  For the laser wakefield acceleration, suppression of beam energy spread while
keeping sufficient charge is one of the key challenges. In order to achieve
this, we propose bichromatic laser ionization injection with combined laser
wavelengths of $2.4\rm \mu m$ and $0.8\rm \mu m$ for wakefield excitation and
for triggering electron injection via field ionization, respectively. A laser
pulse at $2.4\rm \mu m$ wavelength enables one to drive an intense acceleration
structure with relatively low laser power. To further reduce the requirement of
laser power, we also propose to use carbon dioxide as the working gas medium,
where carbon acts as the injection element. Our full three dimensional
particle-in-cell simulations show that electron beams at the GeV energy level
with both low energy spreads (around one percent) and high charges (several
tens of picocoulomb) can be obtained by this scheme with laser parameters
achievable in the near future.
