Two-photon absorption from crossed Gaussian laser beams creates a volume grating containing both a primary and a second-order sinusoidal index modulation. Unlike with linear excitation, the two-photon-induced grating exhibits two Bragg diffraction peaks having different decay rates. Comparison of diffracted orders from volume gratings allows the order of the excitation process to be determined.
© 1985 Optical Society of America
Daniel J. McGraw and Joel M. Harris, "Diffraction from two-photon-excited thermal index gratings," Opt. Lett. 10, 140-142 (1985)