| Two flat field planar concave grating demultiplexers (DMUXes) are presented for Wavelength Division Multiplexing (WDM) based on concentric circles and confocal ellipses, respectively. Theoretical derivations and scalar electromagnetic simulations are given. Effects of microfabrication imperfections on grating performance are numerically analyzed.;The elliptic DMUX is designed to minimize its sensitivity to microfabrication imperfections. With double parabolic waveguide horns to flatten channel passbands, an 18-channel elliptic DMUX working on the ITU coarse WDM wavelength grid gives promising performance according to simulation.;Reactive Ion Etching (RIE) of polymers has been optimized to achieve deep, vertical and smooth sidewalls. Both the circular and elliptic DMUXes have been designed for coarse WDM applications in the 820 nm wavelength range with multimode optical fibers. A circular DMUX has been fabricated in BCB polymers with deep RIE, and an elliptic DMUX in PMMA polymer with the LIGA process. Preliminary test results are given. |
