Dynamically Controllable Photonic Crystals (PhCs) (Ramot)
Dynamically Controllable Photonic Crystals (PhCs) allow for dynamic control of electromagnetic (EM) wave motion through a silicon PhC comprising of arrays of micro-cavities. This is achieved by changing the local refractive index in the vicinity of a micro-cavity. This enables the dynamic manipulation of the light, similar to the manipulation of electrical carriers in semiconductors. This dynamic control may facilitate implementation of various switching and routing elements in PhC-based optical communication systems, thereby enabling the miniaturization of these systems.
Normalized transmission curves versus wavelengths for small variations in the refractive index Dynamically controllable Photonic Crystals (PhCs) have intentional defects otherwise known as micro-cavities. A photonic crystal is the optical equivalent of a semiconductor in terms of having a "band-gap" for light, equivalent for the semiconductor band-gap for mobile electric charge. Micro-cavities cause perturbations in the local refractive index, thus affecting the motion of EM waves (light) through the PhC structure. A PhC typically includes a regular array of elements with one refractive index, interdispersed in a matrix with a different refractive index. In case of a semiconductor such as silicon, a 2-dimensional (2-D) PhC may be formed as an array of holes (air rods) in the silicon substrate, or as silicon "posts" surrounded by air.
A micro-cavity may be for example an air rod with a different diameter than the diameter of the regular array air rods, or missing altogether. Dynamic control is achieved using electrically induced modulation of the local concentration of charge carriers (electrons and holes) in the silicon in the vicinity of the micro-cavity. The local carrier concentration modulation results in a local refractive index modulation ("carrier refraction") in the vicinity of the micro-cavity, leading to measurable and useful changes in the PhC behavior. An example is shown in FIG. 1, which shows shifts in wavelength obtainable with electrically induced carrier refraction.
A Dynamically Controlled Photonic Crystal has a dynamic range that is sufficient to create controllable filters, routers, modulators and switches for many optical communication applications. This can lead to the creation of an all-optical switch and the miniaturization of optical communication devices.
7-2007-62
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