with hard aperture are found and analyzed in detail.