  A two-dimensional optical-phased array is demonstrated by using a
multiple-input star coupler, compatible with FMCW LiDAR. Previous approach
using a single-input design achieves two-dimensional beam-steering by relying
on a tunable laser source, taking advantage of grating coupler radiation angle
wavelength dependance and variation of the waveguide refractive index. While
implementing a convenient way to distribute power in a single step, star
coupler architecture is inefficient in terms of employed waveguide length and
thus, optical loss and footprint. Multi-input approach partially alleviates
this by condensing several single-input devices into one, permitting to reduce
the footprint proportionally to the employed number of inputs. We fabricated in
silicon nitride technology a proof of concept steerer with beam waist 0.36 deg
x 0.175 deg addressing a field of view of 15 deg x 2.8 deg. A new design
iteration is also reported with and 0.24 deg x 0.16 deg beam waist and 15 deg x
11.2 deg field of view. Implications of this optical-phased array chips from a
LiDAR system perspective are also presented.
