Microstub resonators based-waveguides for filtering and multiplexing devices
Résumé
In this chapter, we report numerical simulations, based on a two dimensions Finite Difference Time Domain (FDTD) method, of light propagation in two-dimensional semiconductor micro optical waveguides coupled to one or several lateral stubs. This resonator offers a filtering alternative to well-known micro-disk or micro-ring mainly used in highly integrated optical circuits. The most important advantage of this resonator resides in its small size. It is believed that, owing to their very small dimensions, which is of the same order of magnitude as the width of the waveguide, microstubs could find original applications in future optoelectronic microcircuits. It is shown that when the stub is covered with a perfectly metallic thin layer, the transmission spectrum contains several narrow dips. Such a device could easily be used in the far infrared frequency domain (far from the plasma frequency) where the metal behaves as a perfect mirror. We show that the main features of the transmission spectrum through a waveguide coupled to a lateral stub remain valid if the metal covering the stub is not perfect, but described in the framework of the Drude model. This makes plausible the extension of the above applications to the near optical regime. The frequencies of the zeros of transmission are studied as a function of the geometrical parameters of the stub. We show that the interaction between several stubs produces a widening of the zeros of transmission into band gaps. Inserting an appropriate defect stub between a set of periodical stubs leads to a tunnelling transmission, with a narrow peak inside the gap which can be useful for selective filtering. We use this filtering process to investigate the possibility of a new device for wavelength demultiplexing based on a bent Y-shaped component. © 2011 by Nova Science Publishers, Inc. All rights reserved.