Scalable Switched Slab Coupler Based Optical Phased Array on Silicon Nitride

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
$^\circ$
×0.175
$^\circ$
addressing a field of view of 15
$^\circ$
×2.8
$^\circ$
. A new design iteration is also reported with and 0.24
$^\circ$
×0.16
$^\circ$
beam waist and 15
$^\circ$
×11.2
$^\circ$
field of view. Implications of this optical-phased array chips from a LiDAR system perspective are also presented.