Scalable switched slab coupler based optical phased array on silicon nitride

Abstract: 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.