Multiplexed Holographic Tunable Resonators for Reconfigurable Optical Interconnects

Abstract

The benefits of using optics for massively parallel interconnects between electronic processors are well known. Additional flexibility can be achieved if optical switches are used to create reconfigurable optical interconnects. The enhanced efficiency of holograms placed in optical resonators has been proposed for the use in passive interconnects [1,2], for active devices [3], and for dense wavelength division multiplexing [4]. If a diffraction grating is placed inside a resonator, such as a Fabry-Perot resonator, its interaction length, and consequently its efficiency, can be significantly increased because of multiple paths of the optical beam inside a cavity in resonance. As a result, a combination of the characteristics of diffraction gratings and optical resonators is achieved: the direction of light can be changed and the efficiency of the diffracted beam exhibits peaks similar to that of a Fabry-Perot resonator. If the cavity can be tuned, the features of resonated holograms can be utilized for switching of light beams in optical interconnects. However, optical resonators pose great fabrication difficulties primarily due to stringent alignment requirements. We propose and demonstrate holographically recorded tunable Fabry-Perot resonators for the use in this optical interconnect configuration. Simultaneous recording of two high efficiency reflection gratings, which replace regular mirrors, removes the alignment problems. In addition, the use of volume holographic materials with refractive index modulation allows recording of multiplexed gratings to create multiple mirror resonators in a compact form which results in a much higher effective efficiency of the resonated grating.