Millimeter-wave Bragg diffraction of microfabricated crystal structures

Abstract

A compact diffraction apparatus is developed with millimeter-wave propagation between two parallel plates. Two types of microfabricated model crystals are individually mounted on a rotatable structure. In contrast to previous work, the experimental results agree well with Bragg’s predictions because multiple scattering is minimized in this configuration. Factors that affect the resolution and signal strength, such as the number of scatterers, cylinder radius, and the distance between the detector and the model crystal, are analyzed. The apparatus offers a visually accessible way to teach students about crystal structure as well as scattering and diffraction.

Modal Analysis of Metal-Stub Photonic Band Gap Structures in a Parallel-Plate Waveguide

“…The transmission coefficient can be defined in the far field region kr 1 and θ = 0. Now the incident wave can be approximated to H 0 (kr)kw/2 [25,34], and the total field amplitude is H 0 (kr)kw/2 + H 0 (kr) j ∞ Thus, the transmission coefficient is…”

“…After the mapping between the metal stub and the dielectric cylinder is obtained, a similar property of PBG is also obtained for the metal stub structure. However, owing to the difficulty in matching all scattering coefficients in a board frequency range, a small radius of cylinder is chosen in this work to allow the high order A m to be significantly smaller than A 0 [34]. Thus, only one A 0 should be considered.…”

“…Details of the apparatus can be found in Ref. [34]. Connected to a W -band network analyzer, the transmission can be measured from 75 GHz to 110 GHz.…”