  We present and study theoretically a new design approach for obtaining wide
angle, highly efficient, all-dielectric metasurfaces. As a concrete example we
focus on optimizing flat beam deflector for both the infra-red and visible
spectral regions. Transmission efficiencies of up to 87.2% are obtained
theoretically for deflection angle of 65{\deg} in visible (580nm) spectrum and
up to 82% for deflection angle of 30.5{\deg} at telecom wavelength (1550nm).
The enhanced efficiencies at wide deflection angles are obtained by genetic
optimization of the nano-structures comprising the metasurface. Compared to
previously employed design approaches, our approach enhances the transmission
efficiency substantially without sacrificing rectangular grid arrangement and
facilitates the realization of wide angle flat deflectors and holograms/lenses.
