Demonstration of Two-Dimensional Beam Steering through Wavelength Tuning with One-Dimensional Silicon Optical Phased Array

We demonstrate two-dimensional beam steering through wavelength control using a one-dimensional optical phased array (OPA) in which a path difference is built up in each channel to allocate a phase delay sequentially. Prior to the beam steering through wavelength tuning, phase initialization was performed to form a single beam using electro-optic p-i-n phase shifters to compensate for the phase error due to fabrication imperfections. With a 79.6 mu m path difference in the phase-feeding lines and a 2 mu m pitch in the grating radiators, we achieved a continuous transversal steering of about 46 degrees through a wavelength tuning of about 7 nm. By extending the wavelength tuning range to 90 nm, longitudinal steering was attained near 13 degrees with a discrete interval of about 1 degrees. The beam was maintained during full two-dimensional steering and experienced only a small degree of degradation in the beam divergences and in the side lobe level. We analyzed the parameters to be able to induce the degradation of beam quality considering the fabrication errors of the geometric parameters of the OPA. The results indicated that the scanning scheme employing wavelength tuning after initialization with phase shifters can greatly reduce the realignment process of the beam pattern, even in the presence of some effective index perturbation during the fabrication.