Sub-wavelength-pitch Silicon-Photonic Optical Phased Array for Large Field-of-Regard Coherent Optical Beam Steering

The fabricated 5 mm-long silicon photonic OPA with a 1.3 μm waveguide pitch achieved adjacent waveguide crosstalk below -12dB. A relatively large and uniform emission aperture has been achieved with a low-contrast silicon nitride assisted grating (~20 dB/cm) whose emission profile can be further optimized using an apodized design.

The fabricated silicon-photonic OPA demonstrated > 40º lateral beam steering with no sidelobes in a ±33º field-of-regard and 3.3º longitudinal beam steering via wavelength tuning by 20 nm centered at 1550 nm. We have fully integrated the silicon photonic OPA device with electronic controls and successfully demonstrated 2-dimensional coherent optical beam steering of pre-planned far-field patterns. Future improvements include placement of a distributed Bragg reflector (DBR) underneath the grating emitter to achieve nearly a factor of two improvement in emission efficiency.