Abstract: System and methods for optical power distribution to a large numbers of sample wells within an integrated device that can analyze single molecules and perform nucleic acid sequencing are described. The integrated device may include a grating coupler configured to receive an optical beam from an optical source and optical splitters configured to divide optical power of the grating coupler to waveguides of the integrated device positioned to couple with the sample wells. Outputs of the grating coupler may vary in one or more dimensions to account for an optical intensity profile of the optical source.