  We report the first observation of the periodical properties for Talbot
effect with {\pi} phase jump. Analytical expressions are derived from
simplified modal method to analyze the novelty phenomenon of the Talbot effect
with {\pi} phase jump, which can deepen our understanding of physical
diffraction process. Importantly, the physical reason of {\pi} phase jump can
be attributed to that the two even grating modes make the left derivative and
right derivative of real part of the E1 opposite in sign, which results in the
physical information of first order diffractive wave hidden in the near field
Talbot effect image. We expect that this theoretical work will be helpful for
the tremendous potential applications of the Talbot effect.
