Intensity profile of outgoing beams from uniform and linearly tapered grating couplers

Abstract

Intensity distribution of outgoing beams from a uniform sinusoidal grating is investigated on the basis of first-order perturbation theory by dividing the grating region into short subsections. Intensity distribution of outgoing beams from a linearly tapered sinusoidal grating is also studied by considering it as a chain of uniform gratings with steplike amplitudes and using the results obtained for the uniform grating. The intensity profile of outgoing beams from a uniform grating coupler is theoretically verified to exhibit an extremely asymmetric shape and to differ considerably from the Gaussian shape laser beam usually employed as an incident beam in an input coupler, although this fact has been well recognized by people who have studied gratings. However, the output intensity beam profiles from the linearly tapered grating are found to approach a Gaussian shape similar to the profile of the incident beam.