Scalable Switched Slab Coupler Based Optical Phased Array on Silicon Nitride

Abstract

[EN] 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 degrees x0.17.5 degrees addressing a field of view of 15 degrees x2.8 degrees. A new design iteration is also reported with and 0.24 degrees X0.16 degrees beam waist and 15 degrees x11.2 degrees field of view. Implications of this optical-phased array chips from a LiDAR system perspective are also presented.