  Silicon photonics in conjunction with complementary metal-oxide-semiconductor
(CMOS) fabrication has greatly enhanced the development of integrated optical
phased arrays. This facilitates a dynamic control of light in a compact form
factor that enables the synthesis of arbitrary complex wavefronts in the
infrared spectrum. We numerically demonstrate a large-scale two dimensional
silicon-based optical phased array (OPA) composed of nanoantennas with circular
gratings that are balanced in power and aligned in phase, required for
producing elegant radiation patterns in the far field. For a wavelength of
1.55$\mu m$, we optmize two antennas for the OPA exhibting an upward radiation
efficiency as high as 90%, with almost 6.8% of optical power concentrated in
the field of view. Additionally, we believe that the proposed OPAs can be
easily fabricated and would have the ability of generating complex holographic
images, rendering them an attractive candidate for a wide range of applications
like LiDAR sensors, optical trapping, optogenetic stimulation and
augmented-reality displays.
