ABSTRACT
This chapter explores the analysis of Stamnes (1981a), and examines the focusing properties of two-dimensional wave fields. These are important in integrated optics, in focusing of water waves and in imaging of line sources with cylindrical lenses. To obtain an approximate representation for the diffracted field we may use the Kirchhoff approximation, according to which the field is equal to the unperturbed incident field inside the aperture and vanishes outside it. Computations of two-dimensional wave fields were made by Stamnes (1981a), based on both the angular-spectrum representation and the impulse-response integral. To compare the angular spectra obtained by using the Kirchhoff approximation and the Debye approximation, Stamnes (1981a) used the asymptotic spectrum and the Debye spectrum. Stamnes (1981a) computed the fields of perfect and non-perfect waves on the focal line in the Debye approximation. Stamnes (1981b) applied a phase linearisation procedure to the impulse response integral to compute u(x, z1) and Simpson's integration formula to the integral in the numerator.
