Photonic Crystal Demultiplexer

About

Background: Photonic crystals have not been successfully employed for demultiplexing or for separation of frequency components of optical signals in a compact package due to the fact that inadequate spatial separation of signals has only been achieved due in part to the diffraction of optical beams in photonic crystals resulting in large structures. In addition, the superprism affects of photonic crystals have not been fully realized with respect to spatial separation of frequencies of optical signals. Also, in attempts previously made to employ photonic crystals in demultiplexing environments, the frequency components propagating through photonic crystals generally clustered along the original incident direction of an input optical beam. This invention demonstrates the problems inherent with the use of photonic crystals as described above may be overcome to provide for effective demultiplexing or spatial separation of frequency components of an optical beam. To accomplish this, a number of factors are manipulated. For example, a preconditioning waveguide is employed to provide for diffraction compensation within a photonic crystal to refocus frequency components as they propagate through the photonic crystal. Also, the design of the photonic crystal is optimized to provide for the optimal superprism effect resulting in greater spatial separation and overall compactness of the device. In addition, the photonic crystal is designed to have a negative index of refraction so that a negative angle of refraction is experienced by frequency components propagating through the photonic crystal, thereby providing for more effective spatial separation of frequency components from undesirable frequency components as will be described.