Silicon Ribbon-Based Dual-Beam Optical Phased Array with Low Crosstalk and Large FoV

In this paper, a silicon ribbon (SR)-based microstructure is developed and added to a 32-channel optical phased array (OPA) to reduce the crosstalk between the antennas of grating waveguides. The spacing between the chirped grating antennas can be as close as 600 nm to effectively improve the field of view (FoV) of the OPA in the horizontal direction to 95 degrees. This SR-based approach substantially reduces the side lobe by 10 dB, effectively suppressing the noise and increasing the main lobe by 6 dB and considerably expanding the grating length with linear energy decay. The full width at the half maximum of the light spot reaches about 0.24 degrees. The antenna sites can simultaneously be scanned vertically by bi-directional inputs, effectively increasing the FoV to 30 degrees in the vertical direction.

SEM Characterization of Silicon Layers Grown on Carbon Foil

Characterization of defect structure in silicon ribbon grown on carbon foil has been carried out. The structure of grown Si layers and a dislocation density in these layers have been studied using selective chemical etching and the Electron Backscattering Diffraction. It is observed that the layers consist of rather large grains, the majority of which is elongated along the growth direction with a similar surface orientation and with a misorientation angle between neighboring grains of 60º. This means that such grains are separated by the (111) twin boundaries. The dislocation density in different grains is found to vary from 102 to 107cm-2. The energy dispersive X-Ray microanalysis has shown that some twin boundaries are enriched with carbon.