Structure determination of weak phase objects from interferometric near-field measurements

Area of Science:

• Electromagnetism and Optics
• Wave Diffraction Phenomena

Background:

• Near-field diffraction analysis is crucial for characterizing materials.
• Weak phase objects present challenges for accurate electromagnetic wave interaction studies.

Purpose of the Study:

• To measure and simulate near-field diffraction patterns of 2D weak phase objects.
• To develop an improved numerical method for analyzing diffraction fields.
• To establish procedures for determining object dimensions from measured fields.

Main Methods:

• Experimental measurement of amplitude and phase of diffraction near fields using 3-cm electromagnetic waves (TM and TE polarization).
• Investigation of dielectric slabs and strips with varying geometries (trapezoidal/rectangular cross-sections, dimensions, wedge angles).
• Development and application of a modified first Born approximation for numerical simulation of weak scatterers.

Main Results:

• Successful measurement of diffraction near fields for various weak phase objects.
• Demonstration that the modified Born approximation significantly improves agreement with experimental measurements.
• Validation of the improved numerical method's efficiency compared to the standard first Born approximation.

Conclusions:

• The modified Born approximation offers enhanced accuracy for simulating weak scatterer diffraction fields.
• Effective procedures were developed to determine object width, thickness, and wedge angle from measured diffraction data.
• This work advances the characterization of dielectric materials using electromagnetic wave diffraction.