On chip complex signal processing devices using coupled phononic crystal slab resonators and waveguides

Saeed Mohammadi,Ali Adibi

doi:10.1063/1.3676168

Abstract

In this paper, we report the evidence for the possibility of achieving complex signal processing functionalities such as multiplexing/demultiplexing at high frequencies using phononic crystal (PnC) slabs. It is shown that such functionalities can be obtained by appropriate cross-coupling of PnC resonators and waveguides. PnC waveguides and waveguide-based resonators are realized and cross-coupled through two different methods of mechanical coupling (i.e., direct coupling and side coupling). Waveguide-based PnC resonators are employed because of their high-Q, compactness, large spurious-free spectral ranges, and the possibility of better control over coupling to PnC waveguides. It is shown that by modifying the defects in the formation of the resonators, the frequency of the resonance can be tuned.

Highlights

Micro/nano-mechanical (MM) structures made of silicon (Si) are getting increased attention in communications and sensing due to their small form factors, compatibility with microelectronic and photonic technologies, flexibility and maturity of fabrication, and good mechanical characteristics.[1]. Besides their widespread applications in elements with moving parts,[3] on-chip MM devices based on small mechanical vibrations[4] are proving to be the technology of choice when high quality factors and more functionalities at moderately high frequencies are of demand
We report the design, fabrication, and characterization of different VHF resonators communicating through a phononic crystal (PnC) waveguide to demonstrate the possibility of high-frequency multiplexing/demultiplexing using PnC structures in an appropriate platform
We showed that PnC slab waveguides and waveguide-based resonators can serve as an appropriate platform for performing complex signal processing functions

Summary

INTRODUCTION

Micro/nano-mechanical (MM) structures made of silicon (Si) are getting increased attention in communications and sensing due to their small form factors, compatibility with microelectronic and photonic technologies, flexibility and maturity of fabrication, and good mechanical characteristics.[1]. PnCs composed of a hexagonal (or honeycomb) array of air cylinders embedded in a single-crystal Si slab have been demonstrated to show very large band gaps at VHF frequencies without imposing fabrication difficulties.[8] The range of operation of such PnC slab structures can be extended to even higher (of the order of GHz) frequencies by scaling down the features, while most of the procedures, methods, and arguments will remain true These structures have been shown to be very effective in confining elastic energy. Very high quality factor resonators and low-loss waveguides have been realized by creating defects in the PnC structure.[10,11] It is shown that using the developed structures, support loss, which is an important source of loss in MM resonators especially at high frequencies, can be suppressed.[12] Complex functionalities, such as multiplexing, demultiplexing, and multi-channel filtering are of great demand at high frequencies in communications and multi-analyte sensing elements. This demonstration evidences the possibility of realizing compact high-frequency signal processing devices such as filter banks using PnC platforms through an appropriate resonator/waveguide coupling architecture

THE DESIGN

CHARACTERIZATION

CONCLUSIONS