STRUCTURE DETERMINATION OF WEAK PHASE OBJECTS FROM INTERFEROMETRIC NEAR-FIELD MEASUREMENTS

Amplitude and phase of diffraction near-fields behind two-dimensional weak phase objects (n approximate to 1.02 + i0.0002) are measured with electromagnetic 3-cm waves in TM and TE polarization. Dielectric slab s and strips with a trapezoidal or rectangular cross section are consi dered (width 1.5 lambda-36.0 lambda; thickness 0.6 lambda-2.4 lambda; wedge angle 30 degrees-150 degrees). For numerical simulation of the m easured fields, a modification of the first Born approximation for wea k scatterers is developed, which yields a remarkably better agreement with the measurements but requires no higher numerical efforts than th e first Born approximation. Procedures for the determination of width, thickness, and wedge angle of the objects from measured diffraction f ields are presented.