A directional coupler in a miter bend was designed to monitor the microwave power of the transmission line in an electron cyclotron resonance heating（ECRH） system. It is based on aperture-coupling theory and simulation of an electromagnetic（EM） field to design and optimize the 140 GHz high-power directional coupler. In addition, we simulated the double-aperture directional coupler by using three-dimensional（3D） EM simulation software, in which the central frequency is 140 GHz, coupling factor is about –70 dB, and directivity is greater than 17 dB. The results show that such a coupler is a viable tool for power measurement in high-power transmission systems.
The silver（Ag）/photoresist（PR）/Ag structure, widely used in plasmonic photolithography, is fabricated on silicon substrate. The surface roughness of the top Ag film is measured and analyzed systematically. In particular, combined with template stripping technology, the lower side of the top Ag film is imaged by an atomic force microscope. The topographies show that the lower side surface is rougher than the initial surface of the subjacent PR film, which is mainly attributable to the deformation caused by particle collisions during the deposition of the Ag film. Additionally, further measurements show that the Ag film deposited on the PR exhibits a flatter upper side morphology than that directly deposited on the silicon substrate. This is explained by the different growth modes of Ag films on different substrates. This work will be beneficial to morphology analysis and performance evaluation for the films in optical and plasmonic devices.
