When a laser or a fiber is butt joined to a single mode film waveguide it launches a two-dimensional nearly Gaussian beam in the fundamental film mode. A curved Bragg grating may deflect and even refocus such an incident Gaussian beam. A coupled beam analysis has shown that the distortions of the refocused field may be kept low if the distance between the beam waists and the curved grating is sufficiently long. The greater this distance, the more the curved grating behaves like a concentrated reflector, which has the same wavelength dependence of reflectivity as would result for a plane wave incident upon a corresponding plane grating with straight lines.