  Photoelectron angular momentum distribution of He+ driven by a few-cycle
laser is investigated numerically. We simultaneously observe two dominant
interference patterns with one shot of lasers by solving the 3D time-dependent
Schrodinger equation (TDSE). The analysis of a semiclassical model identifies
these two interference patterns as two kinds of photoelectron holography. The
interference pattern with Pz > 0 is a kind of forward rescattering holography,
which comes from the interference between direct (reference) and rescattered
(signal) forward electrons ionized in the same quarter-cycle. The interference
pattern with Pz < 0 is a kind of backward rescattering holography, which comes
from the interference between direct electron ionized in the third quarter-
cycle and rescattered backward electron ionized in the first quarter-cycle.
Moreover, we propose a method to distinguish this backward rescattering
holography and intracycle interference patterns of direct electrons. This is an
important step for dynamic imaging of molecular structure and detecting
electron in molecules on attosecond time scale by the backward rescattering
attosecond photonelectron holography.
