  Strongly-coupled quantum dot molecules (QDMs) are widely deployed in the
design of a variety of optoelectronic, photovoltaic, and quantum information
devices. An efficient and optimized performance of these devices demands
engineering of the electronic and optical properties of the underlying QDMs.
The application of electric fields offers a knob to realise such control over
the QDM characteristics for a desired device operation. We perform
multi-million-atom atomistic tight-binding calculations to study the influence
of electric fields on the electron and hole wave function confinements and
symmetries, the ground-state transition energies, the band-gap wavelengths, and
the optical transition modes. The electrical fields both parallel ($\vec{E_p}$)
and anti-parallel ($\vec{E_a}$) to the growth direction are investigated to
provide a comprehensive guide on the understanding of the electric field
effects. The strain-induced asymmetry of the hybridized electron states is
found to be weak and can be balanced by applying a small $\vec{E_a}$ electric
field, of the order of 1 KV/cm. The strong interdot couplings completely break
down at large electric fields, leading to single QD states confined at the
opposite edges of the QDM. This mimics a transformation from a type-I band
structure to a type-II band structure for the QDMs, which is a critical
requirement for the design of intermediate-band solar cells (IBSC). The
analysis of the field-dependent ground-state transition energies reveal that
the QDM can be operated both as a high dipole moment device by applying large
electric fields and as a high polarizibility device under the application of
small electric field magnitudes. [abstract is truncated to fit the character
count of arXiv]
